Renal artery and parenchymal changes after renal denervation: assessment by magnetic resonance angiography.

OBJECTIVES: Relatively little is known about the incidence of long-term renal damage after renal denervation (RDN), a potential new treatment for hypertension. In this study the incidence of renal artery and parenchymal changes, assessed with contrast-enhanced magnetic resonance angiography (MRA) after RDN, is investigated. METHODS: This study is an initiative of ENCOReD, a collaboration of hypertension expert centres. Patients in whom an MRA was performed before and after RDN were included. Scans were evaluated by two independent, blinded radiologists. Primary outcome was the change in renal artery morphology and parenchyma. RESULTS: MRAs from 96 patients were analysed. Before RDN, 41 renal anomalies were observed, of which 29 mostly mild renal artery stenoses. After a median time of 366 days post RDN, MRA showed a new stenosis (25-49% lumen reduction) in two patients and progression of pre-existing lumen reduction in a single patient. No other renal changes were observed and renal function remained stable. CONCLUSIONS: We observed new or progressed renal artery stenosis in three out of 96 patients, after a median time of 12 months post RDN (3.1%). Procedural angiographies showed that ablations were applied near the observed stenosis in only one of the three patients. KEY POINTS: • The incidence of vascular changes 12 months post RDN was 3.1%. • No renal vascular or parenchymal changes other than stenoses were observed. • Ablations were applied near the stenosis in only one of three patients.

Invasive assessment of renal artery atherosclerotic disease and resistant hypertension before renal sympathetic denervation.

BACKGROUND: Renal sympathetic denervation (RSD) is emerging as a new therapeutic option for patients with severe hypertension refractory to medical therapy. The presence of a renal artery stenosis may be both a cause of secondary hypertension and a contraindication to RSD if a renal artery stent is implanted; therefore, the definition of the functional importance of a renal artery stenosis in a patient with refractory hypertension is crucial. METHODS: We describe the imaging and functional intravascular assessment of an angiographically severe stenosis of the renal artery in a patient with severe refractory hypertension, by means of intravascular ultrasound (IVUS), and measurement of the translesional pressure gradient with a pressure wire. RESULTS: Pressure wire examination excluded any severity of the stenosis, and IVUS showed the presence of a dissected plaque that resolved spontaneously after 3 months of intensive medical therapy and high-dose statin. Subsequently the patient was treated with RSD, achieving a significant effect on blood pressure control. CONCLUSIONS: Intravascular imaging and functional assessment of renal artery anatomy in patients with atherosclerotic disease may prove particularly suited to patients with refractory hypertension and multilevel vascular disease who are considered for endovascular therapies, either renal artery stenting or RSD.

Usefulness of translesional pressure gradient and pharmacological provocation for the assessment of intermediate renal artery disease.

