Predictors of systolic augmentation from left ventricular preexcitation in patients with dilated cardiomyopathy and intraventricular conduction delay

Abstract

Background - VDD pacing can enhance systolic function in patients with dilated cardiomyopathy and discoordinate contraction; however, identification of patients likely to benefit is unclear. We tested predictors of systolic responsiveness on the basis of global parameters as well as directly assessed mechanical dyssynchrony. Methods and Results - Twenty-two DCM patients with conduction delay were studied by cardiac catheterization with a dual-sensor micromanometer to measure LV and aortic pressures during sinus rhythm and LV free-wall pacing. Pacing enhanced isovolumetric (dP/dt(max)) and ejection- phase (pulse pressure, PP) systolic function by 35 ± 21% and 16.4 ± 11%, respectively, and these changes correlated directly (r = 0.7, P = 0.001). %ΔdP/dt(max) was weakly predicted by baseline QRS (r = 0.6, P < 0.02), more strongly by baseline dP/dt(max) (r = 0.7, P = 0.001), and best by bidiscriminate analysis combining baseline dP/dt(max) ≤ 700 mm Hg/s and QRS ≥ 155 ms to predict %ΔdP/dt(max) ≥ 25% and %Δpp ≥ 10% (P < 0.0005, χ2), with no false-positives. Benefit could not be predicted by %ΔQRS. To test whether basal mechanical dyssynchrony predicted responsiveness to LV pacing, circumferential strains were determined at ≃80 sites throughout the LV by tagged MRI in 8 DCM patients and 7 additional control subjects. Strain variance at time of maximal shortening indexed dyssynchrony, averaging 28.0 ± 7.1% in normal subjects versus 201.4 ± 84.3% in DCM patients (P = 0.001). Mechanical dyssynchrony also correlated directly with %ΔdP/dt(max) (r = 0.85, P = 0.008). Conclusions - These results show that although mechanical dyssynchrony is a key predictor for pacing efficacy in DCM patients with conduction delay, combining information about QRS and basal dP/dt(max) provides an excellent tool: to identify maximal responders.