Comparison of Isovolumic and Ejection Phase Indices of Myocardial Performance

Indices derived from both the isovolumic and ejection phases of left ventricular systole have been advocated as a means of defining the basal level of contractility, but their comparative reliability for separating patients with obvious myocardial disease from a normal population has not been documented. Accordingly, indices of myocardial function were measured and compared in 36 patients, 22 with normal and 14 with abnormal ventricular function, using optimal techniques of pressure measurements by cathetertip micromanometry, signal digitizing at 1 msec intervals with averaging of multiple beats, and left ventriculography by biplane cineangiography. Isovolumic indices derived from developed pressure (DP), including V max, dP/dt/DP at DP = 5, 10, and 40 mm Hg, demonstrated no sensitivity for identifying depressed myocardial function (P > 0.1 in each instance). Using total pressure (TP), V max, peak (dP/dt/TP), and peak dP/dt served to separate the two patient populations from a statistical standpoint (P < 0.001), but individual values in the two groups showed considerable overlap. By contrast, the simplified ejection phase velocity indices, mean velocity of circumferential fiber shortening (mean Vcf) and mean normalized systolic ejection rate (MNSER) showed superior sensitivity for identifying normal and abnormal patient groups and manifested minimal overlap of individual values (P < 0.001). These observations indicate that, in patients with diffuse myocardial involvement, isovolumic indices are not reliable for detecting depressed myocardial function and that ejection phase contractile indices appear to offer a preferable mode for assessing myocardial function in the basal state.