Resistance to anti hypertensive medication as predictor of renal artery stenosis: comparison of two drug regimens

Background. Renal artery stenosis is among the most common curable causes o f hypertension. The definitive diagnosis is made by renal angiography, an i nvasive and costly procedure. The prevalence of renal artery stenosis is le ss than 1% in non-selected hypertensive patients but is higher when hyperte nsion is resistant to drugs. Objective: To study the usefulness of standardised two-drug regimens for id entifying drug-resistant hypertension as a predictor of renal artery stenos is. Design and setting. Prospective cohort study carried out in 26 hospitals in The Netherlands. Patients: Patients had been referred for analysis of possible secondary hyp ertension or because hypertension was difficult to treat. Patients less tha n or equal to 40 years of age were assigned to either amiodipine 10 mg or e nalapril 20 mg, and patients >40 years to either amiodipine 10 mg combined with atenolol 50 mg or to enalapril 20 mg combined with hydrochlorothiazide 25 mg. Renal angiography was performed: (1) if hypertension was drug-resis tant, ie if diastolic pressure remained greater than or equal to 95 mm Hg a t three visits 1-3 weeks apart or an extra drug was required, and/or (2) if serum creatinine rose by greater than or equal to 20 mu mol/L (greater tha n or equal to0.23 mg/dL) during ACE inhibitor treatment. Results: Of the 1106 patients with complete follow-up, 1022 had been assign ed to either the amiodipine- or enalapril-based regimens, 772 by randomisat ion. Drug-resistant hypertension, as defined above, was identified in 41% o f the patients, and 20% of these had renal artery stenosis. Renal function impairment was observed in 8% of the patients on ACE inhibitor, and this wa s associated with a 46% prevalence of renal artery stenosis. in the randomi sed patients, the prevalence of renal artery stenosis did not differ betwee n the amiodipine- and enalapril-based regimens. Conclusions: In the diagnostic work-up for renovascular hypertension the us e of standardised medication regimens of maximally two drugs, to identify p atients with drug-resistant hypertension, is a rational first step to incre ase the a priori chance of renal artery stenosis. Amiodipine- or enalapril- based regimens are equally effective for this purpose.