Incidence, clinical characteristics and prognostic significance of left bundle-branch block in acute myocardial infarction

To assess the current incidence and meaning of left bundle-branch block ass ociated with acute myocardial infarction we studied 1,239 patients consecut ively admitted in three hospitals. Left bundle branch block was present in 42 cases (3.3%). Compared to the patients without; left bundle-branch block , those with left, bundle-branch block were older (70 +/- 8.8 versus 63.9 /- 11.4 years; p < 0.001), and had a more prevalent history of diabetes, an gina, myocardial infarction and heart failure. Left bundle-branch block was associated more frequently with female gender and poor left ventricular ej ection fraction. Patients with left bundle-branch block were admitted with a longer interval from the onset of the symptoms (7.8 +/- 6.3 versus 5.4 +/ - 6.7 hours; p < 0.01) and received in a lesser rate thrombolytics agents ( 21% versus 56%; p < 0.001), than those without left bundle-branch block. Co mplications significatively associated with left bundle-branch block were: complete AV Block; heart failure and one-year mortality (40.4% versus 19.5% , p < 0.01). Female gender, age and heart failure were independent predicto rs of mortality whereas left bundle-branch block was not. In conclusion, cu rrent incidence of left bundle-branch block in acute myocardial infarction is lower than that referred in the pre-thrombolytic era. Left bundle-branch block is accompanied by a low rate of thrombolysis, whereas a higher morta lity rate of these patients seems to depend on their clinical characteristi cs.