Category: Nephrology

Week 44 – SYMPLICITY HTN-3

“A Controlled Trial of Renal Denervation for Resistant Hypertension”

N Engl J Med. 2014 Apr 10;370(15):1393-401. [free full text]
—

Approximately 10% of patients with hypertension have resistant hypertension (SBP > 140 despite adherence to three maximally tolerated doses of antihypertensives, including a diuretic). Evidence suggests that the sympathetic nervous system plays a large role in such cases, so catheter-based radiofrequency ablation of the renal arteries (renal denervation therapy) was developed as a potential treatment for resistant HTN. The 2010 SYMPLICITY HTN-2 trial was a small (n = 106), non-blinded, randomized trial of renal denervation vs. continued care with oral antihypertensives that demonstrated a remarkable 30-mmHg greater decrease in SBP with renal denervation. Thus the 2014 SYMPLICITY HTN-3 trial was designed to evaluate the efficacy of renal denervation in a single-blinded trial with a sham-procedure control group.

The trial enrolled adults with resistant HTN with SBP ≥ 160 despite adherence to 3+ maximized antihypertensive drug classes, including a diuretic. (Pertinent exclusion criteria included secondary hypertension, renal artery stenosis > 50%, prior renal artery intervention.) Patients were randomized to either renal denervation with the Symplicity (Medtronic) radioablation catheter or to renal angiography only (sham procedure). The primary outcome was the mean change in office systolic BP from baseline at 6 months. (The examiner was blinded to intervention.) The secondary outcome was the change in mean 24-hour ambulatory SBP at 6 months. The primary safety endpoint was a composite of death, ESRD, embolic event with end-organ damage, renal artery or other vascular complication, hypertensive crisis within 30 days, or new renal artery stenosis of > 70%.

535 patients were randomized. On average, patients were receiving five antihypertensive medications. There was no significant difference in reduction of SBP between the two groups at 6 months. ∆SBP was -14.13 ± 23.93 mmHg in the denervation group vs. -11.74 ± 25.94 mmHg in the sham-procedure group for a between-group difference of -2.39 mmHg (95% CI -6.89 to 2.12, p = 0.26 with a superiority margin of 5 mmHg). The change in 24-hour ambulatory SBP at 6 months was -6.75 ± 15.11 mmHg in the denervation group vs. -4.79 ± 17.25 mmHg in the sham-procedure group for a between-group difference of -1.96 mmHg (95% CI -4.97 to 1.06, p = 0.98 with a superiority margin of 2 mmHg). There was no significant difference in the prevalence of the composite safety endpoint at 6 months with 4.0% of the denervation group and 5.8% of the sham-procedure group reaching the endpoint (percentage-point difference of -1.9, 95% CI -6.0 to 2.2).

In patients with resistant hypertension, renal denervation therapy provided no reduction in SBP at 6-month follow-up relative to a sham procedure.

This trial was an astounding failure for Medtronic and its Symplicity renal denervation radioablation catheter. The magnitude of the difference in results between the non-blinded, no-sham-procedure SYMPLICITY HTN-2 trial and this patient-blinded, sham-procedure-controlled trial is likely a product of 1) a marked placebo effect of procedural intervention, 2) Hawthorne effect in the non-blinded trial, and 3) regression toward the mean (patients were enrolled based on unusually high BP readings that over the course of the trial declined to reflect a lower true baseline).

Currently, there is no role for renal denervation therapy in the treatment of resistant HTN. However, despite the results of SYMPLICITY HTN-3, additional trials have since been conducted that assess the utility of renal denervation in patients with HTN not classified as resistant. SPYRAL HTN-ON MED demonstrated a benefit of renal denervation beyond that of a sham procedure (7.4 mmHg lower relative difference of SBP on 24hr ambulatory monitoring) in the continued presence of baseline antihypertensives. RADIANCE HTN-SOLO demonstrated a 6.3 mmHg greater reduction in daytime ambulatory SBP among ablated patients than that of sham-treatment patients notably after a 4-week discontinuation of up to two home antihypertensives. However, despite these two recent trials, the standard of care for the treatment of non-resistant HTN remains our affordable and safe default of multiple pharmacologic agents as well as lifestyle interventions.

Further Reading/References:
1. NephJC, SYMPLICITY HTN-3
2. UpToDate, “Treatment of resistant hypertension,” heading “Renal nerve denervation”

Summary by Duncan F. Moore, MD

Week 27 – ELITE-Symphony

“Reduced Exposure to Calcineurin Inhibitors in Renal Transplantation”

by the Efficacy Limiting Toxicity Elimination (ELITE)-Symphony investigators

N Engl J Med. 2007 Dec 20;357(25):2562-75. [free full text]
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A maintenance immunosuppressive regimen following kidney transplantation must balance the benefit of immune tolerance of the transplanted kidney against the adverse effects of the immunosuppressive regimen. Calcineurin inhibitors, such as cyclosporine (CsA) and tacrolimus, are nephrotoxic and can cause long-term renal dysfunction. They can also cause neurologic and infectious complications. At the time of this study, tacrolimus had been only recently introduced but already was appearing to be better than CsA at preventing acute rejection. Sirolimus, an mTOR inhibitor, is notable for causing delayed wound healing, among other adverse effects. The goal of the ELITE-Symphony study was to directly compare two different dosing regimens of CsA (standard- and low-dose) versus low-dose tacrolimus versus low-dose sirolimus, all while on background mycophenolate mofetil (MMF) and prednisone in order to determine which of these immunosuppressive regimens had the lowest nephrotoxicity, most efficacious prevention of rejection, and fewest other adverse effects.

