The Obesity Paradox in Major Adverse Cardiovascular Events After PCI for Acute Coronary Syndrome: A Narrative Review

Obesity is increasing worldwide and remains a major contributor to cardiovascular morbidity and mortality. It is strongly associated with hypertension, dyslipidemia, diabetes mellitus, endothelial dysfunction, and chronic inflammation, all of which promote coronary artery disease and acute coronary syndrome (ACS). Despite this well-established risk profile, multiple studies have described an "obesity paradox," suggesting that obese patients may experience better outcomes after percutaneous coronary intervention (PCI) for ACS than normal-weight individuals.

This narrative review aims to discuss the pathophysiological basis of the obesity paradox and to synthesize contemporary evidence regarding the relationship between body mass index (BMI), major adverse cardiovascular events (MACE), and mortality after PCI in patients presenting with ACS.

Contemporary observational cohorts consistently suggest a non-linear relationship between BMI and MACE outcomes after PCI. Overweight and mildly obese patients often demonstrate lower crude mortality and fewer MACE, whereas underweight patients consistently show the poorest prognosis. However, after adjustment for age, left ventricular ejection fraction (LVEF), renal function, frailty, and nutritional status, obesity is less consistently associated with improved outcomes. Overweight status appears to be more reproducibly associated with better prognosis than obesity itself.

The obesity paradox is likely driven less by a true protective effect of excess adiposity and more by younger age at presentation, preserved physiological reserve, lower frailty burden, and the limitations of BMI as a marker of cardiovascular risk. Underweight status emerges as the strongest predictor of adverse outcomes. Nutritional assessment and body composition should complement BMI in risk stratification after ACS.