Atherosclerotic renal artery stenosis--diagnosis and treatment

Decrease of glomerular filtration rate may be attributed to the microcirculation damage in renal artery stenosis

BACKGROUND

The decrease of glomerular filtration rate has been theoretically supposed to be the result of low perfusion in renal artery stenosis (RAS). But the gap between artery stenosis and the glomerular filtration ability is still unclear.

METHODS

Patients with selective renal artery angiogram were divided by the degree of renal artery narrowing, level of estimated glomerular filtration rate (eGFR), respectively. The different levels of eGFR, renal microcirculation markers, and RAS severity were compared with each other, to determine the relationships among them.

RESULTS

A total of 215 consecutive patients were enrolled in the prospective cohort study. Concentrations of microcirculation markers had no significant difference between RAS group (RAS ≥ 50%) and no RAS group (RAS < 50%) or did not change correspondingly to RAS severity. The value of eGFR in RAS group was lower than that in the no RAS group, but it did not decline parallel to the progressive severity of RAS. The microcirculation markers presented integral difference if grouped by different eGFR level with negative tendency, especially that plasma cystatin C (cysC) and urinary microalbumin to creatinine ratio (mACR) increased with the deterioration of eGFR, with strong (r = -0.713, P < 0.001) and moderate (r = -0.580, P < 0.001) correlations. In the subgroup analysis of severe RAS (RAS ≥ 80%), the levels of plasma cysC and urinary mACR demonstrated stronger negative associations with eGFR, (r = -0.827, P < 0.001) and (r = -0.672, P < 0.001) correlations, respectively.

CONCLUSIONS

Severity of RAS could not accurately predict the value of eGFR, whereas microcirculation impairment may substantially contribute to the glomerular filtration loss in patients with RAS.

Validation of renal artery dimensions measured by magnetic resonance angiography in patients referred for renal sympathetic denervation

RATIONALE AND OBJECTIVES

Magnetic resonance angiography (MRA) is a well-established modality for the assessment of renal artery stenosis. Using dedicated quantitative analyses, MRA can become a useful tool for assessing renal artery dimensions in patients referred for renal sympathetic denervation (RDN) and for providing accurate measurements of vascular response after RDN. The purpose of this study was to test the reproducibility of a novel MRA quantitative imaging tool and to validate these measurements against intravascular ultrasound (IVUS).

MATERIALS AND METHODS

In nine patients referred for renal denervation, renal artery dimensions were measured. Bland-Altman analysis was used to assess the intraobserver and interobserver reproducibility.

RESULTS

Mean lumen diameter was 5.8 ± 0.7 mm, with a very good intraobserver and interobserver variability of 0.7% (reproducibility: bias, 0 mm; standard deviation [SD], 0.1 mm) and 1.2% (bias, 0 mm; SD, 0.1 mm), respectively. Mean total lumen volume was 1035.3 ± 403.6 mm(3) with good intraobserver and interobserver variability of 2.9% (bias, -9.7 mm(3); SD, 34.0 mm(3)) and 2.8% (bias, -11.4 mm(3); SD, 42.4 mm(3)). The correlation (Pearson R) between mean lumen diameter measured with MRA and IVUS was 0.750 (P = .002).

CONCLUSIONS

Using a novel MRA quantitative imaging tool, renal artery dimensions can be measured with good reproducibility and accuracy. MRA-derived diameters and volumes correlated well with IVUS measurements.

Renal artery stenosis-when to screen, what to stent?

Renal artery stensosis (RAS) continues to be a problem for clinicians, with no clear consensus on how to investigate and assess the clinical significance of stenotic lesions and manage the findings. RAS caused by fibromuscular dysplasia is probably commoner than previously appreciated, should be actively looked for in younger hypertensive patients and can be managed successfully with angioplasty. Atheromatous RAS is associated with increased incidence of cardiovascular events and increased cardiovascular mortality, and is likely to be seen with increasing frequency. Evidence from large clinical trials has led clinicians away from recommending interventional revascularisation towards aggressive medical management. There is now interest in looking more closely at patient selection for intervention, with focus on intervening only in patients with the highest-risk presentations such as flash pulmonary oedema, rapidly declining renal function and severe resistant hypertension. The potential benefits in terms of improving hard cardiovascular outcomes may outweigh the risks of intervention in this group, and further research is needed.

Circulating and renal vein levels of microRNAs in patients with renal artery stenosis

BACKGROUND

MicroRNAs (miRs) are small non-coding RNAs that are important regulators of gene expression and have been implicated in atherosclerosis. Kidney injury distal to atherosclerotic renal artery stenosis (ARAS) is aggravated by atherosclerosis. Therefore, this study tested the hypothesis that renal miR expression would be altered in patients with ARAS.

