BACKGROUND Atrial fibrillation is the most common arrhythmia and is associated with adverse outcomes in hypertrophic cardiomyopathy (HCM). Although left atrial (LA) remodeling and dysfunction are known to associate with the development of atrial fibrillation in HCM, the changes of the LA in HCM patients remain unclear. This study aimed to evaluate the changes in LA size and mechanical function in HCM patients compared to control subjects and to determine the characteristics of HCM associated with LA remodeling and dysfunction.

METHODS Seventy-nine HCM patients (mean age, 54 ± 11 years; 76% were men) were compared to 79 age- and sex-matched controls (mean age, 54 ± 11 years; 76% were men) and 20 young healthy controls (mean age, 33 ± 5 years; 45% were men). The LA diameter, volume, and mechanical function, including global strain (ε), were evaluated by 2D-speckle tracking echocardiography. The phenotype of HCM, maximal left ventricular (LV) wall thickness, LV mass, and presence and extent of late gadolinium enhancement (LGE) were evaluated with cardiac magnetic resonance imaging.

RESULTS HCM patients showed increased LA volume index, impaired reservoir function, and decreased LA ε compared to the control subjects. When we divided the HCM group according to a maximal LA volume index (LAVImax) of 38.7 ml/m2 or LA ε of 21%, no significant differences in the HCM phenotype and maximal LV wall thickness were observed for patients with LAVImax >38.7 ml/m2 or LA ε ≤21%. Conversely, the LV mass index was significantly higher both in patients with maximal LA volume index >38.7 ml/m2 and with LA ε ≤21% and was independently associated with LAVImax and LA ε. Although the LGE extent was increased in patients with LA ε ≤21%, it was not independently associated with either LAVImax or LA ε.

CONCLUSIONS HCM patients showed progressed LA remodeling and dysfunction; the determinant of LA remodeling and dysfunction was LV mass index rather than LV myocardial fibrosis by LGE-magnetic resonance imaging.