Permanent Pacemakers and Antiarrhythmic Devices

Anil Rajendra

Michael R. Gold

I. PERMANENT PACEMAKERS (PPMS)

A. General principles.

1. Pacemaker nomenclature (Table 38-1).

2. Current pacemaker designs.

a. Single chamber (SC): lead in only one chamber, usually the right ventricle (RV).

i. Used primarily in patients with chronic atrial fibrillation (AF).

b. Dual chamber (DC): leads in both the right atrium (RA) and RV.

i. Able to mimic normal cardiac physiology with sequential atrial to ventricular (A-V) pacing and have less AF than RV-only devices. However, frequent RV pacing is associated with heart failure and worsening left ventricular (LV) function.

c. Biventricular (BiV) devices: leads in the RV and LV, as well as typically the RA.

i. Simultaneously or sequentially pace the RV and LV.

B. Indications.

1. Dual chamber (DC).

a. Symptomatic bradycardia.

b. Profound bradycardia without symptoms.

c. Conduction system disease with high risk of progression to life-threatening bradycardia.

d. Pause-dependent ventricular tachycardia (VT).

2. Cardiac resynchronization therapy (CRT): BiV pacing (Table 38-2).

a. Reduces mortality/hospitalization in heart failure patients with reduced ejection fraction and prolonged QRS duration (Comparison of Medical Therapy, Pacing, and Defibrillation in Heart Failure [COMPANION], Cardiac Resynchronization Heart Failure [CARE-HF], Resynchronization/Defibrillation in Ambulatory Heart Failure [RAFT]).

b. Most trials, including Multicenter InSync Randomized Clinical Evaluation (MIRACLE), showed improved QOL, exercise tolerance, and reversal of remodeling with CRT.

c. Cardiovascular benefits may be attenuated in the setting of AF.

i. Patients with chronic AF failed to show improvement with CRT in mortality, QOL questionnaire, or 6-minute walk test (RAFT trial). This may be due to less consistent pacing in AF.

TABLE 38-1 Pacemaker Nomenclature Codes

First letter = chamber(s) paced: A, V, or D

Second letter = chamber(s) sensed: A, V, or D

Third letter = what the device does with the sensed information: O, I, or D

Fourth = rate responsiveness: O or R

Examples

VOO

VVI

AAI

DDD

DDDR

CRT = pacing in both ventricles, aka BiV pacing

CRT-P: device with pacing-only function

CRT-D: device with BiV pacing and ICD capabilities

V, ventricle; A, atrial; D, dual (A and V, or pace and inhibit); I, inhibit; R, rate responsiveness; O, does nothing; VOO, ventricular asynchronous; VVI, ventricular inhibited; AAI, atrial inhibited; DDD, dual-chamber pacing and sensing, both triggered and inhibited mode; DDDR, AV concordance with physiologic response; CRT, cardiac resynchronization therapy; BiV, biventricular; ICD, implantable cardioverter-defibrillator.

TABLE 38-2 Indications for Cardiac Resynchronization Therapy^a

Class I

EF < 35%, sinus rhythm, QRS duration >150 ms, NYHA Class II, III, or ambulatory IV

Class IIa

EF < 35%, sinus rhythm, LBBB with QRS duration 120-149 ms, NYHA Class II, III, ambulatory Class IV
EF < 35%, sinus rhythm, non-LBBB with QRS duration >150 ms, NYHA III or ambulatory Class IV
EF < 35%, undergoing device replacement and anticipated significant (>40%) ventricular pacing
EF < 35%, AF, if

a) Requires ventricular pacing or otherwise meets CRT criteria

b) AV nodal ablation or rate control will allow near 100% biventricular pacing.

^aPatients must be on guideline-directed medical therapy (GDMT), including beta-blocker and ACE inhibitor or ARB.
CRT, cardiac resynchronization therapy; NYHA, New York Heart Association; LBBB, left bundle branch block; AF, atrial fibrillation.

C. Procedure.

1. Placed percutaneously through the subclavian/axillary vein, with pulse generator implanted in subcutaneous pocket superficial to prepectoral fascia.

2. Strict sterile technique observed to prevent infection.

3. Leads placed in RA and RV apex/interventricular septum.

4. CRT: LV lead placed on the LV lateral wall via the coronary sinus branches avoiding the apical region.

D. Postprocedure considerations.

1. Complications.

a. Immediate.

i. Pneumothorax/hemothorax.

ii. Pocket hematoma: higher incidence in patients on heparin products versus warfarin.

iii. Pocket and/or lead infection.

b. Immediate to chronic.

i. Lead fracture/malfunction: x-ray usually may detect; presents as loss of capture and increased impedance—occurs at point of mechanical stress.

ii. Lead insulation break: invisible on x-ray; presents as oversensing (inappropriate inhibition) and decreased impedance.