RECOMMENDATIONS OF THE BRITISH PAEDIATRIC CARDIAC ASSOCIATION FOR THERAPEUTIC CARDIAC CATHETERISATION IN CONGENITAL HEART

DISEASE

Recommendations compiled by a sub-committee of British Paediatric Cardiac Association (BPCA), consisting of: Dr Shakeel A Qureshi, Guy’s Hospital, LondonProfessor Andrew Redington, Great Ormond Street Hospital, London Dr Christopher Wren, Freeman Hospital, Newcastle upon TyneDr Inga Ostman-Smith, John Radcliffe Hospital, OxfordDr Raman Patel, Royal Manchester Children’s Hospital, ManchesterDr John Gibbs, Leeds General Infirmary, LeedsDr Joe de Giovanni, The Children’s Hospital, Birmingham Address for correspondence:

Dr Shakeel A Qureshi, FRCPConsultant Paediatric CardiologistDepartment of Congenital Heart DiseaseGuy’s Hospital11th Floor Guy’s TowerSt Thomas StreetLondon SE1 9RT, UKTelephone: 0207 955 8772 Fax: 0207 955 4614E-mail: Shakeel.Qureshi@gstt.sthames.nhs.uk

Aims, scope and limitations of recommendations.

The aims of these recommendations are to improve the patient outcome and to provide acceptable standards of practice of therapeutic cardiac catheterisation procedures in congenital heart disease. The scope of the recommendations includes all interventional procedures, recognising that for some congenital heart defects, surgical treatment is equally as effective as, or occasionally preferable to, interventional treatment. The limitations of the recommendations are that at present no data are available which compare the results of interventional treatment with surgery and certainly none, which evaluate the numbers and types of procedures that need to be performed for the maintenance of skills. Thus there is a recognised need to collect comprehensive data with which these recommendations could be reviewed in the future and re-written as evidence-based guidelines. Such a review will have to take into account the methods of data collection, their effectiveness and the latest developments in technology. The present recommendations should therefore be considered as consensus statements and describe accepted practice, which could be used as a basis for ensuring and improving the quality of care in the future.

INTRODUCTION

During the last fifteen years, major developments have occurred in the use of interventional techniques in paediatric cardiology (1-6). During the same period, advances have also occurred in the imaging techniques in congenital heart disease, which have rationalised the indications for diagnostic cardiac catheterisation, leading to more selective use of diagnostic cardiac catheterisation services in the cardiac catheterisation theatres. Most of the anatomical information required for making decisions on treatment of congenital heart defects can be obtained by cross-sectional and colour Doppler echocardiography. Additional anatomical information can be obtained by magnetic resonance imaging. Shunt quantification can be derived from nuclear medicine techniques. This allows the paediatric cardiologists to perform cardiac catheterisation with the aim of obtaining specific information that has not been obtained by the other imaging techniques or to perform therapeutic procedures. An additional indication is in the assessment of the results of previous surgery for a congenital heart defect.

Interventional paediatric cardiology is appropriate for patients with congenital heart defects in all age groups, ranging from the neonate to the adult. The procedures are performed as primary treatment of a defect or as an interim treatment prior to surgical repair of the defect or for the treatment of a residual defect after previous surgery.

Therapeutic cardiac catheterisation in congenital heart disease have become more complex and the range of their indications has widened. These procedures may be time consuming (7). A reduction in the need for diagnostic cardiac catheterisation, by the non-invasive imaging techniques, has allowed more time in the cardiac catheterisation theatres for therapeutic cardiac catheterisation. These procedures are more costly and may be associated with slightly higher risks than diagnostic cardiac catheterisation. Furthermore, the operators require an increased amount of training and additional expertise (8).

In the early years of interventional techniques, therapeutic cardiac catheterisation in children constituted about 10% of the total workload, but nowadays, this has increased to between 20-60%. An increasing number of centres and an increasing number of operators perform these procedures.

Because of the risks, costs and demands on expertise, it may be considered inadvisable for all of the techniques to be performed in all of the institutions. Some of the more complex techniques may be suited more to catheterisation theatres, which have the appropriate personnel, facilities and programmes. Thus, some guidelines are needed for interventional techniques in the specialty of paediatric cardiology.

The American Heart Association produced a scientific statement on "Paediatric Therapeutic Cardiac Catheterisation" in 1991, which was revised in 1998 (9, 10). Such statements or guidelines cannot be considered ideal, because by the time they are published, further technical

advances have meant that newer techniques have been developed which may not have been addressed. Furthermore, because of the present paucity of appropriate and suitably robust scientific data for therapeutic cardiac catheterisation, the recommendations cannot be entirely evidence-based.

Therefore, such guidelines should only be taken as recommendations and are not intended to be legally binding statements. In order for the recommendations to become robust in the future, they should be reviewed and updated. It is essential that data on interventions are acquired in each institution and nationally and all the units performing these procedures undertake regular audit. For this policy to become successful, a local and central database and mechanisms for peer review and for the validation of data will need to be set up, which would help each unit to compare its results against those available nationally. This approach will allow individual and unit performances to be evaluated objectively.

PRESENT WORKLOAD PATTERNS

The data on the present workloads in paediatric cardiology units are based on a questionnaire sent to all the paediatric cardiology consultants in the UK. In each unit, between 100 and 500 cardiac catheterisation procedures are performed annually, of which between 30 and 250 procedures are interventional. These constitute between 20% and 60% of the total number of diagnostic procedures, the average being about 35%.

A majority of the units have allocated 3 to 4 sessions per week for paediatric cardiology use in the catheterisation theatres. For the remaining time, the theatre is used by the adult cardiology service in about half of the units, by radiologists in 20% and in the remainder by the paediatric cardiologists alone. Almost all of the units have a biplane facility.

The total number of consultant paediatric cardiologists in each unit varies between 2 and 8, with a majority of units having 3 - 4 consultants. In more than half of the units, all the consultants currently perform therapeutic cardiac catheterisation, whilst in the remainder, 2/3rd to ¾ of the consultants undertake interventions. A majority of therapeutic cardiac catheterisation is performed under general anaesthesia.

All the units perform most types of interventions, although of necessity some of the more complex procedures are performed in small numbers. REQUIREMENTS

FACILITIES AND EQUIPMENT

In most paediatric cardiac catheterisation theatres, the services will be shared with adult cardiology, or paediatric radiology, or neuroradiology or adult interventional radiology. Occasionally, the theatre may be available for full time use by the paediatric cardiology department. There are advantages to the cost of running and maintaining the theatre and the catheterisation equipment when the theatre is shared with other services, but there may be disadvantages to the paediatric cardiology service also. The paediatric cardiology unit may have to use imaging equipment preferred by their adult cardiology or radiology counterparts, when the equipment preferred for paediatric cardiology may be superior.

