Haemorheological disturbances in hypertensive type 2 diabetic patients--influence of antihypertensive therapy

Haemorheological changes have been described in hypertension as well as in diabetes mellitus. Antihypertensive treatment improves rheology in hypertensive patients. The aim of this study was to describe the haemorheological profile and its impact on shear stress in hypertensive type 2 diabetes mellitus patients (HT + DM) and to investigate the effect of antihypertensive therapy on blood rheology using a double-blind randomized protocol, comparing the calcium antagonist amlodipine with the angiotensin-converting enzyme (ACE) inhibitor enalapril. A total of 144 patients with hypertension and type 2 diabetes (64 of transversal study and 80 of randomized clinical trial) were compared with 92 controls belonging to a transversal study. Secondarily, in a separate analysis, therapeutic effects of calcium antagonist amlodipine and ACE inhibitor enalapril were compared in a longitudinal, randomized trial in the patients. We assessed whole-blood viscosity, plasma viscosity, partial and total disaggregation times, haematocrit and fibrinogen. Radial artery systolic flow velocity was measured by pulsed Doppler. Shear stress was calculated as the product of flow velocity x whole-blood viscosity. Compared with controls, patients had significantly higher whole-blood viscosity for all shear rates (P < 0.001) as well as higher arterial diameter and systolic blood flow velocity (2.8 +/- 0.3 vs. 2.6 +/- 0.3 mm, P < 0.001; and 50.8 +/- 11.6 vs. 45.6 +/- 9.8 cm/s, P = 0.01, respectively). Whole-blood viscosity at shear rate gamma = 128/s tended to increase with amlodipine (+1.13%) and decrease with enalapril (-2.47%) (P = 0.028 for inter-group difference). In hypertensive diabetic patients, hyperviscosity contributes to increased shear stress. Haemorheological disturbances in these patients are not significantly influenced by blood pressure lowering with antihypertensive therapy by ACE inhibitor enalapril or calcium antagonist amlodipine. Other factors potentially contributing to rheology and arterial changes may be more critical in HT + DM patients and need further investigation.