The Safety Research And Primary Exploration Of Clinical Protocol Of Routine Cardiac Radiofrequency Catheter In Renal Denervation

BackgroundAccording to the Chinese guidelines for the management of hypertension, the investigation of nutrition and health status of270,000, the hypertension incidence in adults has reached18.8%so far, with the population over200million. Among them,15%are resistant hypertension-the patient blood pressure cannot be controlled under the target level by using3or more anti-hypertension medications(one diuretics included). It is the the thorny point in hypertension research at present.Renal sympathetic nerves system has an enormous contribution to the hypertension. The postganglionic efferent fibrous wrap the renal arteries and spread alongside the renal arteries into the small vessels, cortex and juxtamedullary nephron. The afferent nerves project into the various region of the central nervous system to adjust the efferent signal of sympathetic nerves. The activation of renal sympathetic nerves influence blood pressure mainly by stimulating the secretion of renin, adding voluminal burden and activating central sympathetic nervous system.Researchers finished the first renal denervation(RDN) in2009according to the principles of radiofrequency ablation. The procedure not only confirmed the safety but also gained the efficacy in lowering the blood pressure. In the renal denervation, Symplicity catheter system was used in the inner walls of renal arteries and to form a circuit ablation with the energy of no more than8watts and the time of no more than120seconds on each ablation point. Each artery has4-6ablation points. Follow-up compared the blood pressure and complication of45patients. The change of blood pressure was-14/-10(95%CI4/3),-21/-10(7/4),-22/-11(10/5)、-24/-11(9/5) and-27/17(16/11) mmHg, respectively. The spillover of renal noradrenalin has reduced47%in10patients measured by isotope. Serious complications were not found in underwent RDN. The renal function kept intact. However, the follow-up should remain a longer time because of the possibility of the recover of the renal sympathetic nerves.The first multi-center random comparison trial of RDN was published in2010. RDN group (n=54), compared with control group (n=52), has no significant difference in blood pressure at baseline but a (-33/-11)mmHg difference at the6th months (p<0.001). No major complication was found during the procedure. Renal function in the two groups had no significant change during the follow-up period. Pathological changes were not found in this6months either. The research suggested that the catheter ablation is a safe and effective alternative to treat patients with resistant hypertension.There is no published clinical data of RND in China so far. Moreover, the symplicity catheter system has not been listed in China. The system is a non-irrigation catheter system, which is theoretically the same as the cardiac radiofrequency(RF) catheter. If cardiac ablation catheter can be put in use of RDN, it will be a great benefit to this therapy.Objective:1. To explore the proper parameter of cardiac RF catheter in RDN.2. To verify the safety of the cardiac RF catheter in RDN3. To explore a protocol of RDN using cardiac RF catheter.Methods:1. Renal artery ablation in vitro We used38℃Ringer-Locke liquor to as perfusion liquid in a Stockert wetlab with2L/min oxygen input. Ablation catheter was inserted from a fixer vertical to the artery sample. Arteries were fixed on the table of the wetlab. We set the power to6watt,8watt,10watt and12watt and temperature limit to60℃to perform renal artery ablation in vitro. Ablation time was set to30seconds,60seconds and120seconds. We repeated ablations12time with each combination to explore the influence of different parameters. Arteries were taken out and fixed by4%paraformaldehyde and sections were stained with hematoxylin&eosin (H&E) stain. The depth of injury was measured with optic microscope to analyze the best parameter.2. Renal denervation on miniature swines2.1Miniature swines were randomized into sham operation group, instant euthanizing group and long-term follow-up group. Swines in sham operation group underwent anesthesia, puncture, renal angiography, then the catheter was posited into renal arteries without radiofrequency delivery before the final renal angiography. Swines in instant euthanizing group underwent renal angiography, and then renal denervation(refer to2.2), followed by the final renal angiography just before euthanized. Long-term follow-up group were resuscitated after the RDN, and were kept for3months before the follow-up angiography.2.2Renal denervation:Swines were anesthetized, fixed before undergoing mono-lateral incision of arteria femoralis.8F Swartz sheath was located in the abdominal aorta. RDN was allowed after confirming that each main branch of renal artery hat a length no shorter than18mm and a diameter no shorter than3.5mm. Refer to the acquired parameters in vitro, cardiac