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

Background-VDD pacing can enhance systolic function in patients with dilate d cardiomyopathy and discoordinate contraction; however, identification of patients likely to benefit is unclear. We tested predictors of systolic res ponsiveness on the basis of global parameters as well as directly assessed mechanical dyssynchrony. Methods and Results-Twenty-two DCM patients with conduction delay were stud ied by cardiac catheterization with a dual-sensor micromanometer to measure LV and aortic pressures during sinus rhythm and LV free-wall pacing. Pacin g enhanced isovolumetric (dP/dt(max)) and ejection-phase (pulse pressure, P P) systolic function by 35+/-21% and 16.4+/-11%, respectively, and these ch anges correlated directly (r=0.7, P=0.001). %Delta dP/dt(max) was weakly pr edicted by baseline QRS (r=0.6, P<0.02), more strongly by baseline dP/dt(ma x) (r=0.7, P=0.001), and best by bidiscriminate analysis combining baseline dP/dt(max) less than or equal to 700 mm Hg/s and QRS greater than or equal to 155 ms to predict %adP/dt(max) greater than or equal to 25% and %Delta PP greater than or equal to 10% (P<0.0005, chi(2)), with no false-positives . Benefit could not be predicted by %Delta QRS. To test whether basal mecha nical dyssynchrony predicted responsiveness to LV pacing, circumferential s trains were determined at approximate to 80 sites throughout the LV by tagg ed 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). Mechanic al dyssynchrony also correlated directly with %Delta dP/dt(max) (r=0.85, P= 0.008). Conclusions-These results show that although mechanical dyssynchrony is a k ey predictor for pacing efficacy in DCM patients with conduction delay, com bining information about QRS and basal dP/df(max) provides an excellent too l to identify maximal responders.