Urinary mitochondrial DNA copy number identifies renal mitochondrial injury in renovascular hypertensive patients undergoing renal revascularization: A Pilot Study.

AIMS: Patients with renovascular hypertension (RVH) exhibit elevated urinary mtDNA copy numbers, considered to constitute surrogate markers of renal mitochondrial injury. The modest success of percutaneous transluminal renal angioplasty (PTRA) in restoring renal function in RVH has been postulated to be partly attributable to acute reperfusion injury. We hypothesized that mitoprotection during revascularization would ameliorate PTRA-induced renal mitochondrial injury, reflected in elevated urinary mtDNA copy numbers and improve blood pressure and functional outcomes 3 months later. METHODS: We prospectively measured urinary copy number of the mtDNA genes COX3 and ND1 using qPCR in RVH patients before and 24 hrs after PTRA, performed during IV infusion of vehicle (n = 8) or the mitoprotective drug elamipretide (ELAM, 0.05 mg/kg/h, n = 6). Five healthy volunteers (HV) served as controls. Urinary mtDNA levels were also assessed in RVH and normal pigs (n = 7 each), in which renal mitochondrial structure and density were studied ex-vivo. RESULTS: Baseline urinary mtDNA levels were elevated in all RVH patients vs HV and directly correlated with serum creatinine levels. An increase in urinary mtDNA 24 hours after PTRA was blunted in PTRA+ELAM vs PTRA+Placebo. Furthermore, 3-months after PTRA, systolic blood pressure decreased and estimated glomerular filtration rate increased only in ELAM-treated subjects. In RVH pigs, mitochondrial damage was observed using electron microscopy in tubular cells and elevated urinary mtDNA levels correlated inversely with renal mitochondrial density. CONCLUSIONS: PTRA leads to an acute rise in urinary mtDNA, reflecting renal mitochondrial injury that in turn inhibits renal recovery. Mitoprotection might minimize PTRA-associated mitochondrial injury and improve renal outcomes after revascularization.

Editor's Choice - Comparison of Renal Outcomes in Patients Treated by Zenith® Fenestrated and Zenith® Abdominal Aortic Aneurysm Stent grafts in US Prospective Pivotal Trials.

OBJECTIVE/BACKGROUND: Fenestrated endovascular repair (FEVAR) has been used to treat complex abdominal aortic aneurysms (AAAs). The risk of renal function deterioration compared with infrarenal endovascular aortic repair (EVAR) has not been determined. METHODS: Patients with preserved renal function (estimated glomerular filtration rate [eGFR] > 45 mL/minute) enrolled in two prospective, non-randomised studies evaluating Zenith fenestrated and AAA stent grafts were matched (1:2) by propensity scores for age, sex, hypertension, diabetes, and pre-operative eGFR. Sixty-seven patients were treated by FEVAR and 134 matched controls treated by EVAR. Mean follow-up was 30 ± 20 months. Outcomes included acute kidney injury (AKI) defined by RIFLE and changes in serum creatinine (sCr), eGFR, and chronic kidney disease (CKD) staging up to 5 years. RESULTS: AKI at 1 month was similar between groups, with > 25% decline in eGFR observed in 5% of FEVAR and 9% of EVAR patients (p = .39). There were no significant differences in > 25% decline in eGFR at 2 years (FEVAR 20% vs. EVAR 20%; p > .99) or 5 years (FEVAR 27% vs. EVAR 50%; p = .50). Progression to stage IV-V CKD was similar at 2 years (FEVAR 2% vs. EVAR 3%; p > .99) and 5 years (FEVAR 7% vs. EVAR 8%; p > .99), with similar sCr and eGFR up to 5 years. During follow-up, there were more renal artery stenosis/occlusions (15/67 [22%] vs. 3/134 [2%]; p < .001) and renal related re-interventions (12/67 [18%] vs. 4/134 [3%]; p < .001) in patients treated by FEVAR. Rate of progression to renal failure requiring dialysis was low and identical in both groups (1.5% vs. 1.5%; p > .99). CONCLUSION: Aortic repair with FEVAR and EVAR was associated with similar rates of renal function deterioration in patients with preserved pre-operative renal function. Renal related re-interventions were higher following FEVAR, although net changes in renal function were similar in both groups.

