Atrial fibrillation: mechanistic insights from biatrial (and triatrial) mapping

Percutaneous radiofrequency ablation of pulmonary vein potentials has been shown to eliminate atrial fibrillation in a subset of patients characterized by frequent and repetitive paroxysms of atrial fibrillation. However, pulmonary vein disconnection has had only limited success at curing patients with persistent atrial fibrillation. In those patients, left atrial substrate modification and linear ablation strategies have had substantially higher success rates. Furthermore, in other patients, elimination of right atrial triggers (superior vena cava) or modification of right atrial substrate has been required for elimination of atrial fibrillation. Finally, the realization that the coronary sinus is a third atrial chamber that can both initiate and maintain atrial fibrillation has provided new understanding to the pathogenesis of atrial fibrillation. From a clinical perspective, only careful anatomic and mapping strategies specifically aimed at each subset of patients with atrial fibrillation will allow for pattern recognition and establish which mechanisms are responsible for initiation and maintenance of atrial fibrillation. Only the latter will allow for increased long-term success rates of ablation of atrial fibrillation.     

Termination of persistent atrial fibrillation during left atrial mapping

Termination of Persistent AF During Mapping. Complex fractionated atrial electrograms (CFAEs) may represent critical areas for the maintenance of atrial fibrillation (AF). While AF organization and termination have been reported with CFAE ablation, no reports of arrhythmia termination during left atrial mapping exist. We report a case of reproducible AF termination with catheter pressure at a site of CFAE remote from the site of AF. (J Cardiovasc Electrophysiol, Vol. 22, pp. 1171‐1173, October 2011)     

High-resolution mapping and histologic examination of long radiofrequency lesions in canine atria

INTRODUCTION: Catheter ablation may prevent conduction of multiple atrial wavefronts and/or reduce the critical mass of atrial myocardium required to sustain fibrillation. The purpose of this study was to examine the effect of radiofrequency (RF) energy application on conduction in canine atria by performing high-density epicardial mapping and careful histologic examination of the ablation zone. METHODS AND RESULTS: RF energy was applied to the right atrial endocardium in nine anesthetized mongrel dogs in an attempt to create a line of conduction block spanning the vertical length of a 504-channel epicardial mapping plaque. The mean length and width of the histologically determined ablation zone was 34 +/- 4 and 7.3 +/- 2.6 mm, respectively. No thrombus was present. Conduction block that spanned the mapping plaque in 6 of 9 animals was matched histologically by continuous transmural necrosis in five. In one, only a portion of the ablation zone was transmural; the remainder was wide but nontransmural. In 2 of 3 animals with conduction, a narrow region was present where continuous transmural necrosis was absent. In the other animal, conduction was present despite continuous transmural necrosis. CONCLUSION: Conduction block usually occurred when continuous transmural necrosis was present, and conduction usually persisted when continuous transmural necrosis was absent. However, important exceptions were observed, including block when the ablation zone was wide but nontransmural, and conduction despite a thin line of continuous transmural necrosis.     

Noninvasive phase mapping of persistent atrial fibrillation in humans: Comparison with invasive catheter mapping

Background

A novel noninvasive epicardial and endocardial electrophysiology system (NEEES) to identify electrical rotors and focal activity in patients with atrial fibrillation (AF) was recently introduced. Comparison of NEEES data with results from invasive mapping is lacking.

Methods

Six male patients (59 ± 11 years) with persistent AF underwent cardiac mapping with the NEEES, which included the creation of isopotential and phase maps. Then patients underwent catheter mapping using a PentaRay NAV catheter and the CARTO 3 system. Signals acquired by the catheter were analyzed by customized software that applied the same phase mapping algorithm as for the NEEES data.

Results

In all patients, noninvasive phase mapping revealed short‐lived electrical rotors occurring 1.8 ± 0.3 times per second and demonstrating 1–4 (mean 1.2 ± 0.6) rotation cycles. Most of these rotors (72.7%) aggregated in 2–3 anatomical clusters. In two patients, focal excitation from pulmonary veins was observed. Invasive catheter mapping in the dominant rotor aggregation sites and in the three control sites demonstrated the presence of electrical rotors with properties similar to noninvasively detected rotors. Spearman's correlation coefficient between rotor occurrence rate by noninvasive and invasive mapping was 0.97 (p < .0001). Mean rotors' cycle length at dominant aggregation sites, scores of their full rotations, and the proportion of rotors with clockwise rotation were not significantly different between the mapping modalities.

