High-Density Mapping and Ablation of Primary Nonfocal Left Atrial Tachycardia Characterizing a Distinct Arrhythmogenic Substrate

OBJECTIVES This study sought to characterize primary left atrial tachycardia (LAT) mechanisms, electrical properties and substrate using high-density mapping. BACKGROUND Nonfocal LAT can be found in patients without prior substrate modifying interventions. METHODS Of 223 catheter ablation procedures for LAT 15 patients (60% male, age 74 +/- 6 years) had nonfocal AT and no history of LA ablation or cardiac surgery. RESULTS AT (mean cycle length 244 +/- 32 ms) were identified as macro-re-entry (12 of 15) or localized re-entry (3 of 15). High-density electroanatomical mapping (EAM, performed in 13 patients) revealed a high proportion of low voltage areas (LVA, <0.45 mV, 41 +/- 22%). Anterior LVA regions were predominantly related to the macro-re-entry and directly perpetuating the re-entrant circuit in 8 patients by formation of a conductive channel (width: 14 +/- 7 mm, length: 11 +/- 3 mm) between the inferior pole of the scar and the mitral valve (MV) annulus with electrophysiological features of diseased tissue. A tailored anterior ablation line successfully terminated AT in 9 patients (6 dominant circuit MV dependent, 3 dominant circuit scar dependent AT), while a lateral isthmus line was performed in 2 patients. Localized re-entries were successfully targeted by local ablation. Acute successful ablation could be achieved in 14 of 15 patients leading to a freedom from any arrhythmias in 9 of 15 patients (60%) after follow-up of 343 +/- 203 days. CONCLUSIONS Patients with nonfocal left atrial tachycardia without previous iatrogenic interventions show evidence for advanced atrial myopathy. High-density mapping revealed involvement of the anterior LA and allows for an individualized ablation approach beyond strategies usually applied in consecutive AT. (C) 2019 by the American College of Cardiology Foundation.