Predicting Persistent Left Ventricular Dysfunction After Cardiac Resynchronization Therapy Upgrade in Pacing-Induced Cardiomyopathy

Background/Objectives: Pacing-induced cardiomyopathy (PICM) is potentially reversible after cardiac resynchronization therapy (CRT) upgrade, but severe left ventricular dysfunction persists in some patients. We evaluated predictors of persistent left ventricular ejection fraction (LVEF) ≤ 35% after CRT upgrade and long-term outcomes. Methods: We analysed 60 patients undergoing CRT upgrade for PICM. The primary outcome was persistent LVEF ≤ 35% at 12 months. Clinical, electrocardiographic, echocardiographic, and long-term outcomes were assessed. Results: At 12 months, median LVEF increased from 30% to 45% (p < 0.01), and 82% of patients recovered to an LVEF > 35%. Persistent severe left ventricular dysfunction was associated with lower baseline LVEF (22% vs. 30%; p < 0.01), greater left ventricular end-diastolic diameter (LVEDD) (65 mm vs. 58 mm; p = 0.03), and longer post-CRT QRS duration (154 ms vs. 140 ms; p = 0.02); none remained independently significant after multivariable adjustment. No patient with baseline LVEF > 25% and LVEDD < 65 mm had persistent severe LV dysfunction, compared with 46% of those with LVEF ≤ 25% and LVEDD ≥ 65 mm. In the 12-month landmark analysis, mortality through 60 months after CRT upgrade was 55% in patients with persistent severe LV dysfunction and 31% in those with LVEF recovery. Conclusions: CRT upgrade was associated with substantial recovery of LV systolic function in patients with PICM. Severe baseline LV dysfunction and LV dilatation were associated with a lower likelihood of recovery to an LVEF > 35%. These exploratory findings may aid risk stratification but require prospective validation.