Evaluation of Pulmonary Artery Stiffness in Patients with Obstructive Sleep Apnea Syndrome

To investigate whether obstructive sleep apnea syndrome (OSAS) has any effect on pulmonary artery stiffness (PAS) derived from echocardiographic calculation.

Fifty-two patients with newly diagnosed OSAS and forty-two subjects without OSAS matched by age and sex were enrolled in the study. OSAS was categorized according to apnea hypopnea index (AHI, event/h) as follows: normal (AHI<5), mild OSAS (AHI 5-15), moderate and severe OSAS (AHI>15). All participants were evaluated by echocardiography to determine PAS and right ventricle functions. PAS was calculated throughout pulmonary artery flow by the formula; PAS (kHz/sec) = maximal frequency shift/acceleration time.

Demographic and clinical parameters were similar in both groups. PAS significantly increased in OSAS compared with the control group (26.9 ± 6.1 vs. 18.0 ± 3.5, P < 0.001). Additionally, PAS in severe and moderate OSAS was considerably high compared with that in mild OSAS and control group (P < 0.001). Right ventricular myocardial performance index (MPI) and mean pulmonary artery pressures (mPAP) were considerably higher in OSAS group than control group (P < 0.001). Tricuspid E/A, right ventricle tissue Doppler E'/A', and right ventricular ejection time (RVET) decreased in OSAS group compared with control group (P < 0.001). There was a significantly positive correlation between PAS and AHI, mPAP, and MPI (P < 0.001), and a significantly negative correlation between PAS and tricuspid E/A, E'/A', and RVET (P < 0.001). Linear regression analyses showed that PAS was an independent factor for mPAP (ß = 0.595, P = 0.034).

Elastic properties of pulmonary artery deteriorate with severity of OSAS and may be responsible for right ventricular dysfunctions in OSAS.