The equipment for fluoroscopy and angiography should be of the highest quality and should be capable of producing high-resolution images. The fluoroscopy and angiography cameras must be regularly serviced, maintained and regularly replaced or upgraded to maintain the high quality of imaging required in paediatric cardiology.

Rules relating to the measurement of radiation dosage, the reduction of radiation and maximum radiation protection for the patients as well as the staff in the catheterisation theatres must be strictly enforced. These include protection of the pelvic areas of the patients and protection of the thyroid gland and the eyes of the operators. Fluoroscopy times and radiation doses for the theatre personnel must be measured, recorded and audited (11, 12).

Full use of reduced dose rates should be used whenever possible, for example in procedures involving deployment of devices. In infants up to 12 months of age, the anti-scatter grid should preferably be removed and full use made of air gap techniques. If the grid is removed, the air gap should be less than 10-15 cm. New systems in which the grid can be removed are desirable. Pulsed fluoroscopy should be encouraged if it is confirmed by the local physicists that the radiation dose is reduced when compared with continuous fluoroscopy.

In the early 1980s, single plane fluoroscopy with digital subtraction facilities was considered adequate for the purposes of paediatric cardiologists. This may have been true when most of the procedures were mainly in the diagnostic category, but this is no longer the case. With the number of diagnostic procedures falling and the number of therapeutic cardiac catheterisation procedures increasing, practical experience has reinforced the impression that therapeutic cardiac catheterisation takes longer to complete when a single plane fluoroscopy system used than when a biplane system is used.

Therapeutic cardiac catheterisation usually requires multiple angiograms in different projections. If biplane fluoroscopic and angiographic facilities were available, then with intelligent use of different angles, more efficient use is made of the facilities and the procedure may be expedited and performed more safely. Therefore biplane imaging is preferred for use in paediatric cardiology and all single plane imaging systems should eventually be replaced by biplane systems.

Angled views are an important part of the technique to obtain the maximum amount of information prior to and during the interventions. Therefore, the angiographic systems must have the capability of obtaining complex angled views.

In the modern era, there is a tendency to move towards cineless systems and it seems likely that these will be used routinely in the future. Angiographic data will have to be saved on compact disks rather than the old-fashioned cine films. This will lead to a more efficient use of the storage space, which was needed with old cine film systems. An adequate archiving system is essential.

The system must be capable of on-line instantaneous replay of high quality digital images rather than the less than optimal quality replay of videotapes. Facilities for road-mapping and the accurate measurement of vessel dimensions are important in the decision making and performance of interventions and should be available. Purchasing new systems should take these points into account.

It is important that the paediatric cardiac catheterisation theatres are not restricted by the adult cardiology or radiology service with regard to the type of equipment that is used or stocked in the theatre.

The introducer sheaths, the guidewires, the diagnostic catheters, the balloon catheters, various devices for closure of defects, the stents, the coils must all be bought for specific paediatric use rather than modifying the available adult equipment for paediatric use. Therapeutic cardiac catheterisation becomes much less complicated when the correct and appropriate equipment is used.

The items intended by the manufacturer for single use only should not be resterilised.

The paediatric cardiology unit must be committed to therapeutic cardiac catheterisation otherwise the quality of the service, the treatment and the results of these procedures may be less than optimal. Therapeutic cardiac catheterisation in paediatric cardiology, being considerably more complex than diagnostic cardiac catheterisation and interventions in adults, carry slightly higher risks of complications (13, 14). With most of the complications, the paediatric cardiologist performing the procedure may retrieve the situation. Very occasionally, it cannot and then a surgeon may be required to perform an emergency thoracotomy or a sternotomy in the cardiac catheterisation theatre.

It is important that the paediatric cardiac surgical unit is supportive of therapeutic cardiac catheterisation and the programme.

Whilst it is not essential to have a paediatric cardiac surgeon standing by for a procedure, surgical cover/service should ideally be available on site.

Where paediatric cardiopulmonary bypass facilities are not available, it would be advisable for therapeutic cardiac catheterisation procedures to be carried out in another unit where bypass facilities are available and interventions are performed.

A sterile operating room environment must be maintained in the catheterisation theatre. The theatre should have frequent air changes (15-22 room cycles per hour) and the design of the theatre should allow it to be turned into a sterile operating theatre if needed.

When there is a perceived risk of surgery being needed or haemorrhagic complications occurring, consideration should be given to cross-matching of blood prior to the interventional procedure. Antibiotic cover during the procedure may be advisable, although no strong recommendations can be given in this regard.

General anaesthesia should be used, or should be readily available, when therapeutic cardiac catheterisation procedures are undertaken.

PERSONNEL

Interventional techniques in paediatric cardiology require more detailed and intensive training than diagnostic cardiac catheterisation alone. Diagnostic cardiac catheterisation is an important part of the training of specialist registrars, so the trainees should perform an appropriate number, at least the minimum number, of diagnostic cardiac catheterisation procedures, as defined in their curriculum.

At present, the training programmes for the specialist registrars form a part of general paediatric cardiology training with a view to obtaining a CCST (Certificate of Completion of Specialist Training). Such certification does not necessarily allow a potential future consultant to become an interventional paediatric cardiologist. In order to sub-specialise, additional training will be required. The type and the duration of sub-specialty training will need to be defined. Specific criteria for sub-specialisation, certification and revalidation will be required for those wishing to start performing these procedures and for those wishing to continue performing them.

In the cardiac catheterisation theatre, paramedical staff such as nurses, cardiac technicians, radiographers, need to have an adequate amount of training in paediatric cardiac catheterisation, interventional techniques and the related equipment. It is essential that anaesthetists involved in therapeutic paediatric cardiac catheterisation procedures should have obtained experience in paediatric anaesthesia and preferably paediatric cardiac anaesthesia.

INTERVENTIONAL REQUIREMENTS It seems likely that in the future, paediatric cardiologists will move towards further sub-specialisation, such as becoming experts in non-invasive diagnosis/imaging or invasive diagnosis/interventions.

Who should perform interventions is a matter for each unit to decide. It would be advisable to have at least one interventionist taking part in each interventional procedure so that the highest quality treatment is provided for the patient.

Each unit should consider having a designated ‘lead interventionist’, who should perform or who is responsible for interventions, with either one or two other consultant colleagues supporting the lead interventionist in the programme.

It should be the responsibility of the lead interventionist to keep up-to-date with new developments and techniques and institute these programmes in the unit.

The lead interventionist should be given the responsibility for performing regular audit of therapeutic cardiac catheterisation in each unit and comparing the data, when available, with the national data.

