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Electrophysiologic studies in patients with bundle branch block.
Pacing and Clinical Electrophysiology : PACE
|September 1, 1983
Summary
A prolonged infranodal conduction time (H-Q) in patients with chronic bundle branch block predicts atrioventricular block. Prophylactic pacing does not improve outcomes, but electrophysiologic studies are vital for syncope evaluation.
Area of Science:
- Cardiology
- Electrophysiology
Background:
- Chronic bundle branch block (BBB) poses risks for atrioventricular (AV) block.
- Predictive markers for AV block progression in BBB are crucial for patient management.
Purpose of the Study:
- To investigate the predictive value of infranodal conduction time (H-Q interval) for AV block in chronic BBB patients.
- To evaluate the efficacy of prophylactic pacemaker insertion and electrophysiologic studies in managing BBB complications.
Main Methods:
- Electrophysiologic studies were performed on 401 chronic BBB patients, with a mean follow-up of 30 months.
- Infranodal conduction time (H-Q) was measured, and patients were categorized based on H-Q interval duration.
- Subgroups underwent prophylactic pacing or ventricular stimulation studies.
Main Results:
- Patients with H-Q ≥ 70 ms showed a significantly higher incidence of AV block (12%) compared to those with H-Q < 70 ms (3.5%).
- An H-Q interval ≥ 100 ms was associated with a 25% incidence of AV block.
- Prophylactic pacing did not significantly alter symptom relief or survival rates.
- Ventricular tachycardia was induced in 14 of 25 syncope patients undergoing ventricular stimulation.
Conclusions:
- A markedly prolonged H-Q interval (≥ 100 ms) is a valuable predictor of spontaneous AV block in chronic BBB.
- Prophylactic pacing offers no benefit for symptom relief or survival in this patient cohort.
- Electrophysiologic and ventricular stimulation studies are indicated for BBB patients experiencing syncope.