The trial enrolled adults aged 18-75 scheduled to receive kidney transplants. There was a detailed set of exclusion criteria, including the need for treatment with immunosuppressants outside of the aforementioned regimens, specific poor prognostic factors regarding the allograft match or donor status, and specific comorbid or past medical conditions of the recipients. Patients were randomized open-label to one of four immunosuppressive treatment regimens in addition to MMF 2 gm daily and corticosteroids (“according to practice at the center” but with a pre-specified taper of minimum maintenance doses): 1) standard-dose CsA (target trough 150-300 ng/mL x3 months, then target trough 100-200 ng/mL), 2) daclizumab induction accompanied by low-dose cyclosporine (target trough 50-100 ng/mL), 3) daclizumab induction accompanied by low-dose tacrolimus (target trough 3-7 ng/mL), and 4) daclizumab induction accompanied by low-dose sirolimus (target trough 4-8 ng/mL). The primary endpoint was the eGFR at 12 months after transplantation. Secondary endpoints included acute rejection, incidence of delayed allograft function, and frequency of treatment failure (defined as use of additional immunosuppressive medication, discontinuation of any study medication for > 14 consecutive days or > 30 cumulative days, allograft loss, or death) within the first 12 months.

1645 patients were randomized. There were no significant differences in baseline characteristics among the four treatment groups. At 12 months following transplantation, mean eGFR differed among the four groups (p < 0.001). Low-dose tacrolimus patients had an eGFR of 65.4 ± 27.0 ml/min while standard-dose cyclosporine patients had an eGFR of 57.1 ± 25.1 ml/min (p < 0.001 for pairwise comparison with tacrolimus), low-dose cyclosporine patients had an eGFR of 59.4 ± 25.1 ml/min (p = 0.001 for pairwise comparison with tacrolimus), and low-dose sirolimus patients had an eGFR of 56.7 ± 26.9 ml/min (p < 0.001 for pairwise comparison with tacrolimus). The incidence of biopsy-proven acute rejection (excluding borderline values) at 6 months was only 11.3% in the low-dose tacrolimus group; however it was 24.0% in the standard-dose cyclosporine, 21.9% in the low-dose cyclosporine, and 35.3% in the low-dose sirolimus (p < 0.001 for each pairwise comparison with tacrolimus). Values were similar in magnitude and proportionality at 12-month follow-up. Delayed allograft function (among recipients of a deceased donor kidney) was lowest in the sirolimus group at 21.1% while it was 35.7% in the low-dose tacrolimus group (p = 0.001), 33.6% in the standard-dose cyclosporine group, and 32.4% (p = 0.73 for pairwise comparison with tacrolimus) in the low-dose cyclosporine group (p = 0.51 for pairwise comparison with tacrolimus). Treatment failure occurred in 12.2% of the low-dose tacrolimus group, 22.8% of the standard-dose cyclosporine group (p < 0.001 for pairwise comparison with tacrolimus), 20.1% of the low-dose cyclosporine group (p = 0.003 for pairwise comparison with tacrolimus), and in 35.8% of the low-dose sirolimus group (p < 0.001 for pairwise comparison with tacrolimus). Regarding safety events, the incidence of new-onset diabetes after transplantation (NODAT) at 12 months was highest among the low-dose tacrolimus group at 10.6% but only 6.4% among the standard-dose cyclosporine group, 4.7% among the low-dose cyclosporine group, and 7.8% among the low-dose sirolimus group (p = 0.02 for between-group difference per log-rank test). Opportunistic infections were most common in the standard-dose cyclosporine group at 33% (p = 0.03 for between-group difference per log-rank test).

In summary, the post-kidney transplant immunosuppression maintenance regimen with low-dose tacrolimus was superior to the standard- and low-dose cyclosporine regimens and sirolimus regimens with respect to renal function at 12 months, acute rejection at 6 and 12 months, and treatment failure during follow-up. However, this improved performance came at the cost of a higher rate of new-onset diabetes after transplantation. The findings of this study were integral to the 2009 KDIGO Clinical Practice Guideline for the Care of Kidney Transplant Recipients which recommends maintenance with a calcineurin inhibitor (tacrolimus first-line), and antiproliferative agent (MMF first-line), and corticosteroids (can consider discontinuation within 1 week in the relatively few patients at low immunologic risk for acute rejection, though expert opinion at UpToDate disagrees with this recommendation).

Further Reading/References:
1. ELITE-Symphony @ Wiki Journal Club
2. “The ELITE & the Rest in Kidney Transplantation.” Renal Fellow Network.
3. “HARMONY: Is it safe to withdraw steroids early after kidney transplant?” NephJC
4. 2009 KDIGO Clinical Practice Guideline for the Care of Kidney Transplant Recipients
5. “Maintenance immunosuppressive therapy in kidney transplantation in adults.” UpToDate

Summary by Duncan F. Moore, MD

Image Credit: Rmarlin, CC BY-SA 4.0, via Wikimedia Commons

Week 24 – CHOIR

“Correction of Anemia with Epoetin Alfa in Chronic Kidney Disease”

by the Investigators in the Correction of Hemoglobin and Outcomes in Renal Insufficiency (CHOIR)

N Engl J Med. 2006 Nov 16;355(20):2085-98. [free full text]
—

Anemia is a prevalent condition in CKD and ESRD. The anemia is largely attributable to the loss of erythropoietin production due to the damage of kidney parenchyma. Thus erythropoiesis-stimulating agents (ESAs) were introduced to improve this condition. Retrospective data and small interventional trials suggested that treatment to higher hemoglobin goals (such as > 12 g/dL) was associated with improved cardiovascular outcomes. However, in 1998, a prospective trial in ESRD patients on HD with a hematocrit treatment target of 42% versus 30% demonstrated a trend toward increased rates of non-fatal MI and death in the higher-target group. In an effort to clarify the hemoglobin goal in CKD patients, the 2006 CHOIR trial was designed. It was hypothesized that treatment of anemia in CKD to a target of 13.5 g/dL would lead to fewer cardiac events and reduced mortality when compared to a target of 11.3 g/dL.