In the treatment of congenital heart disease, interventional techniques play an important role and complement cardiac surgery. Therefore, co-operation between paediatric cardiac surgeons and paediatric cardiac interventionists is crucial for their success.

At present, the expertise available locally may determine whether or not an interventional technique for the treatment of a particular defect is indicated. However, this should not influence the discussions about how best to treat the patient. A less invasive (interventional) alternative should be considered, but a judgement will have to be made for each individual case in each unit.

A unit should be capable of providing continuity of care every day of the year in all aspects of care in paediatric cardiology. A team approach (consisting of more than one interventionist) will be needed to cover all the aspects of interventional techniques, which will allow uniform standards of treatment and will provide cover for holidays of the colleagues, sick leave and attendance at conferences.

All therapeutic cardiac catheterisation procedures, whether balloon atrial septostomy and balloon dilation of pulmonary valve stenosis or stent implantation in pulmonary arteries, carry additional risks and so require specialised skills and proper training. Each unit and each interventionist should treat an adequate number of patients in order to maintain the requisite skills and expertise in the diverse and increasingly complex therapeutic cardiac catheterisation.

Specialist registrars should be required to perform a number of diverse therapeutic cardiac catheterisation procedures in order to obtain competence.

To perform these as the first operator, the operator should be required to have received procedure-specific training under the supervision of a suitably qualified individual and to have obtained procedure-specific certification.

An interventionist is unlikely to perform a specific number of a specific type of interventional procedure each and every year because of variations in the types of congenital heart defects presenting to each unit. The interventionist should therefore perform, supervise and assist other consultants or trainees, in order to maintain skills and competence.

All therapeutic cardiac catheterisation procedures involve similar types of technical equipment or manoeuvres. Therefore, a minimum number of overall procedures rather than a minimum number of specific types of procedure that should be considered for the maintenance of skills. There is clearly no upper limit, but a minimum of 40 therapeutic cardiac catheterisation procedures of a wide variety of types per year should be regarded as adequate for maintenance of skills for the lead interventionist. These can be performed either as the primary operator or as an assistant but in a teaching capacity.

The interventionist must remain up to date with new trends or techniques through both reading and attendance at specific meetings dealing with interventional techniques. However, none of these is a substitute for personal experience.

Each unit should evolve a decision making forum for elective cases requiring complex therapeutic cardiac catheterisation, in order to maximise the input from within the unit.

When new therapeutic cardiac catheterisation techniques are introduced, discussions should take place with the hospital ethical committee to obtain the appropriate approval.

The results of the procedures in each unit for each operator must be audited and should be compared with the national experience.

The Academy of Medical Royal Colleges has set up the Safety and Efficacy Register of New Interventional Procedures (SERNIP), which attempts to categorise all procedures into different levels of use and acceptance. It would be important to inform SERNIP of all established and new techniques in paediatric cardiology.

In UK, until there is a change in the working practices and if and until a system of sub specialisation is developed, all paediatric cardiologists will continue to carry out on-call duties and deal with emergency admissions.

Balloon atrial septostomy is often performed as an emergency procedure. Paediatric cardiologists performing on-call duties should maintain expertise in this procedure. It is therefore imperative that all paediatric cardiologists should be able to perform balloon atrial septostomy alone and/or with assistance from a trainee.

Whilst balloon dilation of pulmonary valve stenosis in older children is considered as the treatment of choice and carries a low risk, the highest risks and the probability of failure and complications occur in neonates with critical pulmonary valve stenosis. Therefore, in this situation and other similar ones, an interventionist should be involved in the procedures.

The more complex interventions such as stent implantation in the cardiovascular system, catheter valvotomy in atretic valves, catheter closure of intracardiac and extracardiac shunts should be carried out by experienced interventionists or those who have received training in these procedures.

SPECIFIC THERAPEUTIC CARDIAC CATHETERISATION PROCEDURES

Interventional techniques may replace or delay the need for surgery, or form an adjunct to surgery (either before, during or afterwards).

In pulmonary valve stenosis, interventional techniques have eliminated the need for surgery in most cases. Balloon dilation is the treatment of choice for pulmonary valve stenosis (15-17). In aortic valve stenosis, the techniques have enabled surgery to be delayed until the patient is older and should be considered as palliative (18, 19). With complex defects, the techniques have reduced the number of further surgical operations that may be needed.

Procedures to create or enlarge an atrial septal defect have been performed since 1966 (20). The methods have improved and the indications have widened since the early reports. Balloon dilation techniques have been used to relieve valvar and arterial stenoses. Although long term data are not available, in the medium term the results are acceptable. A relatively recent development involves catheter closure of extracardiac and intracardiac defects by interventional techniques (4). Various kinds of devices are used to occlude patent arterial defect, atrial septal defect and some types of ventricular septal defects. Metal stents have been used increasingly for dilating branch pulmonary arteries, aortic coarctation and systemic and pulmonary veins. Metal coils have been used to occlude fistulous vessels.

BALLOON ATRIAL SEPTOSTOMY

Rashkind and Miller first described balloon atrial septostomy in 1966 as a method of palliation in babies with transposition of the great arteries (20). Creating an atrial septal defect in these patients improves bi-directional mixing of the pulmonary and systemic venous blood, thus improving oxygen saturation. Over the years improvements in catheter design have lowered the complications such as failure of balloon deflation or balloon rupture (21-27). Balloon atrial septostomy can be performed from either the umbilical or the femoral venous approach. In the first few days of life, umbilical venous access is easy, whilst in the older babies, femoral vein access is required. Whilst in the past the procedure was performed in the catheterisation theatre under fluoroscopic guidance, nowadays it is possible to perform this in the intensive care unit using echocardiographic guidance without transporting the baby to the catheterisation theatre. The safety of this approach has been shown in several studies (26, 28 – 36).

Although balloon atrial septostomy is usually a safe procedure, complications have been reported. Transient rhythm disturbances are frequent; rarely they can be permanent or fatal. Premature ectopic beats, supraventricular tachycardia, atrial flutter and fibrillation are the most commonly encountered arrhythmias. Partial or complete heart block and ventricular arrhythmias may also occur. Failure to create an adequate communication is a possibility if the balloon is not withdrawn across the atrial septum rapidly enough or if the balloon is not of an adequate size. This may occur more often in infants older than about two months of age because the septum is thicker. Other potential complications include perforation of the heart, balloon fragment embolisation, laceration of the atrioventricular valves, systemic or pulmonary veins, and failure of balloon deflation (37 - 43).

