Bilateral Renal Artery Stenosis After Renal Denervation

Serial changes in vessel walls of renal arteries after catheter-based renal artery denervation: insights from volumetric computed tomography analysis

Aim

Radiofrequency ablation of peri-arterial renal autonomic nerves has been studied as a potential therapeutic option for resistant hypertension. While recent clinical trials have reported its efficacy, there is paucity of data addressing the effects of the procedure on renal arteries, such as changes in vessel and lumen areas. Herein, the effect of atheroma burden on renal arteries after renal denervation was assessed using computed tomography (CT) imaging.

Materials and methods

Serial renal artery CT imaging was conducted in 38 patients from the EnligHTN™ I study, a prospective, multicenter study evaluating the efficacy of the EnligHTN multi-electrode radiofrequency ablation catheter in resistant hypertensive subjects. Cross-sectional images of renal arteries at 1 mm intervals were acquired using commercially available software (3mensio Structural Heart version 5.1). Vessel and lumen areas were manually traced in each image. Vessel wall volume (VWV) and percent vessel wall volume (P-VWV) were calculated. The measurements within the ablation (first 30 mm segments) and the non-ablation (subsequent 30 mm segment after the first bifurcation of renal arteries) zones were compared.

Results

On serial evaluation, greater increase in P-VWV and VWV was observed in the ablation zone (change in P-VWV, 6.7%±5.1% vs 3.6%±2.8%, P=0.001; change in VWV, 106.3±87.4 vs 23.0±18.2 mm³, P=0.001). Receiver-operating characteristic analysis demonstrated baseline P-VWV in the ablation zone >37.1% as an optimal cutoff value to predict its substantial progression after the procedure (area under the curve=0.88, sensitivity 89.8%, specificity 79.1%).

Conclusion

Change in vessel wall was greater within the segments receiving renal artery denervation. Baseline VWV predicted its substantial increase after the procedure. These observations suggest that atheroma burden within the renal arteries is a potential contributing factor to vascular changes after renal sympathetic denervation.

Intravascular imaging, histopathological analysis, and catecholamine quantification following catheter-based renal denervation in a swine model: the impact of prebifurcation energy delivery

The purpose of this study was to evaluate the impact of prebifurcation renal denervation in a swine model and assess its safety through optical coherence tomography (OCT). Prebifurcation renal denervation with a multi-electrode catheter was performed in one renal artery of 12 healthy pigs, with the contralateral artery and kidney being used as controls. Angiograms and OCT pullbacks were obtained peri-procedurally and 1 month post procedure. Renal tissue catecholamines were quantified, and the arterial wall and peri-adventitial tissue were analyzed histologically. Intraluminal changes (endothelial swelling, spasm, and thrombus formation) were observed acutely by OCT in most of the treated arteries and were no longer visible at follow-up. Histology revealed a statistically significant accumulation of collagen (fibrosis) and a near absence of tyrosine hydroxylase labeling in the denervated artery, suggesting a clear reduction in nervous terminals. Renal tissue catecholamine levels were similar between both sides, probably due to the low number of ablation points and the renorenal reflex. The present study demonstrates that renal denervation is associated with acute intimal disruptions, areas of fibrosis, and a reduction in nervous terminals. The lack of difference in renal tissue catecholamine levels is indicative of the need to perform the highest and safest number of ablation points in both renal arteries. These findings are important because they demonstrate the histological consequences of radiofrequency energy application and its medium-term safety.

[Renal artery stenosis long time after renal denervation for resistant hypertension]

The onset of renal artery stenosis following a renal denervation is rare and occurs in the first few months after renal denervation. We report the onset of renal artery stenosis a long time after the renal denervation for resistant hypertension. This is a 74 year-old patient who stopped smoking in 1980 and who was treated for dyslipidemia with a revascularized coronary artery disease in 2011, a well-stabilized peripheral arterial disease since 2001, a stable asymptomatic carotid atheroma and a good kidney function. His hypertension known since 1995 became resistant. After the control of renal arteries by angio-CT scan, he had a renal denervation in October 2012. His blood pressure decreased 3 months later confirmed by self-blood pressure monitoring (SBPM) and ambulatory blood pressure monitoring (ABPM) with a CT scan with a non-significant renal artery stenosis in January 2014. He remained normotensive under treatment until July 2015 but his hypertension became uncontrolled at the end of 2015 then resistant and severe confirmed by SBPM in April 2017, despite a 5-drug antihypertensive treatment associated to atorvastatin and clopidogrel confirmed by SBPM in April 2017. A left post-ostial renal artery stenosis with decrease in size of left kidney and cortex as compared to 2011 was detected at CT and treated by angioplasty. It was associated with a rapid decrease in blood pressure but unfortunately a new increase related to a restenosis occurred at the end of 2017, which justified a new angioplasty. Discussion about the etiology and the management of this renal post-denervation late stenosis.

