Transradial renal stenting: why and how

Interventions for renal artery stenosis: Appraisal of novel physiological insights and procedural techniques to improve clinical outcome

Randomized clinical trials failed to show additional benefit of renal artery stenting on top of medical therapy. Instead of writing an obituary on renal artery stenting, we try to explain these disappointing results. A transstenotic pressure gradient is needed to reduce renal perfusion and to activate the renin-angiotensin-aldosterone system. In only a minority of patients included in trials, a transstenotic pressure gradient is measured and reported. Like the coronary circulation, integration of physiological lesion assessment will allow to avoid stenting of non-significant lesions and select those patients that are most likely to benefit from renal artery stenting. Renal artery interventions are associated with peri-procedural complications. Contemporary techniques, including radial artery access, no-touch technique to engage the renal ostium and the use of embolic protection devices, will minimize procedural risk. Combining optimal patient selection and meticulous technique might lead to a netto clinical benefit when renal artery stenting is added to optimal medical therapy.

Preclinical research performed on reanimated/perfused swine kidneys: The Visible Kidney™ methodologies

Preclinical research remains the essential platform in the development and optimization of medical therapies and advancements in translational medicines. However, specifically to animal research, federal laws, and institutional policies require investigators to apply the principles of the 3R's (replacement, reduction, and refinement). The concept of benchtop models utilizing isolated organs, in which multiple variables can be controlled to recreate human function, has been innovative advancements in preclinical research models that adhere to these principles. More specifically, isolated perfused kidney (IPK) models have been invaluable preclinical tools that have led to numerous advancements over the decades, including understanding renal physiology, pharmacologic therapies, and improvements in renal transplantation. However, pre-existing IPK models are not without their own limitations, leaving areas for improvement. An isolated perfused kidney apparatus was designed to best recreate human use conditions as a preclinical tool. Porcine renal blocks were chosen over the more commonly used rodent models, due to their greater similarities to human anatomies. Sixteen porcine kidney pairs obtained en bloc were extracted and placed onto an apparatus where aortic flows, pressures, and overall systemic temperatures were controlled. Organ viability was assessed in 10 renal blocks (n = 8 fresh and n = 2 previously frozen specimens) via both urinary flows and compositions at timepoints up to 180 min. Multimodality imaging, which included fluoroscopy, ultrasound, optical coherence tomography (OCT), and video scopes, was also employed to capture internal and external images to determine renal artery orientations and dimensions. Anatomical measurements and viability assessments of porcine renal blocks were successfully achieved in our perfusion model. Renal main artery diameters averaged smaller in our sample size than in human anatomy while also having more superior takeoff angles. Yet, the average lengths of each main segment were comparable to human anatomy: 32.09 ± 7.97 mm and 42.23 ± 7.33 mm in the left and right renal main artery, respectively. Urine production and urine composition of the fresh renal blocks, when compared to the frozen blocks and baseline perfusate, showed kidney viabilities of up to 3 h via excretion and retention of various metabolites. In this paper, we described a protocol for an isolated perfused kidney apparatus using large mammalian renal blocks. We believe this protocol to be an improvement from similar pre-existing models in better representing human physiologic function while allowing for multimodal imaging. The resulting Visible Kidney™ preclinical model, which has shown viability after isolation and reperfusion, can be a fast and reliable tool for the development of medical devices while also reducing the unnecessary use of animals for research.

Renal Arteriography via Radial Artery Access with a 125 cm Long Angiographic Catheter

A 125 cm long catheter makes it possible to perform renal arteriography via radial artery, but its feasibility and safety remain unclear. Our study recruited 1,323 patients grouped by two different vascular accesses to renal arteriography, i.e., femoral artery access and radial artery access. The success rate of angiography was 100% in both groups. Differential analysis showed that the overall complication incidence of radial artery access group was significantly lower (2.5% for radial artery access vs. 4.8% for femoral artery access, p = 0.03). From this study, we suggest that using the 125 cm angiographic catheter to perform renal arteriography via radial artery access is feasible and safe.

Usefulness of sheathless guiding catheters in patients with upper extremity vascular anomalies: Sheathless catheters in upper vascular anomalies

AIMS

The transradial approach (TRA) reduces hospitalisation and access-site complications as compared to the transfemoral approach. Nevertheless, the TRA technical failure rate is significantly higher compared to the transfemoral approach. The high failure rate of TRA is due to a series of factors. In particular, a wide range of anatomic vascular variants hindering procedural success may be present in patients undergoing TRA procedures.