Indications for Balloon Atrial Septostomy

I. Conditions for which balloon atrial septostomy is appropriate: Infants less than 6-8 weeks of age with

a. Transposition of the great arteries, with or without associated cardiac defects. However, if the infant is haemodynamically stable with adequate oxygenation and surgery is to be performed within 12 to 24 hours, there may be no added benefit from balloon atrial septostomy.

b. Total anomalous pulmonary venous drainage with restrictive ASD (occasionally needed before surgery if necessary)

c. Tricuspid atresia with restrictive ASD

d. Mitral valve atresia if the Norwood approach is not contemplated

e. Pulmonary valve atresia with an intact ventricular septum

II. Conditions for which balloon atrial septostomy may be indicated: Hypoplastic left heart syndrome

III. Conditions in which balloon atrial septostomy is inappropriate:

a. Interrupted inferior vena cava

b. Infants older than 6-8 weeks. The atrial septum is usually thick and not amenable to balloon septostomy. BLADE ATRIAL SEPTOSTOMY

In older infants (over the age of 6-8 weeks), the atrial septum may be too thick to be torn adequately by balloon septostomy alone. Even if an atrial septal defect is created by a balloon, it may heal and close very rapidly. When the presence of an adequate inter-atrial communication is essential for mixing, blade atrial septostomy is the preferred procedure. This procedure was first described by Park et al in 1975, and has proved safe and effective even in adult patients (44 - 52).

The blade septostomy catheter (Cook, Inc, Bloomington, Indiana) is available in three sizes of blades: 9.4 mm, 13.4 mm, and 20 mm. The protocol and technique of blade atrial septostomy have been described in detail (44 - 52). The procedure is performed under fluoroscopic guidance, but echocardiographic monitoring can also be used (53). Although the procedure is considered safe, there are potential complications. Perforations of the right atrium and ventricle have been reported during prolonged manipulation of the blade. Other complications include air embolism and inability to retract the blade into the catheter (44 - 53).

Indications for Blade Atrial Septostomy

I. Conditions for which blade atrial septostomy is appropriate: Infants older than 6-8 weeks with

a. Transposition of the great arteries, with or without associated cardiac defects. However, if the infant is haemodynamically stable with adequate oxygenation and the arterial switch is to be carried out within 12 to 24 hours, there may be no added benefit.

b. Total anomalous pulmonary venous drainage with restrictive ASD (rarely required).

c. Tricuspid atresia with restrictive ASD

d. Mitral valve atresia if the Norwood approach is not contemplated

e. Pulmonary valve atresia with an intact ventricular septum

II. Conditions for which blade atrial septostomy may be indicated:

a. Hypoplastic left heart syndrome

b. Patients with pulmonary vascular obstructive disease and increased right atrial pressure

c. Infants older than 6-8 weeks. The atrial septum is usually thick and may not be amenable to balloon septostomy.

III. Conditions in which blade atrial septostomy is inappropriate: Interrupted inferior vena cava

STATIC BALLOON ATRIAL DILATION

When the atrial septum is thick, blade atrial septostomy is the preferred method of creating and enlarging the atrial communication. However, the blade septostomy must always be followed by a balloon septostomy, which may still have limitations in a thick and tough septum. To overcome such limitations, static balloon atrial dilation can be used (54 - 57). This technique has proved to be relatively safe and effective. Oversized balloons may be required to tear the atrial septum adequately (56).

The indications for static balloon dilation of the atrial septum are similar to those of balloon or blade septostomy. If the patient is older than 6-8 weeks and the atrial septum is thick, static balloon dilation can be considered, preferably after blade septostomy has been performed. DEVICES FOR CLOSING ATRIAL SEPTAL DEFECTS

Atrial septal defect is a common form of congenital heart disease accounting for approximately 7% of all defects. Secundum atrial septal defects are the commonest and some, but not all, of these are suitable for transcatheter closure techniques. The traditional conventional treatment for clinically significant secundum atrial septal defects is surgical closure, which is associated with less than 1% mortality. There may be residual shunting and some morbidity associated with even surgical closure (58, 59). Transcatheter closure of these defect began in 1976, when King et al reported the first application of a double-umbrella device in humans (60, 61). Subsequently, Rashkind developed a single umbrella with hooks. This device underwent limited clinical trials that were stopped because of the low success rate of implantation leading to the development of modifications of the device (62). At present, several devices have undergone or are undergoing clinical evaluation and their indications and limitations are being determined. These include the Clamshell, the Buttoned, the Angel-wings, the ASDOS, the Cardioseal, the Starflex, the Amplatzer and the Helex devices. Some of these devices have been withdrawn, others modified and others are in use. At present no firm recommendations can be made as to which is the best device. The Clamshell device (a double umbrella system) was first used by Lock et al in 1989 in lambs (4). The device underwent extensive clinical evaluation with a very high success rate of implantation. However, because of a high incidence of device arm fracture (42%) and a high incidence of residual shunt (27% - 44%), its use was stopped (63). After extensive modification of the device (change of metal, arm angles, and enhancement of the joint in the middle of the arms), a new device, the Cardioseal has recently undergone clinical trials in Europe and USA (64-66). A further modification of this device (nitinol microfilaments connecting the ends of the arms of the left and right atrial discs) has made it into more of a self-centring device. This is called the Starflex device and is also undergoing clinical evaluation. The buttoned device has three components, the occluder, the counter-occluder and the loading wire (67). Since 1990, this device has been used extensively, but unbuttoning and device embolisations have caused concerns about its performance (68 - 73). With further modifications, the incidence of complications such as unbuttoning has reduced (68 - 73). The Angel-wings device is a self-centring double disk device made of nitinol wire and dacron. This device has also undergone clinical evaluation, but because of concerns about pointed arms causing perforation and the inability to retrieve the device once partially deployed, it is also undergoing modifications (74 - 76). The ASDOS device is also a double- umbrella device is made of nitinol and polyurethane. It is complicated to implant. Simultaneous venous and arterial access and an arteriovenous guidewire circuit are necessary in order to deploy the left atrial disk separately from the right atrial disk. Once their position is judged to be acceptable, the disks are screwed together and the circuit is broken (77, 78). The Amplatzer device is a double mushroom shaped device with a connecting waist similar to a metal stent. All the device is made of nitinol wire mesh and inside are dacron fibres to promote thrombosis. This has the advantage of retrievability and repositioning if the position is unsatisfactory (79 - 85).

The device selection has to be reasonably accurate with all of the devices and balloon sizing is essential for this. All of the devices require transoesophageal echocardiographic guidance for optimal placement. The use of general anaesthesia is advisable because of the need for transoesophageal echocardiography although in adult patients, the procedure could be performed under local anaesthesia and sedation.

