Congenital Cardiac Malformations in Relation to Central

8/14/2019 Congenital Cardiac Malformations in Relation to Central

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Congenital cardiac malformationin relation to central venous accesChristine Thompso

AbstractD u r in g the third and seventh weeks of gestation, teratogenic exposure maylead to fetal abnormality such as congenital heart defects or intrauterinedeath. Congenital heart defects are present from birth, but may appear atany tiine, or only revealed postniortetn. Often defects are present by degree.Some defects are life-threatening, while other, less severe conditions, mayhave tttininial physiological iinpact. Left superior vena cava exists in earlyembryonic deve lopment , but the vessel degenerates as the cardiovascularsystem matu res . When not associated with other malformations, an incidenceof persistent left-sided superior vena cava (PLSVC) has no clinical signsor sym ptoms . However, tt may not be as innocuous as it appears due toits association with the cyanotic defect, tetralogy of Fallot (TOF). Usinga case history as an illustration it can be shown that all cases of defect orchromosomal suspicion should be d o c u me n te d as there may be implicationsfor future interventions.Key words: Cardiovascular system and disorders Heart disorders

A 46-year-o ld man (KW) of unusual appearanceand manner, with a previous medical his toryof non-in sulin dep ende nce diabetes and newlydiagnosed lyniphoma was referred for insertionof a tunnelled central venous line for the administrationof chemotherapy . There was significant maternal historyof insulin dependence diabetes and epilepsy and his fatlierdescribed mild cyanosis when extremely cold and reported areluctance to exercise in ch i ldhood .ProcedureThe preferred right-sided approach via the internal jugularvein was attempted. Under ultrasound visualization the veinappeared to be small and, although it could be cannulated,venospasm appeared to occur and the guide wire could notbe advanced. The left internal jugular vein appeared largeand compressible and therefore a left-sided approach wasa t tempted . The vessel was cannulated, the guide wire anddilator passed easily, there were no electrocardiograph changesan d tbe catheter flinctioned. A post-procedural chest X-rayshowed the catheter coursing along the left heart bonier,initially suggesting misplacement; however, the patient wasasymptoniatic . A contrast injection study confirmed the

Ciir istint ' Tho mp son , (. l linicjl N iirsi ' SpetKihst.Tunellcd ( 'entr . i l( '.itlietcr ServKC, Cianiuv t'l (ifntT.il Hospit.il, (il.isj;ii\vAccepted for piihlicalion: January 2006

catheter passing through a persistent left-sided supevena cava (PLSVC^), thr ou gh the coronary sinns and wth e tip in the upper right atrium. An abnormal, narrowright superior vena cava (SVC) and a sliglitiy constricpulmonary artery was detected. Later review of his mednotes revealed childhood surgery for repair of hypospadiasno evidence of chmmosomal s tudies . Tbe catheter remaiin position for 5 months and the patient completed his couof chemotherapy without incident.The patient 's unusual appearance and manner suggesthere may be genetic or th romosoina l nnp i ica t ions , buview of his diagnosis, a decision was made to investigatefurther until his prognosis could be d e te rmin e d .

RW was found to sufl^er from a non-cyanotic congenheart defect (C"HD}. whieh is one of over 35 doeunienhuman congenital cardiac malformations. These recognilesions also have many variations. For example, RW's particcondition (PLSVC) can he complicated by unroofing ofcoronary sinus wherein cyanosis would be present; this be discussed later in the text (I'orth, 2002). IncidencesCHI), also referred to as congenital cardiac malformatare found in equal measure in every continent. The mcommon congenital defects are ventricular septal det(VSDs) 2()-25%, atria! septal defects (ASDs) 8-13 % , and p aductus arteriosus (I'DAs) 6-11% (Hanied and Maher, 20Although these lesions will be referred to in tbe course ofarticle, the author will concentrate specifically on PLSVCacyanotic malformation which has an incidence of 0.30of the population and is the most coninion congenital venanomaly of the SVC system (Leibowitz et al, 1992; Bartramal, 1997), and the cyanotic defect with which it has a 15-2association, tetralogy of Fallot (TOF) (Soto et al. 1992;Waet al, 2003; lirzezinski et al, 2005).

