- A prospective study to evaluate the effect of renal denervation on muscle sympathetic nerve activity in patients with resistant hypertension
Vidal-Petiot E.1,4, Duchatelle V.2, Flamant M.1,4, Dalloz M-A.1, Tamisier R.3, Steg Ph-G.2,5 d’Ortho M-P.1
(1)Physiology Department – Bichat Hospital – Paris – France; (2) Cardiology Department – Bichat Hospital – Paris – France; (3) Physiology Department – Grenoble Hospital – Grenoble – France; (4) INSERM U-1149-Bichat Hospital- Paris – France; (5) INSERM U-1148-Bichat Hospital- Paris – France
Introduction: In the past few years, several non pharmacological techniques have been developed to treat hypertension. Percutaneous renal denervation (RDN) is a catheter-based radiofrequency ablation of the renal nerves within the adventitia of the renal arteries, and is believed to reduce not only renal but also systemic sympathetic nerve activity, and thereby lower blood pressure (BP). Clinical trials on RDN in patients with resistant hypertension have yielded conflicting results, leading the scientific community to go back to the physiological basis of renal denervation. The only way to directly measure sympathetic activity in man is muscle sympathetic nerve activity (MSNA), where the sympathetic fibers of the peroneal nerve are recorded through a tungsten microelectrode. However, this challenging technique is only scarcely available worldwide. The purpose of our study is to measure MSNA before and 6 months after RDN in patients with resistant hypertension, in order to answer the following questions. 1/ is baseline sympathetic activity predictive of the BP response to treatment? 2/is MSNA reduced after RDN and if so does this reduction correlate with the decrease in BP?
Methods: In our center, RDN is considered in patients whose blood pressure is uncontrolled by at least four drugs, including spironolactone. Resistance is confirmed with Ambulatory BP Measurement (ABPM). Patients are carefully screened for secondary forms of hypertension, including endocrine hypertension, high salt intake, renal diseases, renovascular hypertension and sleep apnoea. Anatomical suitability is checked with CT-imaging of renal arteries, and decision of RDN is taken by a committee including at least a nephrologist, a hypertension specialist, a physiologist, a radiologist and an interventional cardiologist. Percutaneous RDN is performed under general anaesthesia by a team involving cardiologists, radiologists and anaesthesiologists with transluminal radiofrequency ablations applied via an electrode at the catheter tip. Office BP, home BP, ABPM and routine laboratory evaluations (baseline, M1, M3, M6, M12, M24 and M36) and CT imaging of renal arteries (M12, M36) are performed to evaluate the effects on BP and rule out complications such as renal artery stenosis. MSNA will be measured before and 6 months after renal denervation, in patients taking the same medications for both measurements.
Results and perspectives: After our careful screening process, most patients reached BP target, and very few patients remained eligible for renal denervation. Feasibility of the procedure has been tested in 4 patients, treated with no adverse effects. Baseline 24H-ABPM was 152 ± 7 over 87 ± 1mmHg with a heart rate of 70 ± 3 bpm). Six months after RDN, mean 24H-ABPM was 142 ± 8 over 83 ± 7 a heart rate of HR 69 ± 6 bpm (p=NS for all variables). The MSNA device is now available and we are currently learning the technique, which will be performed in the next RDN patients.
Beyond RDN and hypertension, we believe expertise in MSNA will be a strength for our multidisciplinary Département Hospitalo-Universitaire FIRE, with potential very interesting applications in other fields where sympathetic activity plays a key role, such as sleep apnoea, metabolic syndrome or cardiac failure.