OBJECTIVE: We sought to determine the hemodynamic significance of intermediate RAS by measuring translesional systolic pressure gradients (TSPG), using a pressure-sensing guidewire at baseline and after acetylcholine (ACh) induced hyperemia, following selective renal artery angiography. BACKGROUND: Renal artery stenosis (RAS) is a cause of reversible hypertension and nephropathy. Stenting effectively relieves RAS, however improvement in blood pressure control or renal function is variable and unpredictable. Hemodynamic significance is usually present with RAS when diameter stenosis is >75%, but is less predictable in intermediate (30%-75%) RAS. METHODS: Twenty-two patients (26 renal arteries) with uncontrolled hypertension underwent invasive hemodynamic assessment because of intermediate RAS, defined as radiocontrast angiographic diameter stenosis (DS) between 30% and 75% (quantitative DS was measured prospectively). Translesional pressure gradients were measured using a 0.014" pressure-sensing wire. Hyperemia was induced by administration of intrarenal ACh. RESULTS: Visual and measured angiographic lesion severity did not correlate with TSPG either at baseline (visual DS, R(2) = 0.091, P = 0.13; measured DS, R(2) = 0.124, P = 0.07) or with hyperemia (visual DS, R(2) = 0.057, P = 0.24; measured DS, R(2) = 0.101, P = 0.12). Baseline and maximal hyperemic gradient did correlate (R(2) = 0.567; P < 0.05). Pharmacological provocation produced a significant increase in TSPG (mean; baseline, 18 +/- 21 vs. hyperemia, 34 +/- 41 mm Hg; P < 0.05). A hemodynamically significant lesion (TSPG > 20 mm Hg) was found in 14/26 (54%) arteries (13 patients); 13 (60%) patients subsequently underwent renal artery stenting for hemodynamically significant RAS. At follow-up (at least 30 days), there was a significant decrease in systolic blood pressure (mean; 167 +/- 24 vs. 134 +/- 19 mm Hg; P < 0.001). CONCLUSIONS: Intrarenal administration of ACh induces hyperemia and can be used to unmask resistive renal artery lesions. Gradient measurement and induced hyperemia may be warranted in the invasive assessment of intermediate renal artery stenoses, rather than relying on stenosis severity alone. Further study is needed to determine whether translesional pressure gradients and pharmacological provocation predict clinical benefit after renal artery stenting.

Hypertension and renovascular disease: follow-up on 100 renal vein renin samplings.

The clinical value of renal vein renin sampling (RVRS) as a prognostic tool in the treatment of renovascular hypertension was evaluated. One hundred consecutive patients were included over a 4-year period of time. About half of the patients (49%) were treated interventionally by PTRA (21%), nephrectomy (20%), or vascular surgery (8%). Seven patients (15%) were cured and 15 (32%) had improved (reduction in antihypertensive medicine) after 6 months follow-up, whereas three patients (6%) were cured and 12 (26%) improved after 3-4 years follow-up. Thus, the number of patients cured or improved is comparable with the results from our department reported 20 years ago. However, in the present report, more than twice as many patients were enrolled, leading to double costs. Different indices of lateralisation of the renin generation were calculated for the use in cases of a shrunken kidney (functional share < or =15%). None of the indices clearly discriminated between the patients who did benefit from intervention, and those who did not. The only positive finding was that a peripheral renin concentration lower than 8 mlU/l predicted no effect of intervention, which might lead to the exclusion of 11% of the patients before entering the diagnostic programme. We conclude that the RVRS demands a very restrictive referral pattern if it should be of prognostic value for the blood pressure outcome after intervention. No indices of lateralised renin concentrations proved high predictive value. However, a peripheral renin concentration low in the normal range seems useful as an indicator of no benefit from intervention.

Renovascular disease in blacks: prevalence and result of operative management. Consortium of Southeastern Hypertension Control.

Hypertension in blacks differs in a quantitative sense from hypertension in whites; it occurs in blacks with greater frequency and severity and at a younger age when compared with whites. In addition, elevated blood pressure at any level is associated with increased cardiovascular morbidity and mortality in black patients. Several mechanisms have been suggested to account for this form of hypertension, implying that hypertension in black patients is intrinsically different from that in whites. Although these mechanisms remain unproven, it has generally been accepted that correctable renovascular disease and renovascular hypertension (RVH) occur infrequently in blacks; the authors, however, will review preliminary population-based data which suggest that the presence of renal artery disease is not determined by race or ethnicity. In addition, the prevalence of renovascular disease in a large group of consecutive hypertensive subjects will be presented. Finally, the blood pressure and renal function response after surgical renal artery repair in blacks will be compared with whites treated at the authors' institution. Taken collectively, these data and clinical experience support the search for and treatment of renal artery disease in properly selected hypertensive blacks.

Atherosclerotic renovascular disease as a cause of end-stage renal disease: cost considerations.

