Diagnostic decision support of heart rate turbulence in sleep apnea syndrome

Obstructive sleep apnea syndrome (OSAS) is characterized by repeated upper-airway obstruction during sleep. It is diagnosed by polysomnographic studies, scoring OSAS severity by an apneas/hypopneas index associated to worse prognosis, mainly for an increased cardiovascular morbidity. Cardiac autonomic impairments involved in the development of cardiovascular disease in OSAS can be assessed by heart rate turbulence (HRT) analysis and aim of the paper is to show the increased medical decision support by HRT evaluation in OSAS patients. HRT has been assessed in 274 polysomnographic recordings of mild-to-severe OSAS patients and an overall cardiorespiratory risk scoring (CRRIS) index has been proposed on the base of both OSAS severity and HRT assessment. Results showed that, while the only polysomnografic analysis would have equally ranked OSAS patients within their mild-to-severe classification, CRRIS index allows to identify a 19% of severe-OSAS patients at very high risk of sudden cardiac death, a 13% of moderate-OSAS patients with a risk level comparable to those of severe, and a 17% of mild-OSAS patients with evidence of an autonomic impairment. CRRIS index, detecting patients at greater probability of worsening could give to the physician a very useful medical decision support in the follow up of this particular chronic disease.