Relationship between cardiac function and insulin resistance in obese patients.

Both overweight and insulin resistance predispose to atherosclerosis and cardiovascular diseases, independently of other risk factors. We studied the relationship between insulin resistance and heart function and dimension in 39 patients with different degrees of obesity. Twenty-six women and 13 men with body mass index (BMI) ranging 26.1-41 kg/m2 (mean +/- SD = 33.9 +/- 3.8), without diabetes, hypertension and heart, liver or kidney diseases were studied. Patients were subdivided into 2 groups, 25 with overweight or grade I obesity (group A) and 14 with severe (grade II or III) obesity (group B). Insulin sensitivity was evaluated by the Insulin Tolerance Test (ITT), performed after an overnight fast and K(ITT) was calculated. Echocardiographic measurements were also assessed. Between the two groups no significant difference was observed for either K(ITT) (group A, K(ITT) = 5.47 +/- 1.30; group B, K(ITT) = 4.57 +/- 1.53) or the ejection fraction (EF%) (group A, 71.40 +/- 6.63; group B, 69.86 +/- 7.43). No correlation was observed between BMI and both the EF% and other echocardiographic measurements. In patients with mild obesity (group A) a significant negative correlation between EF% and KITT (r = -0.62,p < 0.001) was observed. In mild obesity, therefore, cardiac function changes occur in relation to the level of insulin resistance but these changes are not related to mass and/or volume changes. The cause(s) of this relationship is not clear, but most likely involves metabolic or endocrine factors. The increased EF% in moderately obese patients that are insulin-resistant may provide an initial compensatory mechanism but may also contribute to a late cardiac damage.