Atherosclerotic Renal Artery Stenosis

Translational research in nephrology: prognosis

Translational research aims at reducing the gap between the results of studies focused on diagnosis, prognosis and therapy, and every day clinical practice. Prognosis is an essential component of clinical medicine. It aims at estimating the risk of adverse health outcomes in individuals, conditional to their clinical and non-clinical characteristics. There are three fundamental steps in prognostic research: development studies, in which the researcher identifies predictors, assigns the weights to each predictor, and assesses the model’s accuracy through calibration, discrimination and risk reclassification; validation studies, in which investigators test the model’s accuracy in an independent cohort of individuals; and impact studies, in which researchers evaluate whether the use of a prognostic model by clinicians improves their decision-making and patient outcome. This article aims at clarifying how to reduce the disconnection between the promises of prognostic research and the delivery of better individual health.

Is stenting for atherosclerotic renal stenosis an effective technique?

INTRODUCTION

One of the treatments for renal artery stenosis is endovascular intervention, but its effectiveness is controversial. The present study aims to analyze the experience of a working group in the endovascular treatment of selected patients with severe obstructive atherosclerotic lesions of the renal arteries, and to characterize early and late results.

METHODS

This is a retrospective study of symptomatic patients with atherosclerotic renal artery stenosis who underwent endoluminal therapy between May 12, 1999 and March 12, 2015 at two institutions. Statistical analysis was performed using the PASW Statistics program.

RESULTS

A total of 99 patients were treated, mean age 66 years and 76.8% male. The mean degree of stenosis measured by renal Doppler echocardiography was 83% and 64.6% were ostial lesions. Mean preoperative creatinine level was higher than the postoperative mean: 1.3 vs. 1.2 mg/dl (p=0.014). The number of antihypertensive drugs in the preoperative period was higher than in the postoperative period: 2.0 vs. 1.3 (p=0.001). The mean follow-up was 40 months (0-164). The mean peak systolic velocity over time in the postoperative period was 77 cm/s (40-250). The restenosis rate was 8%, and 30-day mortality was 0%.

CONCLUSIONS

The results demonstrated that the endovascular technique has a beneficial effect on blood pressure and renal function in selected patients, and is a safe technique associated with a high rate of technical success and few complications.

Percutaneous renal artery stent implantation in the treatment of atherosclerotic renal artery stenosis

We aimed to investigate the clinical curative effect of percutaneous renal artery stent implantation (PTRAS) in the treatment of atherosclerotic renal artery stenosis (ARAS), and to analyze the factors influencing the curative effect of PTRAS. A total of 230 patients with unilateral or bilateral renal artery stenosis were retrospectively analyzed. According to whether adverse cardiogenic or nephrogenic events occurred, 230 patients were divided into two groups to analyze the risk factors of adverse cardiogenic or nephrogenic events. The blood pressure of patients at each time-point after operation was decreased significantly compared with that before operation (P<0.01). The levels of serum creatinine (SCr) at 24 h and 36 months after PTRAS were slightly increased compared with that before operation (P>0.05). The estimated glomerular filtration rate (eGFR) at each time-point after operation was slightly decreased compared with that before operation, but the difference was not statistically significant (P>0.05). Renography showed that GFR on the side of stent implantation at 36 months after PTRAS had no significant change compared with that before operation (P>0.05), but GFR on the unaffected side without receiving PTRAS was significantly increased compared with that before operation (P=0.0014). During the 36-month follow-up, there were a total of 56 cases of adverse cardiogenic or nephrogenic events. Multivariate regression analysis results showed that adverse cardiogenic or nephrogenic events after PTRAS were obviously associated with age (≥65 years old), Charlson comorbidity index (CCI) score (≥2 points), diabetes mellitus, stroke and congestive heart failure (CHF) (P<0.05). In conclusion, PTRAS can effectively control the blood pressure and reduce the types of antihypertensive drugs used by patients with ARAS, but it has no definitely protective effect on renal function. Age (≥65 years old), CCI score (≥2 points), diabetes mellitus, stroke and CHF are risk factors leading to adverse cardiogenic or nephrogenic events after PTRAS.

A feasibility study on model-based evaluation of kidney perfusion measured by means of FAIR prepared true-FISP arterial spin labeling (ASL) on a 3-T MR scanner

RATIONALE AND OBJECTIVES

A feasibility study on measuring kidney perfusion by a contrast-free magnetic resonance (MR) imaging technique is presented.

MATERIALS AND METHODS

A flow-sensitive alternating inversion recovery (FAIR) prepared true fast imaging with steady-state precession (TrueFISP) arterial spin labeling sequence was used on a 3.0-T MR-scanner. The basis for quantification is a two-compartment exchange model proposed by Parkes that corrects for diverse assumptions in single-compartment standard models.

