Speakers - 2026

Title: Cilostazol Induced Digoxin Toxicity Presenting as Accelerated Idioventricular Rhythm and Recurrent Syncope

Abstract

Introduction: 

Digoxin remains a clinically relevant therapy for ventricular rate control in atrial fibrillation, particularly in patients with concomitant heart failure. However, its narrow therapeutic index predisposes patients to toxicity even when measured serum levels appear therapeutic. Electrolyte disturbances and drug–drug interactions that alter digoxin pharmacokinetics or pharmacodynamics frequently exacerbate toxicity. While many interactions are well described, the potential interaction between digoxin and phosphodiesterase-3 (PDE-3) inhibitors such as Cilostazol is under-recognized. We report a case of accelerated idioventricular rhythm (AIVR) likely precipitated by this interaction, highlighting that clinical toxicity may occur despite a “normal” serum digoxin concentration obtained outside the peak distribution window [1].

Case presentation:
A 77-year-old man with coronary artery disease, chronic heart failure with preserved ejection fraction, and paroxysmal atrial fibrillation presented with two days of dizziness, generalized weakness, nausea, vomiting, and blurred vision. His home medications included digoxin 0.125 mg twice daily, and cilostazol had recently been initiated for peripheral arterial disease. 
On presentation, he reported palpitations with transient hypotension. Initial electrocardiogram (EKG) demonstrated normal sinus rhythm (Figure-1). A subsequent symptomatic tracing revealed accelerated idioventricular rhythm with inferior and lateral ST depressions (Figure-2). Serial troponins and potassium levels were normal. The serum digoxin level was within the therapeutic range; however, the sample was obtained more than 30 hours after the last dose. 
Transthoracic echocardiography showed a low-normal left ventricular ejection fraction (50–55%) with diffuse hypokinesia and no significant valvular disease. Digoxin was discontinued, while other home medications were continued. Following cessation of digoxin, the AIVR resolved completely, and the patient remained in stable sinus rhythm without recurrent syncope or palpitations.