Left atrial phasic volumes are modulated by the type rather than the extent of left ventricular hypertrophy.

BACKGROUND: The aim of this study was to evaluate whether maximal left atrial (LA) volume and phasic atrial function would be further altered in patients with hypertrophic cardiomyopathy (HCM) compared with patients with systemic hypertension (HT) with similar left ventricular (LV) mass. LA enlargement on echocardiography has been documented in HCM and moderate or severe HT, both conditions causing LV hypertrophy.

METHODS: Thirty-five patients with HCM were compared with patients with HT matched for LV mass and normal controls matched for age and gender. Maximal, minimal, and pre-"p" LA biplane and real-time 3-dimensional volumes and LA phasic function were evaluated. Atrial function was estimated by LA ejection force, atrial fraction, and A' velocity.

RESULTS: Maximal, minimal, and pre-"p" LA volumes were significantly increased in the HCM group compared with the HT group and controls. Additionally, LA phasic volumes demonstrated that conduit volume and total, passive, and active emptying fractions were decreased in the HCM group. Despite similar LV mass, the HCM group had a higher incidence of abnormal diastolic filling (60% vs 34%, P = .001).

CONCLUSIONS: Patients with HCM appeared to have larger LA volumes, poorer LA function, and greater severity of diastolic dysfunction compared with those with HT having comparable LV mass. LA changes may be due to coexistent atrial myopathy associated with other pathophysiologic aspects of HCM, including outflow obstruction, mitral regurgitation, and myocardial fibrosis in HCM.