Depression of cardiac performance by ethanol unmasked during autonomic blockade

Effects of alcohol on atrial fibrillation: myths and truths

Alcohol is the most consumed drug worldwide. Both acute and chronic alcohol use have been associated with cardiac arrhythmias, in particular atrial fibrillation, or so-called 'holiday heart syndrome'. Epidemiological, clinical and experimental studies have attempted to elucidate the mechanisms involved in this association. However, because most of these studies have shown conflicting results, the connection between ethanol and atrial arrhythmias remains controversial. Historical, epidemiological and pharmacological aspects of alcohol, as well as recent concepts on atrial fibrillation are reviewed. We then examine the literature and provide a critical point of view on the still elusive association between alcohol and atrial fibrillation.

Characterization of the Acute Cardiac Electrophysiologic Effects of Ethanol in Dogs

BACKGROUND

Alcohol has been related to atrial fibrillation (holiday heart syndrome), but its electrophysiologic actions remain unclear.

METHODS

We evaluated the effects of alcohol in 23 anesthetized dogs at baseline and after 2 cumulative intravenous doses of ethanol: first dose 1.5 ml/kg (plasma level 200 mg/dl); second dose 1.0 ml/kg (279 mg/dl). In 13 closed-chest dogs (5 with intact autonomic nervous system, 5 under combined autonomic blockade and 3 sham controls), electrophysiologic evaluation and monophasic action potential (MAP) recordings were undertaken in the right atrium and ventricle. In 5 additional dogs, open-chest biatrial epicardial mapping with 8 bipoles on Bachmann's bundle was undertaken. In the remaining 5 dogs, 2D echocardiograms and ultrastructural analysis were performed.

RESULTS

In closed-chest dogs with intact autonomic nervous system, ethanol had no effects on surface electrocardiogram and intracardiac variables. At a cycle length of 300 milliseconds, no effects were noted on atrial and ventricular refractoriness and on the right atrial MAP. These results were not altered by autonomic blockade. No changes occurred in sham controls. In open-chest dogs, ethanol did not affect inter-atrial conduction time, conduction velocity, and wavelength. Atrial arrhythmias were not induced in any dog, either at baseline or after ethanol. Histological and ultrastructural findings were normal but left ventricular (LV) ejection fraction decreased in treated dogs (77 vs. 73 vs. 66%; p = 0.04).

CONCLUSION

Ethanol at medium and high doses depresses LV systolic function but has no effects on atrial electrophysiological parameters. These findings suggest that acute alcoholic intoxication does not directly promote atrial arrhythmias.

Interaction of alcohol and an alpha1-blocker on ambulatory blood pressure in patients with essential hypertension

Ingestion of alcohol acutely decreases vascular resistance and blood pressure (BP) with activation of the sympathetic nervous system in Orientals. Although alpha1-blockers are widely used in the treatment of hypertension, the possible interaction between alcohol and alpha1-blockers has not been clarified. We examined the effects of prazosin on the alcohol-induced BP changes in Japanese men with mild hypertension. Ten hypertensive patients (54 +/- 3 years, mean +/- SE) were given 1 mL/kg of alcohol or isocaloric control drink with a light meal in the evening before and 5 to 7 days after treatment with prazosin (1 mg three times daily). Ambulatory BP monitoring was carried out every 30 min for 24 h in each period using Colin ABPM-630. Blood samples were obtained before and 2 h after intake of alcohol or control drink. Before prazosin treatment, alcohol ingestion decreased BP for several hours with a significant reduction in average 24-h BP, whereas it increased heart rate, plasma norepinephrine, and plasma renin activity. Treatment with prazosin caused a significant decrease in 24-h BP (136.3 +/- 4.0/82.8 +/- 2.5 v 131.6 +/- 3.2/80.0 +/- 2.3 mm Hg). The alcohol-induced hypotension at 2-4 h after ingestion was enhanced by prazosin (-18.0 +/- 3.7/-11.8 +/- 2.7 v -24.4 +/- 4.9/-17.8 +/- 2.8 mm Hg, P < .05 for diastolic BP). These results suggested that inhibition of the sympathetic nervous system with alpha1-blockers accentuates alcohol-induced hypotension. Ingestion of alcohol may cause a marked BP reduction in hypertensive Orientals treated with alpha1-blockers.