The outcome of patients with nephrogenic systemic fibrosis after successful kidney transplantation.

Nephrogenic systemic fibrosis (NSF) is a debilitating disease in patients with severely diminished kidney function. Currently, no standard treatment exists but improvement has been reported after restoration of kidney function. We retrospectively studied 17 NSF patients with and without successful kidney transplantation (KTx) to evaluate the effects of KTx on NSF. Nine of the 11 KTx developed NSF pretransplant whereas two developed NSF immediately after KTx with delayed graft function. Two of the six dialysis patients had previous failed kidney transplants. Age and sex were well matched. All but one patient was dialysis dependent at the time of NSF. Median follow-up was 35 months for KTx patients and 9 months for dialysis patients. Kidney transplants achieved adequate renal function with median serum creatinine of 1.4 (0.9-2.8) mg/dL and a glomerular filtration rate of 42 (19-60) mL/min/1.73 m(2). NSF improved in 54.6% of the transplanted patients and 50% of the nontransplanted patients (p = 0.86). Two KTx patients had complete resolution of their symptoms whereas four had partial improvement. Improvement in the dialysis patients was all partial. Successful KTx did not insure improvement in NSF and in fact appeared to have no significant benefit over dialysis.

Glomerular volume and renal histology in obese and non-obese living kidney donors.

The link between obesity and renal disease is unclear, and there is no consensus as to whether obese individuals are at increased risk for kidney disease after living kidney donation if they otherwise meet acceptance criteria. We retrospectively studied time-zero (implantation) biopsies in 49 obese (body mass index (BMI) > or = 30 kg/m2) and 41 non-obese (BMI < 30 kg/m2) renal donors that met acceptance criteria. We found that our obese donor population had higher systolic blood pressure (P < 0.001 vs non-obese) and higher absolute iothalamate clearance (P = 0.001 vs non-obese) before donation. The obese donors had larger glomerular planar surface area compared to non-obese controls (P = 0.017), and this parameter correlated with patient weight and urinary microalbumin excretion. Detailed examination of the biopsies revealed that although most histologic findings were similar between groups, the obese donors had more tubular dilation (P = 0.01), but less tubular vacuolization (P = 0.02) than the non-obese controls. There was also a trend toward more arterial hyalinosis in the obese patients than controls (P = 0.08). From these data, our studies detected subtle differences in donor organs obtained from obese compared to non-obese individuals. Further studies should be carried out to quantify the long-term impact of these findings.

Kidney transplant function and histological clearance of virus following diagnosis of polyomavirus-associated nephropathy (PVAN).

Polyomavirus-associated nephropathy (PVAN) is managed by reduced immunosuppression with or without antiviral therapy. Data from 55 patients with biopsy-proven PVAN were analyzed for adverse outcomes and influence of baseline variables and interventions. During 20+/-11 months follow-up, the frequencies of graft loss, major and any functional decline were 15%, 24% and 38%, respectively. Repeat biopsies were performed in 45 patients with persistent PVAN in 47%. Low-dose cidofovir, IVIG and cyclosporine conversion were used in 55%, 20% and 55% of patients. No single intervention was associated with improved outcome. Of the variables examined, only degree of interstitial fibrosis at diagnosis was associated with kidney function decline. In contrast, donor source, interstitial fibrosis, proportion of BKV positive tubules and plasma viral load at diagnosis were all associated with failure of histological viral clearance. This retrospective, nonrandomized analysis suggests that: (i) Graft loss within 2 years of PVAN diagnosis is now uncommon, but ongoing functional decline and persistent infection occur frequently. (ii) Low-dose cidofovir, IVIG and conversion to cyclosporine do not abrogate adverse outcomes following diagnosis. (iii) Fibrosis at the time of diagnosis predicts subsequent functional decline. Further elucidation of the natural history of PVAN and its response to individual interventions will require prospective clinical trials.