METHODS

Patients with essential hypertension (EH; n = 13) or ARAS (n = 13) underwent a 3-day protocol study under controlled conditions. For miR levels, blood samples were collected from EH and ARAS renal vein (RV) and inferior vena cava or peripheral vein of matched normotensive healthy volunteers (HV; n = 13) and patients with coronary atherosclerosis (CA; n = 11). Single-renal blood flow was measured in EH and ARAS using computer tomography to calculate renal gradients and release of miRs.

RESULTS

Glomerular filtration rate (GFR) was lower in ARAS compared with the other groups. Systemic levels of most miRs were elevated in CA. RV miR levels were lower than systemic levels in both ARAS and EH. GFR-adjusted RV levels of miR-21, 155 and 210 were reduced only in ARAS patients compared with systemic levels in HV, although cross-kidney gradients were not different from EH. RV levels of miR-21, 126, 155 and 210 correlated with GFR.

CONCLUSIONS

Levels of atherosclerosis-related miR-21, 126, 155 and 210 are decreased in the stenotic-kidney vein of ARAS compared with EH patients, likely due to decreased GFR. Yet, these miRs might be implicated in modulating renal injury in ARAS, and their RV level may be a marker reflecting their renal expression.

Roles of inflammation, oxidative stress, and vascular dysfunction in hypertension

Hypertension is a complex condition and is the most common cardiovascular risk factor, contributing to widespread morbidity and mortality. Approximately 90% of hypertension cases are classified as essential hypertension, where the precise cause is unknown. Hypertension is associated with inflammation; however, whether inflammation is a cause or effect of hypertension is not well understood. The purpose of this review is to describe evidence from human and animal studies that inflammation leads to the development of hypertension, as well as the evidence for involvement of oxidative stress and endothelial dysfunction--both thought to be key steps in the development of hypertension. Other potential proinflammatory conditions that contribute to hypertension-such as activation of the sympathetic nervous system, aging, and elevated aldosterone--are also discussed. Finally, we consider the potential benefit of anti-inflammatory drugs and statins for antihypertensive therapy. The evidence reviewed suggests that inflammation can lead to the development of hypertension and that oxidative stress and endothelial dysfunction are involved in the inflammatory cascade. Aging and aldosterone may also both be involved in inflammation and hypertension. Hence, in the absence of serious side effects, anti-inflammatory drugs could potentially be used to treat hypertension in the future.

Use of renin-angiotensin inhibitors in people with renal artery stenosis

BACKGROUND AND OBJECTIVES

People with atherosclerotic renal artery stenosis may benefit from renin-angiotensin inhibitors, angiotensin-converting enzyme inhibitors, and angiotensin-receptor blockers, but little is known about the factors associated with their use.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The Cardiovascular Outcomes in Renal Atherosclerotic Lesions study (ClinicalTrials.gov identified: NCT00081731) is a prospective, international, multicenter clinical trial that randomly assigned participants with atherosclerotic renal artery stenosis who received optimal medical therapy to stenting versus no stenting from May 2005 through January 2010. At baseline, medication information was available from 853 of 931 randomly assigned participants. Kidney function was measured by serum creatinine-based eGFR at a core laboratory.

RESULTS

Before randomization, renin-angiotensin inhibitors were used in 419 (49%) of the 853 participants. Renin-angiotensin inhibitor use was lower in those with CKD (eGFR<60 ml/min per 1.73 m(2)) (58% versus 68%; P=0.004) and higher in individuals with diabetes (41% versus 27%; P<0.001). Presence of bilateral renal artery stenosis or congestive heart failure was not associated with renin-angiotensin inhibitor use. Although therapy with renin-angiotensin inhibitors varied by study site, differences in rates of use were not related to the characteristics of the site participants. Participants receiving a renin-angiotensin inhibitor had lower systolic BP (mean ± SD, 148 ± 23 versus 152 ± 23 mmHg; P=0.003) and more often had BP at goal (30% versus 22%; P=0.01).

CONCLUSIONS

Kidney function and diabetes were associated with renin-angiotensin inhibitor use. However, these or other clinical characteristics did not explain variability among study sites. Patients with renal artery stenosis who received renin-angiotensin inhibitor treatment had lower BP and were more likely to be at treatment goal.

