The Clinical Research Of Radiofrequency Ablation Of The Atrioventricular Nodal Reentrant Tachycardia With Cold Saline Infusion Ablation Electrode Catheter

BackgroundAtrioventricular nodal reentrant tachycardia (AVNRT) is one of the common clinical tachyarrhythmia, with the characteristics of paroxysmal, increasing frequency of attacks, and the prolonged duration. During AVNRT attacks the patient would appear palpitations, chest tightness, dizziness, fatigue, and a minority of patients having the history of fainting or syncope. Drugs for treatment of AVNRT did not completely control the seizures, and the long-term use can bring the inconvenience and adverse reaction. RFCA is an effective means to treat AVNRT, having the characteristics of high cure rate, low side effect, less pain. The data in2000from the summary of the domestic radiofrequency catheter ablation for tachyarrhythmia showed that the overall cure rate of the RFCA was98.8%, the recurrence rate was2.3%, and complication rate was0.8%. Although the cure rate is very high, ablation largely depends on X-ray and the special structure of atrioventricular node requires that target should be carefully mapped when discharging so as not to damage the fast pathway and produce severe complication of atrioventricular block. Meanwhile, due to the changeability of the slow path of anatomy, ablation often needs to select multiple targets to ensure the success. Therefore, lots of operation time, long time perspective and much exposure to the X-ray would have a potential hazard for the performers and patients. At present, most clinical practice would use the temperature-controlled catheters with the diameter of4mm to treat AVNRT, and the temperature is controlled between50—60℃. The4mm ablation catheters are perfect one, which can not only ensure enough current output but also a large surface area, thus, it is beneficial for the blood to take away the surface heat, to prevent the rise of the surface impedance of the tissue ablation. Nonetheless, in the discharge process, with the creasing temperature of the electrode, especially when the blood flow is slow, it is more likely to have partial high temperature, which would lead to the formation of thrombus, eschar and carbonization on the catheter surface. Once the thrombus and the eschar occurred, the output and the ablation effect will be affected, the operation time will be prolonged, and the risk of embolism will be increased. Thus, such problems will be the next main study focus for treating AVNRT, for example, how to further improve the ablation efficiency and the success rate of operation, how to reduce disease recurrence, how to shorten the operation time, especially X-ray fluoroscopy time, how to reduce the risk of embolism, and how to avoid severe atrioventricular blockcooled saline-irrigated electrode catheter used the cold saline to reduce the temperature of a catheter end and tissue surface, thus to ensure the low impedance of tissue and promote the energy transfer, increase the scope of damage tissue, finally improve the operation efficiency and the success rate of ablation. Cold saline ablation in human and animal experiments can cause cardiac injury depth up to7mm. In contrast to the normal ablation catheter, cooled saline-irrigated electrode catheter can increase the damage zone by30-50%. Cold saline ablation catheter is divided into closed form and open form, and the former does not enter blood circulation, and do not increase the blood velocity. Electrode carbonization and thrombosis are related to the temperature of the bulk electrode and local blood velocity. The faster the local blood velocity is, the more difficult it is to form the blood clots and carbonization. The head end of the open-type cooled saline-irrigated electrode has the cold saline exit, from which cold saline water directly flush the head end of the catheter and the tissue surface then enter the blood. So it is more effective than the close one to prevent the thrombosis and carbonization, especially in the part of the slow blood flow. Meanwhile, the risk of embolism will also be decreased, for the tip temperature of the catheter decreased and the formation of blood clots reduced because of the cold saline flushing effect. This is mainly applicable to the deep focus or the need for transmural ablation to achieve electrical isolation or electrical conduction etc. At present, it has been widely used in the ablation treatment of atrial flutter(atrial fibrillation), ventricular tachycardia, the epicardial accessory pathway, and showed superiority to the normal ablation catheter. So far, it is not seen at home and abroad relevant studies and reports on the saline ablation catheter ablation in the treatment of AVNRT. This study used cooled saline-irrigated electrode instead of normal ablation catheter to treat AVNRT. By using the randomly controlled design, this study compared and analyzed the efficiency, success rate and the complications rate of the cold saline ablation catheter and the normal ablation catheter in treatment of AVNRT, thus we try to explore the feasibility of saline ablation catheter to treat AVNRT.The research is divided into two parts, by comparing the clinical data from the present experiment and analyzing the change of the electrophysiology of atrioventricular node after successful ablation by saline ablation catheter and normal ablation catheter, and investigate the feasibility of the cooled saline-irrigated electrode catheter for AVNRT treatment:(1) Comparative analysis of cooled saline-irrigated electrode catheter and normal electrode electrode catheter.