Alternative Approach for Ablation of the Mitral Isthmus
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See Article by Maurer et al
Linear ablation of the mitral isthmus from the lateral mitral annulus to the left inferior pulmonary vein orifice, as an important adjunct to pulmonary vein isolation, is commonly deployed to improve long-term success in patients with nonparoxysmal atrial fibrillation. Beyond that, mitral isthmus ablation is also an important tool for the treatment of left atrial macrore-entrant tachycardia. Once mitral isthmus ablation is attempted, achievement of complete block should be obligatory because an incomplete line could be counterproductive and potentially proarrhythmic, leading to conduction delay and facilitating the subsequent development of atypical left flutters.1 Nevertheless, the creation of contiguous and transmural linear lesions across the mitral isthmus by point-by-point ablation is well-known to be technically challenging and may be associated with significant complications. Some electroanatomical features of this region impede successful ablation at the mitral isthmus: local heat-sink effects mediated by epicardial vessels that may produce resistance to transmural myocardial lesions; myocardial sleeves around the coronary sinus and also the vein of Marshall bypassing the endocardial mitral isthmus line2; endocardial cavities with resultant poor tissue contact and catheter instability; in addition to relatively thick atrial tissue. Epicardial ablation from the coronary sinus is, therefore, frequently required in up to 75% of patients,3 resulting in an increased risk of cardiac tamponade and circumflex coronary artery injury.4–6
Alternative strategies have been proposed to overcome certain anatomic limitations and achieve durable mitral isthmus block. These methods include occlusion of coronary sinus blood flow during …