[Relationship between E/Em ratio and exercise capacity in patients with atrial fibrillation]

To explore the relationship between the ratio of early diastolic transmitral velocity to early diastolic mitral annular velocity (E/Em) and exercise capacity in patients with atrial fibrillation.

A total of 94 consecutive patients with non-valvular atrial fibrillation and preserved left ventricular ejection fraction admitted into our department from December 2011 to June 2013 were included. Echocardiography and cardiopulmonary exercise test were performed. According to E/Em, they were divided into two groups of normal E/Em (E/Em ≤ 9) and elevated E/Em (E/Em>9). The parameters of exercise capacity, including VO2max/kg, anaerobic threshold/kg (AT/kg) and exercise time duration were compared between two groups. And the determinants of VO2max/kg were identified by multivariate regression analysis.

The number of patients was 57(60.6%) with normal E/Em and 37 (39.4%) with elevated E/Em. As compared to those with normal E/Em, the patients with elevated E/Em had lower VO₂max/kg [(26 ± 4) vs (20 ± 4) ml × min⁻¹ × kg⁻¹, P < 0.001], lower AT/kg [(25 ± 4) vs (19 ± 5) ml ×min⁻¹ × kg⁻¹, P < 0.001] and shorter exercise time duration [(7.2 ± 1.3) vs (5.8 ± 1.3) min, P < 0.001]. Multivariate regression analysis revealed that three significant variables were independently associated with VO₂max/kg: age (r = -0.412, P < 0.001), gender ((25 ± 5) and (21 ± 4) ml × min⁻¹ × kg⁻¹ for males and females separately, P < 0.001) and E/Em (r = -0.535, P < 0.001).

E/Em was independently associated with exercise capacity in patients with atrial fibrillation.