初步确定房早的起源部位后，即应于局部进行细致标测，以寻找较体表心电图异位P波的起点最为提前的电位。正常人在窦性心律时于肺静脉内可记录到一高频的刺突样电位(spike)，在其前方通常还有心房电位［19］。在肺静脉开口处这两个电位常融合在一起，或刺突样电位位于心房电位终末部，而在肺静脉开口以内二者之间常存在等电位线。有作者认为，刺突样电位代表肺静脉局部的电活动，表明激动的传导模式是由左房到肺静脉，而当房早起源于某一肺静脉时，该肺静脉内电图特征显示与窦性心律时完全不同的激动顺序，即由肺静脉到左房，刺突样电位跃至心房电位之前［3，19］。通常是肺静脉内几个刺突样电位连续出现而诱发房颤，其周长不规则，多在180 ms左右。少数情况下单一刺突样电位亦可诱发房颤［4］。需要指出的是在部分患者其异位兴奋灶存在多个肺静脉起源，在某一肺静脉又可能并存多个兴奋灶(plurifocal)，可能会给标测造成困难［11］。
3.2 射频消融异位兴奋灶 异位兴奋灶一旦确定，即可对其进行射频消融。Hsieh等［17］报道42例肺静脉起源的局灶性房颤，消融靶点处的刺突样电位较体表心电图异位P波的起点提前85±30 ms；在Haissaguerre等［3］报道的41例肺静脉起源的局灶性房颤中这一数字为106±24 ms。因在肺静脉内进行消融有导致严重并发症的危险，故应采用温控(55～60℃)消融。消融终点包括①房颤消失，且重复消融前的诱发方案不能再诱发房颤。②肺静脉电图出现以下特征：a刺突样电位消失；b刺突样电位虽仍然存在，但振幅较消融前降低并延迟10～50 ms；c刺突样电位每隔2或3个心房电位间歇出现；d刺突样电位规律出现，但节律缓慢且与心房活动无关［3］。上述判断标准与最终成功率之间的关系尚须大样本的临床研究加以评价。心房短阵猝发刺激不宜作为评价消融是否成功的指标。Lau等［16］报道7例局灶性房颤患者，射频消融位于上肺静脉异位兴奋灶后行心房短阵猝发刺激，所有患者均可诱发出房颤，但术后随访8±4个月，仅1例患者房颤复发。对这一结果可能的解释是：长期的房颤导致心房发生电重构(electrical remodeling)，其主要表现是心房不应期的缩短及频率适应不良，这一电生理基础使心房肌易于发生房颤。房颤消失后电重构可以逐渐逆转［20］。Vergara等［21］分析了预测消融成功的临床因素，发现年龄、性别、有无器质性心脏病与消融成功与否无显著相关，而较少的异位兴奋灶数目和较低的合并左房扑动的比例是预测消融成功的临床因素。
3.3 并发症 最严重的并发症是肺静脉狭窄，可导致严重的肺动脉高压、肺水肿，但其发生率、影响因素及严重程度尚不清楚。Robbins等［22］曾报道18例慢性房颤患者，在左房内做经过肺静脉口的多条线性消融后有2例发生严重的肺水肿。最近Jais等［23］报道33例经射频消融治疗的肺静脉起源的局灶性房颤，术后随访6±5个月有3例患者出现肺静脉狭窄，但仅1例有症状。其他的并发症包括心包填塞、心动过缓-低血压综合征、窦性心动过缓、一过性Ⅲ度房室阻滞、咳嗽、咯血及血栓形成等［24］。
3.4 复发率 Chen等［25］报道79例经射频消融治疗成功的局灶性房颤患者，术后72 h内有13.9％的患者房颤复发(11例)，经静脉注射胺碘酮后所有患者均恢复窦性心律，最终复发率仅为5％(4例)，故认为对术后早期复发的病人可不必急于行第二次消融治疗。术后复发的主要原因包括：初次消融不彻底；初次消融时未能发现其他部位的异位兴奋灶［26］。
4 面临的问题及对策
虽然文献报道的射频消融治疗局灶性房颤的成功率多在80％以上，但仍有许多问题有待解决。①目前除房颤伴频发房早外，尚无一种可靠的提示局灶性房颤的临床线索；②尚无一种诱发率高重复性好的诱发方案；③左房内特别是肺静脉内消融有导致肺静脉狭窄的潜在风险；④肺静脉具有主干短(肺外部分平均<3 cm)［6］、分支多的解剖特点，而部分异位兴奋灶又位于肺静脉深部，故在消融技术上存在困难。上述问题的解决一方面有赖于房颤机制的进一步阐明，特别是明确局灶机制在房颤发生中的地位及局灶性房颤的临床特点；另一方面消融器械和消融思路的创新可望在提高消融成功率的同时降低并发症，有动物实验表明采用射频球囊于肺静脉内消融并扩张即可达此目标［27］。新近研究表明整个肺静脉区域对于房颤的发作和(或)维持均有重要意义［28，29］。故有作者提出，如局灶性房颤的起源部位已确定在肺静脉(一个或多个)，可不必再行进一步的标测，而直接将四个(或某个)肺静脉口与左房的其他部分进行电学隔离，从而达到治疗的目的。虽然这一设想有悖于传统的电生理检查方法，但从理论上讲其成功率应高于单点消融［30］。 * 同济医科大学附属协和医院
作者单位：中日友好医院心内科(北京 100029) 参考文献
1 Haissaguerre M,Jais P,Shah DC,et al.Right and left atrial radiofrequency catheter therapy of paroxysmal atrial fibrillation.J Cardiovasc Electrophysiol,1996,7:1 132
2 Jais P,Haissaguerre M,Shah DC,et al.A focal source of atrial fibrillation treated by discrete radiofrequency ablation.Circulation,1997,95:572
3 Haissaguerre M,Jais P,Shah DC,et al.Spontaneous initiation of atrial fibrillation by ectopic beats originating in the pulmonary veins.N Engl J Med,1998,339:659
4 Hocini M,Haissaguerre M,Jais P,et al.Predominant origin of ectopic triggering atrial fibrillation from the pulmonary veins:mapping and ablation in 100 patients.PACE,1999,22(pt Ⅱ):A75
5 Chen SA,Tai CT,Yu WC,et al.Right atrial focal atrial fibrillation:electrophysiologic characteristics and radiofrequency catheter ablation.J Cardiovasc Electrophysiol,1999,10:328
6 Cheung DW.Pulmonary vein as an ectopic focus in digitalis-induced arrhythmia.Nature,1981,294:582
7 Nathan H,Eliakim M.The junction between the left atrium and the pulmonary veins:an anatomic study of human hearts.Circulation,1996,34:412
8 Haissaguerre M,Shah DC,Jais P,et al.P on T extrasystoles are highly predictive of a pulmonary vein origin.PACE,1999,22(pt Ⅱ):836
9 Takahashi A,Jais P,Shah DC,et al.Successful focal ablation of ectopy reinitiating persistent atrial fibrillation.PACE,1999,22(pt Ⅱ):905
10 Haissaguerre M,Jais P,Shah DC,et al.Successful focal catheter ablation of chronic atrial fibrillation.PACE,1999,22(pt Ⅱ):A26