What Is a congenital heart defect?A CHI.) can be defined as the structural, funetionalpositional defect of the heart occurring either in isolation oa combination ofseveral lesions collectively Defects areprefrom birth, but may appear at any time after birth, or noall, often o nly bein g revealed po stm orte m (Lilly, 1998). Sodefects are life-threatening and require iniiiiediate surgcorrection or palliation, while other, less severe conditimay have niininial physiological impact (Lilly, 1998).

C H D s can be broadly classified into two categories: thcausing little or no cyanosis, classed as acyanotic. and thc-ausing cyanosis (Lilly, 1998; Porth, 2002).

Eight coniinon lesions account for 85%) of all cw o r ld w id e and are listed in 'liihlf / .The remain ing 1


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CARDIAC NURSINGaccounts for a variety rare detects, inckidiiig PLSVC^ (Lilly,199S; Porth, 2002).Cyanotic and acyanotic defectsIn the presence of CHDs, pressure gradients between chambersmay be created which lead to haemodynamic compromise.This effect is produced by alterations in pulmonary bloodflow and the abnormal shunting (diversion) of blood from onesystem to another through aberrant openings between bothsides of the heart. l.,eft-to-right shunts are mainly acyanoticconditions and push blood from tbe arterial circulation intotbe venous circulation resulting in oxygenated blood beingrecycled through the right heart, increasing the load andleading to enlargement of the right heart. Conversely, right-to-left shunts produce cyanosis as a result of deoxygenatedblood being forced into tbe systemic circulation via the leftheart as in TOF (Forth. 20(12).Causes of CHD( ; H 1 ) occurs with equal frequency in males and femalesand IS the cause ot S0% ot deaths withm the first year oflife (Hamed and Maher, 2(10(1). Approxima tely 13% of thoseborn with a cardiac detect will bave another non-cardiac,chromosomal ahnormality (Forth, 2002).The prevalence ot'maltorniation among the siblings and near relatives of sucha cbild IS sigiiiticantly higher [ban in the general population(Hamed and Maher, 2000).

The crticial phase tor tetal heart development is between thethird and seventh week of gestation (dittenberger-De Grootet al, 2005). During that tune, teratogemc (a tactor increasingthe incidence of maltoniKition development) exposure maylead to tetal abnormality such as C^Hl), or intrauterine death ifexposure is prolonged (Lilly, I 99K; Hamed and Maher,200(l).The involvement of a heredity tactor associated with theselesions is widely acknowledged within the literature, withmany sutierers having a genetic predisposition to disease.Embryonic mesoderm is the source of the cardiogenic place,giving rise to the future myocardium, and endocardium,which lines the heart. Genetic cascades are triggered thatgive rise to interactions between competing chemicalsignals 111 tbe primitive beart and several mutated genes

Table 1. Most commonMalformationVentricular septal detectPatent ductus arteriosusAtrial septal defectPulmonary valve stenosisAortic valve stenosisCoarctation of tine aortaTetralogy of FallotTransposition ot great arteries

lesionsCyanotlc/acyanoticAcyanoticAcyanoticAcyanoticAcyanoticAcyanoticCyanoticCyanoticCyanotic

Adapted from: Lil ly (1998); Porth (2002)

are thought responsible for numerous C^HHs (Bruneau,2003; Ciittenberger-De Groot et al, 2005). Botb intrinsictranscription factors that are required for induction of cardiacdifferentiation, in particular the family NKX2-5, which arerecessive genes, and theT -box transcription factor TBX5 areimplicated in the development ot a wide variety of CHUssucb as ASD,VSD, Ebsteins anomaly of the tricuspid valve,aortic valve stenosis atrioventricular (AV) block, and TOF.Further, as ditlerent areas ot the developing lieart are moresensitive to the effect of these agents it is now possibleto predict at what stage of development the CHI) wasestablished, as shown in Tahlc 2 (Bruneau, 2003).

Although no one specific cause of all t\'pes of congenitalheart detects has yet been identified, the currently prevailingnotion, running in tandem with the above, is that theoccurrence ot a ("HI) is more likely to be the result of agenetic and environmental interaction rather than that ot asingle chromosomal abnormality. A triad of predisposition,vulnerability and teratogemc agents may all be necessary toproduce sucb detects (Lilly. 1998; Hamed and Maher, 2000;Porth, 2002).There aremany risk factors tor CHI), and theseare ldentitied in 'Ihhlcs J and4.

In addition to the above, the relevance of lowsocioeconomic status reflecting maternal nutrition and theissue of matrilineal transmission have also been recognizedas significant factors m the development of CHD (Hamedand Maher, 2(.)00).