Indications for Use of Atrial Septal Defect Devices

I. Conditions for which atrial septal defect devices are appropriate: Patients with secundum atrial septal defects or patients with patent foramen ovale and an associated stroke (or a transient ischaemic attack) who meet the following criteria:

a. Atrial septal defect with stretched diameter of less than 38 mm

b. The presence of sufficient rim of tissue (at least 4 mm) surrounding the defect

c. Patients with fenestrated Fontan

d. Patients with right-to-left atrial shunt and hypoxaemia

II. Conditions for which atrial septal defect devices may be indicated: Divers with neurological decompression sickness

III. Conditions for which atrial septal defect devices are inappropriate:

a. Sinus venosus atrial septal defect

b. Primum atrial septal defect

c. Secundum atrial septal defect with significant forms of other congenital heart defects requiring surgical correction

DEVICES FOR PATENT ARTERIAL DUCTS

Patent arterial duct was closed by transcatheter techniques in 1967, when Porstmann et al reported the use of an Ivalon plug and thus alternatives to surgery became available (86). However, because of the large size of the introducer needed to insert the plug the technique was not widely adopted. In 1979, Rashkind et al reported on a small hooked umbrella device for the transcatheter closure of a patent arterial duct (5). This subsequently evolved into the double-umbrella, non-hooked Rashkind PDA occluder. The latter device was available in two sizes, 12 mm and 17 mm, and could be delivered through 8F and 11F sheaths, respectively. It was used extensively around the world for several years but suffered from the main disadvantage of cost and an incidence of residual leak after one device of 10-20% (6, 87 - 89). The residual leak needed either another device or coils to achieve a high rate of complete occlusion (89). The buttoned device has also been used for closing patent arterial ducts (90). The incidence of residual shunting was similar to the Rashkind device. Over the last few years, coils have been used extensively for closing arterial ducts. These are discussed below. The Rashkind PDA device has now gone out of favour because of these less costly alternatives. For arterial ducts of less than 4-5mm in diameter, with one or more coils, complete occlusion can be achieved in 95-97% cases. Coils are easy to use and inexpensive compared with the other methods. For larger ducts, other devices such a the Cardioseal, the Starflex or the Amplatzer devices can be used. The Amplatzer device (PDA plug) has been developed to close such large ducts effectively and safely with a high closure rate (91, 92).

Indications for Patent Arterial Duct Devices

I. Conditions for which catheter closure of the arterial duct is appropriate:

a. Symptomatic patients with the diagnosis of patent arterial duct

b. Asymptomatic patients with a patent arterial duct with a continuous murmur

c. Asymptomatic patients with colour Doppler evidence continuous flow due to patent arterial duct and a systolic murmur

II. Conditions for which closure of patent arterial duct is not appropriate: Patent arterial duct with irreversible pulmonary vascular obstructive disease

COIL OCCLUSIONTranscatheter occlusion of unwanted vascular communications has played an important role in paediatric interventional cardiology since the technique was first described by Gianturco and colleagues more than 20 years ago (93, 94). The most commonly used embolisation materials include the Gianturco stainless steel coils and the platinum microcoils (95). The Gianturco coil is a stainless steel wire to which Dacron fibres have been attached to increase its thrombogenicity. After implantation of the coils, occlusion of the vessel occurs as the result of thrombus formation and its subsequent organisation. A detachable coil-delivery system is also available. This can result in more control during the coil placement, in that if the position of the coil is unsatisfactory or causes concern, then it can be withdrawn into the catheter and repositioned. Platinum microcoils can be delivered through 3F delivery catheters, passed through a 5Fguiding catheter to selectively occlude very tortuous vessels, which may be difficult to occlude using the stainless steel coils. The technique of coil occlusion depends on the type of vascular connection with a helical diameter 20% to 0% larger than the diameter of the target vessel or malformation, but if there is a discrete stenosis, then a smaller size coil can be chosen. Usually several coils have to be tightly packed in order to achieve complete occlusion, especially if there is a high flow in a vessel. Sometimes, the blood flow has to be stopped by using a balloon angiographic catheter in order to facilitate coil implantation. Patent Arterial Duct

As mentioned above, a variety of devices have been used for closing the patent arterial duct. They all require large delivery catheters and are expensive. Coil occlusion of the patent arterial duct is simple and effective. It requires only a 4F or 5F catheter and is relatively inexpensive. Since first described in 1992, coil occlusion of the small arterial duct has now become the treatment of choice (96 - 101). The types of coils include the Gianturco coils, the controlled-release Cook PDA coils, the PFM Duct-Occlud coils, all of which have been evaluated (96 - 102). The technique provides effective therapy for the large majority (more than 90%) of small arterial ducts when the minimum angiographic diameter is less than about 4-5 mm. Arterial ducts up to 7mm have been closed with coils but many coils may be required and there may be higher probability of coil embolisation and residual flow (103). Coil occlusion technique is not appropriate for the non-restrictive larger arterial duct and alternative techniques may be required. The use of coils in the clinically silent arterial ducts is also debatable. Coil occlusion of the arterial duct can be performed by the retrograde arterial or the antegrade transvenous routes and some ducts, even small ones, may require the implantation of more than one coil, although the majority requires a single coil. Tiny residual shunts noted immediately after coil implantation often resolve spontaneously. Complications after coil occlusion include a persistent residual shunt in 5% to 10% of cases, embolisation of a coil to the pulmonary artery or rarely to a systemic artery requiring catheter retrieval, occasional femoral artery injury following cannulation, and very rarely haemolysis associated with a residual shunt. Significant left pulmonary artery stenosis, aortic coarctation, thromboembolism and endarteritis have not been reported, although late recanalisation can rarely occur after coil occlusion of the arterial duct (96 - 105).

Aortopulmonary Collateral Arteries

Aortopulmonary collateral arteries occur most commonly in infants with pulmonary atresia with ventricular septal defect. They may also occur with tetralogy of Fallot. The collaterals may require occlusion before and/or after surgical treatment. They may also be seen in after a bi-directional Glenn or a Fontan operation. Occlusion of the collaterals may be useful because this may reduce competitive pulmonary blood flow, or reduce systemic ventricular volume overload, or assist in the staged process of unifocalisation of the pulmonary artery tree (94, 95, 106, 107). The collateral vessels to be occluded must supply a segment of the pulmonary artery, which receives dual arterial supply from the central pulmonary artery as well as from the collateral.

Surgical Aortopulmonary ShuntsOccasionally in patients with a surgical aortopulmonary shunt such as a Blalock-Taussig shunt, the shunt has become redundant because the right ventricle has grown in size and improved in function or there is residual shunting through the shunt after surgical repair. Instead of a further operation to close the shunt, coil occlusion can provide a better non-surgical alternative (106,107).