Sexually dimorphic hemodynamic effects of intragastric ethanol in conscious rats

This study investigated the gender-related differences in hemodynamic effects of small to moderate doses of intragastrically (i.g.) administered ethanol in conscious rats. Changes evoked by ethanol (0.25, 0.5 or 1 g/kg) in mean arterial pressure (MAP), heart rate, cardiac index (CI), stroke volume (SV), and total peripheral resistance (TPR) were followed for 90 min in age-matched male and female Sprague-Dawley rats. Baseline values of MAP (121+/-2 vs. 124+/-2 mm Hg) were similar whereas CI (55+/-2 vs. 43+/-2 ml/min/100 g) and TPR (2.2+/-0.1 vs. 3.0+/-0.1 mm Hg/ml/min/100 g) were significantly (P<0.05) higher and lower, respectively, in female compared with male rats. In male rats, the middle dose (0.5 g/kg) of ethanol caused a slight increase in MAP due to significant (P<0.05) increases in CO whereas the other two doses (0.25 and 1 g/kg) had no effect on MAP. In female rats, MAP was not affected by ethanol (0.25 and 0.5 g/kg) and showed a significant reduction by the higher dose (1 g/kg) that was associated with decreases in CO and SV while TPR did not change. The hypotensive effect of ethanol (1 g/kg) in female rats started after 50 min, was maximal (13+/-1.7 mm Hg) at 70 min and remained so for the remaining 20 min of the study. Blood ethanol concentrations were similar in male and female rats. These findings suggest that the hemodynamic responses to i.g. ethanol are gender-related and that ethanol-evoked hypotension in female rats appears to involve a reduction in cardiac output.

Effects of propranolol on cardiovascular and neurohumoral actions of alcohol in hypertensive patients

Alcohol ingestion acutely lowers blood pressure (BP) with vasodilation and sympathetic activation in Oriental subjects. We examined the effects of beta blockade on cardiovascular and neurohumoral actions of alcohol in Japanese men with mild-to-moderate essential hypertension. Ten hypertensive patients (54+/-5 years, mean+/-SE) were given 1 ml/kg of alcohol or isocaloric control drink with a light meal in the evening before and 5-7 days after treatment with propranolol (20 mg three times daily). BP and heart rate (HR) were measured every 30 min for 24 h in each period. Blood sampling and echocardiographic examination were carried out before (17.00 h) and after (19.00 h) intake of alcohol or control drink, Before treatment, alcohol ingestion caused significant decreases in BP, total peripheral resistance and serum potassium concentration, while it increased heart rate (HR), cardiac output (CO), plasma norepinephrine and plasma renin activity (PRA). Treatment with propranolol significantly decreased BP and HR for 24 h. Propranolol and alcohol showed an additive depressor effect on night-time BP, and the alcohol-induced hypotension was similar before and after propranolol treatment. The alcohol-induced changes in HR, CO, PRA and serum potassium were significantly attenuated by propranolol. These results suggest that activation of the sympathetic nervous system plays a role in alcohol-induced cardiac stimulation, renin release and hypokalemia through beta receptors. Moderate doses of beta-blockers may not modify alcohol-induced BP reduction in Oriental subjects with hypertension.

Influence of hypoxia and hyperoxia on the cardiovascular and lethal effects of ethanol

The mutual potentiation of the hepatotoxic effects of ethanol and hypoxia raised the question of whether such an interaction also occurs in the cardiovascular system. Therefore, anaesthetized rats were infused intravenously with ethanol (25 mg/kg x min.) over 90 min. to reach blood ethanol concentrations between 2.2 and 2.6 g/l and were ventilated artificially either with room air, 10% O2/90% N2 or 100% O2. Under normoxic conditions, ethanol produced a slow decrease of mean arterial blood pressure from 130 to 100 mmHg due to the decline in cardiac output and stroke volume (-20%) while heart rate and peripheral resistance remained unchanged. Hypoxia (arterial oxygen tension 35-38 mmHg) without ethanol produced immediate hypotension (-60 mmHg) without decreasing the cardiac output, i.e. by reducing peripheral resistance. In combination with ethanol, hypoxia produced an even stronger hypotension (-90 mmHg) due to reduction in both cardiac output and peripheral resistance. On the other hand, respiration with 100% O2 (arterial oxygen tension about 500 mmHg) elevated peripheral resistance, attenuated ethanol-induced cardiodepression and prevented ethanol-induced hypotension. The lethal doses of ethanol evaluated by infusing 75 mg/kg x min. ethanol until death amounted to 4.1 g/kg with 10% O2, to 5.5 g/kg with 20% O2 (room air) and to 6.9 g/kg with 100% O2. Thus decrease in vascular contractility induced by hypoxia combined with ethanol-induced cardiodepression may result in lethal cardiovascular failure. Hyperoxia, on the other hand, counteracts ethanol-induced cardiodepression and its acute toxicity by raising the vascular contractility.

