Cardiac autonomic function and cardiac arrhythmias in patients with obstructive sleep apnea

OBJECTIVES
We assessed the effect of obstructive sleep apnea syndrome (OSAS) on cardiac autonomic function with the parameters of heart rate variability (HRV) and heart rate turbulence (HRT) and investigated the frequency of cardiac arrhythmias in patients with OSAS.

STUDY DESIGN
Seventy-six patients (27 women, 49 men; mean age 50.6±10.7 years; range 33 to 75 years) with an initial diagnosis of OSAS underwent polysomnography and simultaneous Holter monitoring. The diagnosis of OSAS was based on an apnea-hypopnea index (AHI) of ≥5. The patients were evaluated with time-and frequency-based parameters of HRV, and turbulence onset (TO) and turbulence slope (TS) parameters of HRT. Cardiac arrhythmias were also assessed on Holter monitoring.

RESULTS
Fifty-three patients (69.7%) were diagnosed with OSAS, being mild in 25 (47.2%), moderate in 23 (43.4%), and severe in five (9.4%) patients based on the AHI. The patients were divided into two groups as those having an AHI of <5 (n=23) and ≥5 (n=53). There were no significant differences in HRV parameters between the two groups, but patients with OSAS exhibited a significantly higher TO (p=0.02) and a significantly lower TS (p<0.001). In bivariate correlation analysis, AHI showed a significant negative correlation with TS (r=-0.37, p=0.009) and a significant positive correlation with TO (r=0.36, p=0.01). The frequencies of short-sequence premature atrial and ventricular contractions were significantly higher in patients with OSAS (p<0.001).

CONCLUSION
Our findings suggest that blunting of HRT is more prominent than changes in HRV parameters in patients with OSAS, accompanied by increased frequency of cardiac arrhythmias.