Table 2. Gestatlonal age atOestational aee (days) 15Events Heart

differentiates

Some of t t ie Not knownCHD occuring

which a congenital heart defect2 0Heart tubeforms.Heart beats

Cardia bifida,Laterality defect

28Early chambersform andloop to right

Hypoplastic5 L and R tieart

(CHD) may32Chamberb rma t ion .septates

defectivevalves. AVcanal defects.tetraiogyof Fallot

ASD = Atrial septal defect: AV - Aortic valve; DORV = Double outlet right ventricle: VSD = Ventricuiar septai defect

arise50 +Valves form.Septation occurs.conductionsystems form ,connects togreat vesselsASD. VSD,DORV.tetralogycf Faliot.conduction defects

Source: Bruneau (2003)


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Table 3. Congenital heart defect with chromosomalabnormalitiesChromosomal Name of syndromeabnormality Type of defect resulting211813XO

trisomytrisomytrisomysyndrome

Down--Turner

s syndrome

"s syndrome

V SDVSD. PDA. DORVDextocardia. VSD,Coarctat ion of the

DORV = Double outlet right ventride: PDA = Patent ductus arteriosus; VSDAdapted from: L il ly (1998); Hamed and

P D Aaorta, stenosis= Ventricuiar septal defect

Maher (2000); Portf i (2002)

Normal embryonic cardiac development111 rhe limiian emb ryo, the meso dcrma l germ layer givesrise tothe entire cardiovascular system. Th e he art developstrom two simple epithelial tubes which tlise to form a singlechambered heart.Twenty-three days tollowing conception the single, simpleepithelial heart tube lies within theembryo's pericardialcavity and is layered with cells which are known as thecardiac mantle, which eventually give rise to the epicardiumand myocardium. As development progresses, the crania!one-third ot the tube dilates toform the aortic sac whichwill give rise to the aortic arches. The caudal one-thirdalso dilates to form the early embryonic ventricle aroundthe 2Sth day. The remaining mid -portion forms the bulbuscordis, which has three distinct areas of developmen t: Tlie proximal on e-thi rd gives rise ro the bocly of the riglitventricle The distal section, known as the trunciis arteriosus,develops into the aortic root and ascending aorta The rem aining mid portion, the conus cordis, connects theprimitive right ventricle to the truncus arteriosus.

The conus cordis partitions to torm the outflow tracts otthe right and left ventricles.l)-looping (where the heart tube grows longer and bendsto tbe right) is responsible tor die initial positioning of tbeprimitive ventricle.Distal to tbe primitive rigbt ventricle !s an area known asthe conotriincai region (maldevelopment of this area leadsto TOF) containing tbe conus cordis and truncus arteriosus.

'fbe conotruncal region and tbe primitive rigbt ventricle collectively known as tbe bulbus cordis. As growth continthe conotruncal region moves centrally with torsion twisting, giving rise to the anatomical curve oi the aoand the pulmonary artery and aligns the heart in its normposition. By the 56th day, valves and septation has occurthe conduction system is forming and it is connected to great vessels {H-^iirc /)(Larson, l'/JS; Lilly, 1998; Porth, Gittenb erger-Ue Groot et al, 2005).Persistent left-sided superior vena cavaIbe worldwide incKlence of PLSVCJ is approximately 0.(Leibowitz et al, 1992; Bartram et al, 1997). In those with ocongenital cardiac defects the incidence is considerably higbetween 3% and H*34% and is tbe most commo n anomof systemic venous return {Leibowitz et al, 1992; 13artram e1997). Diagnosis is often incidental and in approximately 2of cases it is associated with TOF and other cardiac as welnon-cardiac malformations (Bartram et al, 1997).