Atherosclerotic vascular disease affects an increasing number of patients with end-stage renal disease. A review of comorbid atherosclerotic disease in 7,200 end-stage renal disease patients indicated that occlusive disease of the renal arteries may contribute to progressive renal failure in 1.34% of the US dialysis population or in 14% of the Caucasian patients with hypertensive nephrosclerosis. The costs of dialytic care in such patients exceed USD 87 million annually. The risks and costs of surgical revascularization of such patients are large, however. These data argue that prospective trials of intervention in atherosclerotic renal artery disease are urgently needed.

Unilateral renal artery stenosis seen initially as severe and symptomatic hypokalemia. Pathophysiologic assessment and effects of surgical revascularization.

Hypokalemia is an uncommon presentation of renovascular hypertension. Although renal artery stenosis has been associated with hypokalemia secondary to hyperreninemic hyperaldosteronism, few reports have actually evaluated the pathophysiologic changes in such a patient with renovascular hypertension. We studied a patient before and after surgical revascularization who presented with severe hypertension and marked, symptomatic hypokalemia. Before surgery, the patient had excessive urinary potassium secretion, markedly increased secretion of renin after captopril stimulation, and mild secondary hyperaldosteronism. Postoperatively, the patient's blood pressure decreased moderately and the serum and urinary potassium values normalized. After revascularization, plasma renin activity both before and after captopril stimulation and serum aldosterone levels decreased markedly. These findings demonstrate that renovascular hypertension may rarely present with symptomatic hypokalemia secondary to excessive aldosterone secretion. Improvement in the renal ischemic state is accompanied by rapid correction of the metabolic disturbances associated with hyperreninemic hyperaldosteronism.

Aortorenal arterial autografts: long-term assessment.

Ninety-four iliac arterial autografts were placed in 86 hypertensive patients (age range, 7 to 57 years) during a 16-year period for renal artery reconstruction of nonatherosclerotic lesions. Ten patients were children, and nine patients had a solitary kidney. Ex vivo repair was used in 21 patients. There were no early postoperative deaths; one patient died three months postoperatively of unrelated disease. Two grafts occluded in the early postoperative period. Follow-up of one to 16 years (mean, 5.6 years) was available in 77 patients (93%). Forty-one patients underwent late arteriography at an average of 5.7 years postoperatively. Fifty-one patients (66%) were regarded as cured of their hypertension, the conditions of 25 patients (32%) improved, and the condition of one patient (1.2%) was unchanged. There were no late autograft occlusions. Atherosclerotic anastomotic stenosis developed in one autograft 13 years postoperatively and was relieved by reoperation. Dilation of one autograft was observed seven years postoperatively but did not increase on subsequent arteriograms. In five children, follow-up angiograms showed that the size of the autograft paralleled that of the contralateral renal artery. These results support the preferential use of an autograft during reconstruction of nonatherosclerotic lesions that cause renovascular hypertension.

Percutaneous transluminal dilatation: the treatment of choice for renal artery stenosis causing hypertension.

During the last 3 yr a large number of patients with renal artery stenosis have undergone attempted treatment of their stenosis by the technique termed percutaneous transluminal angioplasty or dilatation (PTD) using the balloon tipped catheter developed by Gruntiz. A number of publications have documented that this technique is reasonably safe and effective in renal artery lesions due to fibromuscular disease (FMD), atherosclerosis (AS), or prior surgery such as renal artery bypass or transplantation. Although initially many of the patients that were treated were felt to be poor surgical risks, many patients have now been treated who were excellent candidates for renal artery bypass. The cumulative experience argues that PTD should be the first treatment tried in any patient with significant renal artery stenosis causing hypertension. It should be noted that the cumulative experience is not based on any controlled trial and therefore may well be biased. Nevertheless, I will present this argument based on the published data and our own experience at Indiana University. This argument pertains to any patient with incomplete renal artery occlusion who has a functionally significant stenosis (determined by renal vein renin sampling) and who is a good surgical candidate. Those patients who are at high risk for major surgery will obviously be best treated by PTD or medical management. The argument has four major points: safety, effectiveness, cost analysis, and availability.