Complete avoidance of calcineurin inhibitors in renal transplantation: a randomized trial comparing sirolimus and tacrolimus.

Calcineurin inhibitors have decreased acute rejection and improved early renal allograft survival, but their use has been implicated in the development of chronic nephrotoxicity. We performed a prospective, randomized trial in kidney transplantation comparing sirolimus-MMF-prednisone to tacrolimus-MMF-prednisone. Eighty-one patients in the sirolimus group and 84 patients in the tacrolimus group were enrolled (mean follow-up = 33 months; range 13-47 months). At 1 year, patient survival was similar in the groups (98% with sirolimus, 96% with tacrolimus; p = 0.42) as was graft survival (94% sirolimus vs. 92% tacrolimus, p = 0.95). The incidence of clinical acute rejection was 10% in the tacrolimus group and 13% in the sirolimus group (p = 0.58). There was no difference in mean GFR measured by iothalamate clearance between the tacrolimus and sirolimus groups at 1 year (61 +/- 19 mL/min vs. 63 +/- 18 mL/min, p = 0.57) or 2 years (61 +/- 17 mL/min vs. 61 +/- 19 mL/min, p = 0.84). At 1 year, chronicity using the Banff schema showed no difference in interstitial, tubular or glomerular changes, but fewer chronic vascular changes in the sirolimus group. This study shows that a CNI-free regimen using sirolimus-MMF-prednisone produces similar acute rejection rates, graft survival and renal function 1-2 years after transplantation compared to tacrolimus-MMF-prednisone.

Renal artery stenosis: a common, treatable cause of renal failure?

Chronic azotemic renovascular disease is common in patients with atherosclerosis. Its prevalence appears to be increasing in the aging population. How often it is the primary cause of end-stage renal disease (ESRD) is not yet certain. Some studies suggest that 10%-40% of elderly hypertensive patients with newly documented ESRD and no demonstrable primary renal disease have significant renal artery stenosis (RAS). Atherosclerotic vascular occlusive disease of the renal arteries does progress, but current rates of progression and occlusion are lower than those reported a decade ago. Methods of identifying patients whose renal function is at true risk from vascular occlusive disease and determining who will benefit from intervention remain elusive. The presence of RAS in an azotemic patient can be assessed with noninvasive and risk-free radiologic techniques, including Duplex doppler velicometry and magnetic resonance angiography. Functional tests that predict the change in renal function after revascularization are not yet available. However, a renal length of greater than 7.5 cm in the absence of renal cysts and a short history of renal functional deterioration indicate a good prognosis. Patients with recent deterioration in renal function, those with bilateral renal artery stenosis or stenosis to a single functioning kidney, those with flash pulmonary edema, advanced chronic renal failure, or ESRD (who have much to gain), those with reversible azotemia during angiotensin-converting enzyme inhibitor (ACEI) or angiotensin receptor antagonist (ARB) therapy, and those whose conditions cannot be managed medically should be considered for revascularization. Results from recent controlled clinical trials of the response to percutaneous transluminal renal artery angioplasty (PTRA) and stenting indicate that improvement in blood pressure control or renal function is not a predictable outcome of renal revascularization. In azotemic groups, 25%-30% of patients achieve important recovery of renal function. Thus, significant progress has been made recently in determining whether RAS is a frequent, treatable cause of renal failure. The decision to recommend revascularization remains a difficult balance between the risks and expense of the procedure and the undoubted benefits that accrue if renal function is successfully stabilized.

Pathophysiology of ischemic nephropathy.

Loss of renal function beyond a renal vascular lesion presents a complex challenge to clinicians. This article summarizes current understanding of critical vascular lesions to the kidney and putative mechanisms by which loss of perfusion activates fibrogenic mechanisms in the kidney. The authors emphasize alterations in vasoactive pathways, including disturbed oxidative stress, activation of endothelin, and reduced nitric oxide, which modulate cytokines and inflammatory mediators within the renal parenchyma. Improved understanding of these mechanisms is essential in preventing irreversible interstitial fibrosis and restoring renal perfusion.

