V max as an Index of Contractile State in Man

Abstract

The maximal, no-load, velocity for the contractile element (V_max) was estimated in 45 patients. The patients included: 17 with normal left ventricular dynamics; eight with volume overload, compensated; 11 with volume overload, decompensated; three with pressure overload; and six with cardiomyopathy. Contractile element velocity (V_CE) during isovolumic contraction was estimated in two ways: (1) from left ventricular pressure data alone, where V_CE=(1/28.8p) (dp/dt), and (2) pressure data combined with measurement of left ventricular geometry (right anterior oblique cine). V_max obtained in these two ways agreed well for most patients (r = 0.82). In the normal patients, V_max varied from 1.46 to 2.64 muscle lengths per sec; in contrast that of the patients with cardiomyopathy varied between 0.71 and 1.34 muscle lengths per sec. Other indices of contractility (ejection fraction, peak dp/dt, peak velocity of circumferential fiber [peak V_CF], peak V_CE, and V_CE at zero stress) were compared on the basis of statistical correlation and consistency of other clinical evidence (presence or absence of congestive failure). Good correlation was obtained between V_max and peak V_SE (r = 0.68). Ejection fraction and peak V_CF were less sensitive. Neither the peak rate of pressure rise or V_CE at peak stress show any significant correlation with V_max or clinical state. Previous studies have shown that V_max can be evaluated from pressure data alone; this study confirms this finding in patients with mitral regurgitation as well as in those with normal outflow impedance.