The pathophysiology of ventricular arrhythmia in DHF patients with SAS is complex and not completely understood. It has been shown that the frequency and severity of arrhythmia can increase in SAS patients . Firstly, we clarified the difference of SDNN between the SHF and the DHF group in this study. This result demonstrated that the impairment of cardiac autonomic function in DHF patients with SAS might be a trigger for ventricular arrhythmia. Nasal oxygen therapy may be effective for the suppression of ventricular arrhythmia through the improvement of cardiac autonomic function. It has been reported that an altered autonomic balance has been suggested as a possible pathogenetic factor, and autonomic dysfunction is implicated in the subsequent development of heart failure patients with SAS . From our results, nasal oxygen therapy may be effective to suppress PVCs in DHF patients with SAS when the patients have impaired autonomic function.