Study Of Catheter Ablation Treatment For Atrial Fibrillation With Ultrasound Energy

As for catheter-based treatment for patients with paroxysmal atrial fibrillation (PAF), electrical isolation of pulmonary veins (PVs) emerged as an important therapeutic strategy. Currently, segmental PV ostium isolation with radiofrequency ablation (RFA) is the main approach to achieve electrical isolation of PVs. However, RFA within PVs does not completely prevent the recurrence of AF, and the most recurrent cases are associated with recurrent conduction between left atrium (LA) and PVs. Meanwhile, RFA occasionally induces PV stenosis and resultant pulmonary hypertension, which is the most serious complication of the procedure. To avoid the recurrence and complications after the abaltion, creation of a transmural and circumferential lesion around PV from LA is considered an alternative. However, it is often difficult and time-consuming to achieve effective isolation of PVs with conventional RFA, because it does not promise a transmural and continous lesion, even with the electroanatomic mapping system. Ultrasound is a common energy source in clinical field, compared with RFA, tissue can be grangually heatened from the outer part to the inner part of tissue, and no scarring and clotting developed during the abaltion, these advantages make it a good option to isolate PVs.The aim of present study was to evaluate the feasibility and safety of ablation by ultrasound energy catheters in patients and in canines, and determine the optimal energy output and discharging time of these catheters.First Part: To evaluate the efficacy and safety of eletrical isolation of pulmonary veins with ultrasound balloon catheter in patients with paroxysmal atrial fibrillation (PAF). Consecutive patients with PAF from March of 2001 to April of 2003 were enrolled for present study, only those whose PAF was refractory to antiarrhythmia drug therapy were included. The patients were divided into either radiofrequency (RF) group or into ultrasound group. Magnetic resonance angiography (MRA) of pulmonary veins (PVs) and transesopheageal echo (TEE) were performed before procedures, so three-demension images of PVs were obtained and atrialthrombi were excluded. Intracardiac electrophysiological study was carried out post trans-septal puncture and venogram of PVs, then ablation was administered according to different energy resources applied. The primary end-point of study was electrical isolation of PVs, and the secondary end-point was freedom of atrial fibrillation during follow-up. Other complications were registered and analysed. P<0.05 was considered significant. A total of 98 cases were included in present study (male 59.1%, female 40.9%), 58 cases were divided into RF group, 40 into ultrasound group. 97.1% of RF group reached primary end-point, while that in ultrasound group was only 73.1%, more cases in RF goup demonstrated electrical isolation of PVs immediately after the procedure. After a follow-up of mean 11.7+5.1 months(3~32), no difference was seen in terms of secondary end-point ((40.1% VS 39%, P>0.05)). Right phrenic nerve paralysis ( 2 patients), transient ST segmental elevation in inferior leads ( 4 patients) and severe vagus reflex ( 2 patients) were mainly seen in ultrasound group, while narrowing of PVs was solely seen in RF group. Conclusions: electrical isolation of PVs with ultrasound balloon catheter is reliable , but improved design of the ultrasound balloon catheter and energy output at a higher temperature ( 60 C) may be needed to improve the current results.Second part: To investigate the efficacy and safety of eletrical isolation of pulmonary veins with ultrasound balloon catheter preset at a higher temperature under unconscious state in patients with paroxysmal atrial fibrillation (PAF). Consecutive patients with PAF from April of 2001 to April of 2003 were enrolled for present study, only those whose PAF was refractory to antiarrhythmia drug therapy were included. The patients were randomized into either tranquillizer group or into unconscious group. Magnetic resonance angiography (MRA) of pulmonary veins (P...