Reliability of captopril renography in patients under chronic therapy with angiotensin II (AT1) receptor antagonists.

UNLABELLED: Captopril renography is a reliable, widely used test for the functional diagnosis of renovascular hypertension. Well-recognized drawbacks of the procedure include reduced accuracy in patients with bilateral disease or renal impairment as well as the possible interference from concurrent antihypertensive medication (diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, calcium channel blockers). Currently, no data exist regarding the reliability of captopril renography in patients with renovascular hypertension evaluated while they are under chronic treatment with angiotensin II (AT1) receptor antagonists (Sartans). Moreover, the renographic response of the kidney with renal artery stenosis to prolonged therapy with angiotensin II receptor antagonists has not yet been evaluated.

METHODS

We investigated the diagnostic effectiveness of (99m)Tc-mercaptoacetyltriglycine captopril renography performed after acute addition of 25 mg of captopril to the daily dose of AT1 receptor antagonist in 13 patients with unilateral renal artery stenosis and subsequent evidence of renovascular hypertension, based on short-term (3 mo) blood pressure outcome after revascularization. The renographic evaluation was first performed after ingestion of the daily therapy of angiotensin II receptor antagonist alone (Sartan renography) and was repeated within 7 d after the acute addition of 25 mg of captopril to chronic treatment with angiotensin II receptor antagonist (captopril-Sartan renography). A cohort of 13 patients with a final diagnosis of essential hypertension was chosen as the control subjects.

RESULTS

Twelve of 13 patients were correctly detected by captopril-Sartan renography (92% sensitivity), and 3 subjects were also identified without the addition of captopril. Adding captopril to Sartan therapy resulted in a slight reduction in mean arterial blood pressure, while significant side effects were never observed. No false-positive results were found in the 13 patients with essential hypertension.

CONCLUSION

We conclude that performing captopril renography with the acute addition of 25 mg of captopril to the chronic monotherapy with Sartans has the same diagnostic effectiveness as performing captopril renography alone. Interrupting the vasoactive action of angiotensin II alone on the efferent glomerular arteries, which can also be selectively achieved by chronic administration of angiotensin II receptor antagonists, does not fully explain the effectiveness of captopril renography in detecting renovascular hypertensive patients.