RF catheter was used to perform six ablations on the stem of right renal artery. After each artery was treated,200μg nitroglycerin was given through Swartz sheath. Then5ml contrast agent was given to perform angiography. Each swine was treated with the same method and parameters on each left renal artery by using irrigated tip catheter (irrigation rate10ml/h) as control. Impedance, power and ECG was monitored and recorded during the duration of ablation.2.3Confirm of the injury of sympathetic nerves:After the swines were euthanized, kidneys, proximal ureters and renal arteries (adventitia and fat must be intact together with the vessels). Renal arteries underwent fixation with4%paraformaldehyde and section. H&E stain, silver stain were performed so as to evaluate the injury of sympathetic nerves. Plasma renin activity of each miniature swine was measured.2.4Evaluation of safety:The health condition of each miniature swine in follow-up group was recorded. Blood routine tests, hepatic function, renal function and electrolyte test was made before RDN and after3months of RDN. Angiography was used to exclude renal artery stenosis, perforation and dissection. If there was stenosis, the severity of stenosis was recorded. Each renal artery of the3group swines was examined histologically with H&E stain. Severity of injury was judged refer to histologic vascular injury grading scale. After confirming the injury of renal sympathetic nerves, we can judge the safety by evaluating the results of blood tests, angiography and histology altogether.3. Primary exploration of the method of a clinical research Based on the exploration of safety in animal study and the frame of other clinical trials, the protocol of RDN was made. We analyzed the safety of using cardiac RF catheter in RDN and explore the inclusion and exclusion criteria, essential tests as well as the criteria of safety and effectivity. Eventually the protocol of clinical research was concluded.4. Statistical analysis:The database was established via Microsoft EXCEL. The analysis The normal distribution of measurement data was expressed with x±S and the difference among the groups was tested by t test. The lab results were tested by rank sum test. Spearman correlation coefficients were used to analyze the relationship between two variables. Goldarchive1.0was used to produce and achieve the data of angiography, A two-tailed P value<0.05was considered as significant.Results: 1. Ablation of renal arteries in vitroTotally144points of ablation have been done on the arteries. All arteries have been successfully ablated. No perforation has been found during the process of ablation. When the time was set to60seconds and120seconds, the injury of arteries had no significant difference under the power of8watts, lOwatts and12watts. For the combinations of parameters over8watts-60seconds could already cause the full-thickness injury of artery wall, there could not be any increase of depth, but only area of surface of the injury. Therefore, we choose8watts-60seconds as a proper parameter to avoid unnecessary injury of vessels, kidneys and ureters.2. Renal denervation on miniature swines2.1Evaluation of destruction of renal sympathetic nerves The sympathetic nerves in sham group remained intact. Injuries could be found in the other two groups, which were mainly disruption of the nerve tracts being replaced by connective tissues, and hyperplasia or destruction of perineurium. The main changes inside of the axons were vacuolar degeneration.2.2Evaluation of the safety (instant).2.2.1Angiography2.2.1.1Preoperative angiography:The process of inducing and maintaining anesthesia has been successfully completed. Preoperative angiography showed the average length of the stem of renal arteries was36.17±10.22mm, minimum18.5mm. The average diameter was4.58±0.55mm, minimum3.7mm. All arteries were eligible according to the criteria of RDN.2.2.1.2Operation:All12miniature swines underwent RDN. No death, artery perforation, artery dissection or other complications. According to power-impedance, we guess that the tip of cardiac RF catheter has been always pressed on the artery walls.2.2.1.3Postoperative angiography:All renal arteries were found focal stenosis after being given radiofrequency ablation. The severity of stenosis was37.5%±12.74%with routine RF catheter and42.5%±6.35%with irrigated tip RF catheter, P=0.229. The stenosis could be partially relieved after nitroglycerin was given.2.2.1HistologyNo gross injuries were found in both intima and adventitia. Sections showed focal necrosis of medial smooth muscle and apparent bound between disrupted and normal tissues. Break, bleeding and inflammation of media could be found in some samples. Structural disorder and coagulation necrosis could be seen in adventitia. There was no disorder to be found in the samples of sham group.2.3Evaluation of the follow safety (follow-up)2.3.1Follow-up angiography:The severe renal artery stenosis has vanished. Only four points could be found to have a stenosis<5%. Two of them were caused by routine cardiac RF catheter, two by irrigated tip catheter.2.3.2Follow-up histology:Histological results showed that30%-50%range of renal intima-media had apparent hyperplasia. There were also node-like hyperplasia in some sections. The area and depth of the injury were more than the instant euthanized group. No significant pathological change has been found in the sample of proximal ureters and kidneys.3. Primary exploration of the method of a clinical research3.1Research type:self-control research3.2Inclusion and exclusion criteria3.2.1Inclusion criteria:(?) Diagnosed history of hypertension for more than5years, routine anti-hypertension treatment for more than1year.