VDD pacing acutely enhances contractile function in heart failure patients with intraventricular conduction delay. Single-site pacing at the site of greatest delay achieves similar or greater benefits to biventricular pacing in such patients. These data clarify pacing-effect mechanisms and should help in candidate identification for future studies.

Ventricular resynchronization by left ventricular or biventricular pacing/stimulation in DCM patients with left bundle-branch block acutely enhances systolic function while modestly lowering energy cost. This should prove valuable for treating DCM patients with basal dyssynchrony.

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 35Ϯ21% and 16.4Ϯ11%, respectively, and these changes correlated directly (rϭ0.7, Pϭ0.001). %⌬dP/dt max was weakly predicted by baseline QRS (rϭ0.6, PϽ0.02), more strongly by baseline dP/dt max (rϭ0.7, Pϭ0.001), and best by bidiscriminate analysis combining baseline dP/dt max Յ700 mm Hg/s and QRS Ն155 ms to predict %⌬dP/dt max Ն25% and %⌬PP Ն10% (PϽ0.0005, 2 ), with no false-positives. Benefit could not be predicted by %⌬QRS. To test whether basal mechanical dyssynchrony predicted responsiveness to LV pacing, circumferential strains were determined at Ϸ80 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 28.0Ϯ7.1% in normal subjects versus 201.4Ϯ84.3% in DCM patients (Pϭ0.001). Mechanical dyssynchrony also correlated directly with %⌬dP/dt max (rϭ0.85, Pϭ0.008). 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.

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Acute intravenous verapamil reduces ventriculovascular stiffening and improves aerobic exercise performance in healthy aged individuals. This highlights a role for heart-arterial coupling in modulating exertional capacity in the elderly, suggesting a potentially therapeutic target for aged individuals with exertional limitations.