Drug-Induced Complete Atrioventricular Block in an Elderly Patient: A Case Report Highlighting Digoxin-Beta Blocker...

Complete atrioventricular (AV) block is a severe conduction abnormality caused by intrinsic cardiac disease, ischemia, electrolyte imbalances, or drug interactions. Elderly patients on multiple medications are particularly vulnerable to polypharmacy-related interactions. This case report describes an 82-year-old female presenting to the emergency department with fatigue, syncope, and disorientation. Her medical history included atrial fibrillation, hypertension, and heart failure, with a medication regimen of digoxin 0.25 mg given daily 5 days out of 7, metoprolol 50 mg twice daily, lisinopril 10 mg daily, furosemide 40 mg daily, and spironolactone 50 mg daily. Clinical examination revealed bradycardia and a holosystolic murmur in the mitral valve area, while the electrocardiogram showed complete AV block at a ventricular rate of 35 bpm. Laboratory results indicated mild hyperkalemia (4.9 mmol/L). Suspecting a digoxin-beta-blocker interaction, antiarrhythmic therapy was discontinued. Within three days, the AV block resolved, transitioning to atrial fibrillation with a high ventricular rate. Bisoprolol was introduced for rate control, and hemodynamic stability was achieved. The patient was discharged with a revised medication regimen and showed no recurrence of AV block. This case emphasizes the importance of recognizing drug interactions as a reversible cause of AV block and using drug interaction checkers to manage polypharmacy, especially in elderly patients with multiple comorbidities. It also highlights the rare and paradoxical combination of atrial flutter and complete AV block.