RESULTS

Eleven healthy volunteers (mean age, 42.3 years; range 24-55) were examined. The calculated mean renal blood flow values for the exchange model (109 +/- 5 [medulla] and 245 +/- 11 [cortex] ml/min - 100 g) are in good agreement with the literature. Most important, the two-compartment exchange model exhibits a stabilizing effect on the evaluation of perfusion values if the finite permeability of the vessel wall and the venous outflow (fast solution) are considered: the values for the one-compartment standard model were 93 +/- 18 (medulla) and 208 +/- 37 (cortex) ml/min - 100 g.

CONCLUSION

This improvement will increase the accuracy of contrast-free imaging of kidney perfusion in treatment renovascular disease.

Disseminated multiple ostial stenoses in a young woman presenting as unstable angina

A previously healthy 40-year-old woman presented as unstable angina. She had a family history of stroke as the only cardiovascular risk factor. Her blood pressure on admission was 150/90 mmHg. Laboratory study showed absolutely all negative markers of inflammation, autoimmune disorders, or atherosclerosis. Coronary angiography revealed subtotal ostial stenosis of the right coronary artery (RCA). Additionally, total occlusion of the ostium of the right subclavian artery and severe discrete ostial stenoses of left subclavian, celiac, superior mesenteric, both renal arteries were demonstrated on multidetector computed tomographic and magnetic resonance angiographies. She underwent stent implantation at the culprit lesion of RCA, and the left subclavian and both renal arteries. The fluorine-18-fluorodeoxyglucose positron-emission tomography-computed tomography showed slightly increased glucose metabolism at the proximal left subclavian artery. She is doing very well for 10 months during taking antiplatelet agents only.

Renal artery calcium is independently associated with hypertension

OBJECTIVES

We tested the hypothesis that renal artery calcium (RAC), a marker of atherosclerotic plaque burden, is also significantly associated with higher blood pressure levels and a diagnosis of hypertension.

BACKGROUND

In the nonrenal systemic vasculature, atherosclerotic plaque burden has been shown to be significantly associated with hypertension.

METHODS

A total of 1,435 consecutive patients were evaluated at a university-affiliated disease prevention center for the extent of calcified atherosclerosis in the systemic vasculature.

RESULTS

The overall prevalence of calcium in either renal artery was 17.1%, with men having a significantly higher prevalence (19.0%, 153 of 804) than women (14.7%, 93 of 631) (p = 0.03). After adjustment for age and gender, subjects with a RAC score >0 had a significantly higher prevalence of hypertension (41.2 vs. 29.5, p < 0.01). In a logistic model that adjusted for age, gender, body mass index, percent body fat, diabetes, smoking, dyslipidemia, and the extent of calcified atherosclerosis in the nonrenal vasculature, those with any RAC had a significantly higher odds ratio (1.61, p = 0.01) for hypertension than those with no RAC.

CONCLUSIONS

The results of this study suggest that the presence of RAC is associated with higher odds for prevalent hypertension, independent of CVD risk factors and the extent of calcified atherosclerosis in the nonrenal vasculature.

Contrast nephropathy may be partly mediated by autonomic dysfunction: renal failure considered as a modern maladaptation of the prehistoric trauma response

The mechanism behind iodinated radiocontrast nephropathy remains elusive. Direct oxidative damage is the prevailing hypothesis, but the apparent protective effect of iodine against oxidation contradicts this view. We propose that autonomic dysfunction participates in the pathogenesis of radiocontrast nephropathy and may account for other contrast-associated reactions previously attributed to allergy. Iodine, through its effects on thyroid function and chemoreceptor response to metabolic acidosis, may induce hyperadrenergia and consequently diminish renovascular flow and urine output. The renal response to adrenergia likely served an adaptive function during prehistoric evolution when trauma was a dominant source of hypovolemia and adrenergia, but the response may behave maladaptively today as evolutionarily nai ve triggers for adrenergia have emerged. Autonomic dysfunction can further impair renal function by deranging renovascular autoregulation and inducing oxidative reperfusion injury as a secondary phenomenon. Many other causes of acute renal failure such as drug toxicity, surgery, hospitalization, and diabetes may operate through hyperadrenergia, impaired renovascular autoregulation, and oxidative reperfusion injury. Dialysis, a volume reduction therapy for renal failure, can counterintuitively worsen renal dysfunction by exacerbating adrenergia, which may explain its association with accelerated atherosclerosis, inflammation, and cancer. Other examples of vicious cycles that perpetuate renal dysfunction may include renal artery stenosis, carotid stenosis, and atherosclerosis as well as the cardio-renal, hepato-renal, and pulmonary-renal syndromes. The benefits of hydration and bicarbonate in protecting renal function may operate in part through baroreceptor- and chemoreceptor-mediated reduction of sympathovagal ratio, respectively. New treatment paradigms for renal failure including pharmacologic and electro-mechanical therapies are envisioned based on autonomic remodeling, reduced sympathovagal ratio, and neuromodulation of pathways typically associated with trauma such as renin, angiotensin, vasopressin, and aldosterone.

