Vmax as an Index of Contractile State in Man
The maximal, no-load, velocity for the contractile element (Vmax) 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 (VCE) during isovolumic contraction was estimated in two ways: (1) from left ventricular pressure data alone, where VCE=(1/28.8p) (dp/dt), and (2) pressure data combined with measurement of left ventricular geometry (right anterior oblique cine). Vmax obtained in these two ways agreed well for most patients (r = 0.82). In the normal patients, Vmax 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 VCF], peak VCE, and VCE 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 Vmax and peak VSE (r = 0.68). Ejection fraction and peak VCF were less sensitive. Neither the peak rate of pressure rise or VCE at peak stress show any significant correlation with Vmax or clinical state. Previous studies have shown that Vmax 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.
- Received August 12, 1970.
- Accepted November 30, 1970.
- © 1971 American Heart Association, Inc.