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Abstract
Sleep- related breathing disorders (SRBDs) are a group of conditions that range from simple snoring with sleep disruption, to Upper airway resistant syndrome ( UARS), to sleep apnea (Bananian et al., 2002 SRBDs) are common disorders in which repetitive apneas expose the cardiovascular system to cycles of hypoxia, exaggerated negative intrathoracic pressure, and arousals. These noxious stimuli can, in turn depress myocardial contractility, activate the sympathetic nervous system, raise blood pressure, heart rate, and myocardial wall stress depress parasympathetic activity, provoke oxidative stress and systemic inflammation, activate platelets, and impair vascular endothelial function Bradley and Floras, 2009 The acute hemodynamics alterations of SRBDs include systemic and pulmonary hypertension, increased right and left ventricular afterload and decreased cardiac output (Robert et al., 2003). Right heart catheterization is the gold standard method for assessing pulmonary hemodynamics (Morera et al., 1989). Recent advances in tissue Doppler imaging have enhanced the ability to identify early abnormalities in systolic and diastolic ventricular function (Maria et al 2007 The relation of SRBDs to right heart structure and function is controversial. The prevalence of right ventricular hypertrophy on twodimensional echocardiography in patients with SRBD ranged from 0 to 71 % (Jacek et al., 2006).