Purpose

Obesity is a well-known risk factor for adverse cardiovascular events, but some studies suggest higher body mass index (BMI) is associated with better outcomes after ST-segment elevation myocardial infarction (STEMI). We sought to determine the effect of body surface area (BSA) on adverse events after primary percutaneous coronary intervention (PCI) for STEMI and how this relates to the reported obesity paradox theory.

Methods

We analyzed a prospective registry of patients with STEMI who underwent primary PCI at a tertiary care hospital from 2003 to 2009. Post-PCI complications and 1-year all-cause mortality were compared across BSA quartiles. Relationship with 1-year mortality was compared between BSA and BMI using logistic regression.

Results

Of 2,195 study patients (31.5% women), mean BSA and BMI were 2.0 ± 0.3 m2 and 29.2 ± 6.2 kg/m2, respectively. The 1-year all-cause mortality from the lowest to highest quartiles of BSA was 11.0%, 6.5%, 5.5% and 5.1%, Ptrend<0.0001. Over a mean 5-year follow-up, there was a 76% relative risk reduction in death for each 1 m2 increase in BSA. Higher BSA was associated with lower incidence of cardiogenic shock, acute renal failure, coronary dissection and vascular and bleeding complications post-PCI. In multivariate analysis, BSA remained strongly predictive of 1-year mortality (odds ratio 0.4 per m2 of BSA, 95% confidence interval 0.15–0.9), but BMI showed no independent association with mortality (odds ratio 0.99, 95% confidence interval 0.95–1.04).

Conclusions

In STEMI patients undergoing primary PCI, high BSA is associated with lower mortality and complication rates. BMI is not independently associated with 1-year mortality after adjusting for BSA and sex.