Abstract
Obstructive sleep apnea (OSA) is an independent risk factor for cardiovascular morbidity and death. Little information is available regarding the relationship between the severity of OSA and myocardial performance in OSA patients who have normal ejection fractions. We prospectively investigated this relationship, using the tissue-Doppler myocardial performance index (TD-MPI). We conducted overnight, full-laboratory polysomnographic examinations of 116 patients, and calculated the left and right ventricular TD-MPIs. Patients were classified into 3 groups in accordance with their apnea-hypopnea index (AHI) levels: AHImild (≥5 to <15), AHImoderate (≥15 to <30), and AHIsevere (≥30). Left and right ventricular TD-MPI values were higher in the AHIsevere group than in the AHImild and AHImoderate groups (all P <0.05). In addition, right ventricular TD-MPI values in the AHImoderate group were higher than those in the AHImild group (P <0.05). Right ventricular TD-MPI was significantly associated with AHI (β=0.468, P <0.001), left ventricular TD-MPI, and right ventricular early-to-late filling velocities (E/A ratio) in multiple linear regression analysis. On the other hand, left ventricular TD-MPI was significantly associated with right ventricular TD-MPI and left ventricular E/A ratio (both P <0.05). Our results show that OSA severity, determined by means of AHI, is independently associated with impaired right and left ventricular function as indicated by TD-MPI in patients who have OSA and normal ejection fractions.