Which Is Better For Renovascular Hypertension, Surgery Or Drugs?

Clinically, renal artery stenosis (RAS) is mainly characterized by secondary hypertension, renal insufficiency, and acute pulmonary edema. According to different pathophysiological processes, renal artery stenosis is divided into renal artery atherosclerosis, renal artery fibromuscular dysplasia, and other types of lesions. The choice of drug therapy or surgical revascularization has been full of controversy. Professor Wan Jianxin from the First Affiliated Hospital of Fujian Medical University gave an in-depth interpretation of this controversial topic.

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How is RAS assessed?

Revascularization surgery, represented by renal artery stenting, has changed the drug dependence status of RAS treatment. However, according to the results of a number of randomized controlled trials (RCTs) in recent years, some researchers have shown that patients benefit from revascularization and that they have Its choice as the best treatment has been questioned. In the past 20 years, with the development of diagnostic technology, the detection rate of renal artery stenosis has been increasing, and renal artery ultrasound Doppler can only detect renal artery stenosis exceeding 60 percent , and a smaller degree of stenosis requires angiography. Surgical diagnosis, including direct angiography, CT, MAR, etc.

Most studies define renal artery stenosis as more than 50 percent stenosis and severe stenosis as more than 70 percent . Most believe that unilateral renal artery stenosis must exceed 70 percent to constitute a risk to the kidneys. Stent placement has therefore become the standard treatment for renal artery stenosis. Due to the ease of operation and the high consistency of radiological evaluations, a considerable number of interventional specialists place stents once they find renal artery stenosis, regardless of clinical benefit. At present, there are at least three interventional experts in different fields competing for interventional treatment of renal artery stenosis, and patients often find renal artery stenosis in other angiography procedures. Therefore, further standardization of surgical indications and initiation timing is required in diagnosis and treatment.

In addition to radiological evaluation, invasive tests, represented by transcatheter renal arteriography, can also be used as an American College of Cardiology/American Heart Association (ACC/AHA) I Class (level B evidence) recommended diagnostic approach. It is worth noting that if there are clinical manifestations recommended by class I, and the patient is going to undergo peripheral or coronary angiography, renal angiography should be performed at the same time, otherwise, if renal arteriography is performed alone, it is called "contrast-driven". promote.

Should surgery be an option for RAS treatment?

In terms of the pathophysiological process, RAS is a part of systemic atherosclerosis and usually requires antihypertensive drugs, statins, and antiplatelet drugs. Therefore, the elderly, women, hypertension, coronary three-vessel disease, peripheral arterial disease, chronic kidney disease (CKD), diabetes, smoking, low levels of high-density lipoprotein and the use of more than two cardiovascular drugs are all RAS of risk groups.

The main clinical manifestations of RAS are asymptomatic stenosis, renovascular hypertension, ischemic nephropathy, and recurrent pulmonary edema. Therefore, the overall goal of RAS treatment is to lower blood pressure and save the kidney. For patients with RAS with different manifestations, the specific treatment directions are also different:

In patients with predominant renovascular hypertension, the goal is to improve blood pressure control;

In patients with ischemic nephropathy as the predominant manifestation, the goal is to delay renal decline or improve renal function;

In patients with other complications as the main manifestation, symptomatic treatment is the main treatment, including recurrent pulmonary edema, acute renal failure after the application of renin-angiotensin blockers, etc.

In contrast, in the vast majority of evidence, interventional therapy is of no benefit if patients with RAS do not have clinical manifestations. Although retrospective studies have shown that interventional therapy improves survival, prospective studies have not. At the same time, although renal artery stenosis is closely related to cardiovascular risk, no studies have shown that interventional therapy can improve cardiovascular prognosis [1-2]. The reason why not all interventional treatments can bring benefits lies in the following aspects:

Hypertension complicated with renal artery stenosis cannot be distinguished from renovascular hypertension: essential hypertension and RAS without clinical manifestations often coexist, which is the most fundamental reason why blood pressure cannot be effectively controlled after stent placement. In addition, essential hypertension can also coexist with renovascular hypertension, in which case stent placement also cannot completely free the patient from antihypertensive drug therapy.

In addition, RAS with ischemic nephropathy is not distinguished from RAS with other CKDs: the vast majority of patients with ischemic nephropathy do not benefit from angioplasty, so it is challenging to determine which patients will benefit from it the subject. In a study of 68 patients with CKD and RRAS greater than 70 percent who did not undergo intervention for 3 years, only 10 patients (15 percent ) had a glomerular filtration rate (GFR) decrease of more than 50 percent from baseline [3] , which means that many patients without interventional surgery are likely to maintain stable renal function.

Renal revascularization has two outcomes for changes in renal function, positive, that is, GFR improvement, stabilization, or slow decline, and negative, that is, accelerated deterioration of renal function, indicating its corresponding side effects (arterial thrombosis, ischemia-reperfusion injury, and contrast medium damage). ) caused deterioration of renal function. Therefore, Professor Wan Jianxin believes that if the renal function is stable before the interventional treatment, the renal function is really improved after the treatment, otherwise, any other outcome will be the unsuccessful interventional treatment. Multiple clinical evidence suggests that in nonselective populations, stenting has no benefit in improving renal function, and the risk of renal function deterioration after stenting is roughly equal to the benefit [4-6]. Therefore, a functional assessment of patients with RAS is required to decide whether to use surgery:

Renal resistance index (RI) < 0.8, which predicts that interventional therapy is beneficial to the improvement of renal function, but is less reliable;

Trans-lesion pressure gradient (GR)>20mmHg is functionally significant stenosis;

The renal cinematic frame (RFC) is a useful method to assess renal blood flow;

Fractional renal blood flow reserve (FFR).

