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His-Optimized Cardiac Resynchronization Therapy to Maximize Electrical Resynchronization: A Feasibility Study

Background: Cardiac resynchronization therapy (CRT) is an established therapy for patients with cardiomyopathy, left bundle branch block, and heart failure. His bundle pacing (HBP) may also improve clinical outcomes by narrowing QRS duration. The QRS narrowing by HBP may not always be optimal. The aim of the study was to determine if CRT could be optimized by sequential HBP followed by left ventricular (LV) pacing (His-Optimized CRT [HOT-CRT]) to maximize electrical resynchronization. Methods: We attempted permanent HBP in 27 patients (left bundle branch block 17, intraventricular conduction defect 5, and right ventricular pacing 5) referred for CRT in addition to LV lead. HBP was followed by LV pacing at a delay equal to His-ventricular interval. QRS duration at baseline, during HBP, biventricular pacing, and HOT-CRT was measured. Echocardiographic parameters and New York Heart Association functional class were assessed at baseline and during follow-up. Results: HOT-CRT was successful in 25 of 27 patients (age 72±15 years, men 23, ischemic 21). QRS duration at baseline was 183±27 ms and significantly narrowed to 162±17 ms with biventricular pacing (P=0.003), to 151±24 ms during HBP (P<0.0001), and further to 120±16 ms during HOT-CRT (P<0.0001). During a mean follow-up of 14±10 months, LV ejection fraction improved from 24±7% to 38±10% (P<0.0001), and New York Heart Association functional class changed from 3.3 to 2.04. Twenty-one of 25 patients (84%) were clinical responders while 23 of 25 (92%) showed echocardiographic response. Conclusions: In this feasibility cohort, HOT-CRT resulted in improved electrical resynchronization. HOT-CRT may improve clinical and echocardiographic outcomes in advanced heart failure patients requiring CRT.