Contrary to the popular notion that moderate alcohol consumption is good for the heart, an Australian study shows that even modest levels of drinking has deleterious effects on atrial function.
Using cardiac MRI images, cardiologists in Melbourne found that regular alcohol intake at even modest doses was associated with adverse left atrial mechanical remodelling, predisposing drinkers to AF recurrence and stroke.
Dr Peter Kistler and colleagues enrolled 160 patients with paroxysmal or persistent AF to undergo 3-T cardiac MRI in sinus rhythm. Patients were categorised according to self-reported alcohol consumption over the preceding 12 months as either lifelong nondrinkers; mild drinkers (3 to 10 standard drinks/week); moderate drinkers (11 to 20 standard drinks/week) or heavy drinkers (>20 standard drinks/week).
They found that regular consumption of mild to moderate levels of alcohol (mean 16 standard drinks/week in the previous year) was associated with larger left atrial size compared to non drinkers (LA volume index 50 vs. 43ml/m2).
Regular drinkers also showed reductions in left atrial ejection fraction (LAEF, 40% vs 52%), and reservoir function (77% vs. 119%) compared with teetotallers.
There were also progressive dose-related impairments in LAEF seen with increasing levels of alcohol consumption (mild 45.4% vs. moderate 39.1% vs heavy drinkers 35.6%) and reservoir function (mild 95.8% vs moderate 74.8% vs. heavy drinkers 61.7%).
Predictors of atrial mechanical dysfunction included weekly alcohol intake, older age and persistent AF, but not binge drinking or beverage type.
Lead study investigator study authors led by Dr Aleksandr Voskoboinik, a cardiologist at the Royal Melbourne Hospital said the findings helped explain why long-term habitual alcohol consumption is increasingly being recognised as a risk factor for incident AF, even at levels as low as one standard drink per day.
While it had long been believed that binge drinking was a factor in precipitating AF (the so called ‘holiday heart syndrome’) the new findings also showed that chronic consumption of low levels of alcohol might have “direct myopathic and fibrotic effects on the thinner-walled atria,” they wrote.
“The deleterious downstream structural effects of heavy alcohol consumption on the ventricle are well established; however, low to moderate alcohol intake is generally considered cardioprotective in patients with dyslipidaemia and coronary disease. The impacts of alcohol on the atrium are only beginning to emerge.”
The cardiotoxic effects of alcohol on the atria might be mediated via several mechanisms including inflammation, oxidative stress, apoptosis, mitochondrial dysfunction, deranged fatty acid metabolism, and accelerated protein degradation.
They also noted that reducing alcohol consumption to less than three standard drinks per week had been shown to reduce AF recurrence rates.
The findings are published in JACC: Clinical Electrophysiology.