Reduced high harmonic power spectra in patients with old myocardial infarction.

Abstract

Acceleration of blood flow ejected from the ventricle into the aorta and the hydraulic power state of blood flow in the aorta may be affected by asynchronous or locally depressed contraction of the left ventricle as well as by arterial impedance. In order to evaluate the effect of an infarcted heart on the hydraulic power state of blood flow, the aortic input impedance spectrum and the hydraulic power spectrum were calculated from simultaneous recordings of pulsatile aortic pressure and flow velocity at the aortic root in 6 normal controls (group 1), 6 patients with old myocardial infarction (OMI) without aneurysm (group 2), and 6 patients of OMI with aneurysm (group 3). The ratios (Rh) of power in high harmonics to that of fundamental harmonics, that is, Rh = (E2 + E3 + ...E10)/E1, where E represents hydraulic power and the numbers represent harmonic numbers, were 0.64 +/- 0.17, 0.23 +/- 0.09, and 0.22 +/- 0.10 in groups 1, 2, and respectively (p less than 0.001 between groups 1 and 2; p less than 0.001, between groups 1 and 3). As the acceleration of ejecting flow of blood by the left ventricle is inversely related with arterial impedance, Rh will be also inversely related with arterial impedance. Then, the product of Rh and the characteristic impedance (Zc) would be an indicator of the left ventricular contractility. In fact, the products were 64 +/- 15, 32 +/- 14, and 31 +/- 13 dyne.sec.cm-5 in groups 1, 2, and 3 respectively (p less than 0.005, between groups 1 and 2; p less than 0.005, between groups 1 and 3). These results suggest that asynchronous or locally depressed contractions of the left ventricular wall are closely related to depressed Rh and further to depressed values of the products of Rh and Zc. It is concluded that analysis of the power spectrum of blood flow in the root of the aorta provides information of the left ventricular contractility in connection with arterial impedance.