Obstructive sleep apnea (OSA) may predispose to left ventricular (LV) remodelling, hypertrophy and heart failure. Our aim was to determine relationships between OSA and myocardial mechanics reflected by myocardial deformation and LV diastolic function. In twenty patients with severe OSA [47.9 +/- 3.6 years; apneahypopnea index (AHI) 72.4 +/- 6.0 events/h; lowest SaO(2) 62.0 +/- 5.6%] and 20 control subjects [40.7 +/- 3.3 years; AHI 7.4 +/- 1.0 events/hour; lowest SaO2 88.3 +/- 1.4%], no differences were observed between control subjects and patients in LV ejection fraction, LV mass and LV mass index (60.8 +/- 1.6 vs 59.2 +/- 1.5%, p = 0.467; 184.0 +/- 7.5 vs 198.0 +/- 11.5 g, p = 0.310; 89.9 +/- 2.6 vs 89.4 +/- 5.0 g/m(2), p = 0.929, respectively). Compared to control subjects, patients with OSA had significantly reduced GLS (-17.3 +/- 0.8 vs -14.4 +/- 0.7%, p = 0.009), and higher A wave in association with reduced E/A ratio (59.2 +/- 2.1 vs 70.7 +/- 3.4 cm/s, p = 0.007; 1.28 +/- 0.08 vs 0.97 +/-.07, p= 0.006, respectively). Our results suggest that OSA is related to impairments in LV relaxation and contractility.