Arteriovenous Fistulas

Coronary arteriovenous fistulas can be treated by transcatheter coil occlusion techniques (108 – 111). The technique is complex in this situation and requires a high degree of skill and knowledge of the coronary artery anatomy. These fistulas may arise from the left or right coronary artery and communicate with the right atrium, right ventricle, or pulmonary artery. Coils can successfully occlude most types of these fistulas. Gianturco coils or the platinum microcoils can be used and the selection of these is determined by the anatomy and the degree of tortuosity of the fistula vessel (108 – 110). Coils can be delivered by the retrograde arterial route but the transvenous route has also been used. About a third of the coronary arteriovenous fistulas have multiple feeding vessels and so after the occlusion of the main vessel, these should be looked for by further selective angiography and if found, attempts should be made to occlude these also (110). Complications may include incomplete occlusion, myocardial ischaemia if a more distal coronary artery is inadvertently occluded, and inadvertent embolisation of a coil to the right heart or pulmonary artery, requiring retrieval (108 – 110). Coil occlusion has also been used to treat pulmonary arteriovenous malformations (111 – 112). Such malformations can be hereditary or acquired following a previous Glenn or a modified Fontan operation and can be single or multiple. When intrapulmonary right-to-left shunting is significant enough to cause cyanosis, treatment is indicated to improve the systemic arterial oxygen content. Here, the catheter occlusion technique may require many coils to occlude the solitary malformation and also to occlude the multiple ones in order to effectively relieve hypoxaemia (112).

Anomalous Veno-venous Connections

Children with a complex congenital heart defect, who have undergone a Glenn shunt or a modified Fontan operation may develop persistent or recurrent cyanosis as a result of anomalous veno-venous connections, which cause right-to-left shunting and decrease effective pulmonary blood flow (94, 95). These connections include those causing retrograde flow through the azygos vein or hemiazygos vein to the inferior vena cava after a Glenn shunt or retrograde flow to the right atrium through a persistent left superior vena cava. After a Fontan operation, right-to-left veno-venous shunting may occur as the result of communication between the inferior vena cava and the pulmonary venous atrium, particularly in children whose hepatic veins are excluded from the Fontan pathway. Transcatheter coil occlusion of these veno-venous connections may therefore be indicated.

Indications for Coil Occlusion

I. Conditions for which coil occlusion is appropriate:

a. Aortopulmonary collaterals with dual supply to the pulmonary artery segment

b. Small patent arterial duct (diameter less than 4-5 mm)

c. Surgical aorto-pulmonary shunts

d. Pulmonary arteriovenous malformations

e. Anomalous veno-venous connections (post bidirectional Glenn or Fontan operations)

f. Coronary arteriovenous fistulas

II. Conditions for which coil occlusion may be indicated:

a. Moderate patent arterial duct (diameter of 5 to 7 mm)

III. Conditions for which coil occlusion is inappropriate:

a. Aorto-pulmonary collaterals without dual supple

b. Non-restrictive large patent arterial duct

BALLOON DILATION OF CARDIAC VALVES

Pulmonary Valve Stenosis Since 1982, percutaneous balloon dilation of pulmonary valve stenosis has become the mainstay of treatment as an alternative to surgery in all age groups and can be considered as the treatment of choice (1, 15 – 17, 113 - 115). Balloon dilation effectively reduces the right ventricular systolic pressure and transpulmonary valve gradients in the majority of patients in all age groups. Complications are rare, but are more frequently encountered in the neonates (113 – 115). Pulmonary regurgitation may occur in some patients but is usually mild and well tolerated.

The indications for balloon dilation of the pulmonary valve are the same as those for surgical pulmonary valvotomy. These include a valvar gradient greater than 50 mm Hg for a patient with a normal cardiac output. In neonates with critical pulmonary valve stenosis, the gradient may be significantly higher or lower than 50 mm Hg, depending on the cardiac output and the right ventricular function.

Both increasing experience and recent advances in equipment used in the catheter laboratories, such as guidewires and low profile balloons, have made balloon dilation for critical pulmonary valve stenosis feasible and safe, and now it compares favourably with surgical pulmonary valvotomy for neonates as well as older children. It is recognised that the technique is much more demanding in the neonates, where speed is essential and super-floppy guidewires need to be passed through a very small opening in the pulmonary valve. The guidewire may need to be passed through the arterial duct to facilitate the passage of the required balloon or increasingly larger sized balloons are used starting with a small balloon (113 – 115).

The use of balloon dilation in patients with dysplastic pulmonary valves is debatable. However, occasionally it may be worthwhile attempting balloon dilation of these valves to avoid or delay surgery (116 – 117). It is worth remembering that most of the pulmonary valves in neonates with critical stenosis appear dysplastic, but acceptable results are produced by balloon dilation. The dysplastic valves in the older patients may behave in a different manner to the neonates.

Balloon dilation of the right ventricular outflow tract has been used successfully in patients with tetralogy of Fallot and other forms of cyanotic heart defects in which pulmonary valvar stenosis is an important feature. The overall results are encouraging. and the procedure may allow adequate relief of cyanosis, increase the pulmonary blood flow and allow some increase in the size of the main and branch pulmonary arteries. Balloon dilation of the right ventricular outflow tract in the tetralogy of Fallot need only be considered as an alternative to a surgical Blalock-Taussig shunt if the patient is considered unsuitable for primary repair and a stage approach has been recommended (118 - 121). Balloon dilation is ineffective in the treatment of isolated infundibular pulmonary stenosis without additional pulmonary valve stenosis.

Aortic Valve Stenosis

Since the early reports of balloon dilation of the aortic valve in children, good short and medium-term results have been reported with balloon dilation of the aortic valve (3, 18, 19, 122 - 134). The pressure gradient across the aortic valve and the left ventricular peak systolic pressure can usually be reduced after balloon dilation and the improvement appears to persist in patients beyond infancy. As with surgery, aortic regurgitation may develop or increase after balloon dilation and the prevalence and the degree of aortic regurgitation appears to be comparable with surgery. However, iliofemoral arterial injury and occlusion can occur after balloon dilation, especially in neonates and infants (13,14, 123 - 134). The development of very low profile balloons that can be inserted through small arterial sheaths has reduced these arterial complications.

The results are similar to those obtained with surgery and therefore balloon dilation can be considered as an alternative to surgery (122 – 134). At present there are insufficient data to suggest that balloon dilation is the treatment of choice although continued evaluation of the safety and long- term efficacy is required.

As in pulmonary valve stenosis, the indications for performing balloon dilation of aortic valve stenosis are similar to those used in surgery. However, those patients who have significant aortic regurgitation in addition to aortic valve stenosis should be excluded.

The technique of balloon dilation is fairly standard, although several approaches can be adopted in different age groups. In the neonates, antegrade femoral venous or umbilical venous, or retrograde umbilical arterial or femoral arterial or axillary arterial or carotid arterial approaches can be used. In older patients, the retrograde femoral arterial approach is most commonly used. In the young infants and especially in the neonates, the technique may be more demanding and speed is essential. Superfloppy guidewires and low profile balloons have greatly improved the chances of a successful procedure.

