Early left ventricular functional alterations in patients with obstructive sleep apnea syndrome

Background: The knowledge regarding myocardial alterations in patients with obstructive sleep apnea syndrome (OSAS) in the absence of any known cardiovascular disorders including hypertension is limited. The aim of this study was to assess the early alterations of left ventricular (LV) functions caused by OSAS before the development of hypertension and other cardiovascular manifestations of OSAS. Methods: Eighty consecutive patients who underwent polysomnography (PSG) were enrolled in the study. Patients with hypertension, diabetes mellitus or any other known cardiac diseases were excluded from the study. Subjects were separated into two groups by their apnea/hypopnea index (AHI) (group 1: AHI < 15, and group 2: AHI >= 15). Fourty-three patients with normal polysomnographic examination or mild OSAS (group 1) and 37 patients with moderate to severe OSAS (group 2) were compared. After PSG examination, LV functions were assessed by using the conventional and tissue Doppler echocardiographic methods. Results: The mean age was similar between the groups. The ratio of male patients was higher in group 2 (male/female: 31/12 in group 1 vs. 34/3 in group 2, p = 0.04). Body mass index was higher in group 2 (p = 0.05). Conventional echocardiography showed that interventricular septum thickness was 9.5 +/- 1.1 mm in group 1, and 10.5 +/- 1.4 mm in group 2 (p = 0.02). Mean left atrial diameter was 35.6 +/- 4.1 mm in group 2, and 33.8 +/- 3.1 mm in group 1 (p = 0.04). Ratio of early to late transmitral diastolic velocities was lower in group 2 (p = 0.01), indicating that impairment of diastolic function was more frequent in moderate to severe OSAS patients. Tissue Doppler echocardiography showed that early diastolic myocardial velocity was lower in group 2 (21.1 +/- 5.6 cm/s in group 1 vs. 18.3 +/- 5.3 cm/s in group 2, p = 0.01). Conclusions: Left ventricular diastolic dysfunction, LV hypertrophy and left atrial dilatation occur in patients with OSAS even before the development of hypertension and other cardiovascular diseases.