MRI with paramagnetic contrast enhancement of the arterial vascular wall in follow-up control of therapeutic effect in resistant arterial hypertension treated with radiofrequency ablation of sympathetic plexus of the renal arteries

Abstract

Aim . Quantitative follow-up of the intensity of paramagnetic contrast enhancement of the aortal wall and renal arteries walls, as indicator of the pathological subinitimal and media neoangiogenesis was carried out in patients with arterial hypertension, focusing on changes after renal denervation. Material and methods . 31 patients (as old as 57.3 ± 9.8 years) with resistant hypertension comprised the study group. The average systolic/diastolic pressure obtained from 24-h monitor study was as high as 154 ± 12 / 89 ± 9 mm Hg. The MRI studies were carried out using 1.5 Т MRI Toshiba Vantage Titan scanner. After this the intravenous contrast enhancement has been carried out (with 0.5 М paramagnetic, as 0.2 ml/Kg). The radiofrequency ablation (RFA) desympathising the kidneys was performed on X-ray operating room using the Symplicity system: Symplicity Flex renal ablation electrode with a 4F end electrode as thin as 1.33 mm and with length of 1.5 mm, and also automated RF voltage generator with built-in power management algorithms temperature (Medtronic, USA) were employed. The comparison group included 28 people who were referred for MRI study of lumbar spine (average age - 53.2 ± 17.8), without any evidence that could be attributed to the pathology of the cardiovascular system. Results . Enhancement index (EI) of the aortic wall of patients with hypertension (1.57) was significantly over the aortic EI of healthy people (1.23), p < 0.0001, reflecting inflammatory neoangiogenetic changes in the vascular wall in hypertension. The correlation between EI in the wall of both renal arteries is highly reliable and linear, which confirms the idea of the systemic nature of neoangiogenesis in hypertension. Analysis of data from an MRI study of the renal arteries showed that the intensity of the accumulation of the contrast agent in their wall after RD, as a rule, decreases (the right RA distal segment 1.78, 1.61, 1.59 - at baseline, at 6 and 12 months after RD, respectively (p < 0.05). Thus, a visual MRI proves electro-induced damage to the wall of the renal artery and the development of fibrosis at the site of radiofrequency exposure. At the same time, there are no significant differences in EI between studies at the sixth (p = 0.56) and twelfth (p = 0.48) months of observation after RFA, which argues in favor of maintaining fibrosis and, respectively, the absence of reinnervation and inflammatory neoangiogenesis of the arterial wall. Conclusion. MR-tomographic examination of the aorta and renal arteries with contrast enhancement should be carried out to assess the state of the walls of these vessels and to dynamically monitor their condition after renal denervation.