The effect of methyldopa on retinal artery circulation in pre-eclamptic gravidae.

OBJECTIVE: To evaluate the effect of methyldopa on retinal artery circulation in pre-eclamptic gravidae using color Doppler imaging and spectral analysis.

METHODS: Fifty-three pre-eclamptic singleton gravidae of gestational age greater than 22 weeks were examined. Patients with sustained hypertension after 1-2 days hospital rest were treated with oral antihypertensive medication, 250-500 mg methyldopa, three to four times a day for a minimum of 5-7 days. The right central retinal arteries were insonated and Doppler waveform values were analysed before and after medication.

RESULTS: The change of the maternal heart rate after methyldopa treatment was -3.96 +/- 7.88 beats per min (P = 0.0006). The change of fetal heart rate was not significantly altered. The change of the diastolic arterial blood pressure after treatment was -4.19 +/- 12.36 mmHg (P = 0.0169). In 36 gravidae, in whom hypotensive effects were noted after treatment with methyldopa, the increase in peak velocity, end-diastolic velocity and mean velocity of the retinal artery were 2.41 +/- 2.20 (P < 0.0001); 1.48 +/- 1.23 (P < 0.0001) and 1.70 +/- 1.42 (P < 0.0001), respectively. The decrease in pulsatility index of the retinal artery after treatment with methyldopa was -0.17 +/- 0.22 (P < 0.0001). In the remaining 17 gravidae, in whom no hypotensive effects were noted after treatment with methyldopa, the decrease in end-diastolic velocity and mean velocity were -1.50 +/- 1.70 (P = 0.0022) and -0.98 +/- 1.90 (P = 0.0488), respectively. The increase in pulsatility index was 0.34 +/- 0.30 (P = 0.0003).

CONCLUSIONS: In pre-eclamptic gravidae in whom the hypotensive effects were noted after treatment with methyldopa, the mean velocity of the retinal arteries was significantly higher and the mean pulsatility index lower after treatment. We conclude that the hypotensive effect of methyldopa in pre-eclamptic gravidae is associated with a significant decrease in retinal artery vascular resistance.