Epidemiology and clinical presentation.

Renovascular disease appears to be increasing in prevalence, particularly in older subjects with atherosclerotic disease elsewhere. Its clinical manifestations and presentation are changing because of rapid advances in medical therapy and other comorbid events. Although fibromuscular dysplasia and other diseases affecting the renal artery can produce the syndrome of renovascular hypertension, atherosclerotic renal artery stenosis is the most common clinical entity. It can produce a spectrum of manifestations, ranging from asymptomatic ("incidental"), identified during angiographic evaluation of other conditions, to progressive hypertension to accelerated cardiovascular disease with pulmonary edema and advanced renal failure. With the widespread application of drugs which block the renin-angiotensin system, including angiotensin-converting enzyme inhibitors and angiotensin antagonists, many cases of renovascular hypertension remain unsuspected and never produce adverse effects. Clinicians need to be alert to the potential for disease progression, with the potential for total renal artery occlusion and/or loss of viable renal tissue. Selection of patients for renal revascularization depends on individual balance of risks and benefits regarding the likely outcomes regarding both improvements in blood pressure control and preservation of renal function.

Ischemic nephropathy/azotemic renovascular disease.

Atherosclerotic renal vascular disease can impair kidney perfusion and lead to deterioration of kidney function. The mechanisms by which reversible tissue injury becomes irreversible are not yet certain, although multiple pathways for activation of inflammatory cytokines and tissue fibrosis have been identified. The clinical hallmark of this disorder is loss of glomerular filtration beyond renal artery stenosis affecting the entire renal mass, usually associated with progressive hypertension and fluid retention. Some investigators believe that 12% to 18% of patients reaching end-stage renal disease in western countries may have lost kidney function because of azotemic renovascular disease. This is an important disorder to identify, because reduction of arterial pressure from antihypertensive therapy may further reduce kidney perfusion. Although administration of angiotensin-converting enzyme (ACE) inhibitors and angiotensin II antagonists lead to functional loss of glomerular filtration rate (GFR) beyond a stenotic lesion because of the removal of efferent actions of angiotensin II, other antihypertensive agents reduce renal perfusion also. Restoration of renal blood flow by surgical or endovascular methods can prevent progressive disease and sometimes improves renal function. However, clinical series commonly indicate that some patients lose further kidney function after revascularization. This may be explained partly by undetected renal atheremboli or other toxicity related to vascular repair. Hence, selection of patients for renal revascularization requires careful consideration of comorbid disease risk and the balance of risks and benefits regarding progressive renal disease. Searching for better methods of identifying those individuals at risk for irreversible loss of renal function and who might benefit from vascular repair is a high research priority.

Posttransplantation hypertension related to calcineurin inhibitors.

Calcineurin inhibitors are a mainstay of transplant immunosuppression and commonly induce hypertension. They are highly lipid soluble and penetrate vascular smooth muscle cell membranes readily. Changes in vascular tone are universally observed during administration of these agents, particularly within the kidney, leading to diminished glomerular filtration and enhanced sodium retention. Disturbances of endothelial function are prevalent in many tissues, including stimulation of endothelin and impaired nitric oxide synthesis. Multiple additional pathways produce increased vasoconstriction, leading to an increase in arterial pressure. Clinical manifestations include disturbances in circadian blood pressure patterns, left ventricular hypertrophy, and acceleration of atherosclerotic and renal injury. Rapid increases in pressure occasionally produce accelerated hypertension and microangiopathic tissue damage. Principles of therapy require recognition of hazards of changing arterial pressures during calcineurin use and preferential use of vasodilating drugs, particularly dihydropyridine calcium channel blocking agents. Attention must be paid to interactions between antihypertensive agents and calcineurin inhibitor blood levels.

