title: A computer program for determining Vmax from the uncalibrated left ventricular pressure signal and its first derivative.
abstract: 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 encompassed 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 conventional Vmax obtained from calibrated LV and aortic pressure signals. In 5 dogs both in the control state and during inotropic (epinephrine, 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 less than 0.001) or exponential (Vmax = 0.99 V'max - 0.06; r = 0.959; P less than 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.
mesh_terms: D000818:Animals; D001794:Blood Pressure; D003201:Computers; D003911:Dextrans / Q000494:pharmacology; D004285:Dogs; D004837:Epinephrine / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D010656:Phenylephrine / Q000494:pharmacology; D011312:Pressure; D011433:Propranolol / Q000494:pharmacology; D016276:Ventricular Function
chemical_list: D003911:Dextrans; D010656:Phenylephrine; D011433:Propranolol; D004837:Epinephrine