Clinical Significance and Prognosis of Acute Myocardial Infarction with Right Bundle Branch Block

We investigated the clinical characteristics of patients with acute myocardial infarction (MI) complicated by right bundle branch block (RBBB), and examined cardiac function and long term prognosis in those with transient RBBB and those with RBBB persistent until discharge. Of 1,345 patients with first time MI who were admitted to our hospital between January 1980 and December 1997, we studied 111 patients in whom a complete RBBB wave form appeared during hospitalization. Of these 111 patients, 75 who were discharged alive were divided into two groups comprising those in whom RBBB continued until discharge (persistent RBBB group: 27 patients) and those in whom RBBB subsided during hospitalization (transient RBBB group: 48 patients). Left ventricular (LV) end-diastolic dimension, LV end-systolic dimension, and LV wall motion abnormalities were measured using echocardiography at admission and at dischage. The LV ejection fraction was measured by cardiac blood pool scan and the total defect score was determined by thallium-201 cardiac scintigraphy one month after MI. The in-hospital and long-term mortality rates were also investigated in the two groups. The patients with acute MI complicated by RBBB had severer LV wall motion abnormalities, more extensive infarction as indicated by a higher total defect score (p<0.01), a lower LV ejection fraction (p<0.05), and a higher in-hospital mortality rate (p<0.05) than the patients without RBBB. There were no significant differences between the persistent and transient RBBB groups with respect to LV function or in-hospital mortality rate in the acute phase. One month after the onset of MI, however, the persistent RBBB group had significantly severer LV wall motion abnormalities, a higher total defect score (p<0.01), and a lower LV ejection fraction (p<0.01) than the transient RBBB group. The mortality rate three years after discharge was also higher in the continuous RBBB group (p<0.05). In conclusion, patients with acute MI complicated by RBBB had more extensive MI, poorer LV function, and a worse acute and long-term prognosis when compared with patients without RBBB. Cardiac function and prognosis were poorer in the patients in whom RBBB continued after discharge than in those with transients RBBB. The presence or absence of RBBB and whether it is transient or continuous therefore appear to be useful for evaluating cardiac function and long-term prognosis at discharge in patients with MI.