Left ventricular pressure-diameter relations in the conscious rabbit.
A model for the study of left ventricular (LV) contractility in a small species was developed using conscious rabbits previously instrumented with a LV catheter and ultrasonic crystals measuring LV internal diameter. Afterload increase produced by methoxamine infusion was associated with a reduction in heart rate from 272(SEM18) to 214(20) beats.min-1, p less than 0.01; and an increase in LV end systolic pressure from 76.3(4.1) to 101(6.5) mm Hg, p less than 0.001, and in end systolic diameter from 8.7(0.7) to 9.9(0.7) mm, p less than 0.01. For matched end systolic pressure and heart rate, the increase in inotropic state produced by noradrenaline infusion significantly shifted the pressure-diameter relation to the left. Similarly, end systolic pressure and diameter were significantly lowered by sodium nitroprusside infusion, with a reflex increase of heart rate; and a decrease in inotropic state produced by verapamil infusion was demonstrated by a significantly larger end systolic diameter for matched end systolic pressure and heart rate. The pressure-diameter relation was not modified by volume loading, which increased end diastolic diameter by 9.6(1.1)% with no evidence of a Bainbridge reflex. The mild depressant effect of diltiazem was not detected by peak dP/dt changes but was demonstrated by the analysis of end systolic pressure-diameter relations. The instrumented rabbit thus appears to be a sensitive model for studying LV function and the cardiovascular effects of drugs.
INSERM U2, Hôpital Léon Bernard, Limeil-Brévannes, France.
N
N
Gilson
B
B
Crozatier
M
M
Laplace
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003243:Consciousness; D004110:Diltiazem / Q000494:pharmacology; D006321:Heart / Q000502:physiology*; D006339:Heart Rate / Q000187:drug effects; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D008954:Models, Biological; D009200:Myocardial Contraction / Q000187:drug effects; D009599:Nitroprusside / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology; D011817:Rabbits; D014700:Verapamil / Q000494:pharmacology
D009599:Nitroprusside; D014700:Verapamil; D004110:Diltiazem; D008729:Methoxamine; D009638:Norepinephrine