***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: OBJECTIVES The effects of continuous positive airway pressure ( CPAP ) therapy on right ventricular ( RV ) function in patients with obstructive sleep apnea syndrome ( OSAS ) has not been previously studied by tissue Doppler imaging ( TDI ) . The aim of this study was to assess RV function using TDI in patients with OSAS before and after CPAP therapy .  METHODS Twenty-eight patients with newly diagnosed OSAS in the absence of any confounding factors and 18 controls were included in this study . The peak systolic velocity ( S'm ) , early ( E'm ) and late ( A'm ) diastolic myocardial peak velocities at tricuspid lateral annulus , isovolumic acceleration ( IVA ) , myocardial precontraction time ( PCT'm ) , myocardial contraction time ( CT'm ) , and myocardial relaxation time ( RT'm ) were measured . All echocardiographic parameters were calculated 6 months after CPAP therapy . RESULTS The RV diastolic parameters such as E'm velocity and E'm-to-A'm ratio were significantly lower , RT'm was significantly prolonged , A'm velocity was similar in patients with OSAS compared to controls ; and the RV systolic parameters such as IVA and CT'm were significantly lower and S'm was similar in patients with OSAS compared to controls . At the end of the treatment , 20 of 28 patients were compliant with CPAP therapy . E'm velocity , E'm-to-A'm ratio , IVA , and CT'm increased , PCT'm , PCT'm-to-CT'm ratio , and RT'm decreased significantly after therapy , whereas S'm velocity and A'm velocity did not change after CPAP treatment in the compliant patients . CONCLUSION OSAS is associated with RV systolic and diastolic dysfunction , and 6 months of CPAP therapy improves the RV systolic and diastolic dysfunction Background : Obstructive sleep apnea ( OSA ) is characterized by repetitive upper airway obstructions during sleep , and it might cause cardiovascular complications such as heart failure , arrhythmias , myocardial infa rct ion , systemic and pulmonary hypertension . Objectives : To determine right ventricular diameters and myocardial performance index ( MPI ) reflecting ventricular global function in uncomplicated OSA patients . Methods : 49 subjects without hypertension , diabetes mellitus , or any cardiac or pulmonary disease referred for evaluation of OSA had overnight polysomnography and complete echocardiographic assessment .  According to the apnea-hypopnea index ( AHI ) , subjects were divided into three groups : group 1 : control subjects  ( AHI < 5 , n = 20 ) , group 2 : patients with mild OSA ( AHI : 5–14 , n = 11 ) , and group 3 : moderate-severe OSA  ( AHI ≧15 , n = 18 ) . Right ventricular free wall diameter was measured by M mode , and right ventricular MPI was calculated as ( isovolumic contraction time + isovolumic relaxation time)/pulmonary ejection time . Results : There were no differences of age , body mass index , heart rates , systolic and diastolic blood pressures among the groups ( p > 0.05 ) . Right ventricular end-diastolic and end-systolic diameters were not statistically different between the groups , and were within normal limits . Also , right ventricular free wall diameter was not significantly different between the groups of control , mild OSA and moderate-severe OSA ( 6.7 ± 0.9 , 6.9 ± 1.0 , 7.1 ± 1.1 mm , p > 0.05 ) . Right ventricular diastolic dysfunction was shown only in group 3 patients . Right ventricular MPI was statistically higher in group 3 ( 0.62 ± 0.18 ) than in group 2 patients ( 0.50 ± 0.10 ) , and group 1 patients ( 0.48 ± 0.08 , p < 0.001 ) . Conclusions : It wassuggested that patients with moderate-severe OSA had a right ventricular global dysfunction , in addition to the presence of a diastolic dysfunction BACKGROUND In patients with obstructive sleep apnea syndrome ( OSAS ) , repetitive hypoxia due to sleep-induced apnea adversely affects the interaction between myocardial oxygen dem and and supply , result ing in the development of sub clinical cardiac dysfunction . The purpose of the study was to analyze the different involvement of left and right heart myocardial function in patients with OSAS treated with noninvasive ventilation ( NIV ) .  METHODS Conventional Doppler echocardiography , Doppler myocardial imaging ( DMI ) , and two-dimensional speckle tracking echocardiography ( 2DSTE ) of left ( LV ) and right ventricular ( RV ) longitudinal and right atrial ( RA ) deformation were performed in 55 patients with OSAS undergoing NIV ( M/F 38/17 ; mean age 67.8 ± 11.2 years ) . LV and RV global longitudinal strain ( GLS ) was calculated by averaging local strain along the entire right and left ventricle , before and during NIV , and after 6 months of nocturnal NIV therapy . RESULTS LV morphology was comparable before and during NIV , whereas LV ejection fraction and LV DMI early diastolic peak velocity were significantly improved in patients with OSAS during NIV , as was LV regional peak myocardial strain ( P < 0.001 ) . RV diameters were slightly increased in patients with OSAS during ventilation , whereas pulmonary artery systolic pressure ( PASP ) , RV GLS , and regional peak myocardial RV strain were significantly reduced during ventilation ( P < 0.0001 ) . RA transverse diameters and RA area were also slightly increased during NIV , whereas RA lateral wall strain was reduced ( P < 0.001 ) . Acute RV myocardial impairment completely reversed at follow-up , with a decrease in PASP and subsequent increase in both RV and RA myocardial performance . CONCLUSIONS Conventional 2DSTE is a useful tool for assessing left and right heart morphology and myocardial deformation in patients with OSAS and for monitoring both acute and chronic effects of NIV Obstructive sleep apnea syndrome has been linked to cardiovascular complications . The diagnosis of effects of sleep apnea on heart may be difficult before apparent examination findings . The aim of the present study was to evaluate changes of myocardial contractile properties in patients affected by sleep apnea showing tissue Doppler imaging , in the face of quite normal myocardial contractility on st and ard echocardiography . Shortly , tissue Doppler imaging may represent an early stage of myocardial abnormality despite a preserved global function 
    Output:
    
Conclusion OSA patients display RV dilatation , increased wall thickening , and altered RV function