Right ventricular geometry and mechanics in patients with obstructive sleep apnea living at high altitude

Purpose

Repetitive obstruction of larynx during sleep can lead to daytime pulmonary hypertension and alterations in right ventricular morphology and function in a small fraction of obstructive sleep apnea syndrome (OSAS) patients. Environmental effects, particularly high altitude, can modify the effects of OSAS on pulmonary circulation, since altitude-related hypoxia is related with pulmonary vasoconstriction. This potential interaction, however, was not investigated in previous studies.

Methods

A total of 41 newly diagnosed OSAS patients were included in this study after pre-enrolment screening. Two-dimensional, three-dimensional, and Doppler echocardiographic data were collected after polysomnographic verification of OSAS. Three-dimensional echocardiograms were analyzed to calculate right ventricular volumes, volume indices, and ejection fraction.

Results

Systolic pulmonary artery pressure (38.35?±?8.60 vs. 30.94?±?6.47 mmHg; p?=?0.002), pulmonary acceleration time (118.36?±?16.36 vs. 103.13?±?18.42 ms; p?=?0.001), right ventricle (RV) end-diastolic volume index (48.15?±?11.48 vs. 41.48?±?6.45 ml; p?=?0.009), and RV end-systolic volume index (26.50?±?8.11 vs. 22.15?±?3.85; p?=?0.01) were significantly higher in OSAS patients, with similar RV ejection fraction (EF) between groups. No significant differences were noted in other two-dimensional, Doppler or speckle-tracking strain, measurements. Both RVEF and pulmonary acceleration time were predictors of disease severity.

Conclusions

A greater degree of RV structural remodeling and higher systolic pulmonary pressure were observed in OSAS patients living at high altitude compared to healthy highlanders. The reversibility of these alterations with treatment remains to be studied.