Outcomes of atherosclerotic renal artery stenosis managed without revascularization.

OBJECTIVE: To determine how often patients with renal artery stenosis (RAS) managed without revascularization progress to accelerated hypertension and/or renal failure. PATIENTS AND METHODS: We examined the outcomes of 68 patients (mean +/- SEM age, 71.8 +/- 0.9 years) with high-grade (>70%) RAS identified between 1989 and 1993 who were treated without renal revascularization for at least 6 months after angiography. The time to last follow-up averaged 38.9 +/- 2.8 months. Other vascular beds were affected in 66 of the 68 patients. End points were revascularization, nephrectomy, dialysis, or death. RESULTS: The mean +/- SEM serum creatinine level rose from 1.4 +/- 0.1 to 2.0 +/- 0.2 mg/dL (P<.001). Mean +/- SEM blood pressure did not change (157 +/- 3/83+/-2 vs 155 +/- 3/79 +/- 2 mm Hg), but the need (mean +/- SEM) for medication increased from 1.6+/-0.1 to 1.9+/-0.1 drugs (P=.02). Four patients (5.8%) eventually underwent renal revascularization for refractory hypertension (1 patient), for progressive stenosis (1 patient), and during aortic reconstruction (2 patients). One additional patient underwent nephrectomy to improve blood pressure control. Five others (7.4%) developed end-stage renal disease (ESRD) for reasons other than progressive vascular disease, namely, diabetes (3 patients), atheroemboli (1 patient), and contrast toxicity without RAS progression (1 patient). In 1 further case, the reason for ESRD was unknown, and it may have been caused by vascular occlusion. During follow-up, 19 patients died of unrelated causes, including myocardial infarction and stroke. CONCLUSIONS: These data indicate that antihypertensive medication requirements increased and renal function deteriorated modestly in a subset of patients with atherosclerotic RAS managed initially without vascular intervention. Many achieved stable blood pressure for many years. Deterioration of renal function and mortality risk were greatest in patients with bilateral stenosis or stenosis to a solitary functioning kidney. These results reinforce the need for meticulous follow-up for disease progression but underscore the role of competing risks and high mortality from other cardiovascular diseases, which primarily determine the outcomes in patients with RAS and widespread atherosclerotic disease.

Hypertension after liver transplantation: a predictive role for pretreatment hemodynamics and effects of isradipine on the systemic and renal circulations.

Hypertension developing after liver transplantation during immunosuppression with cyclosporine A reflects an unusual hemodynamic transition from peripheral vasodilation to systemic and renal vasoconstriction. Although dihydropyridine calcium channel blockers are often administered for their efficacy in promoting vasodilation, some liver transplant recipients report marked symptomatic intolerance to these agents. In the present study we examined systemic and renal responses to isradipine using systemic (thoracic bioimpedance) and renal hemodynamic measurements in 15 liver transplant recipients studied at the time of initial diagnosis of posttransplant hypertension and after 3 months of treatment. Circadian blood pressure patterns were examined by overnight ambulatory blood pressure monitoring before and during antihypertensive therapy. During isradipine administration, blood pressure decreased from 151 +/- 3/91 +/- 2 to 130 +/-3/81 +/- 2 mm Hg (P < .01) without change in renal blood flow (406 +/- 43 to 425 +/- 52 mL/min/1.73m2, P = NS) or renal vascular resistance index (25,674 +/-3312 to 20,520 +/- 2311 dynes x sec x cm(-5)/m2, P = NS). Pre-treatment differences in systemic vascular tone persisted during treatment and predicted the tendency for symptomatic tachycardia and flushing, predominantly in those with hyperdynamic circulations. Twice daily dosing of isradipine was associated with partial and significant restoration of the nocturnal decrease in blood pressure (systolic blood pressure decreased 5.5%, normal 13%), usually absent early after transplantation. Our results demonstrate the ability of hemodynamic measurements to predict the symptomatic response to antihypertensive therapy in the posttransplant setting.

A hemodynamic approach to resistant hypertension.

