CAPTOPRIL-ENHANCED (99)TC(M)-MAG3 RENAL SCINTIGRAPHY IN SUBJECTS WITHSUSPECTED RENOVASCULAR HYPERTENSION

This pilot study was undertaken to generate preliminary data on the ac curacy of captopril-enhanced renal scintigraphy with a relatively new radiopharmaceutical, Tc-99m-mercaptoacetyltriglycine (Tc-99m-MAG3) for detecting significant renal artery stenosis. Truth data was based eit her on arteriographic or outcome criteria (blood pressure response to therapy). Twenty-seven subjects with suspected renovascular hypertensi on were studied with baseline and captopril-enhanced Tc-99m-MAG3 renal scintigraphy and renal arteriography. Scan interpretations were expre ssed as a probability of a significant renal artery stenosis. Scan int erpretations were compared with renal arteriographic results, renal ve in renin levels, blood pressure values after renal artery repair, and blood pressure control after 4-26 months of clinical follow-up. Using greater-than-or-equal-to 50% luminal obstruction on arteriography as t he reference standard for renal artery stenosis and a high probability scan representing a positive test, the test sensitivity and specifici ty were 33 and 97%, respectively (using high or indeterminate probabil ity to represent a positive scan, the test sensitivity and specificity were 67 and 83%, respectively). The negative predictive value of a lo w probability scan for renal artery stenosis was 80%. However, includi ng a measure of renovascular hypertension (blood pressure response to renal artery repair) as the reference standard, the accuracy of the sc an improves, with the negative predictive value of a low probability s can for renovascular hypertension increasing to 97%. Scintigraphic res ults were also positively correlated with renal vein renin values in a statistically significant fashion (two-tailed Fisher exact test stati stic = 6.43, P = 0.0219). Captopril-enhanced Tc-99m-MAG3 renal scintig raphy is a moderately accurate technique for detecting renal artery st enosis. More importantly, our preliminary findings suggest that the sc intigraphic technique using Tc-99m-MAG3 appears to predict the blood p ressure response to renal artery repair in subjects with suspected ren ovascular hypertension, thereby separating subjects with haemodynamica lly insignificant renal artery stenosis from those with renovascular h ypertension.