Role of cardiac output in ethanol-evoked attenuation of centrally mediated hypotension in conscious rats

Our previous studies have shown that ethanol selectively counteracts centrally mediated hypotensive responses. This study investigated the role of cardiac output and peripheral resistance in the antagonistic interaction between ethanol and antihypertensive drugs. Changes in blood pressure, heart rate, cardiac index, stroke volume, and peripheral resistance elicited by clonidine and subsequent ethanol or saline administration were evaluated in conscious rats. The aortic barodenervated rat was employed because it exhibits greater hypotensive responses to clonidine compared with the intact rat. Aortic barodenervation elicited acute rises in blood pressure, heart rate, and peripheral resistance, whereas cardiac index and stroke volume were not altered. The blood pressure of conscious aortic barodenervated rats returned to sham-operated levels by 48 hours due to concomitant reductions in cardiac index and stroke volume; the peripheral resistance, however, remained significantly elevated. Clonidine (30 microg/kg, I.V.) elicited greater decreases in blood pressure in aortic barodenervated compared with sham-operated rats. The hypotension was caused by decreases in cardiac index and stroke volume because peripheral resistance did not change. Ethanol (1 g/kg, I.V.) counteracted the hypotensive effect of clonidine and raised blood pressure to levels higher than preclonidine values. Significant (P<.05) increases in cardiac index and stroke volume and decreases in peripheral resistance accompanied the pressor effect of ethanol. Additional control groups were included in the study to determine the selectivity of the interaction. A dose of hydralazine (0.5 mg/kg, I.V.) was used that produced similar hypotension to that evoked by clonidine in aortic barodenervated rats. Hydralazine-evoked hypotension was similar in denervated and control rats and resulted from significant reductions in peripheral resistance. Reflex increases in heart rate and stroke volume and hence cardiac output were observed. Ethanol given after hydralazine produced a short-lived pressor effect (<5 minutes versus 40 minutes in the case of clonidine) and counteracted the sympathetically mediated increases in cardiac output, stroke volume, and heart rate. These findings support our hypothesis that ethanol selectively counteracts hypotensive responses of central origin by reversing the reduction in cardiac output elicited by clonidine.

Ethanol inhibition of Ca2+ and Na+ currents in the guinea-pig heart

The effects of ethanol on L-type Ca2+ and fast Na+ currents (ICa and INa, respectively) were examined using the whole-cell patch-clamp experiments on guinea-pig ventricular cells. At a clinically relevant concentration of 24 mM, ethanol slightly but significantly shortened the action potential duration, and reduced the ICa by 7 +/- 4% (mean +/- S.D.). This concentration of ethanol did not affect INa, but a lethal concentration of ethanol (80 mM) significantly inhibited INa by 13 +/- 5%. The voltage dependence of INa activation was not affected by ethanol, whereas the inhibitions of ICa by 80 mM ethanol and INa by 240 mM were both accompanied by a several mV shift in the channel availability curve toward more negative potentials, suggesting that the channels in the inactivated state are more susceptible to ethanol. The ICa inhibition by ethanol at clinically relevant concentrations could contribute to a negative inotropic effect, action potential shortening and development of arrhythmias, while the pathophysiological significance of ethanol inhibition of INa seems less important.

Alcoholic cardiomyopathy

Chronic alcoholism is one of the most important causes of dilated cardiomyopathy, and a large proportion of chronic alcoholics demonstrate impairment of cardiac function. The development of cardiac dysfunction is apparently related to the total lifetime dose of ethanol. Studies in experimental animals have demonstrated that both acute and chronic ethanol administration impair cardiac contractility. However, the relationship, if any, between the acute effects of alcohol and the development of irreversible cardiomyopathy remain to be elucidated.

