Captopril stimulation of differential renins in renovascular hypertension.

Abstract

SUMMARY Twenty-six patients being evaluated for renovascular hypertension were studied to assess the diagnostic value of enhancing the differential between renal venous renins (PRA) by a single 25 mg oral dose of converting enzyme inhibitor (CEI, captopril). Antihypertensive medications were not discontinued prior to the study, and renal venous effluent was sampled before and 30 minutes after CEI. Eight patients without stenosis who did not have surgery had post-CEI ratios of less than 3.0. The other 18 patients had operative intervention, with 14 subsequently having improved blood pressure control. Of these 14, seven patients with unilateral stenosis, four patients with bilateral stenosis, and one patient without overt stenosis but with other evidence of reduced renal blood flow had 30-minute PRA ratios of 3.0 or greater. Five of these 14 patients had prestimulation ratios of less than 1.5 and might not be considered operative candidates by conventional criteria. Four other patients unimproved by surgery had post-CEI ratios of less than 3.0 despite a baseline ratio of greater than 1.5 in two of four. Only two patients with post-CEI ratios of less than 3.0 were improved with surgery. We conclude that a 30-minute post-CEI renal venous ratio of 3.0 or greater enhances the probability that patients with renovascular disease, and hypertension will respond to surgical intervention with improved blood pressure control. (Hypertension 5: 615-622, 1983) KEY WORDS • captopril • converting enzyme inhibitor plasma renin activity • renovascular hypertension R ENOVASCULAR hypertension constitutes less than 5% of hypertensive diseases; yet the potential for successful treatment with surgical intervention, percutaneous dilation, or specific medical management places a premium on accurate diagnosis. Unfortunately, the discovery of renal artery stenosis by angiography does not prove a functional relationship between the vascular lesion and the hypertension.1 ' 2 To clarify the functional role of the stenotic lesion, a ratio of renal venous plasma renin activity (PRA) of 1.5 or greater has been generally accepted as indicative of physiologically significant renal artery stenosis.3 " 7 On occasion this ratio is less than 1.5, yet surgical intervention results in significant improvement in the blood pressure.

Simplified captopril renography in diagnosis and treatment of renal artery stenosis.

“…3 Though the comparison of renal vein renin activity in each kidney is quite sensitive, especially in patients with unilateral renal artery stenosis and normal renal function, it is not sufficiently accurate in patients with bilateral disease or renal insufficiency. 34 Therefore, we and others have advocated proceeding directly to arteriography as the sole diagnostic procedure in patients believed, on clinical grounds, to have a high likelihood of renal artery stenosis.…”

Renin-Dependent Hypertension Caused by Nonfocal Stenotic Aberrant Renal Arteries

“…The renal vein renin ratio peaked at 30 minutes after oral captopril with a (right/left) ratio of 4.3:1, compatible with that observed in patients with renin-dependent renovascular stenosis (Ͼ3:1 under similar conditions). 19 The rapid decrease in the plasma aldosterone concentration confirmed that angiotensin II blockade was achieved by the captopril. The patient's blood pressure decreased concurrently with administration of the captopril and remained suppressed for 4 to 6 hours.…”

“…Confirmation would then be performed by measuring stimulated renal vein renins as previously published. 19 Because of dilutional effects from the ipsilateral normally perfused segments, it would be important to either obtain segmental venous effluent renins 24 and/or use efforts to maximally stimulate the abnormal segment while the renin released from the normal segments is still suppressed. This may be difficult to achieve in those patients on long-term diuretic therapy.…”

“…However, we have reported that the acute administration of furosemide on the day preceding the study and an oral converting enzyme inhibitor immediately after obtaining the baseline values followed by sampling renal vein renins and a peripheral renin at 15 and 30 minutes led to differentiation and accurate prediction of a successful operative outcome in 15 of 17 patients with conventional unilateral or bilateral renal artery stenosis. 19 Several of these patients had been on a diuretic before the study. Our 2 patients demonstrated a relatively sharp and transient increase in the renal venous ratio and would have been missed if not for multiple sampling.…”

“…After baseline samples were obtained from the renal veins and a peripheral vein, he was given 25 mg of captopril orally. 19 Samples were then obtained at 15-minute intervals. Plasma renin activity and plasma aldosterone concentration values are shown in Table 1.…”