Vasoreactivity is rapidly improved in obese subjects after gastric bypass surgery

Obesity is associated with increased risk of cardiovascular disease. We investigated vasoreactivity in conduit and resistance arteries in morbidly obese subjects, and the effect of weight loss after gastric bypass surgery.

A total of 19 obese subjects (body mass index (BMI): 43.8+/-3.1 kg m(-2), 75% female, mean age 41 years) were investigated before surgery and after 1 and 12 months of surgery. Nineteen non-obese controls matched for age and gender were examined. Vasoreactivity was evaluated by ultrasound to measure flow-mediated dilation (FMD, evaluating a conduit vessel) and pulse-wave analysis with terbutaline provocation (change in reflectance index (RI), evaluating resistance vessels).

Before surgery, the obese showed a low change in RI (18+/-12 vs 37+/-15% in controls, P=0.0001), but not significantly regarding FMD (7.9+/-6.4 vs 8.9+/-5.4% in controls). Surgery resulted in a weight loss of 9% at 1 month and 30% at 1 year. Change in RI markedly improved to 36+/-12% at 1 month (P=0.0001 vs baseline) and further to 44+/-11% at 1 year (P=0.014 vs 1 month). FMD did not change significantly. Heart rate and brachial artery diameter were reduced, with no significant change in blood pressure. The improvement in resistance vessel vasodilation, estimated as change in RI, was not correlated to changes in weight or measures of glucose and lipid metabolism.

Obese patients showed impaired vasoreactivity in resistance arteries that was normalized already 1 month after gastric bypass surgery. The basis for this remarkable outcome, not significantly related to changes in body weight and metabolic variables, remains to be clarified.