The basis of the I'LSVC ispoorly understood. It resfrom in utero failure of the left cardinal vein to develop acan take various forms. In most cases it results in abilatSVC, often with a venous bridge joining the two, or tmay becompletely separate from eacb other (Soto e1992). Occasionally the right SVC. is absent and the venreturn trom the upper body enters the coronary sinus to right atrium (vvww.pediheart.org). PLSVC draining into right atritiin via an enlarged coronary sinus, and rarely wan absent rigbt SV C, will rarely produc e any pbysiologderangement asvenous blood continues to return toright atrium and, therefore, the condition requirestreatment, as in the case of the patient l^W (Leibowitz et1992; Gcrber and Kuzuzo, 2002) {Fi^^mr 2) .More infrequently, a FLSVC] can be connected to roof of tbe lett atriinn instead of the coronary sinus whthen continues as an inter-artrial conduit that ailows venreturn to the left atrium. This is known as 'unroo fing' andclinically signiticant (Sabiston and Spencer. 1995). A I'LSdraining into the lett atrium is associated with anAwhich produces right-to-left shunting and haemodynamcompromise resulting incyanosis which isusually mild peripheral, and is the main clinical sign (Bartram et al. 19

Table 4. Environmental factors significantly increasingmalformationMaternal infectionsMaternal drugsMaternal diseaseOther maternalfactors

ASD = Atrial septal defect:

Rubella, mum ps, intrauterine infectionAnti convulsants (phenytoin), vitamin D,anti-depressantsDiabetes, systemic lupus erythematosis, hypertension .phenylketonuria, phenylalanaemiaMaternal agePre-natal alcohol consum ptionSmoking accompanied by low birth weightExposure to X-raysExposure to toxins

VSD = Ventricular septal delect

incidence of cardiovascular

Pulmonary stenosis, VSD, ASD,endocardial fibroelastosisAortic stenosisTransposition of greatarteries, congenital heart blockChromosomal defects (down s syndrome}Fetal alcohoi syndrome

Adapted from; Lil ly (1998); Hamed and Maher (2000); Porth (200


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CARDIAC NURSINGHsu et .tl. 200 4). Associated cardiac ar rhyt hini .i, p.irticularlyatrioveiitricula r block, com plet e heart block and ventricularfibrillation, which can instigate atrial fibrillation, have beenreported and these may be treated by ablation techniques(I)har ctal. 1998; Sarodia and StoUer, 2


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l-'ijiurc 2: Norma ldei'clopment of tin-

stiperiar veua cuni ontill- lij'l lij^iirc ioiiijuin'd

ii'irli pi-rshreni left-sided superior veiui

cai'ii uti the right.IVC-Inferior vetui

caim; Sl'C=Siipcriorvetm Ciii'a.AdiipU'd

from Bergman vi al(2004).

Figure 3: Anatomicalahtiormatities in

tetralogy ofFatlot onleft compared witit

normal heart on right.Adapted front Lilly

(1998).

SubcicMsn vein

atnum

IVC -

jugiiat veins ^^ ^

1 /ghlvemncie):::z3

, Left auium

AF Lefl

Narrowsd SVC

Cwonaiy anus -

- Len SVC

Diirini; fxt-rcisc. increased cardiac output and decreasedsystemic arcerial resistance result in an increase in the degreeof right-to-le tt sh unting. Although etfective cardiac outpu t ismaintained, right-to-lett shunting produces a rapid decreasein systemic arterial oxygen saturation, resulting in dyspnoci(LiDy, 1998; CTSNet, 2000; Porth, 2002; Sierra ct al, 2001).Sufferers often assume a squatting position which results in .inincrease in systemic arteruil resistance caused by compressionof tbe iiKijor arterial circulation to thelower extremities.This increase in peripheral resistance reduces rig!it-to-lettshunting and increases pulnionar^' blood flow, which improvessystemic arterial oxygen saturation. In mtaiits, tetralot^'speUs (self-limiting spells of cyanosis) m.iy result from cryingand defecation as both actions increase pulmonary vascularresistance, increasing right-to-left shunting and decreasingpulmo nary blood flo w (Portb. 2002; Sierra et al, 2001).

Treatment is via reparative surgery to close tbe VSl),and the right-sided obstruction (infundibular stenosis) iscorrected by remowil of tbe muscle obstructing the flow.

Tbe pulmonary vaKe may be widened or repLiceJ to furrelieve obstruction and the aortic ontflow may reqrepositioning (Lilly. 1998; Sierra et al, 2001).Diagnosis of cardiac iesionsTil ere is no treatment available wbicli will altercourse of cardiac malformation mutero, although tbare many options for prenatal testing including genamniocentesis, as illustrated in Tahk 5 (C'.iarleglio e2003; Bhat and Sahn.2004).

