Distal Embolic Protection for Renal Arterial Interventions

The Implications of Acute Anatomic Injury After Percutaneous Renal Intervention

PURPOSE

Percutaneous renal artery revascularization for hypertension and renal dysfunction remains common. The frequency, cause, and outcomes of anatomic injury associated with renal intervention are poorly delineated. This study aims to determine the frequency of acute anatomic renal injury after renal artery interventions, identify factors associated with anatomic renal injury, and determine whether anatomic renal injury related to renal intervention is associated with late adverse clinical events.

METHODS

A retrospective analysis of patients undergoing renal artery interventions for atherosclerotic renal artery disease between 2002 and 2022 was performed. Acute anatomic renal injury encompassed renal artery dissection, renal artery perforation, acute occlusion, renal parenchymal infarction, and renal parenchymal perforation. Freedom from renal-related morbidity (increase in persistent creatinine >20% of baseline, progression to hemodialysis, death from renal-related causes) and patient survival were measured.

RESULTS

A total of 968 patients underwent 1309 renal artery interventions: 47% for hypertension, 25% for hypertension associated with chronic renal dysfunction, and 28% for chronic renal dysfunction. An acute anatomic renal injury occurred in 5.9% of the patients. The occurrence of an anatomic injury was associated with a significant decrement in freedom from renal-related morbidity (79±2% vs 55±8%, no-injury vs injury group, mean±standard error of the mean; p=0.003) and markedly decreased survival at 5 year follow-up (78±3% vs 48±8%; p=0.002). No factor was identified that predicted anatomic injury. In those patients with anatomic injury, perforation was associated with decreased survival, while estimated glomerular filtration rate <60, resistive index >0.8, and dissection were associated with a lack of retained renal benefit.

CONCLUSION

Acute anatomic renal injury occurs in approximately 6% of patients undergoing percutaneous renal artery intervention and is a negative predictor of survival and is associated with subsequent renal failure, need for dialysis, and death from renal-related causes.

CLINICAL IMPACT

Acute anatomic renal injury occurs in approximately 5% of patients undergoing percutaneous renal artery intervention. Modern endovascular interventions allow for the control and remediation of injuries in the majority of cases with an overall low mortality and morbidity. There is a significant early occlusion of renal arteries following the injury within 1 month. In the long term, the occurrence of injury is a negative predictor of survival and is associated with subsequent renal failure, the need for dialysis, and death from renal-related causes.

Introduction of a microsurgical in-vivo embolization-model in rats: the aorta-filter model

Vascular thrombosis with subsequent distal embolization remains a critical event for patients. Prevention of this life-threatening event can be achieved pharmacologically or mechanically with intravascular filter systems. The ability to evaluate the risk of embolization of certain techniques and procedures in vascular and microvascular surgery, such as, tissue glue or fibrin based haemostatic agents lacks convincing models. We performed 64 microvascular anastomoses in 44 rats, including 44 micro-pore polyurethane filter-anastomoses and 20 non-filter anastomoses. The rats were re-anesthetized and the aorta was re-exposed and removed four hours, three, seven, fourteen, thirty-one days, and six months postoperatively. The specimens were examined macro- and microscopically with regard to the appearance of the vessel wall, condition of the filter and the amount of thrombembolic material. Typical postoperative histopathological changes in vessel architecture were observed. Media necrosis was the first significant change three days postoperatively. Localized intimal hyperplasia, media necrosis, increase of media fibromyocytes and adventitial hypercellularity were seen to a significant extent at day seven postoperatively. Significant neovascularization of adventitia adjacent to the filter was seen after 14 days. A significant amount of thrombotic material was seen after four hours, three and 14 days interval. Only three intravascular filters became completely occluded (6.82%). The aorta-filter-anastomosis model appeared to be a valid in-vivo model in situations at risk for thrombembolic events, for microsurgical research and allowed sensitive analysis of surgical procedures and protection of the vascularized tissue. It may be suitable for a wide range of in-vivo microvascular experiments particularly in the rat model.

Renal parenchymal preservation after percutaneous renal angioplasty and stenting

BACKGROUND

The intent of endovascular therapy for symptomatic atherosclerotic renal artery stenosis (ARAS) is to preserve parenchyma and avoid renal-related morbidity. The aim of this study is to examine the impact of renal artery intervention on parenchymal preservation.

METHODS

We performed a retrospective analysis of records from patients who underwent endovascular intervention for ARAS and were followed by duplex ultrasound between 1990 and 2008. Renal volume (in cm(3)) was estimated in all patients as renal length (cm) x renal width (cm) x renal depth (cm) x 0.5. The normal renal volume was calculated as 2 x body weight (kg) in cm(3). Failure of preservation was considered to be a persistent 10% decrease in volume. Clinical benefit defined as freedom from renal-related morbidity (increase in persistent creatinine >20% of baseline, progression to hemodialysis, death from renal-related causes) was calculated.

RESULTS

Five hundred ninety-two renal artery interventions were performed. One hundred eighty-six kidneys suffered parenchymal loss (>5%) with an actuarial parenchymal loss rate of 29% +/- 1% at five years respectively. There were no significant differences in age, gender, starting renal volume, or kidney size. However, patients with parenchymal loss had lower eGFR (45 +/- 24 vs 53 +/- 24 mL/min/1.73 m(2); Loss vs noLoss, P = .0002, Mean +/- SD) higher resistive index (0.75 +/- 0.9 vs 0.73 +/- 0.10; P = .0001) and worse nephrosclerosis grade (1.43 +/- 0.55 vs 1.30 +/- 0.49; P = .006) then those not suffering parenchymal loss. Parenchymal loss was associated with significantly worse five-year survival (26% +/- 4% vs 48% +/- 2%; Loss vs noLoss; P < .001) and freedom from renal-related morbidity (70% +/- 5% vs 82% +/- 2%; P < .05) with increased numbers progressing to dialysis (17% vs 7%; P < .006).

