Po-01-111 prominent aortic root with associated left atrial scar leading to atypical atrial flutter

Left-sided atrial flutters (AFl) rely on areas of increased anisotropy, usually because of scar formation. These scars may be secondary to previous left atrial (LA) ablation procedures, cardiac surgery, heart failure, or infiltrative cardiomyopathies. Less commonly, scar may result from extrinsic compression of the LA secondary to a dilated ascending aorta, bronchogenic cyst, or esophageal dilatation. We present two cases of patients presenting with de novo left atrial atypical flutter arising from a prominent aortic root compressing the anterior LA with associated zones of fibrosis observed with substrate mapping during atypical flutter ablation. Patients with ascending aortic pathology underwent three-dimensional electroanatomic mapping which was correlated with computed tomography (CT) imaging to ascertain zones of LA scarring adjacent to the ascending aorta. A 78-year-old male with a history of ascending aortic aneurysm treated with valve-sparing aortic root replacement and atrial fibrillation treated with prior ablation. He was evaluated in the electrophysiology (EP) clinic for intermittent episodes of pauses and bradycardia. Electrocardiogram (ECG) demonstrated atypical AFl with variable atrioventricular bock. An EP study confirmed mitral flutter involving a zone of slowed conduction through fibrosis on the anterior LA wall secondary to compression by an enlarged ascending aorta. CT imaging confirmed this showing continued filling of the excluded aneurysmal sac from the ascending aorta (Figure 1A). A 74-year-old male with congenital aortic coarctation and bicuspid aortic valve with a history of atrial fibrillation and pulmonary vein isolation (PVI) with posterior LA isolation presented with recurrent tachycardia. ECG revealed atypical AFl. Chest CT revealed the prominent aortic root leading to anterior LA compression (Figure 1B). EP study confirmed mitral flutter with significant fibrosis on the anterior LA wall along the trajectory of the ascending aorta (Figure 1C and 1D). Both patients underwent ablation including an anterior mitral line through the zone of scar (Figure 1E and 1F) which terminated AFl. Extrinsic compression due to an enlarged aortic root may lead to anterior LA fibrosis predisposing to atypical AFl. When planning an ablation strategy, consideration should be given to reviewing ancillary imaging studies such as transthoracic echocardiogram or computed tomography of the chest to guide procedure planning and targets for ablation.