NOW YOU SEE IT, NOW YOU DON‘T: A CASE OF INTERMITTENT LBBB

Introduction/Objective: Left bundle branch block (LBBB) is an electrocardiogram pattern that often occurs in patients with underlying heart disease. The uncommon phenomenon of intermittent LBBB is usually rate dependent, associated with exercise, or the result of an acute coronary syndrome (ACS). Presented is a case of a 27 year-old female, with no cardiac history who was transferred to our facility with a 2-day history of epigastric pain and new LBBB on ECG. Upon arrival, her abdominal pain resolved and continuous cardiac monitoring yielded intermittent LBBB without significant changes in heart rate. Serial cardiac biomarkers were negative, resting and dobutamine stress echocardiograms were unremarkable, but Lexiscan yielded a moderate-sized mixed anterior wall defect extending to the apex. Methods: Chart review after transfer, after discharge and PubMed search of relevant keywords was performed. Results/Conclusions: LBBB rarely occurs in young healthy persons. Multiple studies have shown an association between LBBB and sudden cardiac death. Other studies have not only implied a relationship between intermittent LBBB and ACS but also implicated it as an independent prognostic marker for coronary artery disease. All patients admitted with chest pain or an anginal equivalent should be placed on continuous cardiac monitoring. As this case illustrates, LBBB occurring intermittently could be easily missed on serial ECGs. When intermittent LBBB is detected in younger patients, they should be carefully evaluated for hypertension, CAD, valvular heart disease, and cardiomyopathies. In higher risk individuals with LBBB, more advanced cardiac imaging is preferred for the diagnosis and risk stratification.