The trial enrolled adults with CKD (eGFR 15-50 ml/min) and Hgb < 11.0 g/dL and notably excluded patients with active cancer. The patients were randomized to erythropoietin support regimens targeting a hemoglobin of either 13.5 g/dL or 11.3 g/dL. The primary outcome was a composite of death, MI, hospitalization for CHF, or stroke. Secondary outcomes included individual components of the primary outcome, need for renal replacement therapy, all-cause hospitalization, and various quality-of-life scores.

The study was terminated early due to an interim analysis revealing a < 5% chance that there would be a demonstrated benefit for the high-hemoglobin group by the scheduled end of the study. Results from 715 high-hemoglobin and 717 low-hemoglobin patients were analyzed. The mean change in hemoglobin was +2.5 g/dL in the high-hemoglobin group versus +1.2g/dL in the low-hemoglobin group (p < 0.001). The primary endpoint occurred in 125 of the high-hemoglobin patients (17.5%) versus 97 of the low-hemoglobin patients (13.5%) [HR 1.34, 95% CI 1.03-1.74, p = 0.03; number needed to harm = 25]. There were no significant group differences among the four components of the primary endpoint when analyzed as individual secondary outcomes, nor was there a difference in rates of renal replacement therapy. Any-cause hospitalization rates were 51.6% in the high-hemoglobin group versus 46.6% in the low-hemoglobin group (p = 0.03). Regarding quality-of-life scores, both groups demonstrated similar, statistically significant improvements from their respective baseline values.

In patients with anemia and CKD, treatment to a higher hemoglobin goal of 13.5 g/dL was associated with an increased incidence of a composite endpoint of death, MI, hospitalization for CHF, or stroke relative to a treatment goal of 11.3 g/dL. There were no differences between the two groups in hospitalization rates or progression to renal replacement therapy, and the improvement in quality of life was similar among the two treatment groups. Thus this study demonstrated no additional benefit and some harm with the higher treatment goal. The authors noted that “this study did not provide a mechanistic explanation for the poorer outcome with the use of a high target hemoglobin level.” Limitations of this trial included its non-blinded nature and relatively high patient withdrawal rates. Following this trial, the KDOQI clinical practice guidelines for the management of anemia in CKD were updated to recommend a Hgb target of 11.0-12.0 g/dL. However, this guideline was superseded by the 2012 KDIGO guidelines which, on the basis of further evidence, ultimately recommend initiating ESA therapy only in iron-replete CKD patients with Hgb < 10 g/dL with the goal of maintaining Hgb between 10 and 11.5 g/dL. Treatment should be individualized in patients with concurrent malignancy.

Further Reading/References:
1. Besarab et al. “The Effects of Normal as Compared with Low Hematocrit Values in Patients with Cardiac Disease Who Are Receiving Hemodialysis and Epoetin.” N Engl J Med. 1998 Aug 27;339(9):584-90.
2. CHOIR @ Wiki Journal Club
3. CHOIR @ 2 Minute Medicine
4. National Kidney Foundation Releases Anemia Guidelines Update (2007)
5. Pfeffer et al. “A trial of darbepoetin alfa in type 2 diabetes and chronic kidney disease.” N Engl J Med. 2009;361(21):2019.
6. KDOQI US Commentary on the 2012 KDIGO Clinical Practice Guideline for Anemia in CKD

Summary by Duncan F. Moore, MD

Week 14 – IDNT

“Renoprotective Effect of the Angiotensin-Receptor Antagonist Irbesartan in Patients with Nephropathy Due to Type 2 Diabetes”

aka the Irbesartan Diabetic Nephropathy Trial (IDNT)

N Engl J Med. 2001 Sep 20;345(12):851-60. [free full text]
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Diabetes mellitus is the most common cause of ESRD in the US. In 1993, a landmark study in NEJM demonstrated that captopril (vs. placebo) slowed the deterioration in renal function in patients with T1DM. However, prior to this 2002 study, no study had addressed definitively whether a similar improvement in renal outcomes could be achieved with RAAS blockade in patients with T2DM. Irbesartan (Avapro) is an angiotensin II receptor blocker that was first approved in 1997 for the treatment of hypertension. Its marketer, Bristol-Meyers Squibb, sponsored this trial in hopes of broadening the market for its relatively new drug.

This trial randomized patients with T2DM, hypertension, and nephropathy (per proteinuria and elevated Cr) to treatment with either irbesartan, amlodipine, or placebo. The drug in each arm was titrated to achieve a target SBP ≤ 135, and all patients were allowed non-ACEi/non-ARB/non-CCB drugs as needed. The primary outcome was a composite of the doubling of serum Cr, onset of ESRD, or all-cause mortality. Secondary outcomes included individual components of the primary outcome and a composite cardiovascular outcome.

1715 patients were randomized. The mean blood pressure after the baseline visit was 140/77 in the irbesartan group, 141/77 in the amlodipine group, and 144/80 in the placebo group (p = 0.001 for pairwise comparisons of MAP between irbesartan or amlodipine and placebo). Regarding the primary composite renal endpoint, the unadjusted relative risk was 0.80 (95% CI 0.66-0.97, p = 0.02) for irbesartan vs. placebo, 1.04 (95% CI 0.86-1.25, p = 0.69) for amlodipine vs. placebo, and 0.77 (0.63-0.93, p = 0.006) for irbesartan vs. amlodipine. The groups also differed with respect to individual components of the primary outcome. The unadjusted relative risk of creatinine doubling was 33% lower among irbesartan patients than among placebo patients (p = 0.003) and was 37% lower than among amlodipine patients (p < 0.001). The relative risks of ESRD and all-cause mortality did not differ significantly among the groups. There were no significant group differences with respect to the composite cardiovascular outcome. Importantly, a sensitivity analysis was performed which demonstrated that the conclusions of the primary analysis were not impacted significantly by adjustment for mean arterial pressure achieved during follow-up.