Balloon dilation of subaortic stenosis has been performed but with unpredictable success. There have been a few successful cases of balloon dilation of discrete membranous subaortic stenosis, but the long term efficacy remains unknown (135 – 136). Fibromuscular or tunnel-like subaortic stenosis and supravalvular aortic stenoses are not amenable to balloon dilation.

Indications for Balloon Dilation of Cardiac Valves

I. Conditions for which balloon dilation is appropriate:

a. Pulmonary valve stenosis

b. Congenital noncalcific aortic valve stenosis

II. Conditions for which balloon dilation may be indicated:

a. Dysplastic pulmonary valve stenosis

b. Pulmonary valvar stenosis in complex cyanotic congenital heart defects e.g. tetralogy of Fallot

c. Discrete membranous subaortic stenosis

III. Conditions for which balloon dilation is inappropriate:

a. Infundibular pulmonary stenosis unassociated with pulmonary valve stenosis

b. Fibromuscular tunnel-like subaortic stenosis

c. Hypertrophic cardiomyopathy with subaortic obstruction

d. Supravalvar aortic stenosis

BALLOON ANGIOPLASTY

Balloon Dilation of Aortic Coarctation Surgery is the standard therapy for coarctation of the aorta, but the operation is associated with some morbidity and mortality. Balloon dilation of aortic coarctation was first reported in 1979 in excised segments of coarctation of the aorta (137). The technique was then used clinically (2).

The indications for balloon dilation are the same as those for surgery: upper limb hypertension with a resting systolic pressure gradient between the upper and lower limbs of greater than 20 mm Hg or angiographically severe aortic coarctation with extensive collaterals. The mechanism of relief after balloon dilation has been shown histologically and by intravascular ultrasound studies to involve tearing of the intima and often the media of the vessel. Of necessity the narrowed segment of the aorta has to overstretched. In aortic recoarctation, it is thought that scar formation from a previous operation would help protect a segment dilated by a balloon from rupture and/or aneurysm formation. There is still on-going controversy about balloon dilation of native aortic coarctation especially with regard to the risk of aneurysm formation and the incidence of recoarctation and whether

dilation should be performed only in aortic recoarctation or in both aortic recoarctation and native coarctation (138 – 150). The debate is even fiercer about the role of balloon dilation in native aortic coarctation in the neonatal and early infancy period (144 - 151).

Native Aortic Coarctation

Balloon dilation has been reported to be effective in native aortic coarctation from the neonates to adulthood (138 – 140, 143, 144, 148, 150-151). The pressure gradient across the coarctation can be decreased significantly with an angiographic increase in the diameter. A reduction in the systolic pressure gradient may occur in a majority of patients at the end of the procedure. A complication rate of about 17% was reported in the data of the Valvuloplasty and Angioplasty of Congenital Anomalies (VACA) Registry (148), most of which were related to arterial injury in the smaller patients. These have declined with the use of lower-profile sheaths and balloons. Aneurysms, both acute and late, may occur in 2%-6% of patients. The success rate of the procedure may be less satisfactory in the neonates than in the older infants and children. In theneonates, there may be a need for reintervention because of recoarctation within a very short period of time in 60%-70% of infants, whereas no additional intervention was required in 88% of patients older than 7 months (140, 149-151). The anatomy of the aortic arch is an important determinant of a good result. Patients with isthmus hypoplasia and long segment hypoplasia respond less well to balloon angioplasty, whereas those with a discrete membranous or hourglass-type constrictions respond more favourably.

Because effective palliation can be accomplished in the majority of patients older than 7-12 months, and because the risk of aneurysm formation is relatively low, balloon dilation may be considered as a possible initial treatment in anatomically favourable native aortic coarctations in patients over the age of about a year. However, surgery is still the treatment of choice in native coarctation in the neonates and young infants, especially as, with the advent of extended aortic arch repair, the results of surgery are likely to be better in those with long segment hypoplasia. In selected neonates, who have complex congenital heart defects in addition to aortic coarctation, balloon dilation may provide temporary palliation and therefore could be considered as a short term measure.

Aortic RecoarctationSome patients develop aortic recoarctation despite adequate initial surgical repair. The incidence is up to 20% in the first year, especially in the neonates (140, 149). It is likely to be much less of a problem in the future because of the extended aortic arch repair. Reoperation may carry a significant risk of morbidity and mortality. The indications for treatment are similar to those for surgery. In a multicentre study, balloon dilation of aortic recoarctation produced an effective reduction in pressure gradient in the majority of the patients (152) and relief of recoarctation in approximately 78% of patients, but 5 (2.5%) patients died. Complications included femoral artery damage and occlusion in 8.5%; this rate should diminish with low-profile balloons and sheaths. Late aneurysm development has been rare. Other studies have reported similar results in all age groups (141-142). Balloon dilation is an acceptable alternative to surgery for the treatment of aortic recoarctation.

Branch Pulmonary Artery Stenosis

Branch pulmonary artery stenosis and hypoplasia may occur in with many cardiac defects or may occur postoperatively. These stenoses often require treatment because of right ventricular hypertension, exacerbation of pulmonary regurgitation, and because of an increase in the resistance to flow across the total pulmonary bed (this may be deleterious in Fontan-type operations). Whilst balloon dilation may produce acceptable acute results in about 50-60% of cases with either unilateral or bilateral branch stenoses, there is a high incidence of restenosis (153 – 154). Furthermore, there may be an inadequate reduction of the right ventricular systolic pressure. Complications including arterial rupture, unilateral or segmental pulmonary oedema, haemoptysis, and thrombosis may occur (155). The risk of mortality is related to pulmonary artery rupture (155). It is worth remembering that surgical approach to the treatment of branch pulmonary artery stenosis is often unrewarding because of the location of the stenoses and the course and the access to the left pulmonary artery in particular. In addition, these areas often have scarring and adhesions from previous operations. As a result, balloon angioplasty for branch pulmonary artery stenosis may be justifiable, although stent implantation seems to provide a more sustained relief of stenosis. Studies concerning the use of stents in branch pulmonary arteries have been encouraging, and this treatment may become one of the primary choices in patients who are old enough to allow implantation of adequately sized stents.

Systemic Venous and Pulmonary Venous Stenosis

There have been numerous reports of successful balloon dilation of systemic venous stenoses, especially in patients with postoperative stenosis following the repair of sinus venosus atrial septal defects or the Mustard or the Senning operations for transposition of the great arteries. Balloon dilation (with or without stent implantation) has proved effective in a significant proportion of these patients and is associated with little morbidity and mortality (156). Surgery for systemic venous stenoses is difficult and unrewarding. Even with balloon dilation, there may be a significant incidence of restenosis, but balloon dilation is still a preferable alternative to surgery. Implantation of stents has improved the overall success rates in systemic vein stenoses.

