Impaired myocardial performance and response to calcium in experimental alcoholic cardiomyopathy

The effect of chronic consumption of ethanol upon myocardial function has been in dispute. The mechanical performance of isolated left ventricular papillary muscles was studied in a group of eight male rats which had been on a diet in which ethanol provided 36% of total calories for 5 weeks. This group was compared to a pairfed control group of eight rats. Muscles were studied in oxygenated Krebs-Henseleit solution at 28°C, while stretched to L_max and stimulated at 12/min to contract isometrically. Bath calcium concentrations were varied from 1.25 to 7.5 mm/l. Heart size and chamber weights did not differ between the groups. Peak developed tension, maximum rates of rise and fall of tension, and time to half relaxation were significantly lower in the ethanol group, whereas resting tension and time to peak tension did not differ in the two groups. All parameters except time to half relaxation exhibited a significant dependence on concentration of calcium in the bath. However, the degrees of augmentation of peak developed tension and maximum rates of rise and fall of tension with increase in calcium in the bath from 1.25 to 2.5 mm/l were significantly lower in the ethanol group. In addition to impairment of function with chronic alcohol administration, altered sensitivity to calcium was demonstrated. Thus, isolated muscle studies have defined a defect in defined a defect in myocardial performance not apparent from studies of hemodynamics in the intact animal.