Measurement of ventricular relaxation. An alternative index of isovolumic relaxation to the time constant.
The time constant (T) is commonly used for representing the isovolumic fall in left ventricular pressure (LVP) because the isovolumic fall is monoexponential under most circumstances. However, the determination of T is cumbersome due to the requirement of a set of LVP versus time values in fitting a monoexponential function. RT64, which is the time from the minimum value of the time derivative of LVP (-dp/dtmax) to 36% of -dP/dtmax, can be derived beat-by-beat, on-line, and may be a simple alternative to T. Through the use of 240 pairs of values derived from six conscious instrumented dogs treated with different cardiovascular active agents, RT64 and T were found to be significantly correlated (r = 0.835, p less than 0.05) according to the equation RT64 = 0.725T + 10.2. In conclusion, RT64 may provide a simple alternative to T in representing the isovolumic relaxation process of the left ventricle.
Lee
K C
KC
Cardiovascular Pharmacology, Wyeth Laboratories, Inc., Philadelphia, Pennsylvania.
D000818:Animals; D001341:Autonomic Nervous System / Q000502:physiology; D004285:Dogs; D004562:Electrocardiography; D006321:Heart / Q000502:physiology*; D006439:Hemodynamics / Q000187:drug effects; D006584:Hexamethonium Compounds / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D008954:Models, Biological; D009200:Myocardial Contraction / Q000187:drug effects; D010656:Phenylephrine / Q000494:pharmacology; D012119:Respiration; D014700:Verapamil / Q000494:pharmacology
D006584:Hexamethonium Compounds; D010656:Phenylephrine; D014700:Verapamil; D007545:Isoproterenol