Effect of hypertension and candesartan on the blood flow velocity of the extraocular vessels in hypertensive patients

Objective: To define alterations in the blood flow velocities of the ophthalmic artery (OA), central retinal artery (CRA), posterior ciliary artery (PCA) in essential hypertension and to evaluate the effect of a new antihypertensive drug, candesartan which is an angiotensin II receptor antagonist, on the blood flow velocity in hypertensive patients. Methods: Blood flow velocity and resistive index (RI) of the OA, CRA, and PCA were measured in 22 hypertensive patients off medication and 15 controls by color Doppler imaging. After treatment with candesartan, blood flow velocity and RI were again measured in the hypertensive patients. Results: In controls (n=15), the OA had a mean peak systolic flow velocity (PSFV) of 48.1±2.6 cm/s, mean end diastolic flow velocity (EDFV) of 16±1.0 cm/s, and RI of 0.65±0.01; the CRA had a PSFV of 20.8±0.4 cm/s, EDFV of 9.4±0.3 cm/s, and RI of 0.54±0.01; the PCA had a PSFV of 23.6±0.7 cm/s, EDFV of 11.2±0.3 cm/s, and RI of 0.52±0.01. There was a significant decrease in the PSFV and EDFV of the vessels in the medication free hypertensive patients when compared with controls (P<0.05). In the hypertensive patients off medication (n=22), the OA had a PSFV of 29.4±1.2 cm/s, EDFV of 10.4±0.5 cm/s, and RI of 0.71±0.01; the CRA had a PSFV of 15.1±0.6 cm/s, EDFV of 5.4±0.3 cm/s, and RI of 0.65±0.02; the PCA had a PSFV of 17.2±0.6 cm/s, EDFV of 6.7±0.3 cm/s, and RI of 0.61±0.01. RI measured in the OA, CRA, PCA were significantly increased in the hypertensive patients when compared with the controls (P<0.05). In hypertensive patients after medication (n=22), OA had a PSFV of 38.3±2.5 cm/s, EDFV of 12.3±0.7 cm/s, and RI of 0.68±0.01; CRA had a PSFV of 19.2±0.5 cm/s, EDFV of 7.8±0.3 cm/s, and RI of 0.59±0.01; PCA had a PSFV of 20.8±0.8 cm/s, EDFV of 9.2±0.4 cm/s, and RI of 0.56±0.01. There was a significant increase in the blood flow velocities of the OA, CRA, PCA (P<0.05) and significant decrease in the RI values in the treated hypertensive patients when compared with the controls (P<0.05). But blood flow velocities and RI values did not reach the control level. Conclusion: The increase in the RI values and the decrease in the blood flow velocity of extraocular vessels in the hypertensive patients are thought to be caused by increased peripheral resistance in the vessels of the eye and orbit. Although, it increases blood flow velocity and decreases RI significantly, candesartan treatment in the hypertensive patients cannot increase blood flow velocity and decrease RI to the control level.