In contrast to the success observed with systemic venous stenosis, there is limited experience with balloon dilation of pulmonary vein stenosis, in which dilation has been almost uniformly futile. Even when some initial successes occur, there is a very high rate of restenosis.

Systemic-to-Pulmonary Artery Shunts

Systemic-to-pulmonary artery shunts have been dilated successfully with balloons. The chance of success may be better in patients with the classical Blalock-Taussig shunts than with the modified shunts (157 – 161). However, even the latter can be dilated if there is a discrete stenosis at the anastomotic site. Therefore, balloon dilation of systemic-to- pulmonary artery shunts is a reasonable alternative to surgery. With the recent popularity of the bidirectional Glenn operation, especially when a second palliative procedure is needed after a previous shunt, balloon dilation may be required in fewer patients.

Indications for Balloon Angioplasty

I. Conditions for which balloon angioplasty is appropriate:

a. Aortic recoarctation

b. Systemic vein stenosis

c. Pulmonary artery branch stenosis

II. Conditions for which balloon angioplasty may be indicated:

a. Systemic-to-pulmonary artery shunts

b. Native aortic coarctation (with suitable anatomy) in patients older than 7-12 months

c. Pulmonary vein stenosis - rarely helpful

III. Conditions for which balloon angioplasty is inappropriate: None

STENTS

In recent years, stents have assumed an increasingly important role in paediatric therapeutic cardiac catheterisation. Both balloon-expandable and self-expanding stents have been implanted, which maintain the patency of stenotic vessels. Stents are particularly useful in those dilatable lesions which, because of their intrinsic elasticity, recoil after balloon dilation alone. In paediatric patients, the balloon-expandable Palmaz stent has been used most commonly (162). This stent is made of stainless steel. Other stents are being used increasingly. Some of the currently available stents can be dilated up to 25mm in diameter. Experimental studies have shown that when the stents are apposed to the vessel wall, their surface becomes endothelialized within 8 to 10 weeks of implantation (163 - 164).

Pulmonary Artery Stenosis

Pulmonary artery stenosis may be either naturally occurring or after previous surgery for tetralogy of Fallot or pulmonary atresia or other congenital heart defects. The most common application of stents in paediatric cardiology has been in children with pulmonary artery stenosis and/or hypoplasia (163 – 169). The stents are particularly valuable in pulmonary artery stenoses, which are dilatable but in which vessel recoil produces an immediate restenosis. Stenting of the pulmonary arteries may be a reasonable primary treatment because of a higher immediate success rate and a lower medium- term incidence of restenosis (167, 170 - 171). When pulmonary artery stents are implanted in growing children, the need for future stent enlargement should be anticipated. Redilation has been shown to be safe and effective in stents implanted in pulmonary arteries up to 3 years later (172). In growing patients, the self-expanding type of stents should be avoided as they cannot be redilated beyond their nominal diameter.

Systemic Venous Stenosis

Balloon-expandable stents provide effective relief of systemic venous stenoses. The most common situation in paediatric cardiology is seen in patients who have stenosis of the superior or inferior systemic venous limbs after Mustard or Senning operations for transposition of the great arteries. Stenting of the superior or the inferior limb produces improvement of both haemodynamic and angiographic obstruction (173-174). However in the short-term follow-up, cardiac catheterisation may show some neointimal hyperplasia resulting in a small decrease in the lumen diameter. Balloon-expandable stents have also been used successfully to treat superior or inferior vena caval stenosis in children and adults with obstruction from other causes, such as the presence of indwelling central venous lines after cardiac catheterisation.

Other Applications of Stents

Stents have been implanted in the treatment of stenotic right ventricle-to-pulmonary artery conduits, stenotic aorto-pulmonary collateral arteries, aortic coarctation, in the arterial duct to maintain duct patency in infants with duct-dependent pulmonary or systemic blood and to treat pulmonary vein stenosis (175 – 185). Whilst in most of these, the stents have an important role in the management, in pulmonary vein stenosis, stent implantation has not made much of a difference in the medium term (185). Stents may be used not only in aortic recoarctation, but also in the primary treatment of native aortic coarctation (179 – 181). In the adolescent and adult patients, stents may become the primary treatment in the future.

Indications for Stenting

I. Conditions for which stenting is appropriate:

a. Pulmonary artery stenosis

b. Superior or inferior vena caval stenosis

c. Systemic venous obstruction of the superior or inferior limb after Mustard or Senning operation for transposition of the great arteries

II. Conditions for which stenting may be indicated:

a. Stenotic right ventricle-to-pulmonary artery conduit

b. Stenotic aorto-pulmonary collateral arteries

c. Aortic coarctation or recoarctation

d. Arterial ducts in neonates with duct-dependent pulmonary or systemic flow

III. Conditions for which stenting may be inappropriate: Pulmonary vein stenosis - unlikely to be helpful Electrophysiology procedures

There are few if any indications for catheter ablation in infancy because most tachycardias can be controlled and many will resolve spontaneously in the longer run (186). Taking into account the risks, disadvantages, and benefits of treatments available, catheter ablation is probably the treatment of choice for symptomatic tachycardias associated with accessory pathways and for atrioventricular nodal re-entry tachycardia in school age. Less common arrhythmias, such as permanent junctional reciprocating tachycardia and atrial ectopic tachycardia, need precise identification because they are also suitable for catheter ablation. Catheter ablation is an option for some children with ventricular tachycardia after expert evaluation and it is to be hoped that it will eventually have a significant role in the management of late postoperative atrial and ventricular arrhythmias. For continuing competence in paediatric electrophysiological techniques, it is difficult to specify numbers as the overall numbers are small (187). It is unreasonable to expect a paediatric electrophysiologist to perform adult investigations and pacemaker implantation to maintain competence. Competence should be maintained by the total involvement of the paediatric cardiologist in the interventional techniques undertaken in their unit. It would be rare for a paediatric cardiology unit to have more than one paediatric electrophysiologist and so the experience will have to be concentrated on that individual. If a complex procedure is considered necessary, it is important that two or more electrophysiologists collaborate (187). NATIONAL REGISTER OF INTERVENTIONS

In order to promote acquisition of solid and reliable data, a register of interventions should be established, which should be available for the comparison of the results of therapeutic cardiac catheterisation procedures of each unit and each operator against the national results. The register should promote an auditing role. Participation in this register may have to be a requirement in order for interventionists to continue to perform therapeutic cardiac catheterisation.

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