In summary, irbesartan treatment in T2DM resulted in superior renal outcomes when compared to both placebo and amlodipine. This beneficial effect was independent of blood pressure lowering. This was a well-designed, double-blind, randomized, controlled trial. However, it was industry-sponsored, and in retrospect, its choice of study drug seems quaint. The direct conclusion of this trial is that irbesartan is renoprotective in T2DM. In the discussion of IDNT, the authors hypothesize that “the mechanism of renoprotection by agents that block the action of angiotensin II may be complex, involving hemodynamic factors that lower the intraglomerular pressure, the beneficial effects of diminished proteinuria, and decreased collagen formation that may be related to decreased stimulation of transforming growth factor beta by angiotensin II.” In September 2002, on the basis of this trial, the FDA broadened the official indication of irbesartan to include the treatment of type 2 diabetic nephropathy. This trial was published concurrently in NEJM with the RENAAL trial [https://www.wikijournalclub.org/wiki/RENAAL]. RENAAL was a similar trial of losartan vs. placebo in T2DM and demonstrated a similar reduction in the doubling of serum creatinine as well as a 28% reduction in progression to ESRD. In conjunction with the original 1993 ACEi in T1DM study, these two 2002 ARB in T2DM studies led to the overall notion of a renoprotective class effect of ACEis/ARBs in diabetes. Enalapril and lisinopril’s patents expired in 2000 and 2002, respectively. Shortly afterward, generic, once-daily ACE inhibitors entered the US market. Ultimately, such drugs ended up commandeering much of the diabetic-nephropathy-in-T2DM market share for which irbesartan’s owners had hoped.

Further Reading/References:
1. “The effect of angiotensin-converting-enzyme inhibition on diabetic nephropathy. The Collaborative Study Group.” NEJM 1993.
2. CSG Captopril Trial @ Wiki Journal Club
3. IDNT @ Wiki Journal Club
4. IDNT @ 2 Minute Medicine
5. US Food and Drug Administration, New Drug Application #020757
6. RENAAL @ Wiki Journal Club
7. RENAAL @ 2 Minute Medicine

Summary by Duncan F. Moore, MD

Image Credit: Skirtick, CC BY-SA 4.0, via Wikimedia Commons

Week 6 – Bicarbonate and Progression of CKD

“Bicarbonate Supplementation Slows Progression of CKD and Improves Nutritional Status”

J Am Soc Nephrol. 2009 Sep;20(9):2075-84. [free full text]
—

Metabolic acidosis is a common complication of advanced CKD. Some animal models of CKD have suggested that worsening metabolic acidosis is associated with worsening proteinuria, tubulointerstitial fibrosis, and acceleration of decline of renal function. Short-term human studies have demonstrated that bicarbonate administration reduces protein catabolism and that metabolic acidosis is an independent risk factor for acceleration of decline of renal function. However, until this 2009 study by de Brito-Ashurst et al., there were no long-term studies demonstrating the beneficial effects of oral bicarbonate administration on CKD progression and nutritional status.

The study enrolled CKD patients with CrCl 15-30ml/min and plasma bicarbonate 16-20 mEq/L and randomized them to treatment with either sodium bicarbonate 600mg PO TID (with protocolized uptitration to achieve plasma HCO3–  ≥ 23 mEq/L) for 2 years, or to routine care. The primary outcomes were: 1) the decline in CrCl at 2 years, 2) “rapid progression of renal failure” (defined as decline of CrCl > 3 ml/min per year), and 3) development of ESRD requiring dialysis. Secondary outcomes included 1) change in dietary protein intake, 2) change in normalized protein nitrogen appearance (nPNA), 3) change in serum albumin, and 4) change in mid-arm muscle circumference.

134 patients were randomized, and baseline characteristics were similar among the two groups. Serum bicarbonate levels increased significantly in the treatment arm. (See Figure 2.) At two years, CrCl decline was 1.88 ml/min in the treatment group vs. 5.93 ml/min in the control group (p < 0.01). Rapid progression of renal failure was noted in 9% of intervention group vs. 45% of the control group (RR 0.15, 95% CI 0.06–0.40, p < 0.0001, NNT = 2.8), and ESRD developed in 6.5% of the intervention group vs. 33% of the control group (RR 0.13, 95% CI 0.04–0.40, p < 0.001; NNT = 3.8). Regarding nutritional status, dietary protein intake increased in the treatment group relative to the control group (p < 0.007). Normalized protein nitrogen appearance decreased in the treatment group and increased in the control group (p < 0.002). Serum albumin increased in the treatment group but was unchanged in the control group, and mean mid-arm muscle circumference increased by 1.5 cm in the intervention group vs. no change in the control group (p < 0.03).

In conclusion, oral bicarbonate supplementation in CKD patients with metabolic acidosis reduces the rate of CrCl decline and progression to ESRD and improves nutritional status. Primarily on the basis of this study, the KDIGO 2012 guidelines for the management of CKD recommend oral bicarbonate supplementation to maintain serum bicarbonate within the normal range (23-29 mEq/L). This is a remarkably cheap and effective intervention. Importantly, the rates of adverse events, particularly worsening hypertension and increasing edema, were unchanged among the two groups. Of note, sodium bicarbonate induces much less volume expansion than a comparable sodium load of sodium chloride.

In their discussion, the authors suggest that their results support the hypothesis of Nath et al. (1985) that “compensatory changes [in the setting of metabolic acidosis] such as increased ammonia production and the resultant complement cascade activation in remnant tubules in the declining renal mass [are] injurious to the tubulointerstitium.” The hypercatabolic state of advanced CKD appears to be mitigated by bicarbonate supplementation. The authors note that “an optimum nutritional status has positive implications on the clinical outcomes of dialysis patients, whereas [protein-energy wasting] is associated with increased morbidity and mortality.”

