Abstract 2906: Paradoxic Relation Between Cardiac Output and Exercise Capacity in Severely Obese Patients Undergoing Gastric Bypas Surgery
Background: Increased cardiac output (CO) in severe obesity is thought to be a cause of LVH and potentially of heart failure. We tested the hypothesis that CO decreases after marked weight loss following gastric bypass surgery (GBS). We also investigated the relationship between changes in CO and exercise capacity (Ex Cap).
Methods: 881 severely obese patients (BMI 45.9 ± 7.5) were randomized to roux-en-Y gastric bypass surgery (GBS, n=239) or nonsurgical therapy (NonSurg, n=652). We calculated resting stroke volume (SV), and CO using quantitative echo-Doppler measurements at baseline, and at 2 years. Ex Cap was determined by treadmill testing (modified Bruce protocol).
Results: At 2 years GBS subjects lost 46.3±1.1 kg ( p < 0.001) vs. 3.0±0.7 in the NonSurg group. CO decreased in the GBS group by 24% (5.8±1.5 to 4.4±0.1, p < 0.01) vs. 10 % in Nonsurg patients. This resulted from a 19 % decrease in heart rate (73±11 to 59±9 bpm ) and a 3% decrease in stroke volume (79±16 to 76±17 ml). At 2 years, Ex Cap improved by 40 % in GBS vs. NonSurg subjects. In age and sex adjusted models, weight (r = 0.41), BMI (r = 0.41), waist circumference (r = 0.39), systolic blood pressure (r = 0.18) and left ventricular mass (r=0.22) positively correlated with CO, while Ex Cap showed a strong negative correlation with CO (r = -0.35). LV mass also had an inverse correlation with Ex Cap (r = -0.21)
Conclusion: In this large, prospective, randomized study of GBS for the treatment of severe obesity, we find a reduction in resting CO with a corresponding improvement in Ex Cap following marked weight loss. LV mass showed a positive relationship with CO and an inverse relationship with Ex Cap.
These data support the idea that chronically elevated CO may contribute to cardiac hypertrophy and exercise intolerance in severe obesity.