Abstract and Introduction
Abstract
Background: Atheroemboli are the rule in any intervention and the leading cause of complications during percutaneous coronary intervention, carotid angioplasty (CAS), and probably after renal angioplasty stenting (RAS), which could explain the renal function deterioration after RAS in 20–30% of the cases. Several series of RAS under protection were reported using current embolic protection devices (EPDs), but these EPD have significant limitations that may be addressed by a new EPD, the FiberNet™ (Lumen Biomedical Inc, MN, USA).
Methods: FiberNet is a 3D expandable filter made of fibers, which expands radially to fill the lumen, that is mounted onto a 190-cm long 0.014-inch wire. No delivery sheath is required. The crossing profile (1.7–2.9F) is low. With the retrieval catheter a focal suction can be performed during device removal allowing a meticulous cleaning of the vessel. The filter can fill vessels from 1.75 to 7 mm without requiring a long landing zone, allowing protection in the majority of renal arteries. FiberNet can capture particles as small as 40 µm without compromising the flow.
Results: After a series of 139 protected renal angioplasties performed with current EPDs, we began the first human study with FiberNet. A total of 12 ostial lesions (R: 6, L: 6) were treated in 12 hypertensive patients (Male: ten). The mean age of patients was 64 years, with an average stenosis of 79%, two patients had moderate renal insufficiency. FiberNet crossed 11 lesions without predilatation (one predilatation was necessary for a subocclusive very calcified ostial lesion). Technical success was observed in 100% of patients with no reported complications. All samples visually contained significant amounts of emboli. The mean debris surface area was 106 mm (aspirated debris: 82 mm, debris in the filter: 24 mm). The mean number of particles 28–60 µm: 2136 ± 776, greater than 60 µm: 5918 ± 1362. At 6-month follow-up, we observed no deterioration of the renal function.
Conclusion: The first human use of this new novel EPD in RAS is encouraging. FiberNet was easy to use and it captures particles of 30/40 µm without compromising the flow, which seems to be an improvement in comparison with current EPD. The amount of debris removed is comparable during RAS and CAS. Additional patients will demonstrate the overall performance of this new EPD and its role to preserve the renal function and improve long-term results of RAS.
Introduction
Atherosclerotic renal artery stenosis (RAS) is frequent and increasingly diagnosed due to technical improvements in duplex ultrasound, magnetic resonance angiography, CT scaning, routine renal angiography during cardiac catheterization, particularly in hypertensive patients or those with multivessel disease, and in patients with renal insufficiency. Renovascular disease affects approximately 2–4 million people in the USA. The prevalence of RAS is high in patients with peripheral vascular disease, renal insufficiency and coronary heart disease.
The natural history of RAS is crucial. Atherosclerotic renal artery stenoses have a high tendency to progress with time, resulting in renal artery occlusion (11–16%), loss of renal mass and a subsequent decrease in renal function (RF). Of these patients, where progression was noted over a 2-year period, the progression of RAS and loss of RF are independent predictors of the ability to medically control blood pressure (BP). Atherosclerotic RAS can lead to different clinical conditions:
Renovascular hypertension (secondary hypertension): accounts for 1–5% of all cases of hypertension;
Renal insufficiency: a rise in serum creatinine following initiation of antihypertensive therapy with angiotensin-converting enzyme inhibitors may lead to the diagnosis of RAS. RAS can be severe enough to cause ischemia and tissue damage, as is often shown by asymmetry in kidney size. In patients over 50 years of age, RAS is responsible for 5–15% of the renal failure population and dialysis dependence;
Flash pulmonary edema: often the first clinical symptom of bilateral RAS;
Atherosclerotic renovascular disease represents an important public health problem. It has been demonstrated to increase cardiovascular and all-cause mortality.
Indications for treatment of RAS are debated, but it is generally accepted to treat patients with a severe RAS (defined as a diameter stenosis of at least 70% and/or over 15 mmHg peak systolic pressure gradient) in the setting of uncontrolled hypertension, renal insufficiency, congestive heart failure (flash pulmonary edema), unstable angina and in patients with a solitary or a single functioning kidney. The treatment of RAS without hypertension or renal insufficiency is debatable but could be considered with a view to preserving RF and renal artery patency.
The treatment options for a RAS include medical therapy, balloon angioplasty (with and without stenting) and surgery. Surgery carries a significant risk with a 2–7% perioperative mortality rate and a 17–31% morbidity rate. Indications for surgery should be limited to failed percutaneous approach, hostile aorta or in association with aortic surgery.
Percutaneous transluminal renal angioplasty (PTRA) has become the cornerstone of therapy for addressing RAS and is now the first-line treatment as balloon angioplasty alone was first proposed and is still the first-line therapy for fibrodysplasic RAS. Several authors have reported the successful use of endovascular stents for treating suboptimal angioplasty results. Stents are the primary intervention for atherosclerotic lesions (particularly ostial lesions) with better immediate and long-term results than with PTRA alone.
In the majority of cases, renal angioplasty is performed using the femoral approach, but a brachial approach can also be used. The procedure has benefited from the improvements in coronary technique: monorail systems for balloons and stents, low-profile devices and 0.014- or 0.018-inch guidewires. Direct stenting can be accomplished in 80–90% of the procedures. Procedural success for renal stenting is excellent (98–100%) with a low complication rate, a low restenosis rate and a good long-term patency rate of 85–98%. There are clear benefits in restoring blood flow to the kidney and several reports have shown these positive effects of renal artery revascularization:
The benefit for hypertension includes complete cure (7–19%) or easier management in 52–74% of the cases and a reduction in the number of antihypertensive drugs;
The kidney function may improve or stabilize in 70–80% of the patients following revascularization;
Improvement in patient survival should be obtained after revascularization in patients with improved RF considering that the creatinine level is a predictor of increased mortality;
A reduction of the left ventricular hypertrophy, probably due to the reduction in activation of the renin–angiotensin–aldosterone system, which can lead to lower heart failure and cardiovascular mortality/morbidity rates. It is an argument to consider renal revascularization in patients with severe RAS.
Two randomized studies were recently published, the ASTRAL Study and the STAR Study, comparing PTRA stenting and medical therapy. These studies concluded that stenting is not superior to medical management in patients with a RAS. However, these studies have numerous limitations and flaws. They do not agree with a meta-analysis published by Nordmann et al. who reported better results for BP with balloon angioplasty with stenting compared with medical therapy.
Renal artery stenting should be a treatment option proposed to a patient suffering from a significant RAS. However, some drawbacks have to be mentioned.
It is well-known that postprocedural deterioration of the RF occurs in 20–30% of the patients after renal stenting. We hypothesize that atheroembolism during the procedure is a precipitating factor for this complication and a major factor limiting the benefits derived from renal stenting. This hypothesis is supported by recent studies, including the role of a renal atheroembolism demonstrated and reported by Scolari et al.. Distal embolization of atherosclerotic debris during PTRA and stenting can be a major complication for renal artery intervention. In order to eliminate or reduce the risk of atheroembolic material being carried into the renal parenchyma, we applied an embolic protection device (EPD) using balloon or filters positioned distal to the lesion. This technique was developed and is currently approved for use in the coronary and cerebral circulations.
Different EPDs have been used and there are several series demonstrating promising results with the capture of thousands of atheroembolic particles. However, the current EPDs used in renal vasculature have some limitations, drawbacks and disadvantages. To overcome these problems, we have used the new FiberNet™ Embolic Protection System, a filter approved for carotid angioplasty (CAS) and stenting. We are presenting the results of the first human study of this filter during PTRA stenting procedures.