Effect of obstructive sleep apnea on heart rate, heart rate recovery and QTc and P-wave dispersion in newly diagnosed untreated patients.

INTRODUCTION: Obstructive sleep apnea syndrome (OSAS) is associated with autonomic dysfunction, whereas increased heart rate (HR), HR recovery time (HRR-1), QT-corrected interval (QTc) and P-wave dispersion (Pd) are associated with cardiovascular events. The aim of the current investigation was to clarify the influence of OSAS severity on these cardiac parameters.
METHODS: Ninety newly diagnosed and untreated patients with OSAS underwent overnight polysomnography and cardiopulmonary exercise testing, including HRR-1, echocardiography, 24-hour Holter electrocardiography, surface electrocardiogram (ECG) and measurement of several metabolic parameters. The patients were divided into the following 4 groups: 26 with apnea-hypopnea index (AHI) <5, 20 with 5 ≤ AHI <15, 20 with 15 ≤ AHI <30 and 24 with AHI ≥30. QTc and Pd were calculated in all leads of the surface ECG. Mean HR was measured using 24-hour Holter ECG, and HRR-1 was measured using cardiopulmonary exercise testing.
RESULTS: QTc was increased in patients with moderate-to-severe OSAS. Pd was significantly increased in patients with OSAS compared with those without OSAS. In addition, Pd was correlated with AHI and associated with the severity of disease. Mean HRs over a period of 24 hours during wakefulness and sleep correlated significantly with AHI and the lowest SpO2 in patients with OSAS, whereas HRR-1 was inversely correlated with the severity of OSAS, as expressed by AHI.
CONCLUSION: We showed that HR, Pd, HRR-1 and QT-corrected time are correlated with OSAS severity. Further studies are required in order to investigate the prognostic effect of HRR-1, Pd, HR and QTc in OSAS.