Abstract 14912: Sotalol-induced Wide Complex Rhythm: What is the Mechanism?

Abstract

Introduction: Delta waves associated with atrioventricular accessory pathways (APs) may manifest with autonomic tone, heart rate, and rhythm changes. Rarely, drugs like sotalol can block AV nodal conduction, revealing latent WPW, one treatable cause of sudden death. Case report: A 38-year-old man was admitted for sotalol loading due to frequent typical atrial flutter and SVT and a desire to avoid catheter ablation. He had a history of cardiac arrest with adenosine and tachycardia-induced cardiomyopathy. After recovery, cardiac MRI showed a normal heart without scar. Admission 12-lead ECG ( Figure A ) revealed normal sinus rhythm without other abnormality. With administration of sotalol, the patient developed a wide complex rhythm ( Figure B ). Interpretation of the rhythm indicated presence of a latent AP and a repeat ECG ( Figure C ) confirmed manifest preexcitation. After consenting to electrophysiology study, the patient developed a short RP tachycardia ( Figure D ) which terminated with Valsalva. The patient underwent successful catheter ablation of the pathway located at the anterior floor of the coronary sinus body and the cavotricuspid isthmus. Discussion: The differential diagnosis for a wide complex rhythm in this setting includes rate-related aberrancy, idioventricular rhythm, phase 4 aberrancy, and preexcitation from an AP. Shortened and consistent PR intervals in the tracing lead to preexcitation as the only possible mechanism. APs that are capable of anterograde conduction but are not manifest in sinus rhythm are termed latent APs. Conditions that may cause this phenomenon include opposite autonomic effects on the AP and the AV node, increased atrial conduction time, or concealed retrograde conduction into the AP. Sotalol typically increases the retrograde effective refractory period of the AP but has variable anterograde effect. Sotalol has not previously been reported to reveal a latent AP but may have acted through one of the stated mechanisms.