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Background: Morbid obesity is associated with multiple comorbidities, particularly hypertension, diabetes mellitus, and hyperlipidemia which are the known risk factors for Myocardial Infarction (MI).Objective: Our aim was to identify factors associated with an increased likelihood of developing MI after bariatric surgery.Methods: Using the Nationwide Inpatient Sample (NIS) database, clinical data of patients who underwent bariatric surgery from 2006-2008 was examined. Regression analysis was performed to evaluate effect of patient characteristics (age, sex and race), comorbidities, payer-type and surgical techniques (open vs. laparoscopy and gastric bypass vs. non-gastric bypass) on post-operative MI in bariatric surgery.Result: A total of 304,515 patients underwent bariatric surgery during these three years. The majority of patients were female (80%) and Caucasian (74%). The mean age was 44.1 and 31.7% were older than 50 years. The incidence of comorbidities were high as expected: hypertension (HTN, 54.5%), diabetes mellitus (DM, 29.7%), hyperlipidemia (20.1%), chronic lung disease (18.3%), sleep apnea (15.7%), smoking (13.2%), liver disease (8.9%), congestive heart failure (CHF: 1.3%), renal failure (0.8%), peripheral vascular disease (PVD, 0.5%) and alcohol abuse (0.2%) respectively. The most common payer-type was private including HMO (73.5%). 52.75% of procedures were performed in the academic medical centers.Overall prevalence of MI was 0.20% (612 patients). MI was significantly higher in open procedures compare to laparoscopic procedures (0.32% vs. 0.18%; P<0.001). The prevalence of MI was significantly lower in Non-Gastric bypass compare to Gastric bypass surgery (0.17% vs. 0.21%; P=0.044).Using multivariate regression analysis, age older than 50 [odds ratio (OR): 2.27], male sex (OR:1.62), congestive heart failure (OR:5.38), hypertension (OR: 2.34), chronic lung disease (OR: 2.23), smoking (OR:1.61), hyperlipidemia (OR: 1.43), sleep apnea (1.74%), gastric bypass (OR:1.37) and academic medical center (OR:1.28) were associated with higher MI rate. There was no effect of race, diabetes, liver disease, renal failure, peripheral vascular disease, alcohol abuse and payer-type on MI.Conclusion: Age over 50, male sex, smoking, CHF, hypertention, chronic lung disease, hyperlipidemia and gastric bypass surgery all increase the risk of postoperative myocardial infarction in patients undergoing weight loss surgery. Surgeons should be aware of these risk factors when selecting patients for surgery and further preoperative screening and pre-treatment may be needed in this subset of high-risk patients