(2) The study of the impact on the atrioventricular conduction function by using the different ablation catheter through the slow pathway. PART IThe comparative analysis between cold saline infusion ablation electrode catheter and ordinary electrode ablation catheter in the treatment of the atrioventricular nodal reentrant tachycardiaObjectiveBy comparing effects and complication rates of the cooled saline-irrigated electrode catheter with the normal electrode ablation catheter in the treatment of atrioventricular nodal reentrant tachycardia, this thesis discusses the efficacy and feasibility of the cooled saline-irrigated electrode catheter radiofrequency ablation.MethodWe chose70cases with atrioventricular nodal reentrant tachycardia, with no restriction on age and sex, who have no organic heart disease and systematic disease. Then randomly we divided them into two groups, respectively treated by the cold saline ablation catheter (cold saline group) and normal ablation catheter (normal group). Each group has35cases, cold saline group (16male,19female, average age is35, others older or younger for18years. The normal group has17male,18female, average age is43, others older or younger for15years. The subjects stopped taking arrhythmia treatment before operation and the period must be at least five half life. All the cases adopt interior method for slowly melting. We choose ablation target by imaging anatomy method. The only electrocardio standards is the targets of the A/V ratio<0.5-1.0. The normal group uses temperature-controlled catheters with a tip of4mm diameter, and the preset temperature is60℃, the output energy is limited to20w. If the first melting for the new target is invalid, the highest ablation energy will be increased to30w, and if we did the same target discharge at least twice and it is invalid, we will give up. Cold saline group uses cooled saline-irrigated electrode catheters with the diameter of3.5mm, with six small side hole (open cooling), heparin and brine being1:1(1unit of heparin:1ml of saline). When going on the standard measurement, the cold saline infusion speed is2ml per minute, and when melting, it is17ml per minute, melting temperature being50℃, power limit being30w. If the first melting for the new target is invalid, the highest ablation energy will be increased to40w, and if we did the same target discharge at least twice and it is invalid, we will give up. The only standard of successful melting is not to lead to AVNRT. We telephoned all the postoperative customers and carried on outpatient follow-up, inquiring if they have paroxysmal palpitation or similar attacks with before. By observing the conventional electrocardiogram (ECG), if necessary, dynamic electrocardiogram, we would determine the presence of recurrence or new arrhythmia and the complications such as delayed atrioventricular block. The follow-up time was12±2.6months. Statistics of the two groups after radiofrequency ablation consists of immediate success rate, recurrence rate, average operation time, accumulated perspective time, accumulated ablation time, discharge times and complication rates. By paired "t" test, we compared and analyzed the two group statistics of average operation time, accumulated perspective time, accumulated ablation time, discharge times and surgical complications. Using the Fisher’s exact probability method and four table data card party inspection (correction method), we analyzed the recurrence rate and complication rate, thus explored and evaluated clinical value and safety of cooled saline-irrigated electrode catheter in the treatment of AVNRT.ResultThe immediate success rate of the two groups of radiofrequency ablation was100%. In the follow-up of12±2.6months, the recurrence is one in the cold saline group, the recurrence time is55days after operation, and the recurrence rate was2.86%. In the normal group there is no recurrence. The average operation time of the cold saline group is86.6±20.9minutes, and that of the normal group is88.3±18.6minutes. with no obvious difference. The accumulated perspective time of the cold saline group is18.2minutes, and that of the normal group is19.6minutes, with no statistical differences. The average discharge time of the cold saline group is5±2.3times, and the accumulated time is160±63seconds, and that of the normal group is (?)6±3times and171±50seconds, with no statistical differences. In the cold saline group,6patients suffered with transient atrioventricular block, with the complication rate being17.14%, while in the normal group there is no atrioventricular block. The complication rate of the cold saline group is higher than that of the normal group.ConclusionNormal AVNRT ablation catheter treatment is safe and reliable, with high successful rate, low recurrence rate, less complications. The effect of the cooled saline-irrigated electrode catheter is similar to the normal ablation catheter. And it can not further improve the success rate