Obstructive Sleep Apnea and Right Ventricular Remodeling: Do We Have All the Answers?

Obstructive sleep apnea (OSA) syndrome is a very important sleep-related breathing disorder related to increased cardiovascular and overall morbidity and mortality. It is associated with multisystemic target organ damage due to micro- and macrovascular changes, resulting in carotid and coronary atherosclerosis, increased arterial stiffness, retinal damage, microalbuminuria, and cardiac remodeling. The latter consists of left ventricular (LV) hypertrophy, as well as diastolic and systolic dysfunction. The increasing burden of evidence shows that OSA also induces right ventricular (RV) remodeling that is more difficult to diagnose, but may also contribute to cardiovascular morbidity and mortality in these patients. Conventional echocardiographic parameters for assessment of RV systolic and diastolic functions are often not sensitive enough to detect subclinical and subtle changes in the RV function. Data published over last decade showed that the RV function, particularly systolic, is impaired in OSA patients and related with its severity. However, the introduction of speckle tracking echocardiography and the particularly longitudinal strain enabled the earlier detection of functional and mechanical changes even when conventional echocardiographic parameters of RV systolic function remained unchanged. The 3D echocardiography provided the possibility to evaluate the entire RV, with its unique shape, and determine 3D RV ejection fraction, which is comparable with results obtained by cardiac magnetic resonance. The use of this modality also provided a new insight into RV systolic (dys)function in OSA patients. In addition to weight loss, which has been proven very helpful in OSA patients, the only approved therapeutic approach is continuous positive airway pressure (CPAP) therapy. It is very important to assess if this therapy induces any improvement in cardiac structure and function. Limited data on this topic show that RV longitudinal strain is a more sensitive parameter rather than other conventional RV indexes in the detection of improvement in RV systolic function and mechanics. The aim of this review article is to summarize the current understanding of RV structural, functional, and mechanical changes in patients with OSA. Furthermore, we sought to provide the current knowledge regarding the effect of CPAP therapy on RV reverse remodeling in OSA patients.