Limitations to this trial include its open-label, no-placebo design. Also, the applicable population is limited by study exclusion criteria of morbid obesity, overt CHF, and uncontrolled HTN.

Further Reading:
1. Nath et al. “Pathophysiology of chronic tubulo-interstitial disease in rats: Interactions of dietary acid load, ammonia, and complement component-C3” (1985)
2. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (see page 89)
3. UpToDate, “Pathogenesis, consequences, and treatment of metabolic acidosis in chronic kidney disease”

Summary by Duncan F. Moore, MD

Week 48 – SYMPLICITY HTN-3

“A Controlled Trial of Renal Denervation for Resistant Hypertension”

N Engl J Med. 2014 Apr 10;370(15):1393-401 [free full text]
—

Approximately 10% of patients with hypertension have resistant hypertension (SBP > 140 despite adherence to three maximally tolerated doses of antihypertensives, including a diuretic). Evidence suggests that the sympathetic nervous system plays a large role in such cases, so catheter-based radiofrequency ablation of the renal arteries (renal denervation therapy) was developed as a potential treatment for resistant HTN. The 2010 SYMPLICITY HTN-2 trial was a small (n=106), non-blinded, randomized trial of renal denervation vs. continued care with oral antihypertensives that demonstrated a remarkable 30-mmHg greater decrease in SBP with renal denervation. Thus the 2014 SYMPLICITY HTN-3 trial was designed to evaluate the efficacy of renal denervation in a single-blinded trial with a sham-procedure control group.

The trial enrolled adults with resistant HTN with SBP ≥ 160 despite adherence to 3+ maximized antihypertensive drug classes, including a diuretic. (Pertinent exclusion criteria included secondary hypertension, renal artery stenosis > 50%, prior renal artery intervention.) Patients were randomized to either renal denervation with the Symplicity (Medtronic) radioablation catheter or to renal angiography only (sham procedure). The primary outcome was the mean change in office systolic BP from baseline at 6 months. (The examiner was blinded to intervention.) The secondary outcome was the change in mean 24-hour ambulatory SBP at 6 months. The primary safety endpoint was a composite of death, ESRD, embolic event with end-organ damage, renal artery or other vascular complication, hypertensive crisis within 30 days, or new renal artery stenosis of > 70%.

535 patients were randomized. On average, patients were receiving five antihypertensive medications. There was no significant difference in reduction of SBP between the two groups at 6 months. ∆SBP was -14.13 ± 23.93 mmHg in the denervation group vs. -11.74 ± 25.94 mmHg in the sham-procedure group for a between-group difference of -2.39 mmHg (95% CI -6.89 to 2.12, p = 0.26 with a superiority margin of 5 mmHg). The change in 24-hour ambulatory SBP at 6 months was -6.75 ± 15.11 mmHg in the denervation group vs. -4.79 ± 17.25 mmHg in the sham-procedure group for a between-group difference of -1.96 mmHg (95% CI -4.97 to 1.06, p = 0.98 with a superiority margin of 2 mmHg). There was no significant difference in the prevalence of the composite safety endpoint at 6 months with 4.0% of the denervation group and 5.8% of the sham-procedure group reaching the endpoint (percentage-point difference of -1.9, 95% CI -6.0 to 2.2).

In patients with resistant hypertension, renal denervation therapy provided no reduction in SBP at 6-month follow-up relative to a sham procedure.

This trial was an astounding failure for Medtronic and its Symplicity renal denervation radioablation catheter. The magnitude of the difference in results between the non-blinded, no-sham-procedure SYMPLICITY HTN-2 trial and this patient-blinded, sham-procedure-controlled trial is likely a product of 1) a marked placebo effect of procedural intervention, 2) Hawthorne effect in the non-blinded trial, and 3) regression toward the mean (patients were enrolled based on unusually high BP readings that over the course of the trial declined to reflect a lower true baseline).

Currently, there is no role for renal denervation therapy in the treatment of HTN (resistant or otherwise). However, despite the results of SYMPLICITY HTN-3, other companies and research groups are assessing the role of different radioablation catheters in patients with low-risk essential HTN and with resistant HTN. (For example, see https://www.ncbi.nlm.nih.gov/pubmed/29224639.)

Further Reading/References:
1. NephJC, SYMPLICITY HTN-3
2. UpToDate, “Treatment of resistant hypertension,” heading “Renal nerve denervation”

Summary by Duncan F. Moore, MD

Week 30 – Bicarbonate and Progression of CKD

“Bicarbonate Supplementation Slows Progression of CKD and Improves Nutritional Status”

J Am Soc Nephrol. 2009 Sep;20(9):2075-84. [free full text]
—

Metabolic acidosis is a common complication of advanced CKD. Some animal models of CKD have suggested that worsening metabolic acidosis is associated with worsening proteinuria, tubulointerstitial fibrosis, and acceleration of decline of renal function. Short-term human studies have demonstrated that bicarbonate administration reduces protein catabolism and that metabolic acidosis is an independent risk factor for acceleration of decline of renal function. However, until this 2009 study by de Brito-Ashurst et al., there were no long-term studies demonstrating the beneficial effects of oral bicarbonate administration on CKD progression and nutritional status.

The study enrolled CKD patients with CrCl 15-30ml/min and plasma bicarbonate 16-20 mEq/L and randomized them to treatment with either sodium bicarbonate 600mg PO TID (with protocolized uptitration to achieve plasma HCO3–  ≥ 23 mEq/L) for 2 years, or to routine care. The primary outcomes were: 1) the decline in CrCl at 2 years, 2) “rapid progression of renal failure” (defined as decline of CrCl > 3 ml/min per year), and 3) development of ESRD requiring dialysis. Secondary outcomes included 1) change in dietary protein intake, 2) change in normalized protein nitrogen appearance (nPNA), 3) change in serum albumin, and 4) change in mid-arm muscle circumference.