Conclusion

In patients with persistent AF, phase processing of unipolar electrograms recorded by catheter mapping could reproduce electrical rotors as characterized by NEEES‐based phase mapping.     

Image integration in electroanatomic mapping

Abstract Over the past five years, integration of the pre-procedural MR/CT images with a 3D electroanatomic mapping system has been developed to facilitate catheter ablation of clinical arrhythmias. It presents a significant advantage over the less-detailed surrogate geometry created by the 3D mapping systems. The process of image integration consists of pre-procedural imaging, image segmentation and image registration. Clinical studies have demonstrated the feasibility and accuracy of the use of image integration to guide catheter ablation of atrial fibrillation (AF). Accurate registration of the 3D left atrial MR/CT image to the real-time catheter mapping space can be technically challenging. Several important considerations should be taken into account to minimize registration error. Enhanced ability of catheter navigation with image integration may improve the efficacy and safety of anatomically based ablation strategies such as ablations of AF and nonidiopathic ventricular tachycardia. New developments in the field include integration of pathophysiologic as well as real-time anatomic information to the 3D mapping systems, and the use of new navigation system to improve registration. Drs Dong and Dickfeld are consultants of and received research grants from Biosense Webster Inc.     

心房内双环折返性心动过速的非接触球囊导管标测及射频消融

目的 阐明心房内双环折返性心动过速的电生理机制及导管射频消融的技术。方法 3例患，均为女性，年龄41-66岁，心动过速病史6个月-10年，例1为先天性心脏病房间隔缺损修补术后，例2为特发性心动过速，例3为扩张型心肌病，经左股静脉置入9F球囊电极至右心房中部并展开，球囊中心位于希氏束和冠状静脉窦口中间，进入球囊时，静脉注射肝素100U/kg，并保持手术过程中活化的血小板凝结时间（ACT）位于250s左右，以后经右股静脉进入8F消融导管构建右心房三维几何构型，构型构建完毕后，经高位右心房诱发心动过速，建立心动过速的腔内等电势图，然后分析心动过速的起源，折返激动的环路，传导方向，关键峡部，由此确定线性消融的部位和起止点，经导航系统引导消融导管至拟订靶点处，每点予以60W，60s,60℃温控消融，直至产生消融线径的双向阻滞。结果 3例患均有心房内双环折返性房性心动过速（房速），折返环分别围绕三尖瓣环和病变组织周围，于各自的峡部行线性消融产生双向阻滞后，心动过速不再诱发，随访分别为3、5和12个月，无心动过速复发，例2术后动态心电图记录有频繁房性早搏，部分房性早搏触发短阵心房颤动。结论 心房内存在病变组织如手术瘢痕，补片及梗死病灶时可产生心房内折返，若合并围绕三尖瓣环折返的典型心房扑动则形成心房内双环折返性房速。双环折返性房速也可发生在无器质性心脏病的患，不同的基础心脏病变决定着不同的折返环路和折返方式，双环折返性房速存在两个关键峡部，需要两次线性消融才可阻止心动过速的发生，非接触球囊导管标测系统（EnSite3000)不同可破译心房内双环折返性心动过速的电生理机制，也为其消融方法提供可靠的策略。     

High-resolution mapping around the eustachian ridge during typical atrial flutter

Background: Although the reentrant circuit of typical atrial flutter (AFL) has been well recognized, the activation around the Eustachian ridge (ER) has not been fully characterized. The aim of this study was to delineate the activation patterns around the ER during typical AFL using high-resolution noncontact mapping.
Methods: Fifty-three patients (M/F = 43/10, 62 ± 14 years) with typical AFL were included. The high-resolution mapping of the right atrium using a noncontact mapping system during AFL and pacing from the coronary sinus (CS) was performed to evaluate the conduction through the ER.
Results: Three types of activation patterns around the ER could be classified according to the ER conduction during AFL and CS pacing. Type I (n = 21, M/F = 16/5, 61 ± 13 years) exhibited conduction block at the ER during AFL and CS pacing. The local unipolar electrograms at the ER exhibited long double potentials (DPs) (109 ± 12 ms, range 77–153 ms) during AFL and CS pacing (84 ± 18 ms, range 48–129 ms). Type II (n = 8, M/F = 7/1, 61 ± 15 years) exhibited conduction block at the ER during AFL, but conduction through the ER during CS pacing. The unipolar electrograms exhibited long DPs (119 ± 12 ms, range 97–141 ms) at the ER during the tachycardia and an rS pattern during CS pacing. Type III (n = 24, M/F = 20/4, 61 ± 16 years) exhibited an activation wavefront that passed along the ER, with the sinus venosa as the posterior barrier during AFL. During CS pacing, all cases exhibited conduction through the ER with an rS pattern.
Conclusions: This study is the first to demonstrate the three patterns of activation along the ER during AFL and CS pacing. This finding suggested that the ER is an anatomic and functional barrier during typical AFL.     

