Effect of angiotensin-converting enzyme inhibition with perindopril and beta-blockade with atenolol on retinal blood flow in hypertensive diabetic subjects.

The effect of angiotensin-converting enzyme (ACE) inhibitors on the diabetic retinal circulation has not been studied previously. The aim of this study was to evaluate the effect of ACE inhibition and beta-blockade on retinal blood flow (RBF) in a group of 45 hypertensive diabetic subjects using a randomized double-blind trial over a period of 12 months. Laser Doppler velocimetry and computed image analysis were used to measure RBF. The changes in blood pressure over 12 months were comparable (perindopril [PE]: systolic [SBP] 152.1 +/- 3.3 and diastolic [DBP] 97.2 +/- 1.7 mm Hg to SBP 136.8 +/- 3.4 and DBP 85.8 +/- 2.1; atenolol: SBP 158.9 +/- 5.1 and DBP 97.5 +/- 1.6 mm Hg to SBP 137.9 +/- 3.4 and DBP 85.1 +/- 1.6; P = .607, mean +/- SEM). RBF decreased from 17.19 +/- 2.21 microL x min(-1) to 14.18 +/- 1.50 microL x min(-1) in the PE group (n = 15, P = .208) while it increased with atenolol from 15.80 +/- 1.24 microL x min(-1) to 16.99 +/- 1.18 microL x min(-1) (n = 17, P = .399). The comparison of percentage changes in RBF (PE -7.16% +/- 11.49%; atenolol, +15.31% +/- 9.51%) reached statistical significance (P < .05). There was an increase in RBF in 33.3% of subjects receiving PE and in 70.6% of those receiving atenolol. Similar trends were found for retinal conductance. There were no significant changes in the parameters of retinal vascular permeability. Albuminuria decreased to a greater degree with PE, but did not reach significance (PE, 112.1 +/- 39.5 mg/24 h to 88.6 +/- 30.5 mg/24 h; atenolol, 87.3 +/- 51.7 mg/24 h to 82.1 +/- 47.7 mg/24 h). This suggests that ACE inhibition therapy may promote a hemodynamic milieu in the hypertensive diabetic retinal circulation that serves to protect against the progression of diabetic retinopathy, whereas beta-blockade has the opposite effect.