Abstract 11135: CRT Response is Greater in Patients With Larger Fraction of the Myocardium Performing Negative Regional Work
Previous studies using animal and computational models suggested that increased heterogeneity in regional myocardial work density is a sensitive indicator of the mechanical deficit caused by electrical dyssynchrony in the failing heart. We therefore hypothesized that in dyssynchronous heart failure patients, functional improvements in response to CRT may be greater in subjects with higher baseline heterogeneity of regional myocardial work. To test this hypothesis, we developed patient-specific (PS) computational models of 7 male patients aged >60 years with NYHA class III heart failure, ejection fraction < 33%, left bundle branch block with QRS duration >120ms, mitral regurgitation >10ml (in 3 patients), and myocardial infarction (in 3 patients). Bi-ventricular geometry segmented from end-diastolic cardiac CT images, hemodynamic measurements from cardiac catheterization, electrophysiological measurements from ECG and electroanatomic mapping were used to construct detailed PS finite-element models of ventricular electromechanics coupled to a closed-loop circulation model. Spatial distribution of myocardial work density computed from baseline models (Fig A) varied significantly between patients (mean 0.7-5.3, sd 1.0-6.5 kJ/m3). Two measures of the distribution, LV fraction performing negative work and coefficient of variation (sd/mean) correlated strongly with observed reduction in end-systolic volume after CRT (R2=0.85, 0.80 respectively; Fig B). Clinical indices based on model-computed strains such as internal stretch fraction (ISF) and circumferential uniformity ratio estimate (CURE) as well as the measured QRS duration did not correlate as well (ISF 0.15; CURE 0.23; QRS 0.22) possibly due to infarction. There was no correlation between stroke work at baseline and functional improvement after CRT (0.02). In conclusion, functional improvement following CRT is greatest in patients with the largest region of LV performing negative work.
- © 2013 by American Heart Association, Inc.