134 patients were randomized, and baseline characteristics were similar among the two groups. Serum bicarbonate levels increased significantly in the treatment arm. (See Figure 2.) At two years, CrCl decline was 1.88 ml/min in the treatment group vs. 5.93 ml/min in the control group (p < 0.01). Rapid progression of renal failure was noted in 9% of intervention group vs. 45% of the control group (RR 0.15, 95% CI 0.06–0.40, p < 0.0001, NNT = 2.8), and ESRD developed in 6.5% of the intervention group vs. 33% of the control group (RR 0.13, 95% CI 0.04–0.40, p < 0.001; NNT = 3.8). Regarding nutritional status, dietary protein intake increased in the treatment group relative to the control group (p < 0.007). Normalized protein nitrogen appearance decreased in the treatment group and increased in the control group (p < 0.002). Serum albumin increased in the treatment group but was unchanged in the control group, and mean mid-arm muscle circumference increased by 1.5 cm in the intervention group vs. no change in the control group (p < 0.03).

In conclusion, oral bicarbonate supplementation in CKD patients with metabolic acidosis reduces the rate of CrCl decline and progression to ESRD and improves nutritional status. Primarily on the basis of this study, the KDIGO 2012 guidelines for the management of CKD recommend oral bicarbonate supplementation to maintain serum bicarbonate within the normal range (23-29 mEq/L). This is a remarkably cheap and effective intervention. Importantly, the rates of adverse events, particularly worsening hypertension and increasing edema, were unchanged among the two groups. Of note, sodium bicarbonate induces much less volume expansion than a comparable sodium load of sodium chloride.

In their discussion, the authors suggest that their results support the hypothesis of Nath et al. (1985) that “compensatory changes [in the setting of metabolic acidosis] such as increased ammonia production and the resultant complement cascade activation in remnant tubules in the declining renal mass [are] injurious to the tubulointerstitium.” The hypercatabolic state of advanced CKD appears to be mitigated by bicarbonate supplementation. The authors note that “an optimum nutritional status has positive implications on the clinical outcomes of dialysis patients, whereas [protein-energy wasting] is associated with increased morbidity and mortality.”

Limitations to this trial include its open-label, no-placebo design. Also, the applicable population is limited by study exclusion criteria of morbid obesity, overt CHF, and uncontrolled HTN.

Further Reading:
1. Nath et al. “Pathophysiology of chronic tubulo-interstitial disease in rats: Interactions of dietary acid load, ammonia, and complement component-C3” (1985)
2. KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (see page 89)
3. UpToDate, “Pathogenesis, consequences, and treatment of metabolic acidosis in chronic kidney disease”

Week 27 – Mortality in Patients on Dialysis and Transplant Recipients

“Comparison of Mortality in All Patients on Dialysis, Patients on Dialysis Awaiting Transplantation, and Recipients of a First Cadaveric Transplant”

N Engl J Med. 1999 Dec 2;341(23):1725-30. [free full text]
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Renal transplant is the treatment of choice in patients with ESRD. Since the advent of renal transplant, it has been known that transplant improves both quality of life and survival relative to dialysis. However, these findings were derived from retrospective data and reflected inherent selection bias (patients who received transplants were healthier, younger, and of higher socioeconomic status than patients who remained on dialysis). While some smaller studies (i.e. single center or statewide database) published in the early to mid 1990s attempted to account for this selection bias by comparing outcomes among patients who received a transplant versus patients who were listed for transplant but had not yet received one, this 1999 study by Wolfe et al. was a notable step forward in that it used the large, nationwide US Renal Data System dataset and a robust multivariate hazards model to control for baseline covariates. To this day, Wolfe et al. remains a defining testament to the sustained, life-prolonging benefit of renal transplantation itself.

Using the comprehensive US Renal Data System database, the authors evaluated patients who began treatment for ESRD between 1991 and 1996. Notable exclusion criteria were age ≥ 70 and transplant prior to initiating dialysis. Of the 228,552 patients evaluated, 46,164 were placed on the transplant waitlist, and 23,275 received a transplant by the end of the study period (12/31/1997). The primary outcome was survival reported in unadjusted death rates per 100 patient-years, standardized mortality ratios (adjusted for age, race, sex, and diabetes as the cause of ESRD), and adjusted relative risk of death in transplant patients relative to waitlisted patients. Subgroup analyses were performed.

Results:
Regarding baseline characteristics, listed or transplanted patients were younger, more likely to be white or Asian, and less likely to have diabetes as the cause of their ESRD (see Table 1). Unadjusted death rates per 100 patient-years at risk: dialysis 16.1, waitlist 6.3, and transplant recipients 3.8 (no p value given, see Table 2). The standardized mortality ratio (adjusted for age, race, sex, and diabetes as the cause of ESRD) was 49% lower (RR 0.51, 95% CI 0.49–0.53, p<0.001) among patients on the waitlist and 69% lower among transplant recipients (p value not reported). The lower standardized mortality ratio of waitlisted patients relative to dialysis patients was sustained in all subgroup analyses (see Figure 1). The relative risk of death (adjusted for age, sex, race, cause of ESRD, year placed on waitlist, and time from first treatment of ESRD to placement on waitlist) is visually depicted in Figure 2. Importantly, relative to waitlisted patients, transplant recipients had a 2.8x higher risk of death during the first two weeks post-transplant. Thereafter, risk declined until the likelihood of survival equalized at 106 days post-transplant. Long term (3-4 years of follow-up in this study), mortality risk was 68% lower among transplanted patients than among waitlisted patients (RR 0.32, 95% CI 0.30–0.35, p< 0.001). The magnitude of this survival benefit varied by subgroup but was strong and statistically significant in all subgroups (ranging from 3 to 17 additional projected years of life, see Table 3).

