The left atrium is afterload sensitive, responding to immediate changes in left ventricular (LV) diastolic pressure, and left atrial volumetric remodeling has been reported in conditions associated with abnormal diastolic function. We examined the relationship between left atrial volumetric remodeling and objective measures of exercise capacity in patients with nonobstructive hypertrophic cardiomyopathy (HCM).

We compared LA volume indices, other 2-dimensional and Doppler echocardiographic parameters, invasive hemodynamic measures, and magnetic resonance imaging (MRI)–derived LV mass with exercise duration, maximal oxygen uptake (MV˙o₂), anaerobic threshold (AT), and ventilatory efficiency (VE/V˙co₂ slope) in 43 patients with nonobstructive HCM. Patients underwent cardiac catheterization within 48 hours and metabolic stress testing within 1 week of their echocardiogram and MRI examinations.

Left atrial volume at end-ventricular systole (LA_max) and end-atrial emptying (LA_min) correlated with MV˙o₂ (r = −0.39, P < .01 for both), AT (r = −0.42, r = −0.39, respectively, P < .01 for both), and VE/V˙co₂ slope (r = 0.45, P = .003; r = 0.41, P = .008). Patients with an LA_max ≥33 mL/m² had significantly lower MV˙o₂ (P = .025) and AT levels (P = .017) and higher VE/V˙co₂ slope levels (P = .004) as compared with patients with a smaller LA size. In multivariate analysis, MRI-determined LV mass, which was not a univariate correlate of exercise tolerance, provided additional effect when combined with LA volume index.

Left atrial volumetric remodeling predicts exercise capacity in nonobstructive HCM and may reflect chronic LV diastolic burden. This simple noninvasive measure of LA size may provide a long-term indication of the effects of chronically elevated filling pressures in patients with HCM and further studies testing its prognostic value are necessary.