ECG of the Month. Unexpected Atrioventricular Conduction in High-Grade Atrioventricular Block. DIAGNOSIS: Sinus rhythm; high-grade second-degree atrioventricular block with a junctional escape rhythm and three capture complexes, each with right bundle branch block aberration; possible septal myocardial infarct of indeterminate age; ST-T and U wave changes suggesting hypokalemia.

A 90-year-old man with a history of high blood pressure, a cerebrovascular accident without focal residua, dementia, and stage 3 chronic kidney disease went to the emergency department because of dizziness and near syncope. His medications were aspirin 81 mg qd, clopidogrel 75 mg qod, escitalopram oxalate 10 mg qd, quetiapine fumarate 25 mg qd, and memantine hydrochloride 10 mg qd. He had orthrostatic hypotension with supine blood pressure of 173/77 mmHg falling to 116/68 on standing, while pulse increased from 66 to 84 beats/min. He received IV fluid and returned home. Two days later, he saw his primary care physician because of episodes of dizziness and confusion. The Figure shows an electrocardiogram recorded during that visit.