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Prognosis

Right bundle branch block after myocardial infarction increased mortality in patients with left ventricular failure

ACP J Club. 1991 Sep-Oct;115:59. doi:10.7326/ACPJC-1991-115-2-059


Source Citation

Ricou F, Nicod P, Gilpin E, Henning H, Ross J Jr. Influence of right bundle branch block on short- and long-term survival after acute anterior myocardial infarction. J Am Coll Cardiol. 1991 Mar 15;17:858-63.


Abstract

Objective

To investigate the relation between right bundle branch block (RBBB) and survival after Q-wave anterior myocardial infarction.

Design

Cohort analytic study with 1-year follow-up.

Setting

6 centers in the United States, Canada, and Switzerland.

Patients

1325 patients who survived > 24 hours after Q-wave anterior myocardial infarction between 1979 and 1989 were included. Anterior myocardial infarction was diagnosed by Q waves > 0.04 seconds in duration or a QS complex in the precordial leads (V1 to V4) along with either characteristic chest pain or increased serum creatine kinase. 754 patients had no atrioventricular or bundle branch blockand 178 had RBBB. 393 patients had other blocks but no RBBB and were not included. 10% of patients discharged from the hospital were lost to follow-up. 202 patients received thrombolytic agents or early coronary angioplasty.

Assessment of prognostic factors

Electrocardiographic criteria were used to define RBBB.

Main outcome measures

In-hospital and 1-year survival rates. Cardiac death was defined as death occurring suddenly or secondary to new myocardial infarction, extension of myocardial infarction, congestive heart failure, shock, a cardiac procedure, or cardiac surgery.

Main results

Left ventricular failure was more common in patients with RBBB. Patients with RBBB had higher mortality rates in the hospital and 1 year after discharge (32% and 17%, respectively) than patients without RBBB (8% and 7%, respectively, all P < 0.001). More deaths occurred among patients with RBBB and left ventricular failure both in-hospital (43%) and after 1 year (24%) than among patients with RBBB but without left ventricular failure (4% and 5%, respectively, all P < 0.05). Survival rates were similar for patients with and without RBBB in the absence of ventricular failure but were decreased for patients with RBBB and ventricular failure than for those with left ventricular failure alone (P < 0.001).

Conclusion

Right bundle branch block after Q-wave anterior myocardial infarction was associated with greater in-hospital and 1-year mortality only in those patients who also had left ventricular failure in the hospital.

Source of funding: National Heart, Lung, and Blood Institute.

Address for article reprint: Dr. F. Ricou, Division of Cardiology H811-A, University of California, San Diego Medical Center, 225 Dickinson Street, San Diego, CA 92103-1990, USA.


Commentary

The presence of intraventricular conduction disturbance has been associated with increased in-hospital and late mortality in patients with acute myocardial infarction, probably because of more extensive myocardial damage. The risk is higher in patients when the conduction defect is new, when RBBB is associated with left posterior fascicular block, and when third-degree atrioventricular block occurs. Death is usually caused by heart failure, cardiogenic shock, ventricular tachycardia, or fibrillation; thus pacemaker use does not benefit most of these patients.

This cohort study with almost complete follow-up focuses on patients with anterior wall myocardial infarction with or without RBBB. In-hospital and late mortality was increased in the presence of left ventricular failure, defined by a third heart sound, pulmonary rales, and congestion on the chest roentgenogram. The results provide further evidence of the increased risk for patients with RBBB, isolated or combined with other conduction defects. The key finding is that patients with RBBB and left ventricular failure have a worse prognosis than patients with left ventricular failure without an intraventricular conduction defect. However, patients without left ventricular failure, with or without RBBB, have a similarly favorable prognosis. The results also confirm that ventricular pacing does not benefit most of the patients with third-degree heart block.

RBBB is an independent marker of worse prognosis in patients with anterior wall myocardial infarction and heart failure. The authors suggest that these patients may benefit from early exercise testing, coronary angiography, and revascularization. Further evaluation of these and any other approaches, such as a more widespread use of thrombolytic agents or other pharmacologic treatments, is now needed.

Fernando T. Lanas, MD
Universidad de La FronteraTemuco, Chile