The following sections will explore the pathophysiology of the biphasic effects of alcohol on the cardiovascular system, detailing both its acute and chronic impacts. These include the transient arrhythmogenic “Holiday Heart” phenomenon, the progressive development of ACM, and the roles of alcohol in AF, hypertension, CAD, and DM (Central Illustration).

Alcohol exerts a biphasic effect on cardiovascular health, with moderate intake potentially offering cardioprotective effects, while excessive consumption induces pathophysiological changes that increase cardiovascular risk ( Figure 1 ). The guidelines from the World Health Organization (WHO) on standard drink assume 1 standard drink to be 10 g of pure ethanol. Alcohol consumption has been defined as: light (<7 standard drinks/week); moderate (7 to 21 standard drinks/week); and heavy (>21 standard drinks/week), where 1 standard drink is approximately 12 g of alcohol. Moderate and light consumption has been associated with improved lipid profiles, increased high-density lipoprotein (HDL) levels, and enhanced endothelial function, contributing to reduced cardiovascular mortality in populations that confer cardioprotective benefits from moderate alcohol consumption and reduced cardiovascular mortality. However, these benefits are dose-dependent and rapidly diminish with higher intake.

Pathophysiological effects of excessive alcohol consumption in the CV system.

Heavy alcohol consumption or acute binge drinking episodes, initiates a cascade of deleterious cellular and molecular processes within the cardiovascular system. Ethanol is primarily metabolized in the liver, where it is converted to acetaldehyde, generating a highly reactive intermediate that damages cellular proteins, lipids, and DNA. Additionally, alcohol metabolism impairs mitochondrial function, leading to the accumulation of reactive oxygen species within cardiomyocytes, thereby inducing oxidative stress and compromising ATP production necessary for myocardial contractility.

Excessive alcohol intake also promotes systemic inflammation through the release of proinflammatory cytokines and chemokines, which contribute to endothelial dysfunction characterized by reduced nitric oxide bioavailability and increased vascular tone, facilitating the development of hypertension and atherosclerosis. Furthermore, chronic alcohol consumption disrupts neurohormonal balance by stimulating the renin-angiotensin-aldosterone system and the sympathetic nervous system, leading to vasoconstriction, sodium retention, and volume overload, which further exacerbate hypertension and contribute to adverse cardiac remodeling. ^,

In the context of ACM, persistent oxidative stress damages cardiomyocytes through lipid peroxidation and mitochondrial dysfunction, resulting in cellular apoptosis, cardiac fibrosis, and ventricular desynchrony, ultimately impairing myocardial contractility. ^, Together, these oxidative, inflammatory, and neurohormonal mechanisms underlie the transition from moderate consumption’s potential protective effects to the cardiovascular pathology observed with excessive alcohol intake, emphasizing the importance of dose in determining alcohol’s impact on cardiovascular health.

Holiday heart syndrome (HHS) refers to the occurrence of alcohol-induced atrial arrhythmias, particularly AF, in individuals without underlying structural heart disease, typically following episodes of heavy drinking during weekends or holiday periods. First described in 1978, HHS highlights the arrhythmogenic potential of acute alcohol ingestion.

Pathophysiologically, alcohol’s arrhythmogenicity in HHS is multifactorial, involving direct electrophysiological changes within the atria, autonomic dysregulation, and transient structural alterations. Alcohol acutely alters ion channel function, leading to shortened atrial effective refractory periods (ERP) and impaired cardiomyocyte repolarization. A 2021 single-center, randomized, double-blinded trial of intravenous alcohol versus placebo among patients undergoing pulmonary vein isolation procedures with 100 patients demonstrated that acute alcohol infusion significantly decreased the effective refractory period in the pulmonary veins compared to controls. Secondary analysis revealed a notable reduction in the JTc interval on electrocardiographic measurements, indicating disrupted repolarization and an increased propensity for re-entrant arrhythmias.

Acute alcohol ingestion also impacts atrial mechanical function. In an observational study involving 50 participants who engaged in binge drinking, patients underwent serial cardiac MRI pre and postbinge with continuous Holter monitoring. Time periods analyzed included baseline (24 h prebinge), consumption, hangover (0 to 24 h postconsumption) and posthangover (24 to 48 h postconsumption). A decrease in left atrial emptying fraction (57.9% ± 8.5% to 53.5% ± 6.7%; p = 0.003) was noted, suggesting transient atrial dysfunction that may facilitate the maintenance of AF. Additionally, acute alcohol exposure induces autonomic imbalance characterized by increased sympathetic activity and reduced vagal tone, creating a substrate conducive to arrhythmogenesis.

Volume shifts and electrolyte imbalances, including hypokalemia and hypomagnesemia often associated with alcohol intake, further contribute to the proarrhythmic environment. These alterations can disrupt normal cardiac conduction pathways, lowering the threshold for AF initiation during periods of acute alcohol exposure.

