Cardiovascular morbidity and mortality and renal artery stenosis

Effects of Renal Impairment on the Pharmacokinetics of the Dual GIP and GLP-1 Receptor Agonist Tirzepatide

Background and Aims

The pharmacokinetics (PK) and single-dose tolerability of tirzepatide, a dual glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1 receptor agonist being developed for once-weekly treatment of type 2 diabetes (T2D), weight management, and nonalcoholic steatohepatitis, was evaluated in subjects with renal impairment versus healthy subjects with normal renal function.

Methods

Forty-five subjects, categorized by baseline renal status, i.e. mild (n = 8, estimated glomerular filtration rate [eGFR] 60–89 mL/min/1.73m²), moderate (n = 8, eGFR 30–59 mL/min/1.73m²), severe renal impairment (n = 7, eGFR < 30 mL/min/1.73m²), end-stage renal disease requiring dialysis (n = 8), and normal renal function (n = 14, eGFR ≥ 90 mL/min/1.73m²), received a single subcutaneous dose of tirzepatide 5 mg. Tirzepatide plasma concentrations up to 648 h postdose were measured to compute PK parameters. The primary analysis evaluated the ratios of area under the plasma concentration–time curves (AUCs) and maximum plasma drug concentration (C_max) of renal impairment versus the normal renal function group (90% confidence interval [CI]). In addition, the relationship between PK parameters and continuous variables of renal function was assessed by linear regression.

Results

Tirzepatide exposure was similar across renal impairment groups and healthy subjects. The 90% CI of ratios of AUCs and C_max comparing each renal impairment group versus normal renal function spanned unity, except for a 25–29% increase in AUCs in the moderate renal impairment group. There was no significant relationship between tirzepatide exposure and eGFR. Few adverse events were reported across the renal impairment and normal renal function groups. The majority were mild in severity and of a gastrointestinal nature in the renal impairment groups.

Conclusion

There were no clinically relevant effects of renal impairment on tirzepatide PK. Dose adjustment may not be required for patients with renal impairment.

Clinical Trial Registration

ClinicalTrials.gov NCT03482024.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40262-021-01012-2.

Restenosis Rates After Drug-Eluting Stent Treatment for Stenotic Small-Diameter Renal Arteries

PURPOSE

To determine primary rates in small-diameter renal arteries, including complex bifurcation lesions, treated with drug-eluting stents (DES) in patients with atherosclerotic renal artery stenosis.

MATERIALS AND METHODS

This is a retrospective single-institution study. A total of 37 patients with 39 stented renal arteries were included. Patient and procedural data were obtained from the electronic medical record. Survival free from restenosis was estimated using the Kaplan-Meier method with patients stratified into two groups based on renal artery diameters (≤ 3.5 mm or > 3.5 mm). Univariate Cox proportional models were used to estimate hazard ratios associated with clinical and angiographic variables.

RESULTS

Average renal artery diameter at time of treatment was 3.4 mm ± 0.4 mm. The median survival free from restenosis was 992 days, with 11 out of 37 (29.7%) developing an in-stent restenosis. Renal arteries < 3.5 mm in diameter had similar patency rates as renal arteries > 3.5 mm (P = 0.33). The 1-, 2-, and 5-year patency rates were 71%, 63%, and 38%, respectively. History of stroke was the only comorbidity to portend a significantly greater rate of restenosis (hazard ratio 3.77; 95%CI, 1.05-13.6; P = 0.04). Medications did not statistically alter the risk of restenosis.

CONCLUSION

Revascularization of renal arteries with DES achieved similar primary patency rates irrespective of renal artery diameter. Stent configuration was not associated with time to renal replacement therapy or all-cause mortality.

LEVEL OF EVIDENCE

Level 3, Cohort Study.

Biopolymer-delivered vascular endothelial growth factor improves renal outcomes following revascularization