Effects of ethanol on the contractile function of the heart: a review

Chronic ethanol consumption leads to a number of alterations in the contractile function of the heart and is a leading cause of cardiomyopathy. Ethanol also has an acute negative inotropic effect mediated by direct interaction with cardiac muscle cells, although this action is often masked by indirect actions resulting from enhanced release of catecholamines in vivo. This article reviews the effects of ethanol on the contractile function of the heart. The specific targets affected by ethanol in cardiac muscle cells are discussed in terms of potential mechanisms underlying the depressions of contractility resulting from both acute and chronic actions of ethanol.

Contractile, metabolic and electrophysiologic effects of ethanol in the isolated rat heart

The metabolic, functional and electrical effects of ethanol were studied in the isolated isovolumic rat heart retrogradely perfused at constant flow using phosphorus-31 nuclear magnetic resonance spectroscopy and surface electrogram recordings. Ethanol (0.75 to 6.0 vol%; 128 to 1024 mM) caused a concentration-dependent decline in developed pressure without a change in adenosine triphosphate, phosphocreatine, inorganic phosphate or pH. Ethanol (6%) caused abolition of electrical activity. The functional decline could be rapidly and completely reversed by perfusing with ethanol-free solution and, significantly although not completely, reversed by increasing perfusate calcium to 4 mM. Furthermore, ethanol shifted the perfusate calcium-tetanic pressure relationship in the presence of ryanodine (1 microM) downwards and to the right. The results suggest ethanol's acute effects in this model are not mediated by changes in energy metabolism or cellular pH, but rather by sarcolemmal effects and by a decrease in both myofilament calcium sensitivity and maximal force generating ability.

Acute effects of mildly intoxicating levels of alcohol on left ventricular function in conscious dogs

We assessed the effect of alcohol, before and after autonomic blockade, on left ventricular (LV) performance in conscious dogs. 10 animals were instrumented to determine LV volume from ultrasonic LV internal dimensions and measure LV pressure with a micromanometer. The animals were studied in the conscious state after full recovery from the operation. Blood alcohol was undetectable before and 67 +/- 14 mg/dl (mean +/- SD) at 20 min after alcohol administration. In response to alcohol, the LV systolic pressure was reduced slightly, the left ventricular end-diastolic pressure increased slightly. The maximum time derivative of LV pressure (dP/dtmax) and stroke volume were decreased. The end-systolic volume (VES), as well as effective arterial elastance, were significantly increased. There was no significant change in heart rate. Variably loaded pressure-volume loops were generated by acute caval occlusion before, immediately, and 20 min after the intravenous infusion of alcohol (0.2 g/kg). Three measures of LV performance were derived from these variably loaded pressure-volume loops: the end-systolic pressure-volume relation; the stroke work-end-diastolic volume relation; and maximum dP/dt-VED relation. The slopes of all three relations were significantly decreased in response to alcohol, and all three relations were shifted toward the right, indicating a depression of LV contractile performance. Similar, but greater depressions of LV performance with alcohol were observed following autonomic blockade. LV performance was restored by infusing dobutamine. We conclude that mildly intoxicating levels of alcohol (blood concentration less than 100 mg/dl) are capable of producing LV contractile depression in conscious animals, which is more marked after autonomic blockade. This suggests that patients with impaired LV function should avoid even small amounts of alcohol.

Effects of acute alcohol ingestion on the left ventricular performance of normal subjects before and after incomplete autonomic blockade

The effects of acute alcohol ingestion on the left ventricular performance of nine normal subjects, mean age 25 years, were studied before and after incomplete autonomic blockade, produced by atropine, 0.04 mg/kg body weight, and propranolol, 0.2 mg/kg body weight. Left ventricular (LV) function curves (stroke volume vs. end-diastolic volume) were plotted from data generated before and after large variations in cardiac preload. Increase in preload was produced by five degrees of head-down tilt for 90 minutes; decrease in preload was produced by graduated lower body negative pressure to -40 mmHg. After incomplete autonomic blockade, the negative inotropic effects of acute alcohol ingestion were minimal but significant and manifest by the reduction in mean velocity of circumferential fiber shortening (p less than 0.05). Studies during wide variations in preload confirmed the importance of maintaining central blood volume after alcohol ingestion. Lower body negative pressure after both incomplete autonomic blockade and alcohol produced a further deterioration in mean velocity of circumferential fiber shortening (p less than 0.05).

