What is the recommended treatment for patients with recurrent syncope?

Implantable Loop Recorder-Guided Pacing Therapy for Recurrent Syncope

Pacemaker implantation is recommended for patients ≥40 years with recurrent syncope who have documented asystole ≥3 seconds during syncope or ≥6 seconds without syncope captured by implantable loop recorder monitoring. 1

Patient Selection for Pacing Therapy

The management of recurrent syncope depends on the underlying mechanism, with cardiac pacing being effective only in specific situations:

• Appropriate candidates for pacing:

  • Patients ≥40 years with:
    • Documented symptomatic pause ≥3 seconds during syncope
    • Documented asymptomatic pause ≥6 seconds
    • Recurrent unpredictable syncope episodes (≥3 episodes in 2 years)
    • Documented asystole via implantable loop recorder (ILR)
    • Cardioinhibitory carotid sinus syndrome with asystole ≥6 seconds

• Not appropriate for pacing:

  • Young patients (<40 years) with vasovagal syncope without documented asystole
  • Patients without documented cardioinhibitory reflex
  • Patients with reversible causes of bradycardia

Diagnostic Approach

ILR monitoring is the gold standard for establishing the correlation between syncope and cardiac rhythm:

• ILR should be implanted in patients with recurrent unexplained syncope after initial evaluation
• The ISSUE-3 trial demonstrated that ILR-guided therapy significantly reduced syncope recurrence (10% vs. 41%) compared to non-loop recorder-guided therapy 1
• ILR monitoring allows for precise identification of patients who will benefit from pacing

Evidence Supporting Pacing in Asystolic Syncope

The strongest evidence comes from the ISSUE-3 trial, which showed:

• Dual-chamber pacing reduced syncope recurrence by 57% in patients with documented asystole 2
• Two-year estimated syncope recurrence rates were 25% with pacing ON vs. 57% with pacing OFF 2
• The absolute risk reduction was 32%, supporting this invasive treatment despite syncope being relatively benign 2

In contrast, earlier studies without proper patient selection showed less convincing results:

• The VPS II trial, which did not use ILR for patient selection, showed no significant benefit of pacing (relative risk reduction of only 30%, p=0.14) 3
• Meta-analysis of double-blinded studies without proper patient selection revealed no apparent benefit from pacing (RR: 0.73; 95% CI: 0.25 to 2.1) 1

Pacing Recommendations

When pacing is indicated:

• Dual-chamber pacing is preferred over single-chamber ventricular pacing 4
• Specific programming considerations:
  • Rate drop response feature
  • Manual adaptation of AV interval (up to 250 ms)
  • AV hysteresis to prevent unnecessary right ventricular pacing
  • Rate hysteresis to allow spontaneous sinus rhythm

Important Caveats

• Pacing only addresses the cardioinhibitory component of syncope, not the vasodepressor component

• Despite pacing, syncope may still recur in 20-25% of patients within 2-5 years 4

• Complications of pacemaker therapy include:

  • Lead dislodgement (most common)
  • Subclavian vein thrombosis
  • Infection
  • Pericardial tamponade (rare)

• Before considering pacing, non-invasive approaches should be tried:

  • Patient education
  • Physical counterpressure maneuvers
  • Lifestyle modifications
  • Adequate salt and fluid intake

Algorithm for Management

1. Initial evaluation to rule out cardiac, neurological, or metabolic causes
2. ILR implantation for patients with recurrent unexplained syncope
3. Document rhythm during spontaneous syncope event
4. Consider pacing if:
   • Age ≥40 years AND
   • Asystole ≥3 seconds during syncope or ≥6 seconds without syncope
5. Implant dual-chamber pacemaker with appropriate programming
6. Continue follow-up as syncope may still recur despite pacing

The evidence clearly demonstrates that proper patient selection through ILR monitoring is crucial for successful pacing therapy in patients with recurrent syncope.