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A Computer Program for Determining Vmax from the Uncalibrated Left Ventricular Pressure Signal and its First Derivative

Section of Cardiology, Department of Medicine, Medical College of Georgia, Section of Biomedical Engineering, Medical College of Georgia, Augusta, Georgia 30912

Maryon J. Williams, JR

Section of Cardiology, Department of Medicine, Medical College of Georgia, Section of Biomedical Engineering, Medical College of Georgia, Augusta, Georgia 30912

A computer program was developed to simplify the conventional method for determining the maximal contractile element shortening velocity at zero load (Vmax) by analysis of pressure-velocity graphs during the isovolumic contraction period. From an uncalibrated left ventricular (LV) pressure signal and its first derivative (dP/dt), the graph relating developed LV pressure (Pd) to the corresponding instantaneous value of (dP/dt)/28 Pd was constructed by the computer. The segment of the graph that encom passed approximately the second half of the isovolumic contraction period, as determined by analysis of the dP/dt waveform, was then extrapolated to provide V'max on the ordinate. This V'max was compared with the conven tional Vmax obtained from calibrated LV and aortic pressure signals. In 5 dogs both in the control state and during inotropic (epineprine, propranolol) and noninotropic interventions (phenylephrine or dextran infusion), a high degree of correlation was found relating V'max and Vmax both derived by either linear (Vmax = 0.91 V'max + 0.14; r = 0.933; P < 0.001) or exponential (Vmax = 0.99 V'max - 0.06; r = 0.959; P < 0.001) extrapolation of the pressure-velocity graph to zero load. By use of this program, Vmax can be easily and reliably estimated from the uncalibrated LV pressure signal and its first derivative.

Angiology, Vol. 32, No. 7, 489-501 (1981)
DOI: 10.1177/000331978103200706


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