Resistant Hypertension and Renal Nerve Denervation

Patients with resistant hypertension are a subgroup of the hypertensive population that are at even greater risk of cardiovascular outcomes. Therapeutic options for these patients are limited to antihypertensive medications. However, renal denervation (RDN) is a novel nonpharmacologic intervention that involves a catheter-based ablation of the sympathetic nerves within the renal artery wall. The procedure initially showed promise with remarkable blood pressure reductions until the pivotal SYMPLICITY HTN-3 trial failed to demonstrate superiority of RDN over control. This trial was notable for a substantial placebo effect and an attenuated response to RDN. These findings, which contradicted those of prior studies, have raised numerous questions, including whether adequate RDN occurred in those patients. Further research is planned to resolve some of these questions and to clarify the role of RDN in treating patients with resistant hypertension.

Catheter-based Renal Artery Denervation for Resistant Hypertension: Promise Unfulfilled or Unsettled?

Resistant hypertension affects approximately 10-15 % of the hypertensive population and is associated with an increased occurrence of adverse cardiovascular outcomes. Recently, renal denervation (RDN) has emerged as a novel, non-pharmacologic therapy for resistant hypertension that is designed to ablate the sympathetic nerves distributed around the renal arteries, thus diminishing sympathetic nervous system activity and its influence on hypertension. RDN appeared to have a powerful BP-lowering effect in early clinical trials. However, a pivotal follow-up trial, SYMPLICITY HTN-3, showed no additional benefit of the therapy when compared with a sham procedure. Various aspects of the trial have been examined to explain this inconsistency, including a potent placebo effect and uncertainty about whether RDN actually occurred. Further research is needed to clarify the role of RDN in the management of resistant hypertension.

Long-term follow-up of renal arteries after radio-frequency catheter-based denervation using optical coherence tomography and angiography

Optical coherence tomography (OCT) imaging at the time of renal denervation (RDN) showed that procedure might cause spasm, intimal injury or thrombus formation. In the present study, we assessed the healing of renal arteries after RDN using OCT and renal angiography in long-term follow-up. OCT and renal angiography were performed in 12 patients (22 arteries) 18.41 ± 5.83 months after RNS. There were no adverse events or complications during the long-term follow-up. In ten patients (83 %), significant reductions of blood pressure was achieved without a change of the antihypertensive medications. We demonstrated the presence of 26 areas of focal intimal thickening identified by OCT in 10 (83 %) patients and in 14 (63 %) arteries. The mean area of focal intimal thickening was 0.054 ± 0.033 mm(2). No vessel dissection, thrombus, intimal tear or acute vasospasm were observed during the OCT analysis. Also, the quantitative angiography analysis revealed a significant reduction of the minimal and proximal lumen diameters at follow-up as compared to measurements obtained before RDN. Renal arteries have a favorable "long-term" vessel healing response after RDN. Focal intimal thickening and a modest reduction of the minimal lumen diameter may be observed after RF denervation. Further studies are needed to determine whether intravascular imaging may be helpful in evaluating the vessel healing of RF RDN.

Validation of renal artery dimensions measured by magnetic resonance angiography in patients referred for renal sympathetic denervation

RATIONALE AND OBJECTIVES

Magnetic resonance angiography (MRA) is a well-established modality for the assessment of renal artery stenosis. Using dedicated quantitative analyses, MRA can become a useful tool for assessing renal artery dimensions in patients referred for renal sympathetic denervation (RDN) and for providing accurate measurements of vascular response after RDN. The purpose of this study was to test the reproducibility of a novel MRA quantitative imaging tool and to validate these measurements against intravascular ultrasound (IVUS).

