Angiotensin converting enzyme (
ACE) inhibitors as well as
angiotensin II receptor antagonists are able to prevent the vasoconstrictive effect of
angiotensin II on the efferent renal vessels, which is believed to play an important role in
renovascular hypertension. This effect is assumed to be essential for the demonstration of
renovascular hypertension by
captopril renography. In this study, renographic changes induced by
captopril and the AT1 receptor antagonist
valsartan were compared in patients with a high probability for
renovascular hypertension. Twenty-five patients with 33 stenosed renal arteries (grade of
stenosis >50%) and
hypertension were studied.
Captopril,
valsartan and baseline renography were performed within 48 h using technetium-99m mercaptoacetyltriglycine. Blood pressure was monitored, plasma
renin concentration before and after intervention was determined and urinary flow was estimated from the urinary output of the hydrated patients. Alterations in renographic curves after intervention were evaluated according to the Santa Fe consensus on
ACE inhibitor renography.
Captopril renography was positive, indicating
renovascular hypertension, in 25 of the 33 stenosed vessels, whereas
valsartan renography was positive in only ten. Blood pressure during
captopril and
valsartan renography was not different; reduction in blood pressure was the same after
valsartan and
captopril. Plasma
renin concentration was comparable for
valsartan and
captopril studies, showing suppressed values after intervention in as many as 12 of the 25 patients. Urinary flow after
valsartan was higher than after
captopril (P<0.05). However, this difference could not explain the markedly higher sensitivity of
captopril compared with
valsartan in demonstrating
renal artery stenosis. In 14 of the 25 patients, blood pressure response to revascularisation was monitored, showing a much better predictive value for
captopril renography. It is concluded that
captopril renography is much more sensitive than
valsartan renography in detecting a clinically significant
renal artery stenosis. Furthermore, our data suggest that other effects, such as that on the
prostaglandin-
bradykinin system, are of at least similar importance to ACE inhibition for the high diagnostic sensitivity of
captopril renography regarding
renovascular hypertension.