Endocardial mapping of atrial fibrillation in the human right atrium using a non-contact catheter.

BACKGROUND: Endocardial mapping of atrial fibrillation in humans is limited by its low resolution and by complexities in the arrhythmia and atrial anatomy. METHODS AND RESULTS: A catheter mounted non-contact multielectrode was deployed in the right atrium of 11 patients with atrial fibrillation and used to reconstruct 3360 electrograms, superimposed onto a computer-simulated model of the endocardium, using inverse solution mathematics. This allows construction of isopotential maps of the right atrium. Patients had either sustained atrial fibrillation (n=3) for >6 months or developed atrial fibrillation during the study (n=8). Spontaneous initiation of atrial fibrillation was recorded in one patient and was demonstrated by the non-contact system to arise from two successive atrial ectopic beats from the site of a roving contact catheter. Reconstruction of electrograms recorded during atrial fibrillation was validated by comparison with contact electrograms with cross-correlation. During established atrial fibrillation, four patients predominantly had a single right atrial wave front, two had two wave fronts and five patients had three to five wave fronts for most of the time. Periods of electrical silence were seen in the right atrium in eight patients, after which, activity emerged from consistent septal sites alone, suggesting a left atrial origin. During intravenous administration of flecainide, atrial fibrillation in two patients terminated spontaneously or following pacing manoeuvres, while in the remaining patient sinus rhythm was restored via atrial tachycardia. CONCLUSION: Non-contact mapping of the right atrium has demonstrated modes of initiation and termination of atrial fibrillation, characterized different patterns of right atrial activation in atrial fibrillation and suggests that the left atrium may sustain atrial fibrillation in some patients. Simultaneous mapping of the right and left atrium is required to further elucidate the mechanisms of human atrial fibrillation.     

三维电解剖标测指导下经导管射频消融治疗心房颤动的初步体会

目的探讨在三维电解剖标测系统(CARTO)指导下经导管射频消融治疗心房颤动(房颤)的安全性和有效性。方法将接受治疗的30例患者(阵发性房颤28例,持续性房颤2例)利用CARTO进行左心房重建后,对阵发性房颤患者行环绕同侧肺静脉的线性消融,射频消融终点为房颤终止且不能诱发;对持续性房颤患者进行左心房和冠状静脉窦的重建,标测射频消融复杂心房碎裂电位区,至房颤终止或行直流电转复。并检测其中16例阵发性房颤患者术后心脏生化标记物动态变化。结果28例阵发性房颤均达到射频消融终点,2例持续性房颤患者中,1例在射频消融中转为窦性心律,1例行直流电转复。术后随访2~14(5.6±3.5)个月,25例患者无房颤复发,单次手术成功率83.3%。16例患者术后第1天肌钙蛋白T由术前的(0.01±0.00)μg/L升至(2.20±0.99)μg/L(P<0.01)。结论在CARTO指导下射频消融治疗房颤安全有效,但肌钙蛋白T明显增高。     