Kegardless of the large number of congenital hmalformations, tbere are a limited number of physiologdisorders caused by th em. These lesions usually preseninfancy as cyanosis, heart tailure, heart murmur, circulashock, tetralogy spells, stridor, respiratory tract infections failure to tbrive (Lilly, 1998; Sierra etal, 2001 ; Porth. 20Gittenberger-l.)e Groot et al, 2005).The investigative tools that aa' available for diagnosis incl

Chest radiography: can determine cardiac size, contours, vasculature, beart chambers and tbe aortic arcb Electrocardiogram: can indicate haemodynamic stand severity of the detect through identifying tracsuggestive of particular defects.

Echoca rdiograpb : using Uop pler technology', this evaluhaemodynamic disturbances caused by pressure ditlerenacross the aortic and pulmonary valves, detect vetficieiicy and shunt flows and as .i non-invasive procedit has become a very powertiil tool tor diagnosis of C(Ciarleglio et al, 2003; Bhat and Salm, 2l)O4).ConciusionTbe reported case illustrates tb.ir t!ie presence of a PLSVshould be considered wben cannulation of tbe cen

AortaPulmonary artet7

SVC

Rightatrium atrium

Leftventricle

Right ventricleTetralogy of Fallot Normal heart


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to be difficult or results in wbatto be malposition. When this occurs it is advisable

a contrast study to confirm malpositioning,or further nialformation.Incidence of PLSVC should be documented as it may have

for future interventions requiring access toor pulmonary artery or techniques thatuse of the cardiac veins overlaying tbe left ventricle,

or percutaneous coronary arteryIn order to minimize tbe effects of the right-to-left shunt,

be placed in the Trendelenburg positionand should bave

in view ofIn the presence of maternal and other risk factors, e.g.

oror chromosomal ibnormality,is an increased likelihood ofCîHD.Tlierefbre, tbere is a

for genetic counsellint; and echocardiographtbe severity of the lesion. Diagnostic techniquesbe applied early enougb in pregnancy for post

as termination to be considered. uH

r a i i iU Vin I 'n iagh S.L mn f j C, H incs M.Bcm ky AS,V;in I' ra agh R (I W7)Absent right superior vena rava in visLcmatrial sitiis solitiis, .Hui / (îiriliol80(2): 175-W I'irru.il Hospii.illlhi'.imtrtl liuiychp.wJi.iof Htmum AiiaUviiic liiriatioii: Ojnis 11 : Cardiovafnilar iyitem. Anatomy Atlases.h t t p : / / w v v w , a n a t o n i y , i t L i s e s . o r g / A n a t o m i c V a r i a n t s /C ^ a r d i o v a s f u la r /Dire itory /niR -cton liyA lphj bL't. sliti til (last acccs.sed 17 February 2l)(lfi)1)J (21104) Latest advances and topics in frtal echocardiography.Cinr Opiii Cardioi 19(2): V7-1II3l!(i (2(Hl3)The developing heart and t oniienit.il hc.irt d etects: a makeor break iitiiation. C7i>i Ct-m-t 63: 252- f i !

M, Keller R, Cr ichn ik KH Swaminathan M (2(lllfi) Persistent leftsuperior vena eava in a patient with a history of tetralog\' of Fallot. .îivithAualg\m{5): I26')-7IILJ. ISennett RL . Williamson J, Mand ellJ B, Marks JH (2(X13) GeneticCouricellini; throughout the L if e C y i l e J Clin Imv.ft 112: 12S1MSS (1974) Tetralogy- of Fallot ni the elderly. ('Hii C.anliol7(8): 453-6T S N et (2110(1) Tetralo gy ot" Fa l lo t . CTSNe t . St Lonis. wwvv.ctsnet.org/doc/4')7f> (last accessed 23 February 200(,)P. Kautinan H. Doertl er M.lXidic !' (I')9H) Unusual course of ,i pnlmonaryartery catheter. / (.lardiotlumu MiîAnavsth 12(4): 4X7-9RS (2(Hl2) Persistent SVC demonstrated with multi-slicespira l computed tomography. Aiucriaiii Hi.m AsfUfiatioii liw 105(14): 79AC;, Bartelings MM. Deruiter Mt;. [\ielnunn RE(2(11)5) Basics of cardiac development for the Lmderstanding of congenitalheart malforcnation, liitiriuitioihil Pctliittrh': RcfCiirch foiiiultitioii 57(2): K)'J-76MA A. Maher KAA (20


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Congenital Cardiac Malformations in Relation to Central