MATERIALS AND METHODS

In nine patients referred for renal denervation, renal artery dimensions were measured. Bland-Altman analysis was used to assess the intraobserver and interobserver reproducibility.

RESULTS

Mean lumen diameter was 5.8 ± 0.7 mm, with a very good intraobserver and interobserver variability of 0.7% (reproducibility: bias, 0 mm; standard deviation [SD], 0.1 mm) and 1.2% (bias, 0 mm; SD, 0.1 mm), respectively. Mean total lumen volume was 1035.3 ± 403.6 mm(3) with good intraobserver and interobserver variability of 2.9% (bias, -9.7 mm(3); SD, 34.0 mm(3)) and 2.8% (bias, -11.4 mm(3); SD, 42.4 mm(3)). The correlation (Pearson R) between mean lumen diameter measured with MRA and IVUS was 0.750 (P = .002).

CONCLUSIONS

Using a novel MRA quantitative imaging tool, renal artery dimensions can be measured with good reproducibility and accuracy. MRA-derived diameters and volumes correlated well with IVUS measurements.

Frequency of renal artery stenosis after renal denervation in patients with resistant arterial hypertension

Catheter-based ablation of nerves in the adventitia of renal arteries (renal artery denervation [RAD]) using radiofrequency energy can reduce blood pressure (BP) in patients with resistant arterial hypertension (RAH). Occurrence of renal artery stenosis after RAD is still an important concern. We systematically investigated the renal artery anatomy using magnetic resonance imaging (MRI) or computed tomography (CT) angiography in a consecutive series of patients 6 months after RAD. Patients with RAH were treated by RAD after exclusion of secondary causes of hypertension. RAH was defined by a mean systolic office BP >160 mm Hg. Renal artery imaging was performed 6 months after RAD by MRI angiography. In case of any contraindication for MRI, a CT angiography was performed. The primary end point was the incidence of significant renal artery stenosis (≥70% lumen diameter reduction). RAD was performed in 76 patients, and evaluation of renal artery anatomy by MRI (n = 66; 87%) or CT angiography (n = 10; 13%) was performed in all patients 6 months after RAD. We found no renal artery stenosis but 2 cases of new nonsignificant stenosis (50% TO 69% lumen diameter reduction). In responders, mean systolic office BP reduction was -30 mm Hg (p <0.001) and mean systolic 24-hour BP reduction was -18 mm Hg (p <0.001). In conclusion, the incidence of significant renal artery stenosis 6 months after RAD seems to be very low. However, late-onset development of nonsignificant renal artery narrowing cannot be excluded in some patients and should be anticipated in the case of RAH relapse or worsening of renal function after successful RAD.

Renal denervation after Symplicity HTN-3: an update

After three years of excessive confidence, overoptimistic expectations and performance of 15 to 20,000 renal denervation procedures in Europe, the failure of a single well-designed US trial—Symplicity HTN-3—to meet its primary efficacy endpoint has cast doubt on renal denervation as a whole. The use of a sound methodology, including randomisation and blinded endpoint assessment was enough to see the typical 25–30 mmHg systolic blood pressure decrease observed after renal denervation melt down to less than 3 mmHg, the rest being likely explained by Hawthorne and placebo effects, attenuation of white coat effect, regression to the mean and other physician and patient-related biases. The modest blood pressure benefit directly assignable to renal denervation should be balanced with unresolved safety issues, such as potentially increased risk of renal artery stenosis after the procedure (more than ten cases reported up to now, most of them in 2014), unclear long-term impact on renal function and lack of morbidity–mortality data. Accordingly, there is no doubt that renal denervation is not ready for clinical use. Still, renal denervation is supported by a strong rationale and is occasionally followed by major blood pressure responses in at-risk patients who may otherwise have remained uncontrolled. Upcoming research programmes should focus on identification of those few patients with truly resistant hypertension who may derive a substantial benefit from the technique, within the context of well-designed randomised trials and independent registries. While electrical stimulation of baroreceptors and other interventional treatments of hypertension are already “knocking at the door”, the premature and uncontrolled dissemination of renal denervation should remain an example of what should not be done, and trigger radical changes in evaluation processes of new devices by national and European health authorities.