Renal angioplasty and stenting (PTRAs) resolves renal artery stenosis, but inconsistently improves renal function, possibly due to persistent parenchymal damage. We developed a bioengineered fusion of a drug delivery vector (elastin-like polypeptide, ELP) with vascular endothelial growth factor (VEGF), and showed its therapeutic efficacy. We tested the hypothesis that combined ELP-VEGF therapy with PTRAs improves renal recovery more efficiently than PTRAs alone, by protecting the stenotic renal parenchyma. Unilateral renovascular disease (RVD) was induced by renal artery stenosis in 14 pigs. Six weeks later, stenotic kidney blood flow (RBF) and glomerular filtration rate (GFR) were quantified in vivo using multidetector CT. Blood and urine were collected during in vivo studies. All pigs underwent PTRAs and then were randomized into single intrarenal ELP-VEGF administration or placebo (n = 7 each) groups. Pigs were observed for four additional weeks, in vivo CT studies were repeated, and then pigs were euthanized for ex vivo studies to quantify renal microvascular (MV) density, angiogenic factor expression, and morphometric analysis. Renal hemodynamics were similarly blunted in all RVD pigs. PTRAs resolved stenosis but modestly improved RBF and GFR. However, combined PTRAs+ ELP-VEGF improved RBF, GFR, regional perfusion, plasma creatinine, asymmetric dimethlyarginine (ADMA), and albuminuria compared with PTRAs alone, accompanied by improved angiogenic signaling, MV density, and renal fibrosis. Greater improvement of renal function via coadjuvant ELP-VEGF therapy may be driven by enhanced MV proliferation and repair, which ameliorates MV rarefaction and fibrogenic activity that PTRAs alone cannot offset. Thus, our study supports a novel strategy to boost renal recovery in RVD after PTRAs.

The Metabolic Syndrome Does Not Affect Development of Collateral Circulation in the Poststenotic Swine Kidney

BACKGROUND

The collateral circulation is important in maintenance of blood supply to the ischemic kidney distal to renal artery stenosis (RAS). Obesity metabolic syndrome (MetS) preserves renal blood flow (RBF) in the stenotic kidney, but whether this is related to an increase of collateral vessel growth is unknown. We hypothesized that MetS increased collateral circulation around the renal artery.

METHODS

Twenty-one domestic pigs were randomly divided into unilateral RAS fed an atherogenic (high-fat/high-fructose, MetS-RAS) or standard diet, or controls (n = 7 each). RBF, glomerular filtration rate (GFR), and the peristenotic collateral circulation were assessed after 10 weeks using multidetector computed tomography (CT) and the intrarenal microcirculation by micro-CT. Vascular endothelial growth factor (VEGF) expression was studied in the renal artery wall, kidney, and perirenal fat. Renal fibrosis and stiffness were examined by trichrome and magnetic resonance elastography.

RESULTS

Compared with controls, RBF and GFR were decreased in RAS, but not in MetS-RAS. MetS-RAS formed peristenotic collaterals to the same extent as RAS pigs but induced greater intrarenal microvascular loss, fibrosis, stiffness, and inflammation. MetS-RAS also attenuated VEGF expression in the renal tissue compared with RAS, despite increased expression in the perirenal fat.

CONCLUSIONS

MetS does not interfere with collateral vessel formation in the stenotic kidney, possibly because decreased renal arterial VEGF expression offsets its upregulation in perirenal fat, arguing against a major contribution of the collateral circulation to preserve renal function in MetS-RAS. Furthermore, preserved renal function does not protect the poststenotic kidney from parenchymal injury.

A concise predictive nomogram for renal artery stenosis in selective patients undergoing coronary angiography

As reported scoring systems of renal artery stenosis (RAS) screening were not easily validated, we further proposed a simple method to predict or rule out RAS in selective patients undergoing coronary angiography (CAG). After preliminary inclusive criterion (severe hypertension or atherosclerosis, flash pulmonary edema, or unexplained renal dysfunction), 503 and 158 consecutive patients undergoing renal arteriography at the timing of CAG were separately enrolled between 2012 and 2015, and 2016 and 2017 as the development and validation cohort. A nomogram was derived from the multivariable logistic regression model, and its accuracy was assessed by the area under the receiver operating characteristic. Hypertension (odds ratio [OR] 17.92), estimated glomerular filtration rate ≤72.66 mL/min·1.73 m² (OR 2.75), early to late transmitral flow velocity ratio ≤1.02 (OR 2.58) and low-density lipoprotein cholesterol ≤3.17 mmol/L (OR 1.85) were identified as independent predictors for RAS. The area under the curve of the nomogram in the development and validation cohort were 0.754 (0.704, 0.804) and 0.772 (0.700, 0.844). The negative predictive value of hypertension (88.9%) was much higher than the other three predictors. The concise predictive nomogram can effectively estimate the probability of significant RAS during CAG. Along with normotensive, findings reported could easily evaluate RAS screening necessity based on clinical data.

