Effects of Percutaneous Transluminal Renal Angioplasty of Atherosclerotic Renal Artery Stenosis in High-Risk Patients.

Inclusion Criteria: 1. One or more severe atherosclerotic renal artery stenoses defined as a stenosis ≥70% by catheter-based angiography. 2. In addition, at least one of the following high-risk clinical syndromes: 1. Resistant hypertension with average 24-hour ambulatory systolic blood pressure ≥150 mmHg despite ≥3 antihypertensive drugs including a diuretic, if tolerated, and each prescribed at optimal doses. 2. Rapidly declining kidney function with a reduction in estimated GFR of \>5 mL/min per 1.73m2 per year and average 24-hour ambulatory systolic blood pressure ≥140 mmHg despite ≥3 antihypertensive drugs including a diuretic, if tolerated, and each prescribed at optimal doses. 3. Hospital admissions with acute decompensated heart failure (≥2 hospitalizations for heart failure or ≥1 hospitalizations for sudden, "flash" pulmonary edema) with no obvious explanations such as nonadherence, left ventricular ejection fraction \<40%, or valvular heart disease and average 24-hour ambulatory systolic blood pressure ≥140 mmHg despite ≥3 antihypertensive drugs including a diuretic, if tolerated, and each prescribed at optimal doses. All 24-hour ambulatory blood pressure monitorings are performed after nurse-administered medication. Exclusion Criteria: * Unable to provide informed consent. * Treatment-resistant heart failure episodes presumed caused by renovascular disease. * Rapidly declining kidney function/acute kidney failure approaching the need for dialysis presumed caused by renovascular disease. * Fibromuscular dysplasia or other non-atherosclerotic renal artery stenosis known to be present prior to randomization. * Pregnancy or unknown pregnancy status in female of childbearing potential. * Kidney size \<7 cm (pole to pole length) supplied by target vessel. * Previous kidney transplant. * Previous PTRA treatment. * Presence of a renal artery stenosis not amenable for treatment with a stent. Patients who are not eligible for randomization but treated with renal artery stenting outside the protocol are followed according to the DAN-PTRAII protocol in order to account for all PTRA treatments performed in Denmark in the study period. Patients treated with renal artery stenting without randomization in the study period include patients with: 1. Treatment-resistant heart failure episodes presumed caused by renovascular disease. 2. Rapidly declining kidney function/acute kidney failure approaching the need for dialysis presumed caused by renovascular disease. 3. At least one of the listed high-risk clinical syndromes AND one or more significant atherosclerotic renal artery stenoses defined as a stenosis of 50-69% by catheter-based angiography with: * a mean translesional gradient of ≥10 mm Hg, or * a systolic translesional gradient of ≥20 mm Hg, or * a renal fractional flow reserve (Pd/Pa) of ≤0.8