Cardiac effects of acute ethanol ingestion unmasked by autonomic blockade.

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Abstract
The effects of ethanol and autonomic blockade were assessed on left ventricular function in 9 normal human subjects, age 20-35 yr, using M-mode echocardiography and systolic time intervals. On day 1, measurements were made of heart rate, mean velocity of circumferential fiber shortening and left ventricular pre-ejection period and left ventricular ejection time ratio (PEP/LVET), during a control period and after autonomic blockade. Autonomic blockade was produced with i.v. propranolol (0.2 mg/kg body weight) and atropine (0.04 mg/kg body weight). On day 2, measurements were again made during a control period, than with ethanol alone, followed by addition of autonomic blockade to ethanol. Ethanol (180 ml) was ingested over 60 min, resulting in a mean blood ethanol level of 110 mg/dl (range 77-135 mg/dl) at 60 min post-ingestion. There were no significant differences between the control data on days 1 and 2. Blood pressure was unchanged throughout the study. On day 1, autonomic blockade alone resulted in the expected increase in heart rate, with a proportional increase in mean velocity of circumferential fiber shortening and an increase in PEP/LVET. On day 2, ethanol alone resulted in no significant changes except for a slight increase in PEP/LVET. Ethanol plus autonomic blockade, (day 2), compared with autonomic blockade alone (day 1), revealed a decrease in mean velocity of circumferential fiber shortening, and an increase in PEP/LVET, with a decrease in intrinsic heart rate. In normal subjects: autonomic blockade probably does not directly affect contractility; acute ethanol ingestion alone does not produce important changes in cardiac function and ethanol in the autonomic blockaded heart apparently causes a significant decrease in contractility. Ethanol apparently has a negative inotropic effect which is masked by catecholamines and/or autonomic nervous system discharge.