Intermittent claudication and severe renal artery stenosis are independently associated in hypertensive patients referred for renal arteriography

OBJECTIVE:

The purpose of this study was to evaluate the association between the presence of clinical symptoms of peripheral artery disease and severe renal artery stenosis in patients referred for renal angiography.

METHOD:

We included 82 patients with clinical suspicion of renovascular hypertension and performed an imaging investigation (renal Doppler ultrasound and/or renal scintigraphy) for possible renal artery stenosis. All patients underwent renal arteriography and were examined for peripheral artery disease based on the presence of intermittent claudication and ankle-brachial index test results. Severe renal artery stenosis was defined as a lesion causing 70% obstruction.

RESULTS:

Severe renal artery stenosis was present in 32 of 82 (39%) patients. Patients with severe renal artery stenosis were older (63±12 vs 56±12 years, p=0.006), had more intermittent claudication (55 vs 45%, p=0.027), and had a greater prevalence of an ankle-brachial index <0.9 (44% vs 20%, p=0.021) than patients without severe renal artery stenosis. Multivariate logistic regression analysis showed that the presence of intermittent claudication was independently associated with renal artery stenosis ≥70% (OR: 3.33; 95% CI 1.03-10.82, p=0.04), unlike the ankle-brachial index, which showed no association (OR: 1.44; 95% CI 0.37-5.66, p=0.60).

CONCLUSION:

Intermittent claudication is independently associated with severe renal artery stenosis (≥70%) in patients clinically suspected of having renovascular hypertension.

Obesity and renovascular disease

Obesity remains a prominent public health concern. Obesity not only contributes greatly to cardiovascular events but has also been identified to initiate and affect the progression of preexisting chronic kidney disease. The prevalence of renal artery stenosis is growing world-wide, especially in the elderly population and in individuals with atherosclerotic risk factors such as obesity. Prolonged renovascular disease causes inflammation and microvascular remodeling within the post-stenotic kidney, which promote tissue scarring and may account for irreversible renal damage. Obesity has been shown to aggravate kidney damage via several pathways, including exacerbation of microvascular regression and renal cell injury mediated by adipocytes and insulin resistance, thereby worsening the structural and functional outcomes of the kidney in renovascular disease. Dietary modification and inhibition of the renin-angiotensin-aldosterone system have been shown to alleviate obesity-induced tissue injury and remodeling. Possibly, angiogenic factors may boost microvascular repair in the ischemic kidney in the obesity milieu. Novel therapeutic interventions targeting deleterious pathways that are activated by obesity and responsible for kidney damage need to be explored in future studies.

Extrarenal atherosclerotic disease blunts renal recovery in patients with renovascular hypertension

BACKGROUND

Atherosclerotic renovascular disease (ARVD) is associated with high rates of coronary events and predicts mortality among patients with coronary artery disease (CAD). However, the impact of coronary atherosclerosis on renal outcomes after revascularization of ARVD is unclear. We hypothesized that CAD negatively impacts renal functional outcomes among patients with ARVD undergoing renal artery revascularization.

METHODS

Patients with ARVD who underwent echocardiography at Mayo Clinic, Rochester, Minnesota, USA between 2004 and 2012 were identified retrospectively and included if they had ejection fraction more than 50%. Renal and overall outcomes were compared among atherosclerotic renovascular disease patients with coronary artery disease (ARVD-C, n = 75) and without coronary artery disease (ARVD, n = 56), within 1 year from initial revascularization and included blood pressure control, renal function, and incident cardiovascular/cerebrovascular events.

RESULTS

Degree of renal artery stenosis was similar in both groups. ARVD-C had higher prevalence of diabetes, peripheral artery disease (PAD), and cerebrovascular disease, and lower baseline renal function. Risk of developing end-stage renal disease was higher in ARVD-C (11 vs. 2%, P = 0.05). Despite better control of blood pressure and cholesterol levels, renal function postrevascularization worsened in 15% of ARVD-C compared with 2% of ARVD (P = 0.01). Differences in clinical outcomes remained statistically significant after adjustment for covariables, including sex, baseline blood pressure, renal function, underlying diabetes, cholesterol levels, and medications. Similar differences in clinical outcomes were also associated with PAD and cerebrovascular disease.

CONCLUSION

CAD in patients with ARVD is a predictor of worse outcomes after renal revascularization, likely reflecting diffuse atherosclerotic disease. Further studies are needed to develop strategies to manage patients with vascular comorbidities and improve their outcomes.