CONCLUSION

While parenchymal preservation occurs in most patients, parenchymal loss occurs in 31% of patients and is associated with markers of impaired parenchymal perfusion (resistive index and nephrosclerosis grade) at the time of intervention. Pre-existing renal size or volumes were not predictive of parenchymal loss. Parenchymal loss is associated with a significant decrease in survival and a marked increased renal related morbidity and progression to hemodialysis.

Endovascular treatment of peripheral vascular disease

Peripheral arterial disease (PAD) affects about 27 million people in North America and Europe, accounting for up to 413,000 hospitalizations per year with 88,000 hospitalizations involving the lower extremities and 28,000 involving embolectomy or thrombectomy of lower limb arteries. Many patients are asymptomatic and, among symptomatic patients, atypical symptoms are more common than classic claudication. Peripheral arterial disease also correlates strongly with risk of major cardiovascular events, and patients with PAD have a high prevalence of coexistent coronary and cerebrovascular disease. Because the prevalence of PAD increases progressively with age, PAD is a growing clinical problem due to the increasingly aged population in the United States and other developed countries. Until recently, vascular surgical procedures were the only alternative to medical therapy in such patients. Today, endovascular practice, percutaneous transluminal angioplasty with or without stenting, is used far more frequently for all types of lower extremity occlusive lesions, reflecting the continuing advances in imaging techniques, angioplasty equipment, and endovascular expertise. The role of endovascular intervention in the treatment of limb-threatening ischemia is also expanding, and its promise of limb salvage and symptom relief with reduced morbidity and mortality makes percutaneous transluminal angioplasty/stenting an attractive alternative to surgery and, as most endovascular interventions are performed on an outpatient basis, hospital costs are cut considerably. In this monograph we discuss current endovascular intervention for treatment of occlusive PAD, aneurysmal arterial disease, and venous occlusive disease.

Revascularization versus medical therapy for renal-artery stenosis

BACKGROUND

Percutaneous revascularization of the renal arteries improves patency in atherosclerotic renovascular disease, yet evidence of a clinical benefit is limited.

METHODS

In a randomized, unblinded trial, we assigned 806 patients with atherosclerotic renovascular disease either to undergo revascularization in addition to receiving medical therapy or to receive medical therapy alone. The primary outcome was renal function, as measured by the reciprocal of the serum creatinine level (a measure that has a linear relationship with creatinine clearance). Secondary outcomes were blood pressure, the time to renal and major cardiovascular events, and mortality. The median follow-up was 34 months.

RESULTS

During a 5-year period, the rate of progression of renal impairment (as shown by the slope of the reciprocal of the serum creatinine level) was -0.07x10(-3) liters per micromole per year in the revascularization group, as compared with -0.13x10(-3) liters per micromole per year in the medical-therapy group, a difference favoring revascularization of 0.06x10(-3) liters per micromole per year (95% confidence interval [CI], -0.002 to 0.13; P=0.06). Over the same time, the mean serum creatinine level was 1.6 micromol per liter (95% CI, -8.4 to 5.2 [0.02 mg per deciliter; 95% CI, -0.10 to 0.06]) lower in the revascularization group than in the medical-therapy group. There was no significant between-group difference in systolic blood pressure; the decrease in diastolic blood pressure was smaller in the revascularization group than in the medical-therapy group. The two study groups had similar rates of renal events (hazard ratio in the revascularization group, 0.97; 95% CI, 0.67 to 1.40; P=0.88), major cardiovascular events (hazard ratio, 0.94; 95% CI, 0.75 to 1.19; P=0.61), and death (hazard ratio, 0.90; 95% CI, 0.69 to 1.18; P=0.46). Serious complications associated with revascularization occurred in 23 patients, including 2 deaths and 3 amputations of toes or limbs.

CONCLUSIONS

We found substantial risks but no evidence of a worthwhile clinical benefit from revascularization in patients with atherosclerotic renovascular disease. (Current Controlled Trials number, ISRCTN59586944.)

Embolic protection devices in patients with renal artery stenosis with chronic renal insufficiency: a clinical study

PURPOSE

To present clinical outcomes with the use of embolic protection devices (EPDs) and renal artery stents in patients with chronic renal insufficiency (CRI) and renal artery stenosis (RAS).

MATERIALS AND METHODS

A retrospective study was conducted in 23 patients with RAS and CRI who were treated with renal artery stent placement with an EPD. Follow-up data were obtained through medical records.

RESULTS

In 23 patients (18 men; 78%) with an average age of 69.4 years +/- 11 (range, 46-86 y), 32 renal arteries were treated for worsening renal function (n = 17; 74%) or uncontrolled hypertension and worsening renal function (n = 6; 26%). Nine FilterWire EZ devices were used in eight patients (35%) and 17 SpideRX devices were used in 15 patients (65%). The average follow-up was 8 months +/- 5. After the stent procedure, the mean systolic blood pressure decreased significantly (P < .05) whereas the diastolic pressure remained unchanged. There was a significant increase in the mean estimated glomerular filtration rate from 32.9 mL/min +/- 12.9 at baseline to 41.3 mL/min +/- 13.7 at last follow-up (P < .05). In 96% of patients, there was improvement or stabilization of kidney function. In six of the 17 SpideRX devices (35%), macroscopically evident embolic material was observed in the device after stent placement. There were two minor and two major complications.

CONCLUSIONS

Renal artery stent placement combined with the use of a SpideRX or FilterWire EZ device is associated with an good clinical outcome with a reasonable safety profile.