How does autonomic dysfunction from Alcohol Use Disorder (AUD) cause tachycardia?

From the Guidelines

Autonomic dysfunction from alcohol use disorder causes tachycardia primarily through the disruption of the normal balance between the sympathetic and parasympathetic nervous systems, leading to increased sympathetic activity and decreased parasympathetic tone. This imbalance results in a persistent elevation in heart rate, as chronic alcohol consumption damages the autonomic nervous system, affecting its ability to regulate heart rate appropriately 1.

Key Mechanisms

• Decreased parasympathetic (vagal) tone, which normally slows heart rate
• Increased sympathetic nervous system activity, leading to a surge in catecholamines like norepinephrine and epinephrine
• Impaired baroreceptor sensitivity, affecting the body's ability to regulate blood pressure and heart rate
• Nutritional deficiencies, particularly thiamine deficiency, damaging cardiac tissue and autonomic nerves
• Electrolyte imbalances, such as magnesium and potassium depletion, further destabilizing cardiac rhythm

Clinical Implications

Alcohol withdrawal syndrome intensifies the effect of autonomic dysfunction on heart rate, as the body experiences a surge in catecholamines when alcohol is removed, further driving tachycardia 1. The Clinical Institute Withdrawal Assessment for Alcohol (CIWA-Ar) is useful in evaluating the severity of alcohol withdrawal syndrome, with a score >8 indicating moderate AWS and a score ≥15 indicating severe AWS 1.

Treatment Approach

Treatment typically involves alcohol cessation with appropriate medical supervision, correction of nutritional deficiencies, and sometimes beta-blockers like propranolol to manage tachycardia during withdrawal. Benzodiazepines, such as diazepam and chlordiazepoxide, are considered the 'gold standard' treatment for AWS, given their efficacy in reducing withdrawal symptoms and the risk of seizures and/or delirium tremens 1.

From the Research

Autonomic Dysfunction and Tachycardia in Alcohol Use Disorder

• Autonomic dysfunction is a known consequence of chronic and excessive alcohol consumption, affecting 16-73% of chronic alcohol abusers 2.
• The most important risk factor for autonomic dysfunction in alcohol use disorder is the total lifetime dose of ethanol 2.
• Autonomic dysfunction can lead to various symptoms, including erectile dysfunction and postural dizziness, with the most sensitive variables being heart rate variation at rest and postural pulse reaction 3.
• Tachycardia can be a symptom of autonomic dysfunction, as the parasympathetic division of the autonomic nervous system is affected, leading to an imbalance in heart rate regulation 3.
• The use of beta blockers, such as atenolol, has been shown to be helpful in the treatment of patients with alcohol withdrawal syndrome, including reducing the severity of tachycardia 4.
• Abstinence from alcohol appears to lead to significant improvement in autonomic investigations, including heart rate variability and other symptoms of autonomic dysfunction 2.

Mechanisms of Autonomic Dysfunction in Alcohol Use Disorder

• Chronic alcohol consumption can lead to overactivity of the central and autonomic nervous systems, resulting in tremors, insomnia, nausea and vomiting, hallucinations, anxiety, and agitation 5.
• The parasympathetic division of the autonomic nervous system is particularly affected, leading to decreased heart rate variation and other symptoms of autonomic dysfunction 3.
• The sympathetic nervous system may also be affected, although the evidence is less clear, with some studies suggesting that sympathetic function is not abnormal in alcoholics 3.

Treatment and Management of Autonomic Dysfunction in Alcohol Use Disorder

• Beta blockers, such as atenolol, may be useful in the treatment of patients with alcohol withdrawal syndrome, including reducing the severity of tachycardia 4.
• Abstinence from alcohol is the most effective management strategy for autonomic dysfunction, leading to significant improvement in autonomic investigations 2.
• Other treatments, such as carbamazepine and gabapentin, may also be useful in managing symptoms of autonomic dysfunction, although the evidence is less clear 5.