Influence of obstructive sleep apnea syndrome on left ventricular performance: a tissue doppler imaging study

ABSTRACT

The syndrome of obstructive sleep apnea [OSAS] is characterized by recurrent upper airway obstructions during sleep, and this might lead to cardiovascular consequences such as heart failure, arrhythmias, myocardial infarction, systemic and pulmonary arterial hypertension. Is to assess, by tissue Doppler imaging [TDI] technique, left ventricular [LV] global systolic and diastolic functions, dimensions, wall thickness and mass index in normotensive patients with obstructive sleep apnea syndrome [OSAS]. Fifty one individuals were recruited in this study. They were divided into 2 groups group 1 included 36 normotensive patients who were referred to sleep laboratory because of symptoms of nocturnal snoring and/or excessive daytime sleepiness and suspected OSAS. Group 2 included 15 healthy individuals of matched age, sex and body mass index. All patients had Epworth Sleepness Scale [ESS] > 10 and were subjected to sleep study by polysomnography. OSAS was considered mild to moderate if apnea- Hypopnea index [AHI] was 5- 20 and severe if AHl was >/= 20. All individuals underwent tissue Doppler imaging study for assessing left ventricular Tei index, mitral annulus systolic, early diastolic and late diastolic velocities [Sa, Ea and Aa, respectively] as well as isovolumetric relaxation and contraction times and ejection times. LV end diastolic and systolic dimensions [EDD and ESD] as well as interventricular septum and posterior wall thicknes [IVST and PWT] were measured by M-mode echocardiography. LV mass index was calculated according to previous formula. AHI was 5-20 in ten patients, and >20 in 26 patients. Patients group had higher Tei index suggesting impaired global systolic and/or diastolic functions [Tei index 0.48 +/- 0.12 versus 0.37 +/- 0.03, p<0.05 in patients versus control groups, respectively]. They, also, had higher Aa and longer IVRT [Aa 9.8 +/- 1.8 versus 8.1 +/- 1.5 cm/sec, p<0.05 and IVRT 99 +/- 113 versus 73 +/- 8.2 msec, p<0.01], but lower Ea and Ea/Aa ratio, consistent with impaired diastolic function [Ea 9.5 +/- 2.9 versus 12.9 +/- 2.6 cm/sec, p<0.01, Ea/Aa ratio 0.85 +/- 0.2 versus 1.2 +/- 0.7, p<0.05. Again, IVST and PWT were more increased in patients group compared to controls. On the other hand, Sa and ejection fraction did not significantly differ from those of control group suggesting an intact LV systolic function [Sa 8.9 +/- 1,8 versus 9.3 +/- 1.5 cm/sec, p>0.05 and EF 61.2 +/- 5 versus 63.9 +/- 6.3%, p>0.05. Again, neither LV-EDD nor ESD differed significantly from control group. There was a significant positive correlation between AHI and Tei index [r= 0.73, p<0.01] and also between AHI and IVST, PWTandLVMI. This study suggests that LV diastolic function is impaired in normotensive patients with OSAS while systolic function is intact. Although these patients had normal blood pressure, they had LVH and increased LV mass index. There was a significant and positive correlation between AHI and Tei index and between AHI and IVST. The impact of these findings on clinical outcome may need further evaluation