Combined effect of low doses of propranolol and ethanol on cardiac function: a comparative study by radionuclide ventriculography in conscious dogs

Trained, chronically instrumented, conscious dogs were used to evaluate the effect of propranolol (PRO), ethanol (ETH) or their combination (P + E) on the left ventricular (LV) function by first-pass radionuclide ventriculography (RNV). Six dogs were trained prior to a sterile left thoracotomy, where a left atrial catheter was implanted. After recovery of four days RNV was carried out by injecting a bolus of technetium-99m diethylenetriamine pentaacetic acid via the catheter to the left atrium. The data was collected for 12 sec. to a computer by frame rate of 20 frames/sec. from left lateral view of the dog. The experiments were performed both in four-leg standing and in 60-degree head-up tilted positions. After control measurements the data were obtained with 0.5 mg/kg of PRO, 0.45 g/kg of ETH and their combination. The P + E combination increased significantly LV end-diastolic and end-systolic volumes, whereas LV peak ejection rate and ejection fraction were decreased. Upright position diminished the LV volume and increased heart rate, while ejection fraction and cardiac output remained unchanged. The first-pass RNV method proved to be promising for measuring the cardiac pharmacological effects in conscious dogs. The combination of propranolol and ethanol in low doses induced an unexpectedly strong depression of LV function, which is supposed to be followed of latent cardiac depressing effect of ETH revealed by blockade of compensatory adrenergic mechanisms with PRO.

Cardiorespiratory reflex effects induced by intravenous administration of ethanol in rats

Intravenous administration of a bolus of ethanol (40 mg/100 g b.w.) to rats induced bradycardia, hypotension and apnea. Bradycardia was dose dependent (r = -0.78, p less than 0.001). Acute bilateral vagotomy blocked bradycardia and hypotension. Apnea, however, persisted in all cases but was of short duration and occurred after a significant delay as compared to an untreated group. Atropine (0.1 mg/100 g b.w.) and hexamethonium (0.75 mg/100 g b.w.) blocked bradycardia and early hypotension. Pretreatment with reserpine (0.25 mg/100 g b.w. IP 24 and 48 hours before the experiment) significantly increased bradycardia induced by ethanol as compared to untreated animals. In rats pretreated with reserpine and vagotomized, IV ethanol did not induce bradycardia, early hypotension or apnea. A bolus of ethanol (20 mg/100 g b.w.) given directly into the left ventricle did not induce reflex changes in heart rate or respiration, while the same dose of alcohol given IV decreased heart rate by 53 +/- 8.9%. Thus, the ethanol effect seems to be initiated in pulmonary J receptors. Bradycardia appeared to be mediated both by increase in vagal tone, and to a lesser extent, by sympathetic withdrawal. Hypotension was due mainly to bradycardia, and apnea might be caused by a dual mechanism, reflex (early) and direct on the respiratory center (late).

Cardiovascular effects of alcohol with particular reference to the heart

Alcohol has acute and chronic cardiovascular effects. Acutely, alcohol depresses cardiac function and alters regional blood flow. Even when withdrawn from alcohol for several days, alcoholics may still manifest evidence of left ventricular dysfunction. In some alcoholics a severe muscle disorder may ensue with the clinical features of a dilated cardiomyopathy. The concomitant presence of a thiamine deficiency or cirrhosis may produce hemodynamic changes that can obscure the clinical features of alcohol-induced heart muscle disease. Alcoholics may also develop acute myocardial infarction with patent coronary arteries; some may have cardiac arrhythmias even without other evidence of heart disease. Although epidemiological studies suggest that moderate users of alcohol have fewer coronary events than teetotalers, such studies also demonstrate a relation between alcohol abuse and hypertension and an increased occurrence of coronary disease. Thus, the injurious cardiovascular effects of alcohol must be considered when establishing recommendations for its use.

Alcohol and the heart

Acute alcohol ingestion can lead to alterations of either mechanical function or electrophysiologic properties of the heart, whereas chronic consumption can lead to progressive cardiac dysfunction and congestive cardiomyopathy. On the other hand, alcohol appears to have a protective effect for coronary artery disease when consumed in low amounts, although prophylactic use of alcohol is not recommended.

