Predictors of Response to Cardiac Resynchronization Therapy in Pediatric and Congenital Heart Disease Patients

Background Cardiac resynchronization therapy (CRT) is an important therapeutic option in selected pediatric and congenital heart disease (CHD) patients with reduced systemic ventricular (SV) ejection fraction (EF). However, the identification of optimal responders is challenging. Objective To identify predictors of response to CRT in children and CHD patients at 5 large quaternary referral centers. Methods Patients were <21 years or had CHD; had SVEF <45%; symptomatic heart failure; and significant electrical dyssynchrony prior to CRT. Primary outcome was defined as an ordinal response at 6/12months: (1) Improved EF [≥5%], (2) Unchanged SVEF, (3) Worse SVEF. Secondary outcome utilized a propensity score-matched control cohort. Response to CRT was defined using longitudinal trajectory of SVEF up to latest follow-up. Results In total, 167 eligible CRT recipients were identified across the 5 centers. 150 had comprehensive data at 6/12months: 96(64%) with improved SVEF, 26(17%) unchanged, 28(19%) worsened. Mean increase in SVEF was 11% [IQR 3-21%]. On univariable ordinal regression, lower SVEF (p=0.013), biventricular circulation (p=0.022), systemic LV (p=0.021), and conduction delay to lateral wall of SV (p=0.01) were associated with positive response. For assessment of secondary outcome, 324 controls were identified. Mean follow-up 4.2(±3.7) yrs. Almost all subgroups demonstrated improved SVEF trend with CRT, except those with systemic RV (p=0.69) or without prior single site pacemaker (p=0.20). Conclusion CRT in children and CHD patients frequently results in an improvement in SVEF. Those with lower SVEF, conduction delay to lateral wall of the SV and those with systemic LV are most likely to respond. Condensed Abstract Cardiac resynchronization therapy (CRT) is an important therapeutic option in selected pediatric and congenital heart disease (CHD) patients with reduced systemic ventricular (SV) ejection fraction (EF). However, the identification of optimal responders is challenging. In this multicenter study, pediatric and CHD CRT recipients with heart failure and EF<45% were identified. The primary outcome was change in EF at 6/12months. Those with lower baseline SVEF, conduction delay to lateral wall of the SV and/or systemic LV were most likely to respond to CRT. When compared to propensity score-matched controls, the CRT groups also demonstrated a significantly better long-term EF trajectory.