Relation of insulin resistance and left ventricular function and structure in non-diabetic patients with essential hypertension

Abstract

Objective - Both left ventricular hypertrophy and insulin resistance (IR) have often been demonstrated in patients with essential hypertension (EH). Insulin may exert a direct growth-promoting effect on cardiomyocytes. The purpose of this study was to examine the relationship between left ventricular structure, function and IR in patients with EH. Methods - We enrolled 73 patients (21 men, mean age 51.7 ± 9.2 years) with untreated hypertension (BP > 140 and/or 90 mm Hg, fasting glycaemia < 110 mg/dl) and 64 healthy subjects without diabetes mellitus and hypertension (21 men, mean age 48.9 ± 10.6 years) constituted the control group. In all subjects, transthoracic echocardiography was performed and blood samples were taken. Homeostasis model assessment (HOMA) was calculated by the formula: HOMA-index = fasting blood glucose (mg/dl) * immunoreactive insulin (µU/ml)/405 for the assessment of IR. Hypertensive patients were divided in two groups by mean HOMA index values. Each subject was examined for LV end-diastolic diameter, septal and posterior wall thickness, LV mass index (LVMI), fractional shortening (FS), mitral inflow velocity pattern, atrial filling fraction (AFF), left ventricular outflow velocity pattern and the total ejection isovolume index (TEI index). Results - The HOMA index (p < 0.001), LVMI (p < 0.001), AFF (p < 0.0001), peak A velocity (p < 0.028), septal (p < 0.0001) and posterior (p < 0.0001) wall thickness were significantly higher and FS (p < 0.001), E/A ratio (p < 0.0001) were significantly lower in hypertensive patients than healthy controls. LVMI (p < 0.01) and septal wall thickness (p < 0.001) were significantly higher in those hypertensive patients with a higher HOMA index. The HOMA-index was univariately related to the TEI index (r = 0.27, p = 0.01) and septal wall thickness (IVS) (r = 0.29, p = 0.01) by Pearson correlation analysis in hypertensive patients. LVMI, FS and mitral inflow velocity pattern were not related to the HOMA index. The TEI index (R 2 = 0.20, p = 0.0001) and IVS (R2 = 0.12, p = 0.002) were significantly related to the HOMA-index as an independent variable by stepwise regression analysis. Conclusions - These results demonstrated that hypertensive patients had both abnormal cardiac structure and function and higher IR index. In our study group, the effect of hypertension on cardiac structure and function was correlated with IR. Our results suggested that IR might be an important factor causing left ventricular dysfunction and wall thickness in non-diabetic patients with EH.