OSA causes transient respiratory airway collapse which leads to transient hypoxemia and cardiac electrical instability [
11]. These effects may progress to supraventricular and ventricular arrhythmia and finally to sudden cardiac death. Ventricular repolarization and arrhythmogenesis can be assessed by several electrocardiographic parameters including QT interval, QT dispersion, and TpTe. [
12] Kilicaslan examined 23 patients with moderate to severe OSA without any cardiac abnormality and 23 patients within the control group. Only TpTe was longer in the OSA group but QT and QTc were not.[
12] . However, they did not include any patients with cardiac disease. TpTe is used as an indicator of trans-mural dispersion in ventricular repolarization. Prolonged TpTe may predict ventricular arrhythmias and mortality. [
13]. Alonso Fernandez et al. reported more daytime and especially nocturnal PVCs and bigeminies in patients with OSA but VT and AF were not found. Again they did not study patients with cardiac disease. [
14] Yamashita et al. showed QT dispersion increased in patients with old MI and also increased in hypertension and OSA which may affect some bias in the study. [
15] however, they didn’t specify any relation between CAD severity and OSA. Dursunoglu et al. studied QT dispersion changes in 96 patients without any previous cardiac and respiratory disorders. QTc was higher in patients with more AHI but patients with CAD were excluded. [
16] Some studies also discussed the effect of obesity in QT interval, QT dispersion, and other ECG parameters but Pontiroli et al. didn’t find this relationship. [
17] Kilicaslan et al. reported increased QT dispersion and TpTe in patients with moderate to severe OSA with CPAP therapy significantly reducing these parameters with a reduction in ventricular bigeminies and tachyarrhythmia. [
12] Tasci et al. measured Pro-BNP as an indicating marker for congestive heart failure in patients with OSA [
18]. They showed that Pro-BNP increased in patients with heart failure and OSA and effective CPAP therapy would reduce this level. [
18] Jarrah et al. assessed 398 patients who underwent coronary angiography for one year and classified them into high-risk and low-risk for OSA based on a questionnaire. They found important relationship between coronary artery stenosis and OSA. [
20] However, severity was classified only based on symptoms and not based on polysomnography. Konishi et al. studied 21 patients with OSA and 30 patients within the control group by OFDI-PCI. They found non-significant more severe stenosis with fibrous cap in the OSA group but the p-value did not reach statistical significance and they did not evaluate QTd or TpTe. [
21] Silveria et al. found no relation between OSA and coronary angiographic findings based on the Gensini score in 80 patients. [
22]. Mustafa Umut et al. did their study on patients with mild to moderate risk for CAD and based on the severity of OSA, they divided them into three categories. They found that patients with more severe findings in polysomnography had more calcified plaques found on CT angiography. [
23] In this study, only patients with CAD risk factors were included and they didn’t include any patients with documented CAD. Based on our experiences, the risk of arrhythmias is higher in patients with prolonged QT and QT dispersions. We suggest that the above indices be followed closely in patients that may represent a group of patients at higher risk for cardiac events.