Influence of ethanol on systemic and pulmonary hemodynamics in anesthetized dogs

Immediate circulatory reactions to acute intragastric ethanol administration were studied by a catheterization technique in spontaneously breathing dogs. Diluted ethanol was given in a dosage of 1 g/kg in test group I (n = 11), and 2/kg in group II (n = 10). The control group (m = 14) received only water. The highest blood ethanol concentration was 0.90 +/- 0.07 mg/ml (mean +/- SE) in group I, and 1.97 +/- 0.10 mg/ml in group II. Heart rate and cardiac output increased (p less than 0.,001), but stroke volume, mean aortic blood pressure and right atrial blood pressure remained practically unchanged. Systemic vascular resistance decreased. Mean pulmonary arterial blood pressure increased markedly in both test groups (p less than 0.001) while pulmonary arterial wedge pressure did not change. The pulmonary arterial resistance increased (p less than 0.01). Changes in respiratory rate or volume and arterial pO2 were negligible in group I, but respiratory minute volume decreased in group II. In conclusion, ethanol in concentrations 0.5 to 2.0 mg/ml increased resistance in the pulmonary arterial tree, indicating pulmonary arterial vasoconstriction, but reduced systemic vascular resistance, thus putting a concept of peripheral vasodilation in favour.

Acute effects of ethanol and acetaldehyde on blood pressure and heart rate in disulfiram-treated and control rats

The cardiovascular effects of ethanol and acetaldehyde were studied in control rats and rats pretreated with disulfiram. Ethanol administration to control rats decreased mean blood pressure and increased heart rate significantly. Injection of ethanol to disulfiram-treated rats decreased mean blood pressure, increases pulse pressure and increased heart rate and respiratory rate. The blood acetaldehyde levels were 10-15 times higher than those found in controls. The effects evoked by ethanol in disulfiram-treated rats were prevented or abolished in rats given 4-methylpyrazole before or after ethanol. Heart rate increased with increasing concentrations of acetaldehyde in control rats given acetaldehyde intravenously. Only a slight decrease in mean blood pressure was seen at high acetaldehyde levels (150-250 microM), whereas pulse pressure increased markedly as well as respiratory rate. At acetaldehyde levels lower than 50 microM, no effects on blood pressure were seen. The effects of acetaldehyde infusion in disulfiram-treated rats were similar to those observed in controls having comparable acetaldehyde levels. The results suggest that the disulfiram-ethanol reaction in rats is caused by the combined action of ethanol and acetaldehyde on the cardiovascular system.

Cardiac effects of acute ethanol ingestion unmasked by autonomic blockade

We assessed the effects of ethanol and autonomic blockade on left ventricular function in nine normal subjects, age 20--35 years, 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 intravenous propranolol (0.2 mg/kg body weight) and atropine (0.04 mg/kg body weight). On day two, measurements were again made during a control period, then with ethanol alone, followed by addition of autonomic blockade to ethanol. One hundred eighty milliliters of ethanol were ingested over 60 minutes, resulting in a mean blood ethanol level of 110 mg/dl (range 77--135 mg/dl) at 60 minutes post-ingestion. There were no significant differences between the control data on days 1 and 2. Blood pressure was unchanged throughout the study. study. On day 1, autonomic blockade alone resulted in the expected increase in heart rate (p less than 0.001), with a proportional increase in mean velocity of circumferential fibr shortening (p less than 0.01), and an increase in PEP/LVET (p less than 0.01). On day 2, ethanol alone resulted in no significant changes except for a slight increase in PEP/LVET (p less than 0.02). Ethanol plus autonomic blockade, (day 2), compared with autonomic blockade alone (day 1), revealed a decrease in mean velocity of circumferential fiber shortening (p less than 0.05), and an increase in PEP/LVET (p less than 0.01), with a decrease in intrinsic heart rate (p less than 0.001). We conclude that in normal subjects: 1) autonomic blockade does not directly affect contractility; 2) acute ethanol ingestion alone does not produce important changes in cardiac function; and, 3) ethanol in the autonomic blockaded heart causes a significant decrease in contractility. Thus, we infer that ethanol has a negative inotropic effect which is masked by catecholamines and/or autonomic nervous system discharge.

