Abstract
Background : It is well known that many patients with heart failure have sleep apnea syndrome (SAS). It is also reported that cycles of apnea and heart rate are similar in SAS. In this study, we examined whether it would be possible to confirm the existence of SAS by fractal analysis as one of the procedures of heart rate variability (HRV) analysis. Methods : Before and after SAS treatment, fifteen patients performed 24-hour ambulatory electrographic recordings and sleep apnea examinations. Thirteen patients were male. The mean age was 72 years old. The basic heart rhythm was sinus rhythm in all cases. HRV analysis was performed by fast Fourier transform analysis and displayed results by the method to calculate a fractal dimension to detect SAS components. Results : Before SAS treatment, the apnea hypopnea index (AHI) was more than 20 in all patients. They also showed the abnormal power increase from 0.01 to 0.04Hz, that is SAS components, in HRV analysis at baseline. After SAS treatment, their AHI decreased and SAS components also became smaller or disappeared, but SAS components still presented when SAS treatment was insufficient. Conclusion : The abnormal power increase shown by fractal analysis of HRV reflected the existence of SAS, and this power disappeared after SAS treatment. Detecting this power is useful for predicting SAS and confirming efficacy of treatment.
