Vector Analysis of Ventricular Function—an Approach to the Study of Myocardial Performance

Abstract

Evaluation of myocardial performance must take into consideration stroke work as related to ventricular force generation. A method has been developed where by pressure, flow velocity and their derivatives could be X-Y correlated and represented as vector loops, with time dashes to facilitate direction and amplitude analyses of the various loop components. Of several X-Y combinations, the most informative loops were those derived from: (1) LV pressure vs. aortic flow velocity (P-F loop); (2) LV pressure vs. derivative (P-dP/dt loop); (3) pressure derivative vs. flow derivative (dP/dt-dF/dt loop). Planimetry and analysis of the outgoing and returning limbs of the P-F loops enable separation of LV stroke work into its major early and late systolic components. These could be correlated with the P-dP/dt loops which reflect the corresponding ventricular force generation, and with the dP/dt-dF/dt loops which relate to work efficiency. In 10 adult dogs with chronically implanted aortic flow probes, various inotropic drugs and adrenergic blockers produced consistent changes in the loops indicating augmented or decreased myocardial performance. Loops obtained from children immediately before and after cardiopulmonary bypass provided information relative to changes in myocardial performance.

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