Ethanol increases rate of isolated atria

Ethanol has a positive chronotropic and negative inotropic effect on isolated spontaneously beating rabbit atria. Both effects increased with increasing ethanol concentrations in the bathing medium. This response is apparently a direct action of ethanol on the myocardium and is not due to the release of catecholamines, acetylcholine, or acetaldehyde produced by the oxidative metabolism of ethanol. Ethanol is one of the few pharmacologic agents having opposite actions on heart rate and force of contraction.

Acute effects of maternal ethanol infusion on fetal cardiac performance

In adult animals and man, both acute and chronic ethanol intake is associated with depression of myocardial performance. Accordingly, the cardiac effects of maternal ethanol infusions, in a manner comparable to common obstetric practice of inhibition of premature labor with ethano mighte for inhibition of premature labor, were evaluated in six chronically instrumented fetal sheep. Fetal and ewe arterial PO2, PCO2, and pH values remained within normal limits with infusion rates of 15 c.c. per kilogram of 10 per cent ethanol over two hours (blood ethanol = 110 mg. per cent) and 15 c.c. per kilogram over one hour (blood ethanol = 210 mg. per cent). Fetal instrument evaluation (for 14 to 30 days after operation) provided data concerning pressures and cardiac dimensions which allowed analysis of left ventricular performance. Ethanol produced a significant depression of the extent (p less than 0.01) and velocity (p less than 0.001) of left ventricular myocardial fiber shortening as well as in the mean rate of left ventricular myocardial fiber shortening as well as in the mean rate of left ventricular circumferential fiber shortening (p less than 0.01). These indices of cardiac contractility were depressed in the absence of changes in end diastolic diameter, left atrial pressure, and systemic arterial pressure. Thus, the practice of inhibition of premature labor with ethano6 might contribute to depressed myocardial performance in the neonatal period.

The basis for differences in ethanol-induced myocardial depression in normal subjects

The acute effects of ethanol (ETOH) on cardiac function in 32 normal subjects has been studied utilizing systolic time intervals. Seven (group I) 13 (group II), and 12 subjects (group III), reported an average daily consumption of less than 1 oz, 1-2 oz, and more than 2 oz of ETOH, respectively. Progressively higher control values from group I to group III in PEP, PEPI, ICT and PET/LVET were observed (PEP-I vs PEPI-III: P smaller than 0.05; PEP/LVET-I vs PEP/LVET-II and PEP/LVET-III: P smaller than 0.05). There was progressively less change in these variables following acute ETOH (P smaller than 0.02-0.05 in group I; P equals NS in group III, group II intermediate). This indicates some degree of chronic myocardial impairment in group II and especially in group III, which tends to be proportionate to the degree of chronic ETOH exposure. These data are not necessarily disparate with previous reports of little or even a salutary hemodynamic effect of ETOH in normal subjects. Thus, the relative stability of LVET post ETOH, coupled with the observed increase in heart rate, is consistent with previous reports of ETOH-induced rate-dependent increments in cardiac output with unchanging stroke volumes, in spite of the presence of acute myocardial depression. The observations reported herein demonstrate the probable incremental influence of ETOH consumption in a chain of events which may culminate in alcoholic cardiomyopathy.

Acute effects of low doses of alcohol on left ventricular function by echocardiography

The ultrasound method for measuring the dimensions of the left ventricle was utilized to study the effect of oral doses of alcohol on left ventricular function in normal volunteers. Systolic time intervals were also measured. Seven subjects received 0.7 g/kg of ethanol (group I) and six subjects recieved 1.15 g/kg (group II). The peak of blood alcohol levels in the two groups were 75 mg/100 ml and 138 mg/100 ml respectively. There was a 6% decrease in the fractional change in the minor axis of the left ventricle in group I patients which resulted in a decrease in ejection fraction (p greater than 0.05). In group II patients, there was a 3% decrease in the fractional change in the minor axis of the left ventricle, but the change of ejection fraction was not significant. Since there was no significant difference between the physiological effects observed in groups I and II, the two groups were combined. In the combined group, at 30 minutes after the ingestion of alchol, the heart rate was increased by 11%, the fractional change in the minor axis of the left ventricle decreased by 6%, the ejection fraction decreased by 4% (p greater than 0.01) and Vcf decreased by 5%. These data suggest that in normal subjects myocardial contractility is depressed following the ingestion of alcohol.