Resistant hypertension affects a minority of treated hypertensive patients, yet the resulting target organ damage causes disproportionate morbidity and increased risk of cardiovascular events. The clinical features and efforts to adjust drug treatment in a resistant hypertensive patient are described. As demonstrated, serial hemodynamic measurements using thoracic bioimpedance may provide a rationale for selection of effective combination antihypertensive therapy. (c)2000 by CHF, Inc.

Cyclosporin-induced hypertension: incidence, pathogenesis and management.

Blood pressure increases soon after administration of immunosuppressive regimens using cyclosporin. Characteristic vascular changes lead to systemic and renal vasoconstriction. Changes in blood pressure are commonly associated with disturbed circadian regulation and may promote the rapid development of target organ injury, including intracranial haemorrhage, left ventricular hypertrophy and microangiopathic haemolysis. The mechanisms underlying this disorder are complex and include altered vascular endothelial function. Vasodilators such as prostacyclin and nitric oxide are suppressed, whereas vasoconstrictors, including endothelin, are increased. Changes in the kidney include vasoconstriction, reduced glomerular filtration and sodium retention. Effective therapy depends upon rigorous blood pressure control by administration of vasodilating agents, with attention to potential interactions with cyclosporin.

Importance of blood pressure reduction for prevention of progression of renal disease.

Despite reduction of stroke and coronary mortality rates, progression of renal disease to end stage continues to occur with increasing frequency. Recent studies emphasize common pathways of elevated arterial pressures that produce increased glomerular capillary pressures and increase filtered proteins in the urinary space. Such proteinuria, along with activation of the intrarenal renin-angiotensin system, endothelin, and inflammatory cytokines, magnifies progressive renal injury and fibrosis. Malignant forms of hypertension with severe arteriolar injury and proteinuria can be treated effectively with current antihypertensive regimens with improved patient survival. Several recent studies indicate improved renal outcomes in proteinuric diseases, generally regardless of the specific antihypertensive agent. Recent trials of hypertensive subjects with minimal proteinuria demonstrate slower rates of disease progression than that seen in subjects with proteinuria above 1 gram per day. Reduction of arterial pressures, particularly when it leads to reduced proteinuria, can slow the progression of many renal diseases.

Late hypertension after liver transplantation: a comparison of cyclosporine and tacrolimus (FK 506).

Hypertension frequently develops early after liver transplantation when cyclosporine-based immunosuppression is used. However, initial experience with tacrolimus has suggested that its use leads to a lower early incidence of hypertension. In this study, the blood pressure status of patients treated with cyclosporine (n = 131) and those treated with tacrolimus (n = 28) was compared 24 months after liver transplantation. At this time interval, the prevalence of hypertension in the cyclosporine and tacrolimus groups were 82% and 64%, respectively (P < .05). For those patients who were hypertensive by 24 months, onset was delayed in the tacrolimus group compared with the cyclosporine group: 40% versus 71% and 73% versus 93% at 1 and 12 months, respectively (P < .05). Within the cyclosporine group, patients with hypertension were heavier than those with normal blood pressure, 84.7 +/- 1.8 versus 73.4 +/- 4.0 kg, respectively (P < .05). Within the tacrolimus group, hypertensive patients had lower glomerular filtration rates and higher renal vascular resistances compared with normotensive patients, 74 +/- 12 versus 47 +/- 6 mL/min and 15,711 +/- 2,445 versus 28,830 +/- 4,310 dyne/s/cm5/m2, respectively (P < .05). There were no within-group differences for age, gender, pretransplant history of hypertension, family history of hypertension, graft function, or daily doses of prednisone, cyclosporine, or tacrolimus. These results indicate that, compared with cyclosporine, the onset of hypertension after liver transplantation is delayed and less prevalent with tacrolimus. Additionally, hypertension is associated with increased body weight in cyclosporine-treated patients and with more severe renal dysfunction in patients receiving tacrolimus. The relationships of these findings to the development of posttransplant hypertension requires further study.