Deficient slowing of the heart among very heavy social drinkers

Heart rate variability biofeedback in patients with alcohol dependence: a randomized controlled study

BACKGROUND AND OBJECTIVE

In patients with alcohol dependence, ethyl-toxic damage of vasomotor and cardiac autonomic nerve fibers leads to autonomic imbalance with neurovascular and cardiac dysfunction, the latter resulting in reduced heart rate variability (HRV). Autonomic imbalance is linked to increased craving and cardiovascular mortality. In this study, we sought to assess the effects of HRV biofeedback training on HRV, vasomotor function, craving, and anxiety.

METHODS

We conducted a randomized controlled study in 48 patients (14 females, ages 25-59 years) undergoing inpatient rehabilitation treatment. In the treatment group, patients (n=24) attended six sessions of HRV biofeedback over 2 weeks in addition to standard rehabilitative care, whereas, in the control group, subjects received standard care only. Psychometric testing for craving (Obsessive Compulsive Drinking Scale), anxiety (Symptom Checklist-90-Revised), HRV assessment using coefficient of variation of R-R intervals (CVNN) analysis, and vasomotor function assessment using laser Doppler flowmetry were performed at baseline, immediately after completion of treatment or control period, and 3 and 6 weeks afterward (follow-ups 1 and 2).

RESULTS

Psychometric testing showed decreased craving in the biofeedback group immediately postintervention (OCDS scores: 8.6±7.9 post-biofeedback versus 13.7±11.0 baseline [mean ± standard deviation], P<0.05), whereas craving was unchanged at this time point in the control group. Anxiety was reduced at follow-ups 1 and 2 post-biofeedback, but was unchanged in the control group (P<0.05). Following biofeedback, CVNN tended to be increased (10.3%±2.8% post-biofeedback, 10.1%±3.5% follow-up 1, 10.1%±2.9% follow-up 2 versus 9.7%±3.6% baseline; P=not significant). There was no such trend in the control group. Vasomotor function assessed using the mean duration to 50% vasoconstriction of cutaneous vessels after deep inspiration was improved following biofeedback immediately postintervention and was unchanged in the control group (P<0.05).

CONCLUSION

Our data indicate that HRV biofeedback might be useful to decrease anxiety, increase HRV, and improve vasomotor function in patients with alcohol dependence when complementing standard rehabilitative inpatient care.

Role of parasympathetic (vagal) cardiac control in elevated heart rates of smokers

Smokers may develop chronic increases in cardiac rate and alterations in cardiovascular control. If the increased mean heart rate (HR) in cigarette smokers is due in part to a deficit in vagal cardiac rate control, this should be reflected in a decreased amplitude of respiratory sinus arrhythmia (RSA). To test this hypothesis we studied 36 smokers and 36 non-smokers, matched for age, race, gender and blood pressure. All subjects were studied in the supine and seated positions. Mean heart rate was determined from the ECG during 30 s of quiet breathing; RSA was determined for 10 consecutive deep (>50% vital capacity) slow (5-7/min) breaths. Mean HRs in smokers were significantly higher than in non-smokers, but the increases in mean HRs evoked by a shift from the supine to seated position were lower in smokers than in non-smokers, suggesting that chronic tobacco use may alter the relative contributions of sympathetic and parasympathetic control of cardiac rate. Because neither the RSAs nor the position-dependent increase in RSA were different between smokers and non-smokers, we conclude that the elevated mean HRs in smokers were not the result of decreased respiratory or vasomotor modulation of vagal cardiac control, but instead were the result primarily of sympathetic stimulation.

Impaired autonomic nervous system in alcoholics assessed by heart rate variation

The suppression of heart rate variation reflects cardiac autonomic nervous dysfunction and is known to be associated with a poor prognosis or sudden death in diabetic patients. We investigated consecutive changes in the heart rate variation in 51 alcoholics using the coefficient of variation of R-R interval (CVRR). To correct for age effects, a ratio of CVRR to the standard predicted value (CVP) was calculated. On the whole, CVRR/CVP was suppressed on admission and on the 7th day of abstinence and increased on the 30th day. However, alcoholics could be divided into two groups by their CVRR/CVP on the 30th day: one group with transient autonomic dysfunction whose CVRR/CVP was more than 0.8 (n = 32), and the other group with persistent autonomic dysfunction whose CVRR/CVP was less than 0.8 (n = 19). Withdrawal hypertension occurred more frequently (63% vs. 19%) and mean systolic pressure (159 +/- 24 mmHg vs. 138 +/- 17 mmHg) was higher in the latter group than in the former, suggesting that persistent autonomic damage might, at least in part, contribute to withdrawal hypertension. To investigate further the relationship between the persistent autonomic damage and other complications, the CVRR/CVP on the 30th day of abstinence was analyzed in an additional 85 alcoholics (total n = 136). Persistent suppression of the CVRR/CVP was more frequently found in alcoholics with leg paresthesia (64%, n = 22), the Wernicke-Korsakoff syndrome (73%, n = 11), or diabetes mellitus (69%, n = 68), than in alcoholics without these complications (31%, n = 35).(ABSTRACT TRUNCATED AT 250 WORDS)

Mortality in alcoholics with autonomic neuropathy

Seventy-nine male chronic alcoholics who had been tested for autonomic neuropathy using four tests of vagus nerve function were followed for up to 7 years (mean 5.5 years). Thirty-two subjects had no vagal neuropathy, 25 had one abnormal test and 22 had two or more abnormal vagal function tests and two of these also had orthostatic hypotension. There were no differences between the reported alcohol consumptions and evidence of central or peripheral nerve or liver damage between the three groups. Twelve patients died during the follow-up period. At 7 years the percentage survival for the subjects with no evidence of vagal neuropathy was 91%, with one abnormal test it was 66% and with two or more abnormal tests it was 79%. The expected percentage survival for each of the group was 94%, 91% and 88% respectively. The results suggest that evidence of vagal neuropathy in chronic alcoholics is associated with a significantly higher mortality than in the general population and that deaths due to cardiovascular disease are a major cause.

The effects of acute and chronic ingestion of ethanol on the autonomic nervous system

Evidence is reviewed linking clinical effects of ethanol with actions on the sympathetic and parasympathetic nervous systems. The studies reported include a series of investigations by the authors. Acutely, ethanol causes peripheral vasodilation and may also result in changes in heart rate and blood pressure. Ethanol may contribute to acute problems which may present clinically, including micturition syncope, accidental hypothermia and facial flushing. However, increased sympathetic nervous activity plays a role in causing hypertension and other symptoms during ethanol withdrawal in chronic alcoholics. Some chronic alcoholics may have neuropathy involving sympathetic nerves, and this can result in distal sweating loss and occasionally in orthostatic hypotension. Also, hypothalamic lesions associated with Wernicke's encephalopathy may result in hypothermia. Neuropathy involving parasympathetic nerves in not uncommon in alcoholics with other evidence of nervous system damage, but it is generally asymptomatic. Occasionally, vagal neuropathy may cause disorder of gastrointestinal motility, and neuropathy affecting the sacral innervation may be a factor in alcoholic impotence.