Effects of cardiac resynchronization therapy in adults with congenital heart disease

Cardiac resynchronization therapy (CRT) is well-established in acquired heart failure, but evidence in adults with congenital heart disease (ACHD) remains limited. Current guidelines, extrapolated from non-congenital populations, may not fully address the anatomical and electrophysiological complexities in ACHD. This study aimed to evaluate the safety and efficacy of CRT in ACHD, focusing on changes in QRS duration, systemic ventricular function (SVF), and New York Heart Association (NYHA) class. A retrospective multicenter cohort study was conducted across two tertiary ACHD centers. ACHD patients who underwent CRT implantation between 2014 and 2024 were included. Primary outcomes were QRS duration, SVF, and NYHA class at 3, 6, and 12 months post-implantation, and peri-procedural clinical and device-related outcomes were assessed. Mixed models were used to analyze longitudinal changes, adjusting for de novo vs. upgrade CRT implantation, left bundle branch block (LBBB) vs. non-LBBB QRS morphology, and systemic left vs. right ventricle (sRV) anatomy. 101 patients were included. The mean age was 53 ± 14 year, 41 (40.6%) were female and 48 (47.5%) underwent an upgrade procedure to CRT. Twenty-two patients (21.8%) had mild, 57 (56.4%) moderate, and 22 (21.8%) severe congenital heart disease, and 16 (15.8%) had a sRV. Six patients (5.9%) experienced a procedure-related complication requiring revision (6.6 per 100 patient-years follow-up), and one patient (1.0%) died from end-stage heart failure in the year after CRT implantation. CRT was associated with significant improvements in QRS duration, SVF, and NYHA class at 3, 6, and 12 months (p < 0.05 for all). QRS reduction was more pronounced after upgrade procedures. Improvements in QRS, SVF, and NYHA class extended to patients with a sRV and with non-LBBB QRS morphology. At one year follow-up, 68 patients (72.3%) showed improvement of at least 1 class of NYHA and/or SVF. This study supports CRT as a safe and effective therapy in ACHD patients, including those with sRV or non-LBBB QRS morphology, emphasizing the need for individualized decision-making beyond standard guidelines.