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