Clinical problems in renovascular disease and the role of nuclear medicine

Although renovascular disease remains defined as a stenosis of the main renal artery or its proximal branches (renal artery stenosis [RAS]), its clinical overview has changed dramatically over the last 15-20 years and its management is more controversial than ever before. The clinical problems, not only diagnosis and treatment but also the relative contribution of different pathophysiological mechanisms involved in the progression of kidney disease, have shifted dramatically. This presentation aims to emphasize the paradigm change revisiting the (recent) past focused on renovascular hypertension (RVH) to the current context of preservation or recovery of threatened renal function in patients with progressive atherosclerotic renovascular disease until its last stage of irreversible "ischemic nephropathy." In the past, the foreground was occupied by RVH, a very rare disease, where the activation of the renin-angiotensin-aldosterone system (RAAS) was supposed to play the major, if not only, role in RVH issues. The retrospective RVH diagnosis was established either on the improvement or, more rarely, on the cure of hypertension after revascularization by, most often, a percutaneous transluminal renal angioplasty with or without a stent placement. At this time, captoptril radionuclide renography was an efficient diagnostic tool, because it was a functional (angiotensin-converting enzyme inhibition), noninvasive test aiming to evidence both the RAAS activation and the lateralization (or asymmetry) of renin secretion by the kidney affected by a "hemodynamically significant" RAS. At present, even if captoptril radionuclide renography could be looked upon as the most efficient (and cost effective in selected high-risk patients) noninvasive, functional test to predict the improvement of hypertension after RAS correction, its clinical usefulness is questioned as the randomized, prospective trials failed to demonstrate any significant benefits (either on blood pressure control or on renal function protection) of the revascularization over current antihypertensive therapy. Today many patients with RVH remain undetected for years because they are treated successfully and at low expense with these new blockers of RAAS. In addition to its well-known role in hemodynamics, angiotensin II promotes activations of profibrogenic and inflammatory factors and cells and stimulates reactive oxygen species generation. The "atherosclerotic milieu" itself plays a role in the loss of renal microvessels and defective angiogenesis. After an "adaptative" phase, ischemia eventually develops and induces hypoxia, the substratum of ischemic nephropathy. Because blood oxygen level-dependent MRI may provide an index of oxygen content in vivo, it may be useful to predict renal function outcome after percutaneous transluminal renal angioplasty. New PET tracers, dedicated to assess RAAS receptors, inflammatory cell infiltrates, angiogenesis, and apoptose, would be tested in this context of atherosclerotic renovascular disease.

Long-term follow-up of patients with atherosclerotic renal artery disease

Atherosclerotic renal artery stenosis (ARAS) is a predictor of increased morbidity and mortality. However, whether ARAS itself accelerates the arteriosclerotic process or whether ARAS is solely the consequence of atherosclerosis is unclear. We imaged renal arteries of 1561 hypertensive patients undergoing coronary angiography and followed this cohort for 9 years (range, 2.4-15.1 years; median, 31.2 months, interquartile range, 13.4/52.9 months). All patients received aspirin, renin-angiotensin system blockade, statins, and beta blockade as indicated. One hundred seventy-one patients had ARAS >50% diameter stenosis and 126 patients an arteriosclerotic plaque (ARAP) without significant stenosis. Blood pressures were not different in ARAS, ARAP, and non-ARAS patients. After adjustment for cardiovascular risk factors by propensity scores and matched pair analysis, ARAS patients had a lower ejection fraction and more coronary artery disease (CAD) than non-ARAS patients. The same was true for brain natriuretic peptide values, troponin I, and highly sensitive C-reative protein. Over 9 years, more ARAS patients died of any cause (34% vs 23%; P < .05). The prevalence of CAD in ARAP patients was higher than in non-ARAS patients and lower than in ARAS patients. The mortality of the ARAP patients at 9 years was 37%, not different from the ARAS patients. Atherosclerotic renal artery disease appears to be a marker for the severity of atherosclerosis rather than a causative factor for atherosclerosis progression.

