The influence of insulin resistance and obesity on left atrial size in Japanese hypertensive patients.

Left atrial (LA) enlargement is an early sign of hypertensive heart disease. Insulin resistance and obesity, integral components of metabolic syndrome, are closely associated with the development of hypertension. However, few echocardiographic studies have assessed the relations of insulin resistance and obesity to LA size in hypertensive patients. We enrolled 106 never-treated hypertensive patients (57 men and 49 women) to assess the possible relations of insulin resistance and obesity to LA size. Insulin resistance was estimated using the homeostasis model assessment (HOMA) formula. Echocardiographically determined LA dimension, left ventricular (LV) mass and relative wall thickness (RWT) were measured as markers of LA size, LV hypertrophy and LV geometry. The E/A ratio estimated by transmitral flow velocity was measured as a marker of LV diastolic function. In addition, body mass index (BMI) was calculated as weight (kg) divided by height (m)(2) as a marker of obesity. Multivariable regression analyses showed that BMI was the strongest independent predictor of LA size (P<0.0001), followed by the HOMA value (P=0.0003). However, LV mass, RWT and the E/A ratio did not bear significant relations to LA size. There were no sex-specific differences in the relations of HOMA value or BMI to LA size. In conclusion, LA size is influenced by insulin resistance and obesity, integral components of the metabolic syndrome, independently of LV hypertrophy, LV geometry or LV diastolic function in nondiabetic Japanese hypertensive patients.