Transient vs. steady end-systolic pressure-volume relation in dog left ventricle.
We compared transient slope of end-systolic pressure-volume line (T-Emax) with steady Emax (S-Emax) in isolated cross-circulated canine left ventricles. T-Emax is the slope of the end-systolic pressure-volume line (ESPVL) determined from the last steady-state ejecting contraction (SEC) and the first transient isovolumic contraction produced by end-diastolic volume clamp. S-Emax is the slope of ESPVL determined from five steady-state contractions by linear regression analysis. We obtained three T-Emax values in the same contractile state by changing ejection fraction (EF) of SEC to three levels (range 14-58%) from the same end-diastolic volume. T-Emax variably increased with EF in any contractile state. The ratios of the three T-Emax values to the same S-Emax value was 1.08 +/- 0.04 (11 ventricles, means +/- SE) for high EF, 0.87 +/- 0.06 for middle EF, and 0.69 +/- 0.07 for low EF in control contractile state. These ratios decreased under epinephrine and increased under propranolol. We conclude that T-Emax depends not only on EF but also on contractile state in isolated dog left ventricles.
D000818:Animals; D001794:Blood Pressure; D001810:Blood Volume; D004285:Dogs; D004837:Epinephrine / Q000494:pharmacology; D006321:Heart / Q000502:physiology*; D006352:Heart Ventricles; D006706:Homeostasis; D009200:Myocardial Contraction; D011433:Propranolol / Q000494:pharmacology; D012044:Regression Analysis; D013997:Time Factors
D011433:Propranolol; D004837:Epinephrine