左房起搏时犬房间隔激动顺序的电生理标测研究

目的 :研究左房起搏时犬房间隔激动的电生理特征 ,进一步了解房间传导在心房颤动发病机制中的作用。方法 :选用 5只犬 ,放置电生理标测导管于 Bachmann束 （BB）右房间隔侧。卵园窝 （FO）及冠状窦 （CS）。同步记录 BB,FO及 CS近端 （CSp）处心内电图 ,作 CS远端 （CSd）及左心耳 （L AA ）处起搏 ,观察房间隔激动顺序变化。结果 :CSd起搏时 CSp为房间隔最早激动点 ,刺激波至 CSp的激动时间短于至 FO及 BB处的激动时间 （17± 10 vs 37± 15 ms及 43± 16 ms,均 P<0 .0 5 ）。 L AA起搏时 BB为最早激动点 ,刺激波至 BB处短于至 FO的激动时间 （15± 5 vs 2 7±8ms,P<0 .0 5 ）且至 FO处短于至 CSp处的激动时间 （2 7± 8vs42± 8ms,P<0 .0 5 ）。CSd及 L AA起搏时的房间隔激动时间与窦性心律时相比无明显变化 （2 8± 11ms及 2 7± 4ms vs2 9± 9ms）。结论 :CSd及 L AA起搏时房间隔激动顺序的标测表明经房间隔的传导存在优势传导径路。CSd起搏时 CS为优势传导径路 ,L AA起搏时 BB为优势传导径路。本研究结果为进一步了解房间传导在房颤发生中的作用提供了理论依据。     

Global right atrial mapping delineates double posterior lines of block in patients with typical atrial flutter: a study using a three dimensional noncontact mapping system

Double Posterior Lines of Block in Typical Atrial Flutter. INTRODUCTION: The crista terminalis (CT) has been shown to be a barrier to transverse conduction during typical atrial flutter (AFL). However, some studies have demonstrated the presence of functional block in the sinus venosa region but not at the CT. The aim of this study was to define these regions of block in the right atrium using a three-dimensional noncontact mapping system. METHODS AND RESULTS: In 39 AFL patients (33 men and six women, mean age 56 +/- 13 years), a noncontact multielectrode array was used to reconstruct electrograms in the right atrium. Isochronal and isopotential propagation mapping was performed during AFL and during pacing from the coronary sinus ostium and the low lateral wall (cycle length from 600 to 240 msec) in sinus rhythm after creation of isthmus block. A single line of block along the CT area was found in 18 patients (46%). Two lines of block were found in 21 patients (54%), with the first line located along the CT area. The second was located in the sinus venosa region in 20 patients (51%) and in the lateral wall in 1 patient (3%). In all patients, the block in the lower part of the CT was observed during AFL (60%) and during pacing at all cycle lengths (48%-62%). The length and proportion of block were inversely proportional to pacing cycle length. CONCLUSION: Double lines of block were frequently observed in patients with AFL, and both lines may form the posterior boundaries of the AFL circuit. Block was fixed in the lower part of the CT and was functional in the upper part of the CT.     

Biatrial and three-dimensional mapping of spontaneous atrial arrhythmias in patients with refractory atrial fibrillation

INTRODUCTION: While atrial fibrillation (AF) initiation in the pulmonary veins has been well-studied, simultaneous biatrial and three-dimensional noncontact mapping (NCM) has not been performed. We hypothesized that these two techniques would provide novel information on triggers, initiation, and evolution of spontaneous AF and permit study of different AF populations. METHODS AND RESULTS: The origin of atrial premature beats (APBs), onset of spontaneous AF and its evolution were analyzed in 50 patients with AF in the presence or absence of structural heart disease (SHD) and in different AF presentations (group A: Persistent, group B: Paroxysmal). In 45 patients, spontaneous APBs in the right atrium (RA; n = 60) and left atrium (LA; n = 25) with similar regional distributions regardless of heart disease status were demonstrated. In total, 22 patients (44%) had > or =2 disparate regional origins. Biatrial regional foci were seen with equal frequency in patients with SHD (31%), without SHD (40%), in group A (32%), and in group B (36%). Biatrial mapping and NCM showed organized monomorphic atrial tachyarrhythmias arising in the RA (17), septum (17), or LA (21) and were classified as atrial flutter (RA = 34, LA = 8), macro-reentrant atrial tachycardia (RA = 1, LA = 3) or focal atrial tachycardia (RA = 2, LA = 7). Their regional distribution was more extensive in patients with SHD and persistent AF compared with patients without SHD or paroxysmal AF. Simultaneous biatrial tachycardias were observed only in group A patients and those with SHD. CONCLUSIONS: Simultaneous biatrial and NCM permits successful AF mapping in different AF populations and demonstrates a biatrial spectrum of spontaneous triggers and tachycardias. Organized monomorphic tachycardias with multiple unilateral or biatrial locations are commonly observed in human AF. Patients with heart disease or persistent AF have a more extensive distribution as well as simultaneous coexistence of multiple tachycardias during AF.