METHODS AND RESULTS

In our retrospective observational study, 1,596 consecutive patients with upper limb vascular anomalies underwent TRA between January 2006 and July 2017. We evaluate the usefulness of the sheathless guiding catheter system (SG) as compared to the conventional guiding catheter (CG). The primary study endpoint was the "procedural success" defined as successful transradial procedure (both selective cannulation of the coronary ostium in the diagnostic procedure and successful stent delivery in the interventional procedure) without access change. All SG procedures were successful, whereas only 1,274 (86%) CG procedures were successfully performed (p=0.0001). At multivariable analysis, age (p=0.001) and sheathless catheter use (p=0.001) were independent predictors of procedural success.

CONCLUSIONS

The sheathless GC is a safe and useful system not only for small radial access but also in the presence of upper vascular anomalies and it can be used in PCI and diagnostic procedures.

When and How Should We Revascularize Patients With Atherosclerotic Renal Artery Stenosis?

Atherosclerotic renal artery stenosis is the leading cause of secondary hypertension and may lead to resistant (refractory) hypertension, progressive decline in renal function, and cardiac destabilization syndromes (pulmonary edema, recurrent heart failure, or acute coronary syndromes) despite guideline-directed medical therapy. Although randomized controlled trials comparing medical therapy with medical therapy and renal artery stenting have failed to show a benefit for renal artery stenting, according to comparative effectiveness reviews by the Agency for Healthcare Research and Quality, the trials may not have enrolled patients with the most severe atherosclerotic renal artery stenosis, who would be more likely to benefit from renal stenting. Because of limitations of conventional angiography, it is critical that the hemodynamic severity of moderately severe (50% to 70%) atherosclerotic renal artery stenosis lesions be confirmed on hemodynamic measurement. The authors review techniques to optimize patient selection, to minimize procedural complications, and to facilitate durable patency of renal stenting. The authors also review the current American College of Cardiology and American Heart Association guidelines and the Society for Cardiovascular Angiography and Interventions appropriate use criteria as they relate to renal stenting.

Vascular Access and Closure for Peripheral Arterial Intervention

Peripheral arterial interventions require safe and effective vascular access and closure. The sites, techniques, and equipment used may vary depending on patient and procedural factors. To minimize the risk of procedural complications, arterial access should use micropuncture technique, ultrasound and fluoroscopic guidance, a compressible arterial access site, and the smallest diameter sheath necessary. Hemostasis at an arteriotomy site may be achieved by manual compression, device-mediated compression, an intravascular closure device, or an extravascular closure device. Although closure devices improve patient comfort and expedite hemostasis, they have not been shown to reduce complications in comparison with compression.

Transradial renal salvage after complex endovascular aneurysm repair complicated by left renal artery thrombosis

Transradial access has been used for percutaneous coronary interventions with success; however, there is limited literature on its use for visceral stenting in the setting of complex endovascular aneurysm repair. We present a case of transradial left renal salvage after renal artery thrombosis in the setting of complex endovascular aneurysm repair.

Comparison of the transradial and transfemoral approach in treatment of chronic total occlusions with similar lesion characteristics

Objective:

There is limited data on the efficacy and the safety of the transradial approach (TRA) for percutaneous coronary intervention (PCI) of chronic total occlusion (CTO), particularly in comparison with the transfemoral approach (TFA) in lesions with similar complexity.

Methods:

We included 358 patients, who underwent elective CTO PCI between January 2012 and August 2017 and compared the radial (179 patients) and femoral (179 patients) approaches. The J-CTO score was similar in both groups (TRA, 2.5±1.3 vs. TFA, 2.8±1.4, n.s.). The endpoints analyzed included (i) the composite of all-cause death and nonfatal myocardial infarction (MI) and (ii) the composite safety endpoint of major adverse cardiovascular and cerebrovascular events (MACCEs), including death, MI, coronary perforation, contrast-induced nephropathy (CIN), bleeding at the vascular access site requiring transfusion, cardiac tamponade requiring pericardiocentesis, and periprocedural stroke.

Results:

Patients’ demographics, lesion location, lesion characteristics, and the proportion of antegrade vs. retrograde approach were similar in both groups. The procedural success rate of 96.4% in the radial group and 92.9% in the femoral group was comparable. The total fluoroscopy time (TRA, 42.4±15.7 min vs. TFA, 40.5±15.3 min, n.s.) and contrast medium use (TRA, 532.2±21.7 mL vs. TFA, 528.2±24.6 mL, n.s.) was similar in both groups. There was no in-hospital death or periprocedural MI in both groups. There were three coronary perforations in the TFA group, among them one with tamponade, and one coronary perforation the TRA group. Vascular access site complications (TRA, 0.01% vs. TFA, 0.02%) and CIN (TRA, 0.006% vs. TFA, 0.006%) were rare. One stroke as a result of the procedure was observed in the TFA group. No death was registered.

