Effect of obesity on left-ventricular function studied by radionuclide angiocardiography

Several studies have shown a significant association of obesity with cardiovascular morbidity and mortality. The present study was carried out to investigate central and systemic haemodynamics in overweight and moderate obese, but otherwise healthy subjects, and in a lean control group to determine whether obesity can influence left ventricular performance per se. In this study an attempt has been made to eliminate misleading factors, such as diabetes, lipid abnormalities and hypertension. A total of 67 subjects, 44 with overweight or moderate obesity and 23 lean healthy subjects, were included. Patients were divided into three groups according to BMI levels and Garrow's criteria as follows: lean control group (BMI < 25 kg/m2); overweight (BMI from 25 to 30 kg/m2); moderate obese (BMI > 30 < 40 kg/m2). Overweight and moderate obese subjects were further subgrouped according to duration of obesity (DO) in subgroup A (DO < 98 months) and in subgroup B (DO > 98 months). Haemodynamic assessment was performed using first pass radionuclide angiocardiography. When compared with lean subjects, overweight and moderate obese subjects were characterized by a significant increase in cardiac output (CO), stroke volume (SV), end diastolic volume (EDV), end systolic volume (ESV), total blood volume (TBV) and total plasma volume (TPV) and by a significant decrease in left ventricular ejection fraction (EF); some of these changes appeared to be related to the degree of obesity. In overweight and moderate obese subjects, total peripheral resistance (TPR) was lower than in lean controls, but this difference was not significant. Moreover EF values were significantly lower in subgroup B in comparison with subgroup A, but only in moderate obese subjects (P < 0.01). In all the subjects studied, BMI was inversely correlated with EF (P < 0.001) and directly with CO (P < 0.01) and with TBV (P < 0.01). In all the obese subjects, EF was inversely correlated with DO (P < 0.01). Multiple regression analysis showed that correlations between EF, BMI and DO were independent of mean blood pressure values. In conclusion, the results support the suggestion that obesity could represent an independent risk factor for congestive heart failure after a long term incubation period.