Severe obstructive sleep apnea increases left atrial volume independent of left ventricular diastolic impairment

Abstract

Purpose: Previous studies have demonstrated that severe obstructive sleep apnea (OSA) itself impairs directly left ventricular (LV) diastolic function. Meanwhile, left atrial (LA) volume index which is an independent predictor of future cardiovascular events is related to the OSA severity. Thus, the purpose of this study was to investigate whether OSA is associated with increase of LA volume index irrespective of LV diastolic function. Methods: We enrolled 450 middle-aged OSA{apnea hypopnea index (AHI) ≥5/h} patients without cardiac disease. All the patients underwent overnight fully attended polysomnograpy. They also underwent 2-dimensional echocardiography in order to estimate LA volumes and LV diastolic function which was assessed by the transmitral flow velocity (E/A ratio), deceleration time (DCT), systolic/diastolic pulmonary vein velocity (S/D), and mitral annular velocity (Ea) was derived from tissue Doppler imaging (TDI). Patients were divided into the mild to moderate OSA (5 ≤AHI < 30/h) group and the severe OSA (AHI ≥30/h) group, and compared LA volume index and LV diastolic function between the groups. Multivariate analysis performed whether OSA is the independent factor of LA volume index irrespective of LV diastolic function. Results: The LA volume index in the severe OSA group was significantly larger than those in the mild to moderate OSA group (23.6±5.9 vs. 21.2±5.0, P<0.0001). The E/A ratio and Ea in the severe OSA group was also significantly lower than those in the mild to moderate OSA group (P<0.0001), whereas the S/D ratio in the severe OSA group was significantly higher than that in the mild to moderate OSA group (P<0.001). AHI showed a statistically significant correlation with the LA volume index (r=0.2, P<0.0001), whereas statistically significant inverse correlations were observed between E/A ratio, Ea and AHI (r= -0.14, -0.26, P=0.003, <0.0001, respectively). Multivariate linear regression analysis revealed that severe OSA was independently related with LA volume index even after adjusting for age, blood pressure, body mass index (BMI), and LV diastolic function (β=0.113, P=0.02). Conclusions: These results suggest that severe OSA itself may increases directly LA volume irrespective of impaired LV diastolic function.