and reduce the recurrence rate, moreover it didn’t reduce the perspective and discharge time. On the contrary, it increased the risk of melting, increased the proportion of atrioventricular block. Therefore, the cooled saline infusion ablation should not be adopted as AVNRT conventional treatment. PARTâ…¡ The influence of the ablation of the slow pathway on atrioventricular conduction function with different ablation catheterObjectiveBy comparing effects and complication rates of the cooled saline-irrigated electrode catheter with the normal electrode ablation catheter in the treatment of atrioventricular nodal reentrant tachycardia, and analyzing the physiological function changes of the posterior chamber room knot after the different ablation electrode catheter, this thesis discusses the efficacy and feasibility of the cooled saline-irrigated electrode catheter radiofrequency ablation.MethodWe chose70cases with AVNRT and randomly divided them into two groups, respectively treated by the cooled saline-irrigated electrode catheter (cold saline group) and th normal ablation catheter (normal group). We try to measure each case before and after ablation (the selected70cases were with immediate success rate of100%) about their atrioventricular conduction time (AV interval), effective refractory period-atrio-ventricular node atrioventricular node effective refractory period (AVN-ERP), Wenckebach’s point-atrioventricular node (AVN-WKB), antidromic effective refractory period-atrio-ventricular node (VAN-ERP), antidromic Wenckebach’s point-atrioventri-cular node (VAN-WKB) and ventriculo-atrial conduction time (VA interval). By paired "t" test, we comparatively analyzed the two groups before and after radiofrequency ablation about the AV, AVN-ERP, AVN-WKB, VAN-ERP, VAN-WKB and VA. By analyzing the data before and after ablation about the AV, AVN-ERP, AVN-WKB, VAN-ERP, VAN-WKB and VA, we try to find the changes of physiological indexes between the two groups, before and after ablation, thus discusses the clinical value and safety of the cooled saline-irrigated electrode catheter in the treatment of AVNRT.ResultBefore RFCA, the physiological index of the atrioventricular node between the two groups about AV, AVN-ERP, AVN-WKB, VAN-ERP, VAN-WKB and VA have no difference. For the normal group, the AV and VA period before the ablation are respectively149±25ms and147.6±30ms, and the data after the ablation have no obvious change, being respectively147±36ms and146.3±38ms. After RFCA, the WKB-VAN shortened, respectively348±59and319.6±58ms, the difference being statistically significant. After RFCA, the ERP-AVN shortened obviously, respectively328±49ms and281.6±55ms, and the ERP-VAN and the WKB-VAN have no change with before. For the cold saline group, after RFCA, the AV and VA lengthened obviously than before, with the AV being respectively146.7±26ms and177±56ms, and the VA being145±31mså'Œ1167.5±41ms. After the ablation, the WKB-VAN did not significantly reduce compared with before, respectively for350±67ms and351.5±70ms, the difference being not statistically significant. After the ablation, the ERP-AVN did not significantly reduce, respectively being330.3±51ms and326±73ms; and after the ablation the ERP-VAN extended obviously, respectively being285±41ms and330±59ms; After the ablation, the WKB-VAN obviously prolonged, respectively being332±46ms and359.3±57ms. After ablation, in the cold saline group, the AV, VA, ERP-VAN and the WKB-VAN were significantly longer than that of the normal group; The ERP-AVN and the WKB-AVN of the normal group were significantly reduced than that of the saline group. After RFCA, the cold saline group and normal group respectively present different electrophysiological characteristics, because cold saline group made a more deeper tissue injury in the Koch triangle which is a relatively small area, and inevitably affected the atrioventricular node conduction ability, however the normal group’s slow diameter ablation made the loss or reduction of the slow path conductive capability, thus improving the atrioventricular node conduction ability.ConclusionAfter the success of the cooled saline-irrigated electrode catheter and the normal ablation, the atrioventricular node electrophysiological function has changed. The normal group mainly showed the shortened ERP-AVN, shortened WKB-VAN, while the cold saline group showed the slow AV conduction, the lengthened AV and VA, the change of the ERP-AVN and WKB-AVN being not obvious, but the ERP-VAN and the WKB-VAN extended. This showed that the cooled saline-irrigated electrode catheter and normal ablation catheter in the treatment of AVNRT directly or indirectly affected the electrophy-siological characteristics of atrioventricular node, which made the atrioventricular node show different physiological function changes, and this change may be due to the different degree caused by different ablation catheter energy output. The cooled saline-irrigated electrode catheter didn’t improve the conduction ability of the slow ablation process, on the contrary it slowed the conduction of atrioventricular node, which may have potential damage to atrioventricular function. Therefore, the cooled saline-irrigated electrode catheter should not be used routinely for the treatment of AVNRT.