Epidemiological evidence further supports the association between alcohol intake and atrial arrhythmias. McManus et al, in a cohort study evaluating 5,220 participants, found that each additional 10 grams of daily alcohol intake correlated with a 0.16 mm increase in left atrial diameter and a 5% increase in the risk of incident AF. Additionally, a prospective study utilizing continuous ECG monitoring among 100 participants demonstrated a clear, quantifiable dose-dependent relationship between alcohol consumption and the likelihood of AF episodes, underscoring alcohol’s acute arrhythmogenic potential.

The exact mechanism behind HHS is still not completely understood, but researchers propose that alcohol consumption leads to the phosphorylation of c-Jun N-terminal kinase (JNK2). ^, Once activated, JNK2 leads to further phosphorylation of Calmodulin kinase II (CaMKII). Consequently, this event contributes to the sarcoplasmic reticulum Ca2+ leakage, diastolic calcium waves, and greater vulnerability to induce paroxysmal AF. ^,

Collectively, these findings emphasize that alcohol facilitates the development of atrial arrhythmias through a complex interplay of electrophysiological alterations, autonomic dysregulation, transient atrial dysfunction, and volume and electrolyte imbalances. Given the high prevalence of binge drinking behaviors, understanding these mechanisms underlying HHS is crucial for the prevention and management of alcohol-induced AF in clinical practice.

ACM is a form of dilated cardiomyopathy characterized by ventricular dilation and impaired contractile function secondary to chronic alcohol consumption in the absence of other identifiable causes of cardiac dysfunction. The amount of alcohol required to produce AC is generally considered as >80 g/day over 5 years, but there is still controversy regarding this definition.

The clinical presentation of ACM mirrors that of chronic heart failure, including exertional dyspnea, fatigue, and peripheral edema, reflecting the progressive nature of alcohol-induced myocardial dysfunction. The pathophysiology of chronic alcohol exposure exerts cardiotoxic effects through multiple mechanisms, including mitochondrial dysfunction, oxidative stress, apoptosis, and dysregulation of calcium homeostasis within cardiomyocytes. Ethanol metabolism leads to the generation of reactive oxygen species, which overwhelm the myocardium’s antioxidant defenses, resulting in lipid peroxidation, protein oxidation, and mitochondrial DNA damage. These oxidative injuries disrupt mitochondrial integrity and function, impairing ATP synthesis critical for myocardial contractility and leading to cellular apoptosis and necrosis.

Additionally, chronic alcohol intake impairs calcium handling within cardiomyocytes, disrupting excitation-contraction coupling and contributing to impaired systolic and diastolic function. Dysregulation of intracellular calcium levels can lead to arrhythmias and further exacerbate myocardial dysfunction.

Emerging evidence suggests that genetic predisposition significantly modifies individual susceptibility to ACM. Truncating variants in the titin (TTN) gene, a well-established risk factor for dilated cardiomyopathy, have also been implicated in ACM. In carriers of TTN truncating variants, heavy alcohol use appears to unmask or accelerate disease expression, suggesting that alcohol exposure and genetic background act synergistically to promote myocardial injury. In addition, polymorphisms in alcohol dehydrogenase genes, which influence the rate of alcohol metabolism and accumulation of toxic metabolites such as acetaldehyde, may further modulate vulnerability to cardiotoxic effects. Other candidate genetic factors are under investigation, highlighting the complex interplay between environmental exposures and inherited susceptibility in the development of ACM.

Advanced imaging studies have demonstrated that individuals with a history of chronic excessive alcohol intake exhibit adverse cardiac remodeling, including lower biventricular ejection fractions, increased dilation of the ventricles and atria, and increased left ventricular hypertrophy. These structural changes reflect the myocardium’s adaptive yet pathological response to chronic injury, ultimately leading to reduced cardiac output and symptomatic heart failure.

Alcohol affects systolic function both acutely and chronically, particularly in the development and progression of ACM. In patients with ACM or chronic heavy alcohol use, acute alcohol ingestion can cause a transient but significant worsening of left ventricular systolic function. Even a single binge episode may lead to acute reductions in LVEF, stroke volume, and contractile reserve, superimposed on an already impaired myocardium. ^, Mechanistically, this acute decline is thought to result from direct myocardial depression, mitochondrial dysfunction, impaired calcium handling, and exacerbated autonomic imbalance. Understanding these underlying mechanisms is critical for the early identification and management of ACM to prevent progression to end-stage heart failure in individuals with both acute chronic alcohol use.

Alcohol consumption significantly influences the development and progression of AF and hypertension, acting as both an acute trigger and a chronic contributor to these cardiovascular conditions. Acute alcohol intake, particularly during binge drinking episodes, can precipitate AF by directly affecting atrial electrophysiology, shortening atrial effective refractory periods, and promoting early afterdepolarizations, thereby creating a substrate for arrhythmogenesis.

