Impact of obstructive sleep apnoea on left ventricular mass and global function.

Obstructive sleep apnoea syndrome (OSAS) might be a cause of heart failure. The present study aimed to assess left ventricular mass and myocardial performance index (MPI) in OSAS patients. A total of 67 subjects without any cardiac or pulmonary disease, referred for evaluation of OSAS, had overnight polysomnography and echocardiography. According to apnoea-hypopnoea index (AHI), subjects were classified into three groups: mild OSAS (AHI: 5-14; n = 16), moderate OSAS (AHI: 15-29; n = 18), and severe OSAS (AHI: > or = 30; n = 33). Thickness of interventricular septum (IVS) and posterior wall (LVPW) were measured by M-mode, along with left ventricular mass (LVM) and LVM index (LVMI). Left ventricular MPI was calculated as (isovolumic contraction time+isovolumic relaxation time)/aortic ejection time by Döppler echocardiography. There were no differences in age or body mass index among the groups, but blood pressures were higher in severe OSAS compared with moderate and mild OSAS. In severe OSAS, thickness of IVS (11.2+/-1.1 mm), LVPW (11.4+/-0.9 mm), LVM (298.8+/-83.1 g) and LVMI (144.7+/-39.8 g x m(-2)) were higher than in moderate OSAS (10.9+/-1.3 mm; 10.8+/-0.9 mm; 287.3+/-74.6 g; 126.5+/-41.2 g x m(-2), respectively) and mild OSAS (9.9+/-0.9 mm; 9.8+/-0.8 mm; 225.6+/-84.3 g; 100.5+/-42.3 g x m(-2), respectively). In severe OSAS, MPI (0.64+/-0.14) was significantly higher than in mild OSAS (0.50+/-0.09), but not significantly higher than moderate OSAS (0.60+/-0.10). In conclusion, severe and moderate obstructive sleep apnoea syndrome patients had higher left ventricular mass and left ventricular mass index, and also left ventricular global dysfunction.

QT interval dispersion in obstructive sleep apnoea syndrome patients without hypertension.

QT interval dispersion (QT(d)) reflects inhomogeneity of repolarisation. Delayed cardiac repolarisation leading to the prolongation of the QT interval is a well-characterised precursor of arrhythmias. Obstructive sleep apnoea syndrome (OSAS) can cause cardiovascular complications, such as arrhythmias, myocardial infarction, and systemic and pulmonary hypertension. The aim of this study was to assess QT(d) in OSAS patients without hypertension. A total of 49 subjects without hypertension, diabetes mellitus, any cardiac or pulmonary diseases, or any hormonal, hepatic, renal or electrolyte disorders were referred for evaluation of OSAS. An overnight polysomnography and a standard 12-lead ECG were performed in each subject. According to the apnoea-hypopnoea index (AHI), subjects were divided into control subjects (AHI <5, n = 20) and moderate-severe OSAS patients (AHI > or =15, n = 29). QT(d) (defined as the difference between the maximum and minimum QT interval) and QT-corrected interval dispersion (QT(cd)) were calculated using Bazzet's formula. In conclusion, the QT(cd) was significantly higher in OSAS patients (56.1+/-9.3 ms) than in controls (36.3+/-4.5 ms). A strong positive correlation was shown between QT(cd) and AHI. In addition, a significantly positive correlation was shown between QT(cd) and the desaturation index (DI). The AHI and DI were significantly related to QT(cd) as an independent variable using stepwise regression analysis. The QT-corrected interval dispersion is increased in obstructive sleep apnoea syndrome patients without hypertension, and it may reflect obstructive sleep apnoea syndrome severity.