Is insulin action a determinant of left ventricular relaxation in uncomplicated essential hypertension?

Objective To examine the relation of insulin action and left ventricular diastolic function in uncomplicated essential hypertension. Methods Doppler echocardiography and glucose clamping combined with indirect calorimetry were performed in 29, newly diagnosed, hypertensive men, free from cardiac and metabolic drugs. They were divided into two groups according to the clamp-derived whole-body glucose disposal level: 20 with insulin resistance (whole-body glucose disposal < 33 mu mol/kg per min) and nine with normal insulin sensitivity. Results The two groups were comparable in age, body mass index, heart rate and blood pressure. No difference in diastolic function was found except for the isovolumic relaxation time, which was prolonged for patients with insulin resistance (P = 0.02). For the population as a whole, the relaxation time had univariate relations with the left ventricular mass index (r = 0.57, P < 0.001), whole-body glucose disposal (r = -0.56, P< 0.001) and non-oxidative glucose metabolism (r = -0.54, P = 0.002). In a multivariate model including age, body mass index, heart rate, diastolic blood pressure, left ventricular mass index and whole-body glucose disposal as potential determinants, only the left ventricular mass index (beta = 0.39, P = 0.02) and whole-body glucose disposal (beta = -0.38, P = 0.03) were independent predictors of the relaxation time (R-2 = 0.43, P < 0.001). Conclusions In uncomplicated essential hypertension the insulin resistance is a determinant of abnormalities in isovolumic relaxation, independently from the influence exerted by increased blood pressure levels, being overweight and left ventricular hypertrophy.