Abstract 4193: New Left Bundle Branch Block in ST-Elevation Myocardial Infarction Patients Undergoing Primary Percutaneous Coronary Intervention
Background: Based on data from early fibrinolytic trials, ACC/AHA STEMI guidelines recommend that patients (pts) presenting with ischemic symptoms and new left bundle branch block (LBBB) receive immediate reperfusion therapy, either fibrinolysis or percutaneous coronary intervention (PCI). Data from the PCI era of reperfusion therapy for suspected AMI in pts presenting with LBBB are scant. Our objective was to determine the prevalence, clinical and angiographic characteristics and outcomes in pts with ischemic symptoms and new LBBB undergoing emergent angiography in two large regional STEMI systems.
Methods: Data were pooled from the Level 1 MI program at Minneapolis Heart Institute at Abbott Northwestern Hospital and the STAT Heart/Star90 program at Prairie Cardiovascular in Springfield, IL. We compared the clinical and angiographic characteristics and outcomes of suspected STEMI pts with and without new LBBB.
Results: Of the 3,310 consecutive suspected STEMI pts in the prospective registries from March 2003 to May 2008, 2.8% (n=94) had a new LBBB. Baseline characteristics of those with and without LBBB were compared (Table⇓). Pts with new LBBB were older, more likely to be female and have a previous history of coronary artery disease. They were less likely to have a clear culprit coronary artery (59% vs. 86% p<0.0001), to require emergent PCI (53% vs. 80% p<0.0001) or to have positive cardiac biomarkers (64% vs. 81% p<0.001). Despite the higher false positive rate, pts with new LBBB had a lower mean ejection fraction (41.2% vs. 46.5% p=0.0002) and higher in-hospital mortality (9.6% vs. 4.5% p=0.039).
Conclusion: Due to the relatively high false positive rate and high risk features in pts with suspected AMI and new LBBB, the optimal reperfusion strategy may be emergent angiography and primary PCI, similar to that recommended for cardiogenic shock. Guidelines regarding reperfusion strategies for new LBBB need to be updated to reflect data from the PCI era.