Atherosclerotic renovascular disease in chronic heart failure: should we intervene?

Renal artery stenosis (RAS) is most commonly caused by atherosclerosis, which is also the most common cause of chronic heart failure (CHF). One-third of patients with CHF are reported to have significant renovascular disease. The presence of RAS confers a worse outcome in studies of hypertension and coronary disease, though data are lacking for patients with CHF. As the kidney is intricately involved in the fluid retention that occurs in CHF, an adverse effect of RAS on outcome would be expected. Presentations of RAS in CHF include flash pulmonary oedema, hypertension, worsening of CHF, and worsening renal function. RAS commonly progresses and may cause worsening of renal function in patients with CHF and previously stable renal function. A variety of investigations that can safely and accurately identify RAS in CHF are available, although none is recommended in current guidelines for the management of CHF. Treatment for RAS, whether for hypertension, for renal dysfunction, or for pulmonary oedema, is at the discretion of the physician due to the lack of adequate randomized controlled trials demonstrating the efficacy and safety of intervention. As it is not clear how RAS should be managed in CHF, screening cannot be advocated. Currently, a multicentre randomized outcome trial, which includes a cohort of patients with RAS and CHF, is in progress to provide answers in this area of uncertainty.

[Renovascular hypertension--diagnosis and therapy]

Atherosclerotic renal artery stenosis accounts for most cases of renovascular hypertension (RVH). Hypertensive patients with clinical features suggesting RVH should be submitted to further noninvasive evaluation including duplex Doppler ultrasonography, CT- or MR angiography. Invasive evaluation by contrast-enhanced angiography confirms the diagnosis of renal artery stenosis. However, neither diagnostic test reliably predicts the course of hypertension after revascularisation. The therapeutic approach in hypertensive patients with hemodynamically important renal artery stenosis includes medical or invasive therapy (renal percutaneous transluminal angioplasty, PTRA; renal arterial stent placement, PTRAS; surgical revascularisation). Randomized trials comparing invasive and conservative approaches demonstrated no differences in blood pressure control or renal function. Only patients with clear clinical indications should be submitted to interventional procedures as PTRA, PTRAS and surgical vascular intervention.

Rapid Improvement of Acute Pulmonary Edema with Angiotensin Converting Enzyme Inhibitor under Hemodialysis in a Patient with Renovascular Disease

A 71-year-old man with bilateral renovascular disease was admitted to Hamamatsu University hospital because of appetite loss and acute shortness of breath due to acute pulmonary edema (APE) with accelerated hypertension and renal failure. Hypertension and APE were controlled by an angiotensin converting enzyme inhibitor (ACEI) and four sessions of hemodialysis with reduction of 1.8 kg bodyweight. Renal function was later stabilized and the patient required no ACEI or hemodialysis. A trial of right renal angioplasty 1 month after admission failed and renal function deteriorated (serum creatinine 7.1 mg/dL) with accelerated hypertension, gain of bodyweight and APE. Even after four sessions of hemodialysis with adequate reduction of bodyweight, APE was not controlled, but it rapidly improved after administration of an ACEI, without major bodyweight change. As no apparent cardiac dysfunction was evident, APE might have been caused by a direct action of angiotensin II on hyperpermeability in pulmonary capillaries. Blocking of angiotensin II should be considered in such patients even after introduction of hemodialysis.

Current issues in the diagnosis and management of patients with renal artery stenosis: a cardiologic perspective

Renal artery stenosis most often is caused by atherosclerosis. Although patients with renal artery stenosis can be managed conservatively, renal revascularization may be indicated, particularly in patients with refractory hypertension on a multidrug regimen and patients with declining renal function. Duplex ultrasonography of the renal arteries and magnetic resonance angiography are currently the most efficient noninvasive methods for the evaluation of renal artery stenosis. Selective digital subtraction renal arteriography remains the gold standard for the definitive diagnosis. In selected patients undergoing coronary studies and angiography immediately after the coronary procedure can be efficient. Atherosclerotic renal artery lesions, which commonly affect the renal artery ostium, can be treated safely and effectively with balloon-expandable stents. Successful angioplasty commonly results in improved control of hypertension, but an overall benefit on renal function and/or patient survival has not been shown. Generally the risk/benefit ratio of renal artery stenting seems favorable, but further randomized studies are needed for evidence-based decision making. All patients with atherosclerotic renal artery stenosis should receive rigorous secondary prevention measures including platelet inhibitors, statins, and beta-blockers.