Morbid obesity is accompanied by platelet hyperactivity, leading to thrombotic events including myocardial infarction and stroke. Bariatric surgery is an effective intervention to reduce cardiovascular risk in obesity. However, the effect of bariatric surgery on platelet function is largely unknown. This study investigated the effects of laparoscopic Roux-en-Y gastric bypass (RYGB) and laparoscopic adjustable gastric banding (LAGB) on prothrombotic monocyte-platelet aggregates (MPAs), markers of platelet activation in vivo. MPA were measured in whole blood by flow cytometry before surgery and 1 and 3 months after surgery. In non-obese healthy controls, MPA level is 13 ± 2 %. MPAs are elevated in morbidly obese subjects. RYGB (n = 12 patients) decreases MPAs 1 month after surgery by a weight-independent mechanism (56 ± 6 % presurgically vs 26 ± 8 % at 1 month, p <0.01). LAGB (n = 5 patients) has a smaller weight-dependent effect (49 ± 8 % presurgically vs 32 ± 6 % at 1 month, p > 0.05). Bariatric surgery may reduce thrombotic events by alleviation of platelet overactivity.

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Morbid obesity is accompanied by platelet hyperactivity, leading to thrombotic events such as myocardial infarction and stroke. Platelets are pivotal for development of thrombosis. Bariatric surgery is the most effective intervention to reduce thrombotic events and alleviate type II diabetes in morbidly obese. However, effect of bariatric surgery on platelet function is largely unknown. In this pilot study we compared the short‐term effects of Roux‐en‐ Y Gastric Bypass (RY) and Lap Banding (LB) on prothrombotic monocyte‐platelet aggregates (MPA) that reflect platelet activation in vivo. MPA were measured in whole blood by flow cytometry pre‐ and post‐surgically at 1 and 3 months. In morbidly obese patients, MPA are drastically elevated compared to non‐obese controls. Both RY and LB decreased MPA in blood (unstimulated and stimulated with ADP). However RY alleviated platelet hyperactivity more rapidly (at 1 month post‐op) and more profoundly compared to LB. Bariatric surgery decreased MPA more profoundly in diabetics than in non‐diabetics. There is no correlation between BMI and decreased platelet activation after RY, but there is strong correlation after LB. Decreased MPA also correlates with decreased IL‐6 post‐surgically. Thus gastric bypass is more efficacious than gastric banding to reduce platelet hyperactivity in morbid obesity leading to a reduction in thrombotic events.

Bariatric surgery is the most effective treatment to alleviate morbid obesity and its comorbidities, such as type 2 diabetes. Platelets are crucial for the development of thrombosis that often accompanies obesity and diabetes. Hypothesis: bariatric surgery attenuates platelet activation therefore decreasing thrombosis risk. Objective: to determine the effect of bariatric surgery on platelet function in morbidly obese diabetics and non‐diabetics, and compare two types of surgery, Roux‐en‐Y Gastric Bypass (RY) and Lap Banding (LB). Prothrombotic platelet‐monocyte aggregates (PMA) and P‐selectin/PAC‐1 expression on platelets were evaluated pre‐and post‐surgically in whole blood by flow cytometry. In morbidly obese patients, PMA are drastically elevated compared to non‐obese controls. Bariatric surgery decreased platelet activation in all patients. PMA levels (baseline and ADP‐stimulated) decreased early at 1 month after surgery. More significant decrease was in diabetics and after RY. P‐selectin/PAC‐1 expression in ADP‐stimulated blood decreased later at 3 months after surgery. There is no correlation between weight loss and decreased platelet activation after RY, but they do correlate after LB. Therefore gastric bypass appears to be more rapid and efficacious than gastric banding in reducing platelet hyperactivity and alleviating thrombosis risk associated with morbid obesity.