Determinants of Reverse Remodeling of the Left Atrium After Transaortic Myectomy

Background: In patients with hypertrophic cardiomyopathy (HCM), enlargement of the left atrium (LA) is associated with increased morbidity and mortality because of risk of atrial fibrillation (AF), stroke, and heart failure. In this study, we investigated whether LA reverse remodeling occurs after septal myectomy. Methods: Between August 2007 and July 2015, 656 patients underwent myectomy at our institution and had preoperative and postoperative transthoracic echocardiographic (TTE) recording of LA volume index (LAVI). We reviewed clinical and echocardiographic data of these patients, and assessed for changes over time by comparing preoperative and postoperative measurements. Results: The median age was 56 (interquartile range [IQR], 46, 65) years, and 370 (56%) were male. New York Heart Association Class III/IV dyspnea was present in 581 (89%). Preoperative TTE showed LAVI of 48 (IQR, 38, 60) mL/m². In patients with history of AF, preoperative LAVI was 57 (IQR, 45, 68) mL/m², and in those without AF, LAVI measured 45 (IQR, 37, 57) mL/m² (p < 0.001). All patients underwent transaortic septal myectomy. Early postoperative TTE (4 [IQR, 3, 5] days) demonstrated LAVI of 43 (IQR, 36, 52) mL/m² (p < 0.001), and late postoperative TTE (2.0 [IQR, 1.1, 4.1] years) showed LAVI of 38 (29, 47) mL/m² (p < 0.001). Preoperative LAVI was associated with late development of AF (p = 0.002). Conclusions: Left atrial volume decreases significantly after surgical relief of left ventricular outflow tract obstruction. Early changes likely reflect lower LA pressure due to gradient relief and abolishment of mitral regurgitation, and late reduction suggests continued reverse remodeling.