Early rhythm control promotes ventricular recovery and reduces ICD requirement in idiopathic LVSD with arrhythmia under WCD protection

Background Sustained arrhythmias can precipitate left ventricular systolic dysfunction (LVSD), which may improve after rhythm stabilization. In patients with newly diagnosed idiopathic LVSD, distinguishing reversible dysfunction from persistent cardiomyopathy is crucial for clinical management and ICD decision-making. Objective To evaluate the impact of early rhythm control on left ventricular functional response and ICD indication in patients with idiopathic LVSD and arrhythmia under wearable cardioverter-defibrillator (WCD) protection. Methods We retrospectively analyzed 780 consecutive WCD-treated patients (2017–2023). Patients with newly diagnosed idiopathic LVSD (LVEF <35%) and atrial fibrillation/flutter or frequent premature ventricular beats (>20%) were included. Those with identifiable etiologies (ischemic, valvular, inflammatory, or infiltrative disease) were excluded after multimodality diagnostics. Rhythm control strategies (cardioversion, antiarrhythmic drugs, ablation) and clinical/echocardiographic follow-up up to 6 months were recorded. Patients were classified as responders if they achieved ≥15% LVEF improvement after sinus rhythm restoration, otherwise as non-responders. Results Of 142 patients with LVSD and arrhythmia, 74 had idiopathic LVSD and were analyzed. Sinus rhythm was restored in 54 patients (73%) after a median follow-up of 4.5 months. Among these, 32 (59%) were responders, with mean LVEF increasing from 28% to 43% (p = 0.001) compared to non-responders (24% to 32%). More than half of responders normalized above 50%. Heart failure therapy was comparable between groups. Non-responders had larger left ventricular end-diastolic and end-systolic diameters, lower baseline heart rates, and more mitral regurgitation. They also showed a trend toward more frequent late gadolinium enhancement (LGE) on cardiac MRI (p = 0.073). Electrical cardioversion was performed in 78% of responders and 82% of non-responders; antiarrhythmic drugs in 47% vs. 50%; catheter ablation was more frequent among responders (53% vs. 23%; p = 0.027). No appropriate WCD shock therapies occurred. ICD indication decreased from 100% at baseline to 17% at follow-up, with markedly lower implantation rates in responders compared to non-responders (3% vs. 36%; p = 0.001). Conclusions In this real-world cohort of idiopathic LVSD with arrhythmia, early rhythm control under WCD protection facilitated substantial functional response and markedly reduced ICD implantation. These findings highlight the clinical utility of early rhythm interventions in identifying reversible LV dysfunction and guiding device therapy.