The Antihypertensive Efficacy and Safety of Catheter-Based Renal Denervation: A Report of 2 Cases

The renal sympathetic nervous system has a decisive role in the induction and maintenance of hypertension [1]. The inhibition of sympathetic overactivity is considered an important target for the treatment of hypertension and its complications. Catheter-based renal denervation (RDN) has emerged as an innovative interventional approach to reduce blood pressure (BP) in patients with resistance hypertension [2-4]. This technique delivers low-level radiofrequency energy throughout the renal artery wall and selective destruction renal nerves and thereby decrease BP. Both the Symplicity HTN-1 trial and Symplicity HTN2 trial significant reduction of BP following RDN [4,5]. However, the Symplicity HTN-3 study did not show effective BP reduction [6]. So, we reported 2 cases of resistance hypertension patients with a long follow-up time of over 6 years to preliminarily investigate the efficacy and safety of RDN.

There was no hematuria or lower back pain. On June 17 th , 2012, routine urine tests and renal function tests were normal, and renal artery imaging showed that no renal arterial stenosis ( Figure 1). BP monitor, a urine tests and renal function tests every 12-month during the 6 years of follow-up is mandatory. The BP and creatinine clearance (CCr) result as show in Figure 2. There were no significant changes in SBP, DBP, and CCr after RDN in the long follow-up period.

a)
Before surgery b) 6-month post-surgery

Case 2
The patient was a 45-year-old male. The patient was admitted to the hospital due to elevated blood pressure for 6 years and After taking 3 types of antihypertensive agents orally, his blood pressure did not reach the goal, which met the diagnostic criteria for resistant hypertension. The patient had RDN indications and was strongly willing to receive surgery; therefore, RDN was performed on February 3 rd , 2012. After operation, the patient received perindopril 4mg/day and amlodipine 5mg/day to reduce blood pressure, and his blood pressure was controlled between 112-126/80-86mmHg. Strict follow-up was conducted after the surgery; the patient did not have obvious dyspnea and had an increased exercise tolerance compared to before the operation. The

Discussion
The American Heart Association published a scientific statement in 2008 to define resistant hypertension as the situation where, after lifestyle improvement, the systolic pressure and diastolic pressure require the concurrent use of 3 antihypertensive agents of different classes (one is a diuretic agent) or at least 4 agents to be controlled at the goal levels (<140/90mmHg) [7]. Currently, it is considered that the development of hypertension is multifactorial. The importance of the sympathetic nerve in influencing hypertension was understood early; therefore, sympathy-splanchnicectomy (including the renal sympathetic nerve) was invented to treat resistant hypertension. However, although this treatment technique achieved very good blood pressure control, it was not promoted due to severe adverse reactions [3]. Because of the rapid development of catheter-based radiofrequency ablation technology and the influence of the renal sympathetic nerve on blood pressure, Krum et al. [3] tested the idea of treating hypertension using RDN in the human body and obtained positive anti-hypertensive efficacy. In a series of HTN [4,5] studies and recently published syudies [8,9], RDN has been shown to have excellent safety, and 97.0% of patients were free of manipulation-related complications.
No RDN-related renal arterial stenosis, aneurysm, or artery dissection was found during the follow up period. There was no death in the Simplicity HTN-1group. There were two deaths in the Simplicity HTN-2 group, which were not related to RDN itself.
Two patients in HTN-2 had a glomerular filtration rate decreased by over 25%, as did 3 patients in the control group; the difference between these two groups did not reach statistical significance.
However, In the Simplicity HTN-3 trial [6], results observed 6-month post-surgery did not show effective BP reduction in resistant hypertension, which may be explained, at least in part, heterogeneity of the population (may be less effect in the African-American population versus others), by Medtronic developed the new surgical learning curve, short follow-up period. Our preliminary experience indicated that RDN can play an important role in longer term BP regulation (at least 6 years) in refractory hypertension, and this new technology also had good safety in Chinese people. Our finding suggests that continued study into RDN for the treatment of resistance hypertension is of interest.