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Limitation of cardiac output by total isovolumic time during pharmacologic stress in patients with dilated cardiomyopathy: Activation-mediated effects of leftbundle branch block and coronary artery disease

^* Department of Echocardiography, The Royal Brompton Hospital and Imperial College of Science, Medicine and Technology, London, United Kingdom

View larger version (33K): [in a new window]   Figure 1 Superimposed aortic and mitral Doppler recordings. (Top) Total isovolumic time (t-IVT) normally falls with stress. (Middle) In left bundle branch block (LBBB), the total filling time is short and t-IVT is prolonged at rest. In the absence of coronary artery disease (CAD), t-IVT falls with stress, but does not change in patients with CAD (bottom), so that one-third of the cardiac cycle is neither ejecting nor filling. A2 = the aortic component of the second heart sound; ECG = electrocardiogram; PCG = phonocardiogram.

View larger version (15K): [in a new window]   Figure 2 Total isovolumic time (IVT) at rest and peak stress in the control group and four patient groups. Total IVT was increased at peak stress in patients with left bundle branch block (LBBB) due to prolongation at rest and only shortened with stress in the absence of coronary artery disease (CAD). Data are given as the mean value ± SD. R = rest; S = stress; ns = not significant. ***p < 0.001.

View larger version (13K): [in a new window]   Figure 3 Correlation between changes in the QRS duration and total isovolumic time (IVT) in control subjects and patients with normal coronary arteries. In all three groups, QRS shortening was associated with a fall in t-IVT. DCM = dilated cardiomyopathy; LBBB = left bundle branch block.

View larger version (17K): [in a new window]   Figure 4 Correlation between peak total isovolumic time (t-IVT) and peak cardiac output (CO). Overall, peak CO correlated closely with peak t-IVT. Patients with both left bundle branch block (LBBB) and coronary artery disease (CAD) had the longest t-IVT and the lowest CO at peak stress.