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Prognostic value of infranodal conduction time in patients with chronic bundle branch block
Insights
His bundle recordings identified patients with chronic bundle branch block at higher risk for atrioventricular block progression and heart failure. Longer infranodal conduction times (H-Q ≥ 70 msec) predict adverse outcomes, including sudden death.
Area of Science:
- Cardiology
- Electrophysiology
- Internal Medicine
Background:
- Chronic bundle branch block (BBB) affects cardiac conduction.
- Predicting adverse outcomes in BBB patients remains challenging.
- Surface electrocardiogram (ECG) has limited prognostic value.
Purpose of the Study:
- To evaluate the prognostic significance of His bundle recordings in chronic BBB.
- To identify predictors of adverse cardiac events in BBB patients.
- To assess the utility of infranodal conduction time (H-Q interval) in risk stratification.
Main Methods:
- His bundle recordings were performed in 121 patients with chronic BBB.
- Patients were categorized based on H-Q interval: <70 msec (n=79) and ≥70 msec (n=42).
- Follow-up averaged 18 months, monitoring for atrioventricular (AV) block, heart failure, and sudden death.
Main Results:
- Patients with H-Q ≥70 msec showed significantly higher rates of progression to second/third-degree AV block (21% vs 1.3%) and severe congestive heart failure (38% vs 16%).
- The risk of sudden death was significantly elevated only in the H-Q ≥70 msec group with severe heart failure.
- No correlation was found between first-degree AV block or BBB pattern and adverse outcomes.
Conclusions:
- An infranodal conduction time (H-Q interval) ≥70 msec is a significant predictor of adverse cardiac events in chronic BBB.
- Electrophysiologic studies, particularly His bundle recordings, are valuable for risk stratification in BBB patients, especially those with unexplained neurological symptoms.
- Surface ECG analysis alone is insufficient for identifying high-risk BBB patients.
Abstract:
His bundle recordings were obtained in 121 patients with chronic bundle branch block and the patients were followed for a mean period of 18 months. Seventy-nine patients had an infranodal conduction time (H-Q) less than 70 msec while 42 had H-Q greater than or equal to 70 msec. There was no significant difference in mean age, smoking history, diabetes, syncope, dizziness, blood pressure, and serum cholesterol or triglyceride levels between the two groups. There was a significantly greater incidence of progresssion to second degree or third degree atrioventricular block (9/42, 21%), and of severe congestive heart failure (16/42, 38%) in patients with H-Q greater than or equal to 70 compared with those with H-Q less than 70 (1/79, 1.3%; and 13/79, 16%, respectively). The risk of sudden death was significantly greater only in the group with H-Q greater than or equal to 70 and severe congestive heart failure. There was no correlation between the presence of first degree atrioventricular block and/or any particular type of bundle branch block pattern with sudden death and/or progression to second degree or third degree atrioventricular block. Analysis of the surface electrocardiogram is only of limited value in predicting high risk patients with chronic bundle branch block. Electrophysiologic studies are of greatest value in patients with bundle branch block with transient neurologic symptoms in whom no cause for the symptoms is evident.