What type of pacemaker is considered in patients with bifascicular block?

Pacemaker Selection in Bifascicular Block

For patients with bifascicular block requiring permanent pacing, dual-chamber pacemakers (DDD mode) are the preferred device type, as they maintain AV synchrony and provide superior outcomes compared to single-chamber ventricular pacing. 1, 2, 3

Device Type Recommendations

Dual-Chamber Pacing (DDD) - Preferred Option

• Dual-chamber pacemakers are recommended as first-line therapy for patients with bifascicular block and AV conduction disease (Class I indication), as they restore both AV synchrony and chronotropic competence. 1, 3

• DDD pacing is superior to single-chamber ventricular pacing for reducing atrial fibrillation risk, preventing pacemaker syndrome, and improving quality of life. 3

• AV synchrony contributes significantly to cardiac output, increasing stroke volume by as much as 50% and decreasing left atrial pressure by up to 25%, particularly important in patients with diastolic dysfunction or left ventricular hypertrophy. 1

• Recent trial data (SPRITELY) demonstrated that dual-chamber pacing programmed to DDD with lower rate of 60 bpm significantly reduced syncope and symptomatic events compared to backup pacing at 30 bpm (hazard ratio 0.32, P=0.042). 4, 5

Single-Lead VDD Pacing - Alternative Option

• Single-lead VDD pacing can be useful in patients with bifascicular block who have normal sinus node function and AV block (Class IIa), particularly in younger patients with congenital AV block. 1, 3

• VDD pacing restores both AV synchrony and chronotropic competence while requiring only a single ventricular lead with atrial sensing capability. 1

Single-Chamber Ventricular Pacing (VVI) - Limited Role

• VVI pacing is acceptable only in specific situations: sedentary patients, significant medical comorbidities limiting life expectancy, or following AV junction ablation for atrial fibrillation rate control. 1, 3

• Dual-chamber pacing should NOT be used in patients with permanent or longstanding persistent atrial fibrillation where rhythm restoration is not planned (Class III). 1, 3

Critical Considerations for Device Selection

Avoiding Pacemaker Syndrome

• Pacemaker syndrome occurs with loss of AV synchrony in ventricular pacing, causing symptoms including lightheadedness, syncope, fatigue, and hemodynamic compromise due to ventriculoatrial conduction or atrial contraction against closed AV valves. 1, 3

• This is a critical reason to avoid VVI pacing in patients with intact atrial function and bifascicular block. 1, 3

Programming Recommendations

• For patients with bifascicular block and syncope, program dual-chamber pacemakers to DDD mode with a lower rate of 60 bpm rather than backup pacing (DDI 30 bpm), as this significantly reduces symptomatic events. 4

• The annual incidence of new rhythm disease development in bifascicular block patients is 7.4%, supporting the need for full dual-chamber capability. 4

Patient-Specific Factors

• Consider the type and severity of cardiac conduction abnormality, presence of comorbidities, degree of left ventricular dysfunction, current and anticipated drug therapy, and anticipated activity level when selecting the specific device. 3

• Technical considerations include vascular access limitations, availability of follow-up services, and expertise of the implant team. 3

Important Clinical Caveats

Syncope Recurrence Despite Pacing

• Even with appropriate dual-chamber pacing, approximately 25-29% of patients with bifascicular block will experience recurrent syncope, likely due to vasodepressor mechanisms rather than bradycardia. 6, 5

• Pacing relieves neurological symptoms from bradycardia but does not reduce sudden death in this population, as death is often due to underlying heart disease rather than bradyarrhythmia. 1, 6

QRS Morphology Does Not Affect Device Choice

• The type of bundle branch block (left bundle branch block vs. right bundle branch block with fascicular block) does not predict outcomes or alter device selection. 7

• Pacemaker implantation reduces adverse events compared to monitoring strategies irrespective of BBB type or presence of PR interval prolongation. 7

Future Capability Planning

• Select a pacemaker with capabilities that may be needed in the future, even if not required at implantation, given the 7.4% annual incidence of new rhythm disease development. 3, 4

• Consider potential need for upgrading to cardiac resynchronization therapy if the patient has or develops left ventricular dysfunction. 3