(?) Age18to75years old, no restrict of sex.(?) Match the criteria of resistant hypertension:The patients who have received at least3sorts of anti-hypertension medication(one diuretic included) for at least3months, but still have a mean blood pressure over the goal BP, will be regarded as resistant hypertension.(?) The patients are willing to join the research and sign the informed concent.3.2.2Exclusion criteria(?) Secondary hypertension:e.g. Renal vascular hypertension, primary aldosteronism, pheochromocytoma, Cushing syndrome.(?) Pregnancy.(?) Unstable angina, acute myocardial infarction or cerebral vascular accident in the recent6months.(?) Bleeding trend which is difficult to control.(?) Severe hepatic or renal dysfunction.(?) Patients whose estimated survival are lower than1year.(?) Active infection.(?) Structural abnormality of renal structure, including renal artery stenosis, history of renal artery stenting or angioplasty.(?) Patients who have contraindication of femoral intervention, e.g. Indirect hernia, inguinal infection and severe stenosis of arteria femoralis(?) Patients who reject to sign the informed consent.3.3Sample size:refer to the literature, we assume that the reduce of24h mean systolic pressure is no less than10mmHg(SD22mmHg), α=0.05,β=0.1, therefore, we need a sample of30people, considering the possible10%lost to follow-up rate,33people are planed to be recruited3.4Research Protocol3.4.1According to the inclusion and exclusion criteria, patients are chosen and sign the informed concent.3.4.2Each patient is numbered and has a case report form (CRF)3.4.3Preparation before RDN:History collection, physical examination, chest X-ray, electrocardiogram, bilateral renal artery ultrasound,24h ambulatory blood pressure monitoring (ABPM), blood routine test, test of fast blood glucose, coagulation function, renal and hepatic function, blood and urine electrolyte, urine Alb/Cr, plasma renin activity (PRA) and angiotensin II.3.4.4Renal denervation:Patients were sterilized, monitored, and locally anesthetized before undergoing mono-lateral incision of arteria femoralis. Intravenous heparin800μg/kg was given for anti-coagulation before a8.5F sheath was located in the abdominal aorta. JR4.0catheter was positioned through the8.5F sheath to perform bilateral renal angiography. RDN was allowed after confirming that each main branch of renal artery hat no stenosis, calcification, and plaque. Cardiac RF catheter was used to perform six ablations on the stem of each right renal artery with8watts-60seconds for each ablation. Temperature, impedance as well as power are recorded during the process of ablation. After right artery was treated, contrast agent was given to perform angiography. Then the left artery is to be treated with the same method. If the patient suffers from diffusive visceral pain, morphine or fentanyl is considered to be given to the patient to relieve pain. BP, HR and response must be monitored during the operation. After the ablation, bilateral renal angiography should be performed at last. After a normal result of angiography was recorded, the sheath is withdrawn and the wound is to be pressed to stop bleeding and wrapped up.3.4.5Follow-up:Time point of the follow-up is considered to be1day after the RDN and every one month, ABPM is needed every month. Serum creatinine, PRA and Ang Ⅱ are tested1day,1month and6month after RDN.3.4.6The database was established via Microsoft EXCEL. The analysis The normal distribution of measurement data was expressed with x±S and the difference among the groups was tested by t test and by rank sum test. A two-tailed P value<0.05was considered as significant.3.5Carrying out the protocol of RDN:Two patients have been followed up to more3months without complication. Renal function and renal artery ultrasound showed no abnormal results. ABPM presents that the reduction of blood pressure is regarded as effective.Conclusion:1.8watts-60seconds was the best combination of parameters for the routine cardiac RF catheter, which was acquired in vitro.2. Referred to the parameters, renal denervation on miniature swine with cardiac RF catheter had satisfying safety.3. Clinical research of renal denervation can be launched with the direction of a proper protocol using cardiac RF catheter.