Evaluation of Safety Mechanisms of Renal Radioablation(RSRA)for Uncontrolled Hypertension

The purpose of this study is to evaluate the efficacy, safety and selected mechanisms of renal sympathetic radioablation. The primary outcome of this study is change in BP 12 months post treatment as assessed from daytime average of systolic BP from 24-hr ABPM.

In this innovation program, we propose to evaluate the following aspects of renal sympathetic radioablation RSRA in Patients with Resistant HTN:

1. Efficacy: Assessment of BP lowering effect in patients with true resistant HTN. In contrast to studies done so far, we will evaluate the true BP lowering effect of RSRA by performance of 24-hr ABPM prior to and at defined time points post procedure. We will screen out pseudohypertension using direct observed therapy. We will employ a rigorous protocol to include only patients with truly resistant HTN. Namely, we will screen for major forms of secondary HTN such as renal artery stenosis, pheochromocytoma, primary hyperaldosteronism, and Cushing's syndrome and exclude these patients from radioablation. We will also address the issue of white coat phenomena as a cause of false diagnosis of resistant HTN by 24-hr ABPM. This innovative approach will ensure a proper evaluation of the BP lowering potential of this method, as patients with secondary forms of HTN may not respond to RSRA. In contrast, those with white coat effect may show gradual improvement in BP control over time unrelated to RSRA.
2. Safety: Imaging of the renal arteries. Our patients will undergo CT angiogram imaging of their renal arteries prior to procedure and at defined time points afterwards. In studies reported so far, imaging of the renal arteries was not standardized. In animals (swines) subjected to RSRA using the same catheter, renal arteries showed fibrosis of 10-25% of the total media and underlying adventitia, with mild disruption of the external elastic lamina. Furthermore, a case report has been published documenting renal artery stenosis within 3 months post RSRA.
3. Education on diagnosis and treatment of resistant HTN. As resistant HTN is frequently misdiagnosed and consequently poorly treated, we will develop teaching sessions for family physicians, general internists, and subspecialists from this LHIN region to make them aware of issues related to diagnosis of true resistant HTN and to educate them on this new option of treatment.
4. Mechanism:

Effects of RSRA on Central Sympathetic Outflow, PWV, and aldosterone will be assessed pre and post RSRA and correlated to (changes in) BP prior to and at defined time points post RSRA.

Clinical relevance:

This is a new method for treatment of patients with resistant HTN. As our team has successfully treated two patients with resistant HTN in June 2012 (as the second team and centre in Canada), TOH/UOHI with experts in Clinical HTN, Nephrology, Interventional Cardiology and Interventional Radiology are uniquely positioned to establish and critically evaluate the suitability of this method for patients from our LHIN region. Pilot data on Pulse Wave Velocity, MSNA and aldosterone by RSRA will shed light on mechanisms involved in BP lowering by RSRA and will be used for the development of grant applications to Canadian peer review funding agencies.