Conclusion:

The radial approach in CTO PCI was as fast and successful as the femoral approach, even in a complex lesion subset.

Transradial Delivery of a Renal Snorkel During Complex Endovascular Aortic Aneurysm Repair

Transradial access has been described in a variety of clinical contexts but has been rarely utilized for visceral artery interventions and during complex endovascular aortic aneurysm repair (EVAR) when upper extremity access is required. This is usually accomplished via brachial artery access, and although brachial access is generally safe and effective, radial access may offer some benefits with regard to patient comfort and potential complications. Here we report a case of successful delivery of a renal snorkel via a radial artery approach during EVAR. A 71-year-old man presented for endovascular repair of an asymptomatic abdominal aortic aneurysm. Anatomic limitations dictated the need for a left renal snorkel in order to augment the proximal seal zone. Via a right radial approach, a 6-Fr sheath and then a 6-mm iCast stent (Atrium Medical, Hudson, New Hampshire) were delivered into the left renal artery. Endovascular aortic aneurysm repair was then completed with a bifurcated Endurant stent graft (Medtronic, Fridley, Minnesota). The renal stent and aortic stent grafts were successfully deployed. Completion angiography demonstrated a patent left renal snorkel, with no evidence of endoleak. Hemostasis was achieved at the radial puncture site with no complications. This demonstrates the feasibility of radial artery access for the delivery of adjunctive stents during complex EVAR.

Renal Artery Stenosis: When to Revascularize in 2017

Atherosclerotic renal artery stenosis is the leading cause of secondary hypertension; it can also cause progressive renal insufficiency and cardiovascular complications such as refractory heart failure and flash pulmonary edema. Medical therapy including risk factor modification, renin-angiotensin-aldosterone system antagonists, lipid lowering agents, and antiplatelet therapy is the first line of treatment in all patients. Patients with uncontrolled renovascular hypertension despite optimal medical therapy, ischemic nephropathy, and cardiac destabilization syndromes who have severe renal artery stenosis are likely to benefit from renal artery revascularization. Screening for renal artery stenosis can be done with Doppler ultrasonography, computed tomographic angiography and magnetic resonance angiography. Invasive physiologic measurements are useful to confirm the severity of renal hypoperfusion and therefore improve the selection patients likely to respond to renal artery revascularization. Primary patency exceeds 80% at 5 years and surveillance for in-stent restenosis can be done with periodic clinical, laboratory, and imaging follow-up.

First-in-man report of a novel dedicated radiofrequency catheter for renal denervation via the transulnar approach

Renal denervation (RDN) has been shown to be safe and efficacious in reducing blood pressure in patients with resistant hypertension. In the present study, we describe a first-in-man report of the Iberis renal denervation device in a patient who underwent two RDN procedures: one via the femoral artery and one via the transulnar approach. RDN was performed in the patient's right renal artery using an Iberis catheter via the transulnar approach, as the transfemoral or transradial arteries could not be approached due to their anatomic constraints. In summary, RDN via the transulnar approach is feasible and represents a technical alternative solution in certain patients.

Cranio-caudal (transradial) approach for renal artery intervention

This report describes the technique of transradial renal angiography and interventions. We illustrate the approach using typical case images. We believe cranio-caudal approach to the renal artery for diagnostic and therapeutic catheterization offers advantages over the traditional femoral approach.

Renal artery intervention using a virtual 4.5-Fr guiding catheter

A 6.5-Fr guiding catheter (Parent Plus 45, Medikit, Tokyo, Japan), composed of a hydrophilic sheathless guiding catheter and a dilator, has recently been developed for the treatment of renal artery stenosis. Because of its unique sheathless configuration, its outer diameter is comparable to that of a conventional 4.5-Fr introducer sheath, with the inner diameter being close in size to a 6.5-Fr guiding catheter. These features allow this sheathless system to be used as the sole guiding catheter while the arterial damage at the puncture site remains equivalent to that of a 4.5-Fr introducer sheath. We thus call this novel sheathless guiding catheter a virtual 4.5-Fr system. To demonstrate the potential of this virtual 4.5-Fr system, we report a case of renal artery stenosis successfully treated via the transradial route. This virtual 4.5-Fr system may become a viable alternative to conventional guiding catheters, and provide a favorable impact upon vascular access complications and patient morbidity.