Electrical dyssynchrony mapping and optimization of nonresponders in patients programmed with the adaptive cardiac resynchronization therapy algorithm.

Background: The adaptive cardiac resynchronization therapy (CRT) (aCRT) algorithm provides an important clinical benefit. However, a significant number of patients are nonresponders.

Objectives: The goals of this study were to quantify electrical synchrony in patients programmed with aCRT and to assess the echocardiographic effects of optimization in CRT nonresponders and incomplete responders.

Methods: We studied 125 patients programmed with aCRT and measured electrical synchrony at multiple device settings using novel electrical dyssynchrony mapping (EDM) technology. Electrical synchrony was quantified as cardiac resynchronization index (CRI), a measure that analyzes areas between multiple pairs of anterior and posterior electrograms and calculates synchrony normalized to native rhythm.

Results: CRI improved from baseline aCRT settings to optimal settings on the basis of EDM (56%±29% vs 92%±12%; P<.001). Patients programmed with left ventricle (LV)-only aCRT (group 1, n=68 [54%]) had a higher CRI (62%±25% vs 48%±31%; P=.014) than did patients programmed with biventricular aCRT (group 2, n=57 [46%]). In group 1 and group 2, optimal CRI during sequential biventricular (92%±13% and 93%±9%, respectively) and LV-only (92%±6% and 91%±7%, respectively) pacing was significantly (P<.001) higher than CRI at baseline aCRT setting. In a subset of 53 nonresponders optimized using EDM, there were significant improvements in CRI (37%±25%; P<.0001), LV ejection fraction (6.2%±6.6%; P<.0001), end-diastolic volume (9.5±28.2 mL; P=.015), end-systolic volume (13.4±24.9 mL; P<.001), and transverse (1.5%±4.4%; P=.014), longitudinal (1.0%±2.5%; P=.003), and circumferential (2.6%±8.5%; P=.047) strain.

Conclusion: Electrical synchrony improves 56% with CRT using aCRT programming and 92% with EDM optimization. Optimization of aCRT-programmed nonresponders results in significant improvements in LV size and systolic function, offering the possibility of converting CRT nonresponders into responders.