| Atrail fibrillation(AF) is the most common arrhythmia seen in medical practice, it can lead to thrombosis and heart failure, contribute significantly to morbidity and mortality in patients suffered from it. Currently, segmental pulmonary vein (PV) ostium ablation with radiofrequency catheter to achieve electrical isolation of PVs is the main approach for the catheter-based treatment of paroxysmal atrial fibrillation. Though radiofrequency ablation(RFA) have high immediate success rate, it's recurrence rate of AF after operation is also high, this mainly due to the lesions created by RFA are not transmural and continuous, meanwhile, RFA occasionally induces PV stenosis which is one of the most serious complications of this procedure and can result in pulmonary hypertension. Compared with RFA, ultrasound energy can injure the PVs more complete and without the instance of PV stenosis, it is a wonderful option for Pulmonary veins isolation(PVI). The aim of this study is to investigate the differences in PVI between irrigated ultrasound catheter and saline-irrigated ablation catheter and the feasibility of irrigated ultrasound catheter's clinical application.Methods23 healthy canines with both sex, weighting 15 to 21 kg, were randomized into saline-irrigated ablation catheter group (Group A, n=12), or irrigated ultrasound catheter group (Group B, n=ll) respectively.The canine was fixed on the operating table under general anesthesia with intravenous injection of sodium pentobarbital(30mg/kg im)(fasting for 12 hours before procedures).Intracardiac electrophysiological study was carried out afteratrial septal puncture and venogram of four PVs, then segmental PV ostium ablation under the guiding of circular mapping was performed according to different energy resource applied, saline-irrigated ablation catheter's energy output was 30W-40W, temperature preset at 40-45 °C, duration of ablation was 30-60s after effective discharge was observed, irrigated ultrasound catheter's energy output was 30W-40W, temperature preset at 55 °C, duration of discharge was 60s one time. The end-point of ablation was pulmonary vein potential (PVP) disappeared or PVP still could be recorded but it had no relation to atrial electrical activity(pulmonary vein-atrium electrical dissociation). Electrical conduction between left atrium and pulmonary veins(LA-PV) was reevaluated 30 minutes after initial pulmonary veins isolation.t-test was used to compare the numerical variables while Chi-square test and Fisher's exact test of probabilities were used to compare the categorical variables P<0.05 was considered significant, all of the data were analysed by SPSS 10.0.ResultImmediate success rate of PVI were 97.9(46/47) in group A and 78.6 % (33/42) in group B respectively, and success rate in group B is much lower than that in group A (P<0.05).During the ablation of LSPV and RSPV there was no difference in immediate success rate between the two groups(90.9% VS 100.0% ; 100.0% VS 91.7 % , P>0.05),but in LIPV and RIPV immediate success rate in group B was lower than that in group A(63.6 % VS100.0 % P<0.05; 60% VS100.0% , P<0.05).30 minutes after initial isolation, electrical conduction between LV-PV were observed in 71.7% (33/46) of the canines from group A and 27.3% (9/33) of the canines from group B , and the recurrence rate in group B was lower than that in group A(P<0.01).In LSPV and RSPV, the recurrence rate in group B is lower than that in group A(20.0 % VS66.7 % ; 20.0 % VS72.7 % , P<0.05),but in LIPV and RIPV, there was no difference in recurrence rate between the two groups(30.0% VS75.0% ; 33.3 %VS72.7%, P>0.05).During the operating procedure, in LSPV and RSPV the average ablated times in group B was less than that in group A(4.0±2.4VS7.3± 2.9; 4.5 + 2.2VS7.1+3.1, P<0.05), while in LIPV and RIPV there was no difference in average ablated timesbetween the two groups(6.5±1.9VS6.8±3.3; 6.1+4.0VS6.4+3.5, P>0.05).ConclusionThough the immediate success rate of irrigated ultrasound catheter is lower than that of saline-irrigated ablation catheter, it's recurrence rate of LA-PV conduction is also lower, this suggest compared with saline-irrigated ablation catheter, irrigated ultrasound catheter injure the PVs more complete and fit for PVI.In LSPV and RSPV there is no difference in immediate success rate between the two kinds of catheter, but the recurrence rate of LA-PV conduction of irrigated ultrasound catheter is lower than that of saline-irrigated ablation catheter, and the average ablated times of irrigated ultrasound catheter is less than that of saline irrigated ablation catheter, these suggest compared with saline irrigated ablation catheter the irrigated ultrasound catheter have higher ablation efficacy.The possible reason for the low immediate success rate of irrigated ultrasound catheter is the difficulty in the catheters' fixation and keeping coaxial with some PVs due to anatomic factors, so improve design of the irrigated ultrasound catheter to overcome this difficulty is necessary.
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