Chronic alcohol exposure further compounds this risk by inducing structural and electrical remodeling of the atria. Prolonged intake leads to atrial fibrosis, enlargement, and conduction heterogeneity, increasing susceptibility to AF. Alcohol-induced oxidative stress within atrial myocytes impairs ion channel function and calcium homeostasis, while autonomic imbalance characterized by heightened sympathetic activity and reduced vagal tone contributes to atrial electrical instability, collectively fostering the development and maintenance of AF.

In addition to its effects on atrial electrophysiology, alcohol consumption plays a multifaceted role in the pathogenesis of hypertension. Although moderate alcohol intake may transiently lower blood pressure due to vasodilatory effects, excessive consumption, particularly in binge patterns, acutely raises blood pressure and can precipitate hypertensive crises. Chronically, alcohol consumption contributes to sustained hypertension through several mechanisms: increased sympathetic nervous system activity, activation of the renin-angiotensin-aldosterone system, oxidative stress-induced endothelial dysfunction, sodium and water retention, and the promotion of vascular inflammation.

These mechanisms synergistically contribute to increased systemic vascular resistance and impaired baroreceptor sensitivity, leading to persistent elevations in blood pressure. Moreover, chronic hypertension induces left ventricular hypertrophy and diastolic dysfunction, which can further exacerbate atrial remodeling and predispose individuals to AF, creating a vicious cycle of cardiovascular risk.

The interplay between alcohol consumption, AF, and hypertension underscores the heightened risk of adverse cardiovascular outcomes, including stroke, heart failure, and myocardial infarction, in individuals with excessive alcohol intake. ^, Understanding the direct electrophysiological effects of alcohol on the atria and its indirect contributions to hypertension is crucial for risk stratification and individualized patient management. In clinical practice, encouraging moderation in alcohol consumption and avoiding binge drinking are essential components in managing both acute triggers and chronic contributors to AF and hypertension, aiming to reduce alcohol-related cardiovascular morbidity.

Chronic heavy alcohol consumption induces dyslipidemia characterized by elevated triglyceriderich remnant lipoproteins, increased oxidation of low-density lipoprotein (LDL) particles, and reduced levels of protective high-density lipoprotein (HDL) cholesterol. ^,,, Oxidized low-density lipoprotein (LDL) promotes the differentiation of monocytes into macrophages, which engulf these lipoproteins to form foam cells, initiating fatty streak formation and progression to atherosclerotic plaques within the coronary arteries. Alcohol also disrupts vascular endothelial integrity, causing endothelial dysfunction and reducing nitric oxide bioavailability, which leads to increased vascular tone, elevated blood pressure, and exacerbation of CAD. ^,, This endothelial injury further facilitates infiltration of inflammatory cells into the arterial wall. Additionally, ethanol enhances circulating thrombogenic factors, such as fibrinogen and von Willebrand factor, increasing the risk of thrombus formation.

Heavy alcohol intake fosters a proinflammatory state by stimulating oxidative stress and promoting the release of cytokines, including interleukin-6 and tumor necrosis factor-alpha. ^, These inflammatory mediators activate vascular smooth muscle cells, inducing their migration and proliferation within the arterial intima, contributing to the development of the fibrous cap characteristic of advanced atherosclerotic plaques. ^,, Alcohol also impairs fibrinolysis and increases platelet aggregation, further elevating the risk of thrombotic cardiovascular events. Collectively, these multifaceted effects accelerate the atherogenic process.

Regarding type 2 diabetes mellitus (T2DM), alcohol impairs pancreatic β-cell insulin secretion through mechanisms involving oxidative stress and direct cytotoxicity to islet cells. The resulting chronic hyperglycemia promotes nonenzymatic glycation reactions between reducing sugars and arterial wall proteins, forming advanced glycation end-products that exacerbate atherosclerosis by altering macrophage function and vascular smooth muscle signaling. ^,, Moreover, alcohol metabolism generates reactive oxygen species and lipid peroxidation products that contribute to insulin resistance in peripheral tissues. Alcohol-induced dysregulation of adipokines, such as leptin and adiponectin, further disrupts glucose and lipid homeostasis. Heavy drinking is also associated with increased visceral adiposity, which promotes secretion of inflammatory cytokines that aggravate insulin resistance.

Ultimately, through direct pancreatic toxicity, induction of chronic hyperglycemia and insulin resistance, and modulation of obesity-related inflammation, excessive alcohol consumption precipitates the development and progression of Regarding type 2 diabetes mellitus (T2DM). This metabolic derangement synergistically accelerates atherosclerotic CAD, as both conditions are intimately linked through alcohol’s disruptive effects on glucose and lipid metabolism.