R

8%

42%

N = number of patients; FU = mean follow-up (± standard deviation, when reported); AF = clinical syndrome (P = paroxysmal, C = persistent or permanent); Atrium = chamber in which ablation was performed (R = right, L = left); Complete cure = free of AF and antiarrhythmic drug; partial cure = free of AF while taking an antiarrhythmic drug which was previously documented to be ineffective. Cure data straddling the 2 columns was not reported separately. NR = not reported.

N = number of patients; FU = mean follow-up (± standard deviation, when reported); AF = clinical syndrome (P = paroxysmal, C = persistent or permanent); Atrium = chamber in which ablation was performed (R = right, L = left); Complete cure = free of AF and antiarrhythmic drug; partial cure = free of AF while taking an antiarrhythmic drug which was previously documented to be ineffective. Cure data straddling the 2 columns was not reported separately. NR = not reported.

has always been considered an essentially anatomical problem. There have been few attempts at utilizing electrophysiologic findings during ongoing AF to guide specific lesion types/locations (65,68). However, like focal ablation, the current art of linear ablation is plagued by several key problems. First, linear ablation is associated with unacceptably long procedure times. Currently, linear ablation is practiced using single (65,69,71,72,77,79) or multielectrode (70,73,74,76,78) catheters; this does not appear to have a major impact on procedure/fluoroscopy time. A major cause of long procedure times is inadequate imaging of the atrial endocardium. Smooth atrial endocardial areas are topographically complex; combined with their phenomenal resistance to stable ablation electrode purchase, imaging becomes critical. Several investigators have incorporated intracardiac echocardiography, the only currently available technology for realtime endocardial imaging, into lesion deployment techniques (65,69,74,86). Second, "completion" (linear lesion as complete barrier to conduction) of planned lesions often cannot be achieved (65). This appears to be particularly common in the left atrium (71). Third, lesion healing with associated recovery of translesion conduction has been a serious problem. This was first shown to be common with cavotricuspid isthmus ablation for atrial flutter (87). The incidence of recovery of conduction appears to increase with the longer, more complex lesions utilized for ablation of AF. Fourth, postlinear ablation recurrence of uniform atrial tachyarrhythmias is common, probably because of incomplete lesion deployment and lesion healing. This has resulted in the need for multiple ablation procedures in many patients. Finally, and most critically, current lesion paradigms are empiric. Most mimic some component of the surgical Maze procedure, but none has intrinsic validity. The marked variation in lesion paradigms has severely limited data comparison among centers, which has hampered the evolution of this technique.

As for focal ablation of AF, linear ablation has been associated with a significant number of procedural complications, including cardioembolism, pulmonary-vein stenosis, and pericarditis (26,28,31,71). Given the variability in techniques and catheter technologies, risk factors and magnitude assessments are difficult. Similar to Maze surgery, linear ablation can be associated with diminished atrial transport function, and the rate and degree of recovery from this procedure is now poorly characterized.

In summary, a reliable ablative cure of AF by targeting sustenance should be currently classified as experimental. Although the Maze procedure provided proof of concept, current catheter ablation procedures are far less extensive, which may render the comparison irrelevant. Some inroads have been made—particularly with "hybrid" treatment, in which antiarrhythmic drugs are combined with ablation. However, procedural complications have been significant, and long-term data is lacking. Future efforts must concentrate on the left atrium, and this will be dependent on new technology development. Notably, there is a growing literature regarding intra-operative linear ablation under direct vision using a catheter-type device (81-83). To date, most procedures have been performed on the left atrium in a dry surgical field in patients undergoing mitral valve repair/replacement. Although they have been short term, success rates have been impressive and ablation-attributable morbidity has been low. Direct-vision ablation eliminates problems with electrode-endocardial contact, power titration, and lesion assessment. If this experience continues to be favorable, it is likely that it will be extended to other groups, such as patients undergoing cardiac surgery in whom left atrial access would not otherwise be needed. In addition, there is significant ongoing development in the area of off-pump epicardial ablation (88). If perfected and combined with rapidly developing minimally invasive/thoracoscopic cardial surgical techniques, the surgical approach may become the approach of choice.

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