Quantitative imaging biomarkers for the evaluation of cardiovascular complications in type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a prevalent condition in aged populations. Cardiovascular diseases are leading causes of death and disability in patients with T2DM. Traditional strategies for controlling the cardiovascular complications of diabetes primarily target a cluster of well-defined risk factors, such as hyperglycemia, lipid disorders and hypertension. However, there is controversy over some recent clinical trials aimed at evaluating efficacy of intensive treatments for T2DM. As a powerful tool for quantitative cardiovascular risk estimation, multi-disciplinary cardiovascular imaging have been applied to detect and quantify morphological and functional abnormalities in the cardiovascular system. Quantitative imaging biomarkers acquired with advanced imaging procedures are expected to provide new insights to stratify absolute cardiovascular risks and reduce the overall costs of health care for people with T2DM by facilitating the selection of optimal therapies. This review discusses principles of state-of-the-art cardiovascular imaging techniques and compares applications of those techniques in various clinical circumstances. Individuals measurements of cardiovascular disease burdens from multiple aspects, which are closely related to existing biomarkers and clinical outcomes, are recommended as promising candidates for quantitative imaging biomarkers to assess the responses of the cardiovascular system during diabetic regimens.

A reversible cause of 'end-stage renal disease': discrepant findings in serial duplex ultrasonograms in a suspected occlusion of a renal arterial bypass graft

Duplex ultrasonography may be inaccurate due to a number of variables in operator and patient characteristics. We describe a 40-year-old woman who presented with acute kidney injury after prior complex abdominal aortic surgery that had left her with an essentially solitary functional kidney. On the basis of normal Doppler findings, she was started on dialysis. Owing to high clinical suspicion and a failure of renal function to return, a second Doppler study was performed 3 weeks after the first, revealing the characteristic tardus-parvus waveform of renal artery stenosis. The patient underwent urgent renal arterial angioplasty and stent placement. She experienced an immediate increase in urinary output, required no further dialysis, and the creatinine improved to 1.7 mg/dL (her prior renal baseline). The case illustrates an important complication of abdominal aortic aneurysm repair, draws attention to a potential source of error in the Doppler measurement, and underscores the limitations of duplex ultrasonography for excluding renal artery stenosis in the presence of high pretest probability.

Renal artery stenosis in patients with resistant hypertension

The aim of the study was to assess the significance of renal translesional pressure gradients in predicting improvement in resistant hypertension after stenting for moderate renal artery stenosis (RAS). In 37 patients with RAS and resistant hypertension subjected to renal stenting, translesional pressure gradients both at rest and hyperemic were measured using a pressure guidewire. Twenty-four-hour ambulatory blood pressure measurements were performed in all patients on admission and 3 months after the intervention. Angioplasty was successful in all patients, with reduction of artery diameter stenosis from 60 ± 12% to 10 ± 6% (p <0.0001). At 3 months, with maintained hypotensive agents (4.0 ± 1.4 vs 4.0 ± 1.6), significant reductions in systolic blood pressure (SBP) and diastolic blood pressure were noted (-5 and -2 mm Hg, respectively). In multivariate analysis, the mean baseline gradient (MBG) was the only independent predictor of improvement in SBP (regression coefficient 0.292; standard error 0.11; p value 0.014). In the receiver operating characteristic curve analysis, MBG had a larger area under the curve than other parameters, and the MBG >22 mm Hg had the highest sensitivity, specificity, and accuracy (50%, 95%, and 0.74%, respectively) in predicting hypertension improvement after stenting. In patients with MBG >22 mm Hg, SBP decreased by 12 versus 3 mm Hg (p <0.01) in patients with MBG ≤22 mm Hg, whereas diastolic blood pressure in both groups decreased by 3 versus 1 mm Hg, respectively (NS). In conclusion, MBG value of >22 mm Hg provides the highest accuracy in predicting hypertension improvement after stenting for moderate RAS in patients with resistant hypertension.

[Medicinal or instrumental (corrected) therapy of renal artery stenosis?]

Arteriosclerotic renal artery stenosis (RAS) has an increased incidence in patients with cardiovascular risk factors. Clinically RAS presents in some patients as secondary, sometimes resistant arterial hypertension and in others as chronic renal insufficiency, sometimes with acute renal failure and in a third group both symptoms are observed. Doppler ultrasound plays a central role in the diagnosis of RAS. Therapeutically, it is important to identify hemodynamically relevant RAS before interventional therapy is initiated. The therapy of RAS has been under intensive debate since the publication of randomized controlled trials (RCT) which showed that only a subset of RAS can be successfully treated by interventional therapy. Since then the medicinal therapy of RAS has gained more and more impact. The following questions are raised: which forms of RAS can be treated by which therapy? What is the best medicinal therapy to treat RAS? What substances are recommended?