Vascular lesions induced by renal nerve ablation as assessed by optical coherence tomography: pre- and post-procedural comparison with the Simplicity catheter system and the EnligHTN multi-electrode renal denervation catheter

Abstract

Aims: Catheter-based renal nerve ablation (RNA) using radiofrequency energy is a novel treatment for drug-resistant essential hypertension. However, the local endothelial and vascular injury induced by RNA has not been characterized, although this importantly determines the long-term safety of the procedure. Optical coherence tomography (OCT) enables in vivo visualization of morphologic features with a high resolution of 10-15 µm. The objective of this study was to assess the morphological features of the endothelial and vascular injury induced by RNA using OCT.

Methods and results: In a prospective observational study, 32 renal arteries of patients with treatment-resistant hypertension underwent OCT before and after RNA. All pre- and post-procedural OCT pullbacks were evaluated regarding vascular changes such as vasospasm, oedema (notches), dissection, and thrombus formation. Thirty-two renal arteries were evaluated, in which automatic pullbacks were obtained before and after RNA. Vasospasm was observed more often after RNA then before the procedure (0 vs. 42%, P < 0.001). A significant decrease in mean renal artery diameter after RNA was documented both with the EnligHTN (4.69 ± 0.73 vs. 4.21 ± 0.87 mm; P < 0.001) and with the Simplicity catheter (5.04 ± 0.66 vs. 4.57 ± 0.88 mm; P < 0.001). Endothelial-intimal oedema was noted in 96% of cases after RNA. The presence of thrombus formations was significantly higher after the RNA then before ablation (67 vs. 18%, P < 0.001). There was one evidence of arterial dissection after RNA with the Simplicity catheter, while endothelial and intimal disruptions were noted in two patients with the EnligHTN catheter.

Conclusion: Here we show that diffuse renal artery constriction and local tissue damage at the ablation site with oedema and thrombus formation occur after RNA and that OCT visualizes vascular lesions not apparent on angiography. This suggests that dual antiplatelet therapy may be required during RNA.

Keywords: Catheter-based renal nerve ablation; EnligHTN multi-electrode renal denervation catheter; Optical coherence tomography; Simplicity catheter system; Vascular lesions.

Figure 1

Study flow chart.

Figure 2

Changes of vessel diameter after renal nerve ablation. Significant differences of vessel diameters before and after renal nerve ablation were observed with both the EnligHTN™ (St. Jude Medical) and the Simplicity® (Medtronic) catheters. Vessel spasm was documented along the whole length of the treated artery.

Figure 3

Vasospasm of renal arteries after renal nerve ablation. Right renal artery (A–E) and left renal artery (F–J). Baseline angiography (A and F) and OCT imaging (B and G) before renal artery ablation with the EnligHTN™ catheter. Vasospasm observed after radiofrequency therapy with both angiography (C and H) and OCT (D and I). Three-dimensional OCT reconstruction of right and left renal artery after renal denervation (E and J).

Figure 4

Vessel wall oedemas after renal nerve ablation. Renal artery before (A) and after (B) Simplicity® catheter-based renal denervation. Direct after ablation vessel notches are inapparent in angiography (B) and discernible at the lesion site by OCT imaging (C, frame and D).

Figure 5

Thrombus formation after renal nerve ablation. Significant intraluminal thrombus formation after renal nerve denervation are inapparent in angiography (A and D), however displayed in different OCT cross-sections (B, C, E, F and I) and in three-dimensional reconstructed renal artery (G and H).

Figure 6

Dissections after renal nerve ablation. Endothelial detachments (A, white box) and vessel wall dissections (B, red arrow) detected in treated renal arteries with the EnligHTN™ catheter.