Predictors of target organ damage in hypertensive blacks and whites

The purpose of this study was to evaluate the association of the insulin re sistance syndrome with both blood pressure and target organ damage in black s and whites with essential hypertension. Eighty-two black and 63 white Fre nch Canadian patients were studied. None had diabetes, and antihypertensive medications had been discontinued for greater than or equal to1 week. Meas urements included 24-hour blood pressure monitoring, fasting plasma lipids, insulin sensitivity determined with the Bergman minimal model, echocardiog ram, microalbumin excretion, and inulin and lithium clearances. Compared wi th the white French Canadians, black patients had an attenuated nighttime r eduction in blood pressure (P<0.02), increased cardiac dimensions (P<0.001) , greater microalbumin excretion (P<0.05), increased inulin clearance (indi cative of glomerular hyperfiltration; P<0.001), and decreased lithium clear ance (indicative of increased sodium reabsorption in the proximal tubule; P <0.001). Blood pressure levels were not related to insulin resistance; alth ough in blacks, the nighttime reduction in systolic blood pressure was inve rsely related to fasting plasma insulin (r= -0.18, P<0.04). In a stepwise m ultivariate analysis (including blood pressure levels and components of the insulin resistance syndrome as independent variables), race was the strong est predictor of left ventricular mass (r=0.53, P<0.000), relative wall thi ckness (r=0.49, P<0.000), and both inulin (r=0.53, P<0.000) and lithium (r= 0.41, P<0.000) clearances. Nighttime systolic blood pressure was also a sig nificant determinant of concentric left ventricular hypertrophy (r=0.37, P< 0.000). In blacks, microalbumin excretion was related to insulin resistance . These observations are consistent with the hypothesis that there is a gen etic contribution to cardiac hypertrophy, glomerular hyperfiltration, and s odium retention in blacks with essential hypertension.