At the same time, once the kidneys are significantly atrophied, the revascularization of interventional surgery will not bring more help. This also suggests that the reversibility of renal function or the viability of renal tissue is a key consideration in evaluating the choice of treatment for RAS. At present, there is still no effective method to identify whether renal tissue is viable or not. Captopril-renin challenge test can provide an effective method, but for patients with bilateral renal artery stenosis or glomerular filtration rate (GFR) less than 50ml/min imprecise, greatly limiting its application. There are new technologies available, such as blood oxygen level-dependent magnetic resonance imaging [7], but the current situation is relatively limited. For patients with declining renal function before the intervention, interventional surgery may be beneficial. In addition, bilateral RAS stent placement is effective in improving acute pulmonary edema. Data show that 94 percent -100 percent of patients have blood pressure controlled and renal function improved, 77 percent -91 percent of patients have a stable renal function after treatment, and 77 percent - Pulmonary edema no longer occurs after surgery in 100 percent of patients.

The clinical study of stent placement, blood pressure, and blood lipid control to prevent renal function progression in patients with renal arteriosclerosis-induced stenosis at the entrance (STAR) showed that [9] subjects receiving stent implantation had no clear benefit compared with the drug treatment group. The ASTAL study [10] also found that patients treated with interventional therapy had no clear benefit compared with the drug treatment group.

The CORAL study [11] also believed that drug therapy plus renal artery stenting did not provide additional benefits in the prevention of cardiovascular and renal events. It must be emphasized that the CORAL study did not end the controversy over the treatment of atherosclerotic renal artery stenosis (ARAS), nor does it mean that ARAS patients should not undergo intervention because of the additional risk of complications associated with RAS interventional therapy. treat.

What to Know About RAS Treatment Options!

After studying different research progress, it seems that the treatment options for RAS are clearer:

First, the importance of drug therapy in RAS cannot be ignored: patients in the CORAL study were all given active drug therapy, and the drug-only group also achieved better outcomes in cardiovascular and renal events at 5 years. In this study, anti-platelet, antihypertensive, lipid-lowering, blood sugar control, and other drug treatments were given according to the guidelines, and candesartan medoxomil was intervened in the antihypertensive treatment according to the plan.

Second, renal artery stenting should strictly follow the indications: it is necessary to further identify RAS patients who can benefit from surgical treatment. Such as those recommended in some guidelines with resistant hypertension, malignant or rapidly progressive hypertension; severe bilateral renal artery stenosis or unilateral severe unilateral renal stenosis; blood pressure reduction accompanied by rapid or recurrent GFR decline; GFR decline with treatment with angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor blocker (ARB); recurrent congestive heart failure and insufficient left ventricular function to explain, etc.

Finally, it is necessary to look for predictors that may be effective for the clinical effect of interventional surgery to detect the real predictive value of these potential indicators, and then to explore the response of patients screened by these predictors to treatment, and compare the pros and cons of various treatment methods. Understand that no single treatment will benefit all RAS patients. For such patients, the risks and benefits associated with treatment should be individualized through careful scientific clinical examination.

Professor Wan Jianxin believes that clinical research has given many important hints, but has not resolved the controversy over the choice of RAS treatment mode. In the post-CORAL era, among the treatment methods for RAS, renal artery stenting for lesions with moderate to severe stenosis without a clear causal relationship with function has no additional benefit and should be discarded; while for patients with indications, renal artery stenting The role of stenting was not shaken by the results of the ORAL study. Reasonable opinions on both sides are worth pondering and exploring.

In RAS interventional surgery, ARAS has a higher risk of atherosclerotic embolism, which can lead to the obstruction of small blood vessels in the kidney and increase the risk of irreversible damage to the kidney, thereby progressing to atheroembolic nephropathy, showing progressive renal disease. failure, which is often misdiagnosed as contrast nephropathy. Placement of an embolic protection device prior to stent placement addresses this problem, and the presence of such complications also affects the potential benefit of interventional therapy in RAS patients. At the same time, Professor Wan Jianxin shared his thoughts and experiences on the clinical indications of RAS interventional surgery:

In patients with stable renal function and stable decline, interventional therapy is unlikely to benefit;

Patients with refractory hypertension may benefit;

The best evidence is in patients with bilateral stenosis with pulmonary edema, but the evidence is not derived from retrospective studies;

There is no obvious benefit for stenting only for bilateral stenosis but no other indications;

Interventional therapy for patients with declining renal function cannot guarantee results;

Severe bilateral stenosis or solitary renal artery stenosis with decreased renal function is less clear.

Summarize

Due to the limitations of interventional procedures, the current clinical practice of RAS intervention is relatively limited. Current interventional indications for RAS will focus on clinical benefit rather than on radiological identification. Therefore, the decision of interventional experts to intervene in renal artery stenosis cannot be isolated, and at least requires multidisciplinary collaboration including nephrologists. Moreover, considering the clinical risks and benefits of RAS intervention, it is also possible to consider involving patients to improve the practical value of multi-party collaboration. Some interventional complications, such as atherosclerotic embolism, also affect the benefit of interventional therapy in RAS patients. As embolic protection devices become more convenient and suitable for various renal interventions, it is possible that the incidence of atherosclerotic embolic nephropathy will decrease.

Research is continuing to find the best way to predict the population who will benefit from renal interventional therapy. Current RCT studies have shown that interventional therapy is not superior to drug therapy. If renal function is stable and hypertension can be controlled by drugs within the past 6-12 months, interventional therapy is not recommended. Most evidence supports interventional therapy for patients with In cases of bilateral stenosis with pulmonary edema, other clinical evidence supporting RAS intervention is still on the way.

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