Implication/Discussion:
Retrospective analysis of this nationwide ESRD database has clearly demonstrated the marked mortality benefit of renal transplantation over waitlisted status. This finding is present to varying degrees in all subgroups and leads to a projected additional 3 to 17 years of lifespan post-transplant. (There is an expected, mild increase in mortality risk immediately following transplantation. This increase reflects operative risk and immediate complications but is present for only 2 weeks post-transplantation.) As expected and as previously described in other datasets, this study also demonstrated that substantially healthier ESRD patients are selected for transplantation listing in the US in comparison to patients who remain on dialysis not on the waitlist.

Relative strengths of this study include its comprehensive national dataset and intention-to-treat analysis. Its multivariate analyses robustly controlled for factors, such as time on the waitlist, that may have influenced mortality. However, this study is limited in that its retrospective comparison of listed to transplanted does not entirely eliminate selection bias. (For example, listed patients may have developed illnesses that ultimately prevented transplant and lead to death.) Additionally, the mortality benefits demonstrated in this study from the first half of the 1990s may not reflect those of current practice, given that prevention and treatment of ASCVD (a primary driver of mortality in ESRD) has improved markedly in the ensuing decades and may favor one group disproportionately.

As suggested by the authors at UpToDate, improved survival post-transplant may be due to the following factors: increased clearance of uremic toxins, reduction in inflammation and/or oxidative stress, reduced microvascular disease in diabetes mellitus, and improvement of LVH.

As a final note: in this modern era, it is surprising to see both a retrospective cohort study published in NEJM as well as the lack of preregistration of its analysis protocol prior to the study being conducted. Preregistration, even of interventional trials, did not become routine until the years following the announcement of the International Committee of Medical Journal Editors (ICMJE) trial registration policy in 2004 (Zarin et al.). Although, even today, retrospective cohort studies are not routinely preregistered, high profile journals increasingly require it because it helps differentiate between confirmatory versus exploratory research and reduce the appearance of post-hoc data dredging (i.e. p-hacking). Please see the Center for Open Science – Preregistration for further information. Here is another helpful discussion in PowerPoint form by Deborah A. Zarin, MD, Director of ClinicalTrials.gov.

Further Reading/References:
1. UpToDate, “Patient Survival After Renal Transplantation”
2. Zarin et al. “Update on Trial Registration 11 Years after the ICMJE Policy Was Established.” NEJM 2017

Summary by Duncan F. Moore, MD

Image Credit: Anna Frodesiak, CC0 1.0, via Wikimedia Commons

Week 5 – IDNT

“Renoprotective Effect of the Angiotensin-Receptor Antagonist Irbesartan in Patients with Nephropathy Due to Type 2 Diabetes”

aka the Irbesartan Diabetic Nephropathy Trial (IDNT)

N Engl J Med. 2001 Sep 20;345(12):851-60. [free full text]
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Diabetes mellitus is the most common cause of ESRD in the US. In 1993, a landmark study in NEJM demonstrated that captopril (vs. placebo) slowed the deterioration in renal function in patients with T1DM. However, prior to this 2002 study, no study had addressed definitively whether a similar improvement in renal outcomes could be achieved with RAAS blockade in patients with T2DM. Irbesartan (Avapro) is an angiotensin II receptor blocker that was first approved in 1997 for the treatment of hypertension. Its marketer, Bristol-Meyers Squibb, sponsored this trial in hopes of broadening the market for its relatively new drug.

This trial randomized patients with T2DM, hypertension, and nephropathy (per proteinuria and elevated Cr) to treatment with either irbesartan, amlodipine, or placebo. The drug in each arm was titrated to achieve a target SBP ≤ 135, and all patients were allowed non-ACEi/non-ARB/non-CCB drugs as needed. The primary outcome was a composite of the doubling of serum Cr, onset of ESRD, or all-cause mortality. Secondary outcomes included individual components of the primary outcome and a composite cardiovascular outcome.

1715 patients were randomized. The mean blood pressure after the baseline visit was 140/77 in the irbesartan group, 141/77 in the amlodipine group, and 144/80 in the placebo group (p = 0.001 for pairwise comparisons of MAP between irbesartan or amlodipine and placebo). Regarding the primary composite renal endpoint, the unadjusted relative risk was 0.80 (95% CI 0.66-0.97, p = 0.02) for irbesartan vs. placebo, 1.04 (95% CI 0.86-1.25, p = 0.69) for amlodipine vs. placebo, and 0.77 (0.63-0.93, p = 0.006) for irbesartan vs. amlodipine. The groups also differed with respect to individual components of the primary outcome. The unadjusted relative risk of creatinine doubling was 33% lower among irbesartan patients than among placebo patients (p = 0.003) and was 37% lower than among amlodipine patients (p < 0.001). The relative risks of ESRD and all-cause mortality did not differ significantly among the groups. There were no significant group differences with respect to the composite cardiovascular outcome. Importantly, a sensitivity analysis was performed which demonstrated that the conclusions of the primary analysis were not impacted significantly by adjustment for mean arterial pressure achieved during follow-up.

