NEW ORLEANS — An obesity paradox applies in non-ST-segment-elevation MI, such that being overweight or obese is associated with a strikingly lower in-hospital mortality than being lean, R. Scott Wright, M.D., said at the annual scientific sessions of the American Heart Association.
The explanation for this phenomenon remains unclear. So do its long-term implications. “I would caution that the obesity paradox is in fact probably not benign, that it's perhaps a predictor of patients who'll present again later and may in fact have increased long-term mortality risk rather than simply lower short-term risks,” said Dr. Wright of the Mayo Clinic, Rochester, Minn.
He decided to take a more comprehensive look at the obesity paradox, this time in patients with NSTEMI, a population not previously examined. He did so using the National Registry of Myocardial Infarction-4 (NRMI-4) database, the largest, most comprehensive registry of MI patients in the United States. He reported on 280,341 patients with NSTEMI, of whom 44.6% were obese.
In-hospital mortality in the obese NSTEMI patients was half that in the 25.8% of the NRMI-4 cohort who were lean, while overweight patients had an intermediate mortality rate. Obese patients with NSTEMI also had significantly lower rates of new-onset atrial fibrillation and heart failure, although their in-hospital recurrent MI rate didn't differ from that of lean patients.
Dr. Wright offered several possible explanations. Perhaps the most compelling was patient age. Advanced age is one of the strongest predictors of poor outcome in acute MI. At a mean age of 65.5 years, obese NSTEMI patients were a full decade younger on average than lean ones.
Also, obese patients tended to present with NSTEMIs having lower-risk features, as reflected in their TIMI risk scores. The prevalence of a high TIMI risk score was only 28.5% in obese patients, compared with 35.4% in overweight and 51.4% in lean patients. Moreover, obese patients in this large registry were more likely than overweight or lean patients to receive appropriate aggressive therapies for their NSTEMI. They had higher rates of utilization of ACE inhibitors, β-blockers, glycoprotein IIb/IIIa inhibitors, and other drugs.
The coronary revascularization rate was 42.4% in obese patients, 39.7% in overweight ones, and only 24.2% in lean patients, which could be yet another key factor in the reduced short-term mortality in the obese, Dr. Wright observed.