11 Haissaguerre M,Jais P,Shah DC,et al.Plurifocal sources of atrial fibrillation initiation from the pulmonary veins.PACE,1999,22(pt Ⅱ):707
12 Haissaguerre M,Marcus FI,Fischer B,et al.Radiofrequency catheter ablation in unusual mechanisms of atrial fibrillation:report of three cases.J Cardiovasc Electrophysiol,1994,5:743
13 Shah DC,Haissaguerre M,Jais P,et al.Provocative manoeuvers for inducing pulmonary vein ectopy.PACE,1999,22(pt Ⅱ):738
14 Hsieh MH,Tai CT,Tsai CF,et al.An algorithm for facilitating spontaneous initiation of pulmonary vein-dependent focal atrial fibrillation.PACE,1999,22(pt Ⅱ):A76
15 Sra J,Biehl M,Blanck Z,et al.Spontaneous re-initiation of atrial fibrillation following transvenous atrial defibrillation.PACE,1998,21:1 105
16 Lau CP,Tse HF,Ayers GM.Defibrillation-guided radiofrequency ablation of atrial fibrillation secondary to an atrial focus.J Am Coll Cardiol,1999,33:1 217
17 Hsieh MH,Chen SA,Tai CT,et al.Double multielectrode mapping catheters facilitate radiofrequency catheter ablation of focal atrial fibrillation originating from pulmonary veins.J Cardiovasc Electrophysiol,1999,10:136
18 Schwartzman D,Predis L.Simultaneous multielectrode microcatheter mapping of the pulmonary veins in patients with paroxysmal atrial fibrillation.PACE,1999,22(pt Ⅱ):710
19 Hwang C,Karagueuzian HS,Chen PS.Idiopathic paroxysmal atrial fibrillation induced by a focal discharge mechanism in the left superior pulmonary vein:possible roles of the ligament of Marshall.J Cardiovasc Electrophysiol,1999,10:636
20 Wijffels MC,Kirchhof CJ,Dorland R,et al.Atrial fibrillation begets atrial fibrillation:a study in awake chronically instrumented goats.Circulation,1995,92:1 954
21 Vergara I,Martin D,Bahnson T,et al.Clinical predictors of successful focal atrial fibrillation ablation.PACE,1999,22(pt Ⅱ):772
22 Robbins IM,Colvin EV,Doyle TP,et al.Pulmonary vein stenosis after catheter ablation of atrial fibrillation.Circulation,1998,98:1 769
23 Jais P,Shah DC,Haissaguerre M,et al.Pulmonary vein patency after radiofrequency ablation.PACE,1999,22(pt Ⅱ):738
24 Tsai CF,Chen SA,Tai CT,et al.Bezold-Jarisch-like reflex during radiofrequency ablation of the pulmonary vein tissues in patients with paroxysmal focal atrial fibrillation.J Cardiovasc Electrophysiol,1999,10:27
25 Chen SA,Hsieh MH,Tai CT,et al.Does early recurrence of focal atrial fibrillation after successful catheter ablation of triggering ectopic foci need reqeated ablation immediately?PACE,1999,22(pt Ⅱ):865
26 Arentz T,Ott P,Rosenthal J,et al.Paroxysmal atrial fibrillation of focal origin:high recurrence rate after initial successful catheter ablation.PACE,1999,22(pt Ⅱ):843
27 Swartz J,Hassett J,Bednared M,et al.Single burn pulmonary vein isolation with a virtual circumferential electrode.PACE,1998,21(pt Ⅱ):803
28 Fieguth HG,Wahlers T,Borst HG.Inhibition of atrial fibrillation by pulmonary vein isolation and auricular resection experimental study in a sheep model.Eur J Cardiothoracic Surg,1997,11:714
29 Kottkamp H,Hindricks G,Hammel D,et al.Intraoperative radiofrequency ablation of chronic atrial fibrillation:a left atrial curative approach by elimination of anatomic "anchor" reentrant circuits.J Cardiovasc Electrophysiol,1999,10:772
30 Guerra PG,Lesh MD.The role of nonpharmacologic therapies for the treatment of atrial fibrillation.J Cardiovasc Electrophysiol,1999,10:450 |