In summary, irbesartan treatment in T2DM resulted in superior renal outcomes when compared to both placebo and amlodipine. This beneficial effect was independent of blood pressure lowering. This was a well-designed, double-blind, randomized, controlled trial. However, it was industry-sponsored, and in retrospect, its choice of study drug seems quaint. The direct conclusion of this trial is that irbesartan is renoprotective in T2DM. In the discussion of IDNT, the authors hypothesize that “the mechanism of renoprotection by agents that block the action of angiotensin II may be complex, involving hemodynamic factors that lower the intraglomerular pressure, the beneficial effects of diminished proteinuria, and decreased collagen formation that may be related to decreased stimulation of transforming growth factor beta by angiotensin II.” In September 2002, on the basis of this trial, the FDA broadened the official indication of irbesartan to include the treatment of type 2 diabetic nephropathy. This trial was published concurrently in NEJM with the RENAAL trial. RENAAL was a similar trial of losartan vs. placebo in T2DM and demonstrated a similar reduction in the doubling of serum creatinine as well as a 28% reduction in progression to ESRD. In conjunction with the original 1993 ACEi in T1DM study, these two 2002 ARB in T2DM studies led to the overall notion of a renoprotective class effect of ACEis/ARBs in diabetes. Enalapril and lisinopril’s patents expired in 2000 and 2002, respectively. Shortly afterward, generic, once-daily ACE inhibitors entered the US market. Ultimately, such drugs ended up commandeering much of the diabetic-nephropathy-in-T2DM market share for which irbesartan’s owners had hoped.

Further Reading/References:
1. “The effect of angiotensin-converting-enzyme inhibition on diabetic nephropathy. The Collaborative Study Group.” NEJM 1993.
2. CSG Captopril Trial @ Wiki Journal Club
3. IDNT @ Wiki Journal Club
4. IDNT @ 2 Minute Medicine
5. US Food and Drug Administration, New Drug Application #020757
6. RENAAL @ Wiki Journal Club
7. RENAAL @ 2 Minute Medicine

Summary by Duncan F. Moore, MD

Week 3 – CHOIR

“Correction of Anemia with Epoetin Alfa in Chronic Kidney Disease”

by the Investigators in the Correction of Hemoglobin and Outcomes in Renal Insufficiency (CHOIR)

N Engl J Med. 2006 Nov 16;355(20):2085-98. [free full text]
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Anemia is a prevalent condition in CKD and ESRD. The anemia is largely attributable to the loss of erythropoietin production due to the destruction of kidney parenchyma. Thus erythropoiesis-stimulating agents (ESAs) were introduced to improve this condition. Retrospective data and small interventional trials suggested that treatment to higher hemoglobin goals (such as > 12 g/dL) was associated with improved cardiovascular outcomes. However, in 1998, a prospective trial in ESRD patients on HD with a hematocrit treatment target of 42% versus 30% demonstrated a trend toward increased rates of non-fatal MI and death in the higher-target group. In an effort to clarify the hemoglobin goal in CKD patients, the 2006 CHOIR trial was designed. It was hypothesized that treatment of anemia in CKD to a target of 13.5 g/dL would lead to fewer cardiac events and reduced mortality when compared to a target of 11.3 g/dL.

The trial enrolled adults with CKD (eGFR 15-50ml/min) and Hgb < 11.0 g/dL and notably excluded patients with active cancer. The patients were randomized to erythropoietin support regimens targeting a hemoglobin of either 13.5 g/dL or 11.3 g/dL. The primary outcome was a composite of death, MI, hospitalization for CHF, or stroke. Secondary outcomes included individual components of the primary outcome, need for renal replacement therapy, all-cause hospitalization, and various quality-of-life scores.

The study was terminated early due to an interim analysis revealing a < 5% chance that there would be a demonstrated benefit for the high-hemoglobin group by the scheduled end of the study. Results from 715 high-hemoglobin and 717 low-hemoglobin patients were analyzed. The mean change in hemoglobin was +2.5 g/dL in the high-hemoglobin group versus +1.2g/dL in the low-hemoglobin group (p<0.001). The primary endpoint occurred in 125 of the high-hemoglobin patients (17.5%) versus 97 of the low-hemoglobin patients (13.5%) [HR 1.34, 95% CI 1.03-1.74, p=0.03; number needed to harm = 25]. There were no significant group differences among the four components of the primary endpoint when analyzed as individual secondary outcomes, nor was there a difference in rates of renal replacement therapy. Any-cause hospitalization rates were 51.6% in the high-hemoglobin group versus 46.6% in the low-hemoglobin group (p=0.03). Regarding quality-of-life scores, both groups demonstrated similar, statistically significant improvements from their respective baseline values.

In patients with anemia and CKD, treatment to a higher hemoglobin goal of 13.5g/dL was associated with an increased incidence of a composite endpoint of death, MI, hospitalization for CHF, or stroke relative to a treatment goal of 11.3g/dL. There were no differences between the two groups in hospitalization rates or progression to renal replacement therapy, and the improvement in quality of life was similar among the two treatment groups. Thus this study demonstrated no additional benefit and some harm with the higher treatment goal. The authors noted that “this study did not provide a mechanistic explanation for the poorer outcome with the use of a high target hemoglobin level.” Limitations of this trial included its non-blinded nature and relatively high patient withdrawal rates. Following this trial, the KDOQI clinical practice guidelines for the management of anemia in CKD were updated to recommend a Hgb target of 11.0-12.0 g/dL. However, this guideline was superseded by the 2012 KDIGO guidelines which, on the basis of further evidence, ultimately recommend initiating ESA therapy only in iron-replete CKD patients with Hgb < 10 g/dL with the goal of maintaining Hgb between 10 and 11.5 g/dL. Treatment should be individualized in patients with concurrent malignancy.

Further Reading/References:
1. Besarab et al. “The Effects of Normal as Compared with Low Hematocrit Values in Patients with Cardiac Disease Who Are Receiving Hemodialysis and Epoetin.” N Engl J Med. 1998 Aug 27;339(9):584-90.
2. Wiki Journal Club
3. 2 Minute Medicine
4. National Kidney Foundation Releases Anemia Guidelines Update (2007) []
5. Pfeffer et al. “A trial of darbepoetin alfa in type 2 diabetes and chronic kidney disease.” N Engl J Med. 2009;361(21):2019.
6. KDOQI US Commentary on the 2012 KDIGO Clinical Practice Guideline for Anemia in CKD

Summary by Duncan F. Moore, MD