Reversal of Pacing-Induced Cardiomyopathy Following CardiacResynchronization Therapy.

Abstract

This study sought to determine the extent, time course, and predictors of improvement following cardiac resynchronization therapy (CRT) upgrade among pacing-induced cardiomyopathy (PICM) patients. PICM is an important cause of heart failure in patients exposed to frequent right ventricular (RV) pacing. CRT may reverse PICM. We retrospectively studied 1,279 consecutive patients undergoing CRT procedures between 2003 and 2016.Patients undergoing CRT upgrade from a dual-chamber or single-chamber ventricular pacemaker for PICM wereincluded. PICM was defined as decrease of≥10% in left ventricular ejection fraction (LVEF), resulting in LVEF <50% among patients experiencing≥20% RV pacing without an alternative cause of cardiomyopathy. Severe PICM was defined as pre-upgrade LVEF ≤35%. Clinical, electrocardiographic, and echocardiographic characteristics associated withboth the extent of LVEF recovery and with post-upgrade LVEF of >35% among those with severe PICM were identified. Of 69 PICM patients, LVEF improved from 29.3% to 45.3% over a median 7.0 months. Of 54 patients with severe PICM, 39 (72.2%) improved to LVEF >35% over a median 7.0 months. Most improvement occurred within thefirst3 months, although improvement continued over the remainder of the first year. In linear regression, narrowernative QRS was associated with greater LVEF improvement following CRT upgrade (+2.00% per 10-ms decrease; p=0.05). CRT is highly efficacious in reversing PICM, with 72% of severe PICM patients achieving LVEF>35%and most of the improvement occurring within 1 year. These data support initial upgrade to a CRT pacemakerwithconsideration of further upgrade to CRT defibrillator after 1 year if LVEF remains ≤35%.