Clinical characteristics and prognosis significance of bundle-branch block (BBB) associated with acute myocardial infarction (AMI)

Introduction: Left and right BBB (LBBB and RBBB) represent an independent predictor of poor outcome in AMI. Objective: To assess the incidence, clinical meaning and evolution of patients with BBB, left and right and AMI. Material and Methods: Retrospective study included 1020 patients with AMI, from which 104 (10,2%) associated BBB at onset, respectively: 62 cases (59%) AMI and left BBB and 42 cases (41%) AMI and right BBB. Average age was 64,5 years and male gender was more frequently (69%). 6 patients from each group received thrombolysis with Streptokinase, respectively 9,6% in AMI and left BBB group and 14,2% in AMI and right BBB group. We investigated for each lot with BBB, compared to standard lot the in-hospital mortality rate and the incidence of other major cardiovascular events: ventricular dysfunction, arrhythmias, recurrent ischemia and mechanical complications. We also analyzed the correlation between the infarct -related artery and the presence of BBB. Results: Compared to the patients without BBB, those with BBB were older (70±7 years) and had a more prevalent history of diabetes, angina, myocardial infarction and heart failure. Particularly, IMA and BBB group had a high degree of ventricular dysfunction (KILLIP class III and IV in 64 cases 61,5%), without coronary pain. Patients with BBB, especially left BBB were admitted with a longer interval from the onset of the symptoms (8,9 versus 5,7 hours, on average -p<0.001) and received in a lower rate thrombolytic therapy compared to group without BBB (12% versus 34% -p<0.001). Patients with AMI and BBB had a lower ejection fractions (average 42%, versus 51% -p<0.001) and a higher peak creatine phosphokinase levels (2245 versus 1190 U/l -p<0.001), as a marker of necrosis severity. First class AMI after Topol and Van de Werf determined in our study group the highest mortality (left anterior descending infarcts accounted for 56% of the BBB and AMI cases anathomopathological analyzed, versus 38% in standard lot p<0.001). In patients with left or right BBB the rate of in-hospital death was similar (29% and, respectively 28%), but significant greater than in patients without BBB (18%) -p<0.001. Discussion: As ECG is a poor predictor of AMI in patients with acute cardiac symptoms and LBBB , the thrombolytic therapy should be initiated immediately in patients with ischemic chest pain suggestive of AMI and LBBB at presentation. The BBB seems to be a stronger predictor in the short-term prognosis of patients with AMI (in-hospital death), compare with those without BBB. The presence of BBB on the onset of AMI could be an independent marker of a larger, anterior infarction. An important limit of our study is that we were unable to determine timing of onset or persistence BBB, so we can't confirm or comment the importance and the significance of a new or a preexisting BBB. Conclusions: Patients with BBB and AMI are less likely to receive thrombolytic therapy, associate more frequently severe heart failure and have an increased risk for in-hospital death. No clinically significant differences in the development of recurrent ischemia, angina or mechanical complications were seen between patients with and patients without BBB. INTRODUCTION Previous studies of patients with AMI and BBB, left and right (LBBB and RBBB) at hospital admission, both in prethrombolytic [1,2] and thrombolytic era [3-9] , have reported in general a poor overall prognosis and a high risk for short-term death. Complete BBB, left or right, on electrocardiogram at presentation occurs in a wide range of 1% to 15% of patients with AMI and represents an independent and very important predictor of inhospital complications and poor survival for the most investigators, even if some controversies still exists [4] . In spite of current guidelines recommendations of using thrombolytic therapy in all patients with BBB and clinical suspicion of AMI [10], there is still unfortunately an obvious and proved under-use of thrombolytics in