title: [Rate constants of left ventricular relaxation: the effect of inotropic and mechanical factors].
abstract: Changes in isovolumetric (IRRC) and auxovolumetric (ARRC) relaxation rate constants in response to inotropic and mechanical influences were studied experimentally in 23 narcotized cats. IRRC was determined by the slope of the curve of isovolumic relaxation pressure, expressed as natural logarithms, in relation to time. ARRC was determined on the basis of auxovolumetric relaxation pressure values. A pressure variation between 100 and 180 mmHg over one cycle had no noticeable effect on either IRRC or ARRC; those only diminished as the pressure rose beyond 200 mmHg. Electric stimulation of heart rate before and after propranolol administration raised both IRRC and ARRC, the latter showing twice the increment of the former. ARRC was also more sensitive to blood Ca2+, as compared to IRRC, that was measured by means of intravenous administration of CaCl2 and sodium citrate. It is concluded that ARRC is more indicative of myocardial relaxation, as compared to IRRC or relaxation time constant.
mesh_terms: D000818:Animals; D001794:Blood Pressure; D002122:Calcium Chloride / Q000494:pharmacology; D002415:Cats; D002951:Citrates / Q000494:pharmacology; D019343:Citric Acid; D003864:Depression, Chemical; D004558:Electric Stimulation; D006352:Heart Ventricles / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D011433:Propranolol / Q000494:pharmacology; D013268:Stimulation, Chemical; D016276:Ventricular Function
chemical_list: D002951:Citrates; D019343:Citric Acid; D011433:Propranolol; D002122:Calcium Chloride
vernacular_title: Konstanty skorosti rasslableniia levogo zheludochka: vliianie inotropnykh i mekhanicheskikh faktorov.