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The clinical significance of bundle branch block complicating acute myocardial infarction. 2. Indications for
Insights
Patients with acute myocardial infarction (MI) and bundle branch block face high risk of high-degree atrioventricular (AV) block. Prophylactic pacing is recommended for high-risk individuals to prevent adverse outcomes.
Area of Science:
- Cardiology
- Electrophysiology
- Internal Medicine
Background:
- Acute myocardial infarction (MI) complicated by bundle branch block (BBB) carries a significant risk of progressing to high-degree atrioventricular (AV) block.
- Progression to high-degree AV block can occur during hospitalization or follow-up, leading to adverse events including sudden death.
Purpose of the Study:
- To identify determinants of high-degree AV block during MI hospitalization.
- To examine risk factors for sudden death or recurrent high-degree AV block during the first year of follow-up in patients with MI and BBB.
- To evaluate the efficacy of prophylactic pacing in this patient population.
Main Methods:
- Retrospective analysis of 432 patients with acute MI and BBB.
- Assessment of timing of BBB onset, involved fascicles, and PR interval as risk predictors.
- Comparison of outcomes between continuously paced and non-paced patients, and those with and without transient high-degree AV block.
Main Results:
- Patients with BBB involving the right bundle and at least one left bundle fascicle, not previously documented, were at highest risk.
- Transient high-degree AV block during MI was associated with a 28% incidence of subsequent sudden death or recurrent block.
- Continuously paced patients had significantly lower rates of sudden death or recurrent high-degree AV block compared to non-paced patients (10% vs. 65%).
- A subgroup with prior MI, anterior/indeterminant MI, and no heart failure symptoms had a 35% risk of sudden death.
Conclusions:
- Prophylactic temporary pacing is indicated for patients with MI and BBB at high risk of developing high-degree AV block.
- Patients experiencing high-degree AV block during MI should undergo temporary and subsequent permanent pacing.
- Permanent pacing may benefit patients with MI and BBB who do not develop high-degree AV block but are at high risk for sudden death.
Abstract:
The indication for prophylactic temporary and permanent pacing during acute myocardial infarction (MI) complicated by bundle branch block is high risk of progression via a Type II pattern to second or third degree (high degree) AV block during hospitalization or follow-up. In this study, determinants of high degree AV block during hospitalization and sudden death or recurrent high degree block during the first year of follow-up were examined in 432 patients with MI and bundle branch block. Timing of onset of bundle branch block, the involved fascicles, and the PR interval were examined as determinants of risk of progression to high degree AV block during MI. At highest risk were 186 patients with blocks involving the right bundle and at least one fascicle of the left bundle which were not documented on prior electrocardiograms. Risk was similar with (38%) or without (31%) accompanying first degree AV block. Patients with transient high degree AV block during MI had a 28% incidence of sudden death or recurrent high degree block during the first year of follow-up. Patients not continuously paced had a higher incidence of sudden death or recurrent high degree block than patients continuously paced (65% vs 10%, P less than 0.001). Sudden death during follow-up also occurred in 13% of patients without high degree block during MI. A subgroup with 1) documented prior MI, 2) anterior or indeterminant acute MI, and 3) no symptoms of cardiac failure had a 35% risk of sudden death. The role of permanent pacing in this group is unknown. Thus, patients at high risk of high degree AV block should receive prophylactic temporary pacing. Patients who survive high degree block with MI should receive temporary and then permanent pacing. Patients without high degree AV block during MI who nervertheless have a high risk of sudden death may benefit from permanent pacing.