Spatial QRS-T angle in patients with obstructive sleep apnea – Impact of cardiac and metabolic comorbidities

Introduction: Obstructive sleep apnea (OSA) is a recognized cardiovascular risk factor. In clinical practice, patients also suffer from other diseases, which may contribute to an increased cardiovascular risk. The spatial QRS-T angle (QRS-TA) is strong predictor of cardiovascular death, which may be used for the stratification of risk. Objectives: The objective of the study was evaluation of the effect of concomitant diseases on the values of QRS-TA in patients with OSA. Methods: The study covered 61 patients - 44 males and 17 females, with OSA diagnosed based on screening polysomnography; mean age 51.5±10.3 yr. The control group were 20 patients (including 12 males) without sleep-disordered breathing. In all patients digital ECG was registered. QRS-TA was calculated according to the method proposed by Kors. Results: QRS-TA was 34.4±19.5° in the study group, and 20.3±13.4° in the control group (p=0.003). Correlations were observed between QRS-TA, and apnea-hyponea index (r=0.31; p=0.007) and respiratory distress time index (r=0.28; p=0.01). Considering comorbidities it was found that only the presence of ischemic heart disease (IHD) was related with a significant widening of QRS-TA (p=0.0001). Such an effect was not observed in the case of arterial hypertension (p=0.41), obesity (p=0.33), type 2 diabetes (p=0.21), and nicotinism (p=0.62). Conclusions: In patients with OSA, the concomitance of IHD is associated with a significant widening of the spatial QRS-T angle, and consequently, with an increased heterogeneity of the cardiac muscle action potential, and risk of arrhythmia and death. Therefore, this group of patients require an especially intensive treatment.