Is myocardial strain an early marker of systolic dysfunction in obstructive sleep apnoea? Findings from a meta-analysis of echocardiographic studies

Aim: We investigated the association between obstructive sleep apnoea (OSA) and subclinical systolic dysfunction through a meta-analysis of echocardiographic studies that provided data on left ventricular (LV) mechanics as assessed by global longitudinal strain (GLS). Design: The PubMed, OVID-MEDLINE, and Cochrane library databases were systematically analyzed to search English-language articles published from inception to 31 December 2021. Studies were detected by using the following terms: ‘obstructive sleep apnea’, ‘sleep quality’, ‘sleep disordered breathing’, ‘cardiac damage’, ‘left ventricular hypertrophy’, ‘systolic dysfunction’, ‘global longitudinal strain’, ‘left ventricular mechanics’, ‘echocardiography’ and ‘speckle tracking echocardiography’. Results: The meta-analysis included 889 patients with OSA and 364 non-OSA controls from 12 studies. Compared with controls, GLS was significantly reduced in the pooled OSA group (SMD −1.24 ± 0.17, CI: −1.58 to −0.90, P < 0.0001), as well as in the normotensive OSA subgroup (SMD: −1.17 ± 0.12 CI:−1.40 to −0.95, P < 0.0001). Similar findings were obtained in sub-analyses performed separately in mild, moderate and severe OSA. This was not the case for LV ejection fraction (LVEF) (i.e. comparisons between controls vs. mild OSA, mild vs. moderate OSA, moderate vs. severe OSA). Conclusion: GLS is impaired in patients with OSA (independently from hypertension), worsening progressively from mild to moderate and severe forms, thus allowing to identify subclinical alterations of the systolic function not captured by LVEF. Therefore, myocardial strain assessment should be implemented systematically in the OSA setting to timely detect systolic dysfunction.