A Case of ST-Elevation Myocardial Infarction With Right Bundle Branch Block, an Ominous Sign of Critical Coronary Occlusion

Coronary artery disease is one of the leading causes of death worldwide, and ST-elevation myocardial infarction (STEMI) is one of its most serious manifestations. While STEMI itself is an ominous sign, there are other sinister electrocardiogram (EKG) patterns that are associated with increased morbidity and mortality, one of which is STEMI with right bundle branch block (RBBB). Blood supply to the right bundle comes from the left coronary circulation. Intuitively, RBBB in the setting of anterior wall myocardial infarction would indicate more extensive myocardial involvement and thus portend a worse prognosis. This case presents the significance of the association of new RBBB with critical lesions of the left anterior descending artery (LAD), therefore a low threshold for emergent coronary angiography and percutaneous coronary intervention (PCI). A 63-year-old man with a known history of non-insulin-dependent diabetes mellitus (NIDDM), hypertension, and hypertriglyceridemia non-compliant with medications presented to the emergency department (ED) after a visit with his primary care physician, with a chief complaint of exertional substernal chest pain for a one-week duration. His EKG on arrival showed significant ST-segment elevation with an atypical EKG pattern showing RBBB in V1-V2 with ST depression in reciprocal leads. Cardiac biomarkers showed an initial troponin I value of 0.441 ng/mL. Due to his persistent, worsening chest pain and associated nausea with episodes of vomiting, he was taken for an emergent cardiac catheterization that revealed a 100% lesion in his proximal LAD. The procedure was complicated by the development of cardiogenic shock requiring intra-aortic balloon pumps and vasopressors. A successful primary PCI was performed with drug-eluting stent (DES) to the 100% lesion in the proximal LAD and DES to the 80% lesions in the mid LAD, with 0% residual stenosis after the intervention. There was thrombolysis in myocardial infarction (TIMI) 0 flow pre-procedure and TIMI 3 flow post-intervention. Left ventriculography revealed anterolateral akinesis, apical akinesis, and diaphragmatic hypokinesis with an estimated ejection fraction (EF) of 20%. Transthoracic echocardiogram was repeated prior to discharge. Left ventricular (LV) systolic function was normal by visual assessment, and EF was noted to be ~55%. The patient continued on dual antiplatelet therapy and the rest of goal-directed medical therapy for coronary artery disease post-procedure. New-onset RBBB in the patient with typical STEMI in the context of ischemic symptoms should raise suspicion of critical proximal LAD coronary occlusion. It is increasingly being recognized as one of the significant EKG patterns for occlusive myocardial infarction associated with the worst outcome and mortality, highlighting the need to pay critical attention to these patients. Given the poor prognosis of these patients in the setting of acute myocardial infarction (AMI), it is essential to minimize the delay in initiating reperfusion therapy as they can potentially benefit from emergent intervention.