Angiotensin receptor blockade has protective effects on the poststenotic porcine kidney

Angiotensin converting enzyme inhibitors (ACEI)/ angiotensin-II receptor blockers (ARBs) may induce an acute decrease of glomerular filtration rate (GFR) in the stenotic kidney in renal artery stenosis, but most patients tolerate these drugs well. We hypothesized that ACEI/ARBs stabilize stenotic kidney function during prolonged treatment by conferring protective effects. We tested this in control domestic pigs and pigs with renal artery stenosis untreated or treated with valsartan, or triple therapy (7 pigs in each group) for 4 weeks starting 6 weeks after stenosis induction. Renal function, oxygenation, tubular function, and microcirculation were assessed by multi-detector computed tomography (CT), blood-oxygen-level-dependent magnetic-resonance imaging, and micro-CT. Valsartan and triple therapy decreased blood pressure similarly, however, valsartan did not change the GFR of the stenotic kidney compared to renal artery stenosis and was similar to triple therapy. Both valsartan and triple therapy stimulated microvascular density, and improved tubular function. Valsartan also caused a greater increase of angiogenic factors and a decrease in oxidative stress, which were related to higher cortical perfusion and tubular response than triple therapy. Thus, valsartan did not decrease stenotic kidney GFR, but improved cortical perfusion and microcirculation. These beneficial effects may partly offset the hemodynamic GFR reduction in renal artery stenosis and preserve kidney function.

Renal artery stenosis predicts coronary artery disease in patients with hypertension

In hypertensive patients with indication of renal arteriography to investigate renal artery stenosis (RAS) there are no recommendations regarding when to investigate coronary artery disease (CAD). Moreover, the predictors of CAD in patients with RAS are not clear. We aimed to evaluate the frequency and the determinants of CAD in hypertensive patients referred to renal angiography. Eighty-two consecutive patients with high clinical risk suggesting the presence of RAS systematically underwent renal angiography and coronary angiography during the same procedure. Significant arterial stenosis was defined by an obstruction ≥ 70% to both renal and coronary territories. Significant CAD was present in 32/82 (39%) and significant RAS in 32/82 (39%) patients. Both CAD and RAS were present in 25.6% from the 82 patients. Patients with severe CAD were older (63 ± 12 vs. 56 ± 13 years; p = 0.03) and had more angina (41 vs. 16%; p = 0.013) compared to patients without severe CAD. Significant RAS was associated with an increased frequency of severe CAD compared to patients without significant RAS (66% vs. 22%, respectively; p<0.001). Myocardial scintigraphy showed ischemia in 21.8% of the patients with CAD. Binary logistic regression analysis showed that RAS ≥ 70% was independently associated with CAD ≥ 70% (OR: 11.48; 95% CI 3.2-40.2; p<0.001), even in patients without angina (OR: 13.48; 95%CI 2.6-12.1; p<0.001). Even considering a small number of patients with significant RAS, we conclude that in hypertensive patients referred to renal angiography, RAS ≥ 70% may be a strong predictor of severe CAD, independently of angina, and dual investigation should be considered.

Percutaneous transluminal renal angioplasty remarkably improved severe hypertension and renal function in a patient with renal artery stenosis and postrenal kidney failure

A 69-year-old man was admitted to our hospital with severe hypertension and rapidly worsening renal function. He presented with a 10-year history of chronic renal failure caused by bilateral ureteral obstruction due to retroperitoneal fibrosis. Magnetic resonance angiography and Doppler ultrasonography suggested severe right renal artery stenosis (RAS). Renal angiography revealed 99% stenosis at the ostium of the right renal artery. We performed percutaneous transluminal renal angioplasty (PTRA) with the support of intravascular ultrasound to decrease the amount of contrast agent needed. In addition, to prevent distal atheroembolism, a distal protection device was used. The procedure was completed without any adverse effects. After PTRA, renal function and blood pressure improved remarkably and remained stable for one year. PTRA for RAS remains controversial, especially in patients with renal insufficiency. Use of new devices should be considered to decrease catheterization-related adverse effects.

Influence and critique of the ASTRAL and CORAL Trials

Optimal management of renal artery atherosclerotic occlusive disease has been widely debated and studied. Although the accepted invasive treatment has evolved into favoring balloon angioplasty and stenting, the indications for intervention or medical therapy have not been universally agreed upon. The Angioplasty and Stenting for Renal Artery Lesions (ASTRAL) trial was conducted to answer the question of whether medical therapy or angioplasty and stenting is the best treatment for hemodynamically significant renal artery stenosis. However, the ASTRAL trial's study design was faulty and therefore did not provide conclusive evidence to answer the question. The Cardiovascular Outcomes in Renal Atherosclerotic Lesions (CORAL) trial was designed to answer the same question as to which treatment (medical or angioplasty and stent) is best for renal artery stenosis, and its methodologies took into consideration the weaknesses of the ASTRAL trial. Results are soon to be released.