Use of relaxation half-time as an index of ventricular relaxation in clinically normal cats and cats with hypertrophic cardiomyopathy.
Relaxation half-time (t1/2) was evaluated as a measure of isovolumic ventricular relaxation in clinically normal cats and cats with hypertrophic cardiomyopathy. Relaxation half-time was determined directly from the left ventricular pressure tracing as the time required for the left ventricular pressure at the beginning of isovolumic relaxation to decrease by half. The value of t1/2 was unaffected by moderate changes in heart rate, inotropic state, and afterload in clinically normal cats. However, t1/2 increased significantly (P = 0.003) with increased preload. The value of t1/2 was significantly higher (P = 0.0003) in a group of cats with hypertrophic cardiomyopathy, compared with that of a group of clinically normal cats. Although t1/2 must be interpreted in the context of changes in loading conditions, the index is useful as a measure of relaxation in clinically normal cats and cats with hypertrophic cardiomyopathy.
Department of Urban Practice, College of Veterinary Medicine, University of Tennessee, Knoxville 37901.
A L
AL
Golden
J M
JM
Bright
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology*; D002122:Calcium Chloride / Q000494:pharmacology; D002312:Cardiomyopathy, Hypertrophic / Q000503:physiopathology / Q000662:veterinary*; D002371:Cat Diseases / Q000503:physiopathology*; D002415:Cats; D003971:Diastole / Q000187:drug effects / Q000502:physiology; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006352:Heart Ventricles / Q000503:physiopathology; D009200:Myocardial Contraction / Q000187:drug effects / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D013997:Time Factors
D010656:Phenylephrine; D002122:Calcium Chloride