ClinicalAblationPeri-mitral atrial flutter in patients with atrial fibrillation ablation
Introduction
In recent years, catheter ablation has become an accepted treatment of atrial fibrillation (AF) for patients who have not responded to antiarrhythmic drug therapy.1, 2, 3, 4 However, despite the success of catheter ablation in treating AF, recurrent atrial tachycardia (AT) is a major complication of AF ablation.4, 5, 6, 7, 8 These ATs often are more symptomatic than the individual patient's AF and normally are unresponsive to antiarrhythmic drugs. The underlying mechanisms of AT following AF ablation have been described, with peri-mitral atrial flutter (PMFL) being the most common macroreentrant AT in the context of AF ablation.5
PMFL is a difficult arrhythmia to treat with antiarrhythmic drugs. A so-called mitral isthmus (MI) line, between the lateral mitral annulus and the isolated left inferior pulmonary vein (PV), is the normal linear lesion created to treat the arrhythmia. However, bidirectional conduction block is difficult to achieve, possibly due to the thickness of the MI and due to the close proximity of the distal coronary sinus (CS), which can act as a heat sink, preventing transmural lesion delivery.9 Ablation within the CS is not without risk; isolated cases of steam pops and tamponade have been reported. Alternative lesions include an anterior line10 or a septal MI line11; however, the efficacy of these ablation strategies remains to be determined.
The present study investigated the clinical and electrophysiologic characteristics of patients undergoing AF ablation who developed PMFL and their subsequent clinical outcome.
Section snippets
Patient population
The study consisted of 50 patients from consecutive series who developed PMFL in the context of AF ablation between November 2006 and September 2007. All patients gave written informed consent.
Electrophysiologic study
All AF patients had effective anticoagulation therapy (target international normalized ratio 2–3) for more than 1 month and underwent transesophageal echocardiography to exclude atrial thrombus prior to the procedure. All antiarrhythmic drugs, except for amiodarone, were discontinued five half-lives
Patient population
Baseline characteristics of the overall study population are given in Table 1. Mean patient age was 56.8 ± 11.5 years, and 90% of patients were male. History (from diagnosis of AF to procedure) and mean duration of persistent AF (from last documentation of sinus rhythm to procedure) were 106.1 ± 85.1 months (median 84 months, interquartile range 48–141 months) and 26.6 ± 39.9 months (median 12 months, interquartile range 6–28 months), respectively. Evidence of structural heart disease was
Main findings
The present study investigated the characteristics and ablation results of PMFL occurring in the context of AF. The main findings of this study are as follows. (1) Ablation of the MI promotes PMFL. (2) Bidirectional conduction block results in fewer recurrences of PMFL. (3) PMFL rarely terminates with ablation unless a previous mitral line has been performed. (4) In the majority of cases following termination of PMFL by ablation, additional lesions are required for bidirectional conduction
Conclusion
Although MI linear ablation was effective treatment in patients with PMFL, this procedure facilitated the development of PMFL. In the majority of patients, epicardial ablation was necessary to establish MI block. Termination of PMFL occurs commonly while conduction through the MI line persists. Complete bidirectional MI block should be achieved to minimize recurrent PMFL.
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Dr. Wright receives financial support from the Department of Health via the National Institute for Health Research (NIHR) Comprehensive Biomedical Research Centre award to Guy's and St. Thomas' NHS Foundation Trust in partnership with King's College London and King's College Hospital NHS Foundation Trust.