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Transvenous endocardial VVIpacemaker
A: conventional single lead pacemakerB: implantable cardioverter-defibrillator (ICD)
Radiographic identifiers for somegenerator manufacturers
Pacemaker Indications
• Symptomatic diseases of impulse formation(sinus node disease)
• Symptomatic diseases of impulse conduction(disease of the atrioventricular node)
• Long QT syndrome• Hypertrophic obstructive cardiomyopathy• Dilated cardiomyopathy
COMMON USES FOR PERMANENT PACEMAKER
Pacemaker System
• Impulse generator• Leads
– Transvenous– Epicardial
• Leadsunipolar (one– unipolar (oneelectrode per lead),
– bipolar (twoelectrodes per lead)
– multipolar (multipleelectrodes)
Examples of single-chamber and dual-chamberpacemakers with both unipolar and bipolar leads.
Pacemakers
• Unipolar leads– The second electrode will be the metal generator case– Requires that the generator pocket be devoid of gas– Electrical continuity has reportedly been disrupted by the
use of nitrous oxide.– More sensitive to the effects of electromagnetic
interference (EMI)– Produce larger "spikes" on an analogue recorded
electrocardiogram.• Bipolar pacing
– usually requires less energy– more resistant to interference from muscle artifacts or
stray electromagnetic fields.– Often can be identified on the chest film since they will
have a ring electrode 1 to 3 cm proximal to the lead tip.
pacemaker wire
The pacing lead system in situ
Excitation threshold & Spike
NASPE/BPEG Revised (2002) GenericPacemaker Code (NBG)
Position I: PacingChamber(s)
Position II:SensingChamber(s)
Position III:Response(s) toSensing
Position IV:Programmability
Position V:Multisite Pacing
O= none O= none O= none O= none O= none
A= atrium A= atrium I= inhibitedR= ratemodulation
A= atrium
V= ventricle V= ventricle T= triggered V= ventricleD= dual (A + V) D= dual (A + V) D= dual (T + I) D= dual (A + V)
North American Society of Pacing and Electrophysiology (NASPE) nowcalled Heart Rhythm Society (HRS)
British Pacing and Electrophysiology Group (BPEG)
The NBG code: NASPE and BPEG Generic code
Pacemaker sensing
• VAT• AAI
Position III NBG Code• D (Dual):
– DDD pacing provides atrioventricular (AV) synchrony. In the DDD setting,atrial pacing will take place in the “inhibited” mode; that is, the pacingdevice will emit an atrial pulse if no sensed atrial event (or interveningventricular event because any ventricular event will reset atrial timing)takes place within the appropriate timeframe. In DDD or VDD devices,once an atrial event has occurred (whether native or paced), the pacingdevice will ensure that a ventricular event follows (up to the uppertracking rate [UTR]).tracking rate [UTR]).
• I (Inhibited):– The appropriate chamber is paced unless intrinsic electrical activity is
detected during the pacing interval. For the DDI mode, AV synchrony isprovided only when the atrium is paced. If intrinsic atrial activity ispresent, no AV synchrony is provided by the pacing function.
• T (Triggered):– The pacing device will emit a pulse only in response to a sensed event.
The triggered mode is used when the device is being tested.
Pacemaker CodesRate modulation (the fourth position)
Pacemaker Codes
• Multisite pacing (fifth column)– Atrial multisite pacing
• Atrial fibrillation– Ventricular multisite pacing
l b ll d di h i ti– also be called cardiac resynchronizationtherapy (CRT) or biventricular (BiV) pacing• Dilated cardiomyopathy.• Heart failure.
Pacing leads for resynchronization therapy
Cardiac Resynchronization Therapy(CRT)
• CRT is currently indicated for the reductionin symptoms of moderate to severe heartfailure (NYHA functional class III or IV) inthose patients who remain symptomaticdespite stable, optimal medical therapy andhave a left ventricular ejection fraction of≤35%, a QRS duration of ≥120 ms, and anICD indication.
PACING MODESSingle chamber pacing
• VVI or VVIR pacing– Ventricular demand pacing– the most commonly used pacing mode– Advantages:
• the requirement for only a single leadthe requirement for only a single lead• the ability to protect the patient from dangerous bradycardias
of any etiology.
– Disadvantages:• cannot maintain AV synchrony• pacemaker syndrome
– should not be used in a patient with normal sinusrhythm
Single-chamber timing cycle
Ventricular-Inhibited (VVI) Pacing
PACING MODESSingle chamber pacing
• AAI or AAIR pacing– appropriate for patients with sinus node dysfunction
who have intact AV nodal function– benefit of requiring only a single lead– will not protect patients from ventricularwill not protect patients from ventricular
bradyarrhythmias due to AV conduction block– a patient who already has sinus node disease will later
develop AV conduction disease– the adult patient should be capable of 1:1 AV nodal
conduction to rates of 120 to 140 beats/min
Atrial-Inhibited (AAI) Pacing
PACING MODESDual chamber pacing
• DDD or DDDR pacing– physiologic pacing– there are four different rhythms:
– appropriate � AV block + normal sinus node function– appropriate � sinus node dysfunction + normal AV conduction– ideal � sinus nodal + AV nodal dysfunction– choice � carotid sinus hypersensitivity + symptomatic cardioinhibition