Ventricular performance in diabetic rabbits with norepinephrine cardiomyopathy.

The purpose of this investigation was to examine the effects of norepinephrine cardiomyopathy (NE-CM) on left ventricular (LV) performance in diabetic rabbits. Diabetes mellitus was produced in 11 rabbits by giving them alloxan monohydrate, 120 mg/kg. Cardiomyopathy was produced in five animals by a 90-min infusion of norepinephrine (2 micrograms/min/kg). Left ventricular contractility and pump function (VF) were examined 2 days later. The effects of hypercapnia and inotropic responsiveness to NE were also determined. VF was assessed by means of left ventricular function curves obtained with constant mean aortic pressure and heart rate and quantified by determining stroke volume (SV) at a left ventricular pressure of 10 cm H2O (SV10). Mean SV10 was 1.22 +/- 0.08 ml in control diabetics but averaged only 0.95 +/- 0.08 ml in diabetics with NE-CM (P less than 0.05). NE-CM markedly reduced LV dP/dt max responses to NE infusion but the increments in SV10 did not differ. Hypercapnia caused significantly greater ventricular depression in NE-CM than in control diabetic rabbits (P less than 0.001). The depressive effect of hypercapnia can be countered in part by the administration of NE in both groups, but differential depression in VF to hypercapnia was persistent between the two groups.