POINT/COUNTERPOINT: Renal artery occlusive disease – To treat or not to treat? ASTRAL and CORAL trials show no indication to treat percutaneously. There are still indications to treat renal artery occlusive disease.

There are still indications to treat renal artery occlusive disease

BY MATTHEW A. CORRIERE, M.D.

Although renal artery revascularization has been grossly overutilized and is not indicated in the majority of patients with renal artery stenosis, I perform renal artery revascularization as part of my routine clinical practice and believe that there are many instances where revascularization should be considered, particularly when patients have severe symptoms despite aggressive medical therapy. While neither ASTRAL nor CORAL observed any benefit associated with revascularization, both have important limitations that should be kept in mind when interpreting the results of these trials.

These limitations can be broadly categorized as mismatch between indications for revascularization and clinical endpoints, selection biases favoring enrollment of patients with relatively mild symptoms, and inconsistencies between study protocols and contemporary decision-making strategies.

Given that ASTRAL’s primary outcome was change in renal function (defined by a 20% or greater reduction in the mean slope of the reciprocal of serum creatinine), it is important to remember that the inclusion criteria were renal artery stenosis with unexplained renal dysfunction or poorly controlled hypertension. Patients who had hypertension in the absence of significant renal dysfunction were therefore eligible, and 40% of the randomized participants had preserved baseline renal function (based on a serum creatinine of < 150 micromol/liter). Unlike patients with baseline renal dysfunction (which, in theory, might improve with revascularization), these patients with normal renal function who were treated with revascularization risked decline in renal function resulting from procedure-related adverse events without any real chance of renal function improvement. It would certainly be difficult to justify revascularization for the sake of renal function salvage in these patients, and their inclusion within a randomized trial with change in renal function as its primary outcome is problematic for the same reason.

ASTRAL also had an additional, somewhat unorthodox inclusion criterion: uncertainty on the part of the treating physician that the patient “definitely would have a worthwhile clinical benefit from revascularization.” Exclusion of patients considered likely to benefit from revascularization would seem to ensure a selection bias favoring the null hypothesis; this approach may also explain the large proportion of participants with relatively mild occlusive disease (40% had stenotic lesions that were < 70% in severity).

A high rate of both technical failure (12%) and adverse events (20%) associated with revascularization, asymmetric crossover between treatment groups (86 of the 110 patients who did not receive their randomized intervention were in the revascularization group), and lack of standardized protocol for medical therapy further limit the conclusions that can be drawn from the ASTRAL results.

Although this trial does not provide us with compelling evidence that renal revascularization should be abandoned for patients failing appropriate medical therapy, ASTRAL demonstrated that no benefit should be expected from nonselective use of revascularization, which can be associated with significant rates of both technical failure and major adverse events.

The CORAL trial overcame many of the design limitations for which ASTRAL drew criticism. CORAL’s primary endpoint (freedom from major adverse cardiovascular or renal events) allowed potential benefit for participants with either systolic hypertension or chronic kidney disease as their indication for treatment. Although participants with systolic hypertension as their inclusion criterion had to be on at least two antihypertensive medications, it is important to acknowledge the growing number of indications for these medications related to cardiovascular risk reduction in the setting of diabetes, heart disease, and other diagnoses that may be unrelated to any specific blood pressure target. Number of antihypertensive medications is therefore often a crude and potentially invalid indicator of hypertension severity or control.

In CORAL, the initial hypertension inclusion criterion of 155 mm Hg was subsequently abandoned during the trial, suggesting that hypertension in many of these patients may have been mild and/or well controlled. Although medical therapy in CORAL was standardized, it also is notable that all patients had their medical therapy adjusted prior to randomization during a roll-in phase to achieve target blood pressure goals of 130/80 in patients with CKD and/or diabetes or 140/90 otherwise. I would suggest that achievement of these blood pressure targets on the study medications (candesartan ± hydrochlorothiazide plus amlodipine-atorvastatin) might be appropriately considered success of medical therapy for patients with hypertension in the absence of renal dysfunction, making it challenging to defend proceeding with revascularization in this scenario.

The study protocol, although well designed from the perspective of attempting to isolate the effect of renal artery angioplasty and stenting, therefore did not uniformly reflect what would be considered responsible utilization of renal revascularization in a real-world environment.

Patient enrollment in CORAL was also very selective; only 947 of the 5,322 patients who were screened went on to be enrolled and randomized. It is likely that at least some of those patients who were not enrolled (especially those who declined to participate or were withdrawn by their physicians) were failing aggressive medical therapy and therefore unwilling to being excluded from angioplasty and stenting through randomization. These limitations aside, however, CORAL does provide some very useful observations that should inform treatment decisions. The results demonstrate the efficacy of contemporary medical therapy for many patients, and show that revascularization offers no additional benefit when medical therapy achieves an acceptable clinical response (defined by stable renal function and reasonable blood pressure control). Additional subgroup analyses of the CORAL data are anticipated, but will likely be underpowered to draw conclusions in the absence of identified revascularization effects.

So when should revascularization be considered for patients with atherosclerotic renal artery stenosis? In general, medical therapy is adequate for most patients and should be implemented prior to any consideration of procedural intervention. Revascularization should be considered only for patients who have failed appropriate, aggressive medical therapy; the medications used in CORAL can certainly be regarded as adequate initial therapy for symptomatic renal artery stenosis, but many providers (including myself) would argue that additional agents should be considered before proceeding with revascularization.

When decline in renal function is the indication for considering revascularization, alternative causes (such as intrinsic renal disease) should diminish enthusiasm for proceeding with angioplasty and stenting, particularly when the anatomic disease distribution does not affect the entire renal mass (as in patients with two kidneys and unilateral stenosis). Appropriate candidates for revascularization include patients with severely impaired renal function (particularly in the setting of a precipitous functional decline) or severe acute blood pressure elevation associated with hypertensive emergency (such as acute congestive heart failure, encephalopathy, acute coronary syndrome, or other signs and symptoms of target organ damage resulting from hypertension and/or volume overload). Continuation of failed medical therapy is often unacceptable to these “no-options” patients as well as their providers, both of whom presumably would be unlikely to accept randomization to ongoing medical management.

Other populations that are not represented within these trials include patients with renal artery restenosis and those with nonatherosclerotic disease; it is therefore important to exercise caution when generalizing these study results to these distinct groups of patients. Enrolling patients with severe symptoms who have failed medical therapy will likely remain challenging for future randomized studies in the absence of alternative treatment options. Although the benefits of renal angioplasty and stenting for these “no-options” patients remain to be proved, the uncertainty of response to revascularization is often easier to accept than the ongoing morbidity and mortality associated with staying the course when medical therapy has failed.

Dr. Matthew A. Corriere is a vascular surgeon at Wake Forest University School of Medicine, Winston-Salem, N.C.

This article developed from a debate held at the 2014 Vascular Annual Meeting.