The role of arrhythmia and left ventricular dysfunction in patients with acute myocardial infarction and bundle branch block.

To determine the immediate and remote prognostic significance of bundle branch block (BBB) associated with acute myocardial infarction (AMI), 40 patients with AMI and BBB were studied. One hundred forty-four patients with AMI but without BBB were evaluated during the in-hospital phase and 45 of them were taken as a control group. These patients were followed for an average of 15 months (3-28 months). Arrhythmias and left ventricular function were investigated with 24-hr Holter monitoring and echocardiography, respectively. The hospital mortality was significantly greater in patients with BBB than in the control group (32.5% vs 10.4%, p < 0.001). The main cause of mortality was pump failure in the group with BBB (76.9%) and ventricular fibrillation in the control group (53.3%). The peak creatine kinase level was significantly higher in the group with BBB than in the control group (2094.8 +/- 288.4 IU/L vs 416.7 +/- 30.5 IU/L, p < 0.001). In patients with BBB prophylactic temporary pacemaker insertion was not found to improve the hospital mortality rate. In the hospital phase, although 32% of the patients with BBB had complicated arrhythmias (multiform, paired VPB, runs, R-on-T) the cause of death in 10 of the 13 patients who died was pump failure but not arrhythmia. In patients with BBB the wall motion index and the number of patients who had a left ventricular aneurysm were greater than in patients without BBB (9.5 +/- 0.9 vs 6.3 +/- 0.6, p < 0.01 and 52.0% vs 14.3%, p < 0.01, respectively). In patients with BBB follow-up mortality (12.0%) was lower than hospital mortality (32.5%). During the follow-up period there was no significant difference between patients with BBB and those without with regard to complicated arrhythmias (14.8% vs 15.6%). These results indicate that the main cause of poor prognosis during the hospital period in patients with AMI and BBB was not arrhythmia or conduction disturbance but severe pump failure due to extensive myocardial necrosis. Prophylactic temporary pacemaker insertion did not improve the hospital mortality rate of these patients, and patients with AMI and BBB who survive the in-hospital phase after infarction have a good prognosis during the following 15 months.