Prevalence and clinical characteristics of patients with lipomatous atrial septal hypertrophy (LASH) in 11,441 transesophageal echocardiograms: a single-center study

Abstract Background Lipomatous atrial septal hypertrophy (LASH) is a rare, typically benign finding on transesophageal echocardiography (TEE), characterized by interatrial septal thickening with fatty infiltration and sparing of the fossa ovalis. Although often incidental, LASH can be associated with atrial arrhythmias and may mimic intracardiac masses, potentially necessitating additional diagnostic imaging. Purpose To determine the prevalence of LASH in a large cohort undergoing TEE and evaluate its association with atrial fibrillation (AF), obesity, structural cardiac abnormalities, and prior arrhythmia interventions. Methods A retrospective review of 11,441 TEE examinations performed between 2013 and 2023 at our institution was conducted. LASH was defined as interatrial septal thickening with classic "dumbbell-shaped" morphology and sparing of the fossa ovalis. Patient demographics, comorbidities, rhythm history, device implantation, transthoracic echocardiography (TTE) findings, and procedural history were extracted from clinical records. Results LASH was identified in 112 patients (0.98%). The mean age was 65.5 years, and 68 (61%) were male. A body mass index (BMI) 30 was present in 75 cases (67%), supporting a possible link between LASH and obesity. Atrial fibrillation was documented in 79 patients (70.5%) and atrial flutter in 24 (21.4%). Among these, 56 patients had previously undergone catheter ablation, and 31 had received electrical cardioversion (7 of them more than once). Device therapy included pacemakers in 19 patients, ICDs in 14, and CRT-Ds in 2. TTE findings showed left ventricular ejection fraction (LVEF) 50% in 34 patients, left atrial (LA) enlargement (40 mm in PLAX view) in 67, and mitral regurgitation (MR) in 53 (mild in 41, moderate in 14, severe ischemic MR in 4). Additional valvular findings included aortic regurgitation in 18 (mild), moderate AR in 4, aortic stenosis in 10 (mild in 7, moderate in 3, severe in 1), and tricuspid regurgitation in 47 (mild in 37, moderate in 16, severe in 1). Only one case of mild mitral stenosis was observed. No pulmonary valve pathology was identified. Conclusion LASH was identified in approximately 1% of patients undergoing TEE at our center, with a notable association with obesity and atrial arrhythmias, particularly AF. While generally benign, LASH may mimic pathological masses, requiring further diagnostic clarification. As TEE is frequently performed to rule out left atrial appendage thrombus, the true prevalence of LASH in the general population may differ.