HEART-RATE-VARIABILITY IN PATIENTS WITH SLEEP-RELATED BREATHING DISORDERS

The increased mortality among patients with obstructive sleep apnea sy ndrome has been explained in part by the increased incidence of arteri al and pulmonary hypertension. A decreased heart rate variability (HRV ) has been shown to be associated with an increased mortality as well. We investigated 53 patients, admitted to the hospital for chest pain for sleep-related breathing disorders (SRBD) with an ambulatory screen ing device (MESAM-IV). HRV was recorded simultaneously. All patients r eceived coronary artery catheterization and 36 had significant coronar y artery disease (CAD; 67.9%). Standard time domain parameters were co mpared by a 4-way Anova for patients with an oxygen desaturation index of more and less than 5/hour and the factors CAD, diabetes and beta-b locker use. The percentage of differences between RR intervals that di ffer more than 50 ms (pNN > 50: 9.0 +/- 11.1 vs, 19.2 +/- 22.2%; p < 0 .05) as well as the root mean square of these differences (38.0 +/- 29 .0 vs. 59.2 +/- 51.5 ms; p < 0.05) were significantly decreased in pat ients with SRBD. In an hourly breakdown the number of desaturations wa s not correlated with a change in HRV. Mean oxygen saturation was sign ificantly decreased in patients with SRBD (95.2 +/- 1.8 vs. 96.2 +/- 1 .42%, p < 0.05), and positively correlated with the pNN > 50 (r = 0.34 , p < 0.01). This correlation might suggest a more profound pathophysi ological interaction between HRV and SRBD than short-term vagal activa tion alone. The results favor HRV for inclusion in future risk stratif ication models in patients with sleep apnea syndrome.