Relations among hypoxemia, sleep stage, and bradyarrhythmia during obstructive sleep apnea

Background Obesity, apneic hypoxemia, and rapid eye movement (REM) sleep ar e supposed to be the major causes for bradyarrhythmia in patients with obst ructive sleep apnea. The aims of this study were to compare clinical findin gs and diagnoses in patients with obstructive sleep apnea with and without nocturnal bradyarrhythmia and to analyze the relations among hypoxemia, sle ep stage, and bradyarrhythmia. Methods During a 17-month period 239 patients were found to have sleep apne a in on ambulatory study. Patients with nocturnal bradyarrhythmia were hosp italized for 3 days and polysomnographies were performed over 2 successive nights. A Halter electrocardiogram was recorded for 48 hours. Results Nocturnal episodes of bradyarrhythmia were identified in 17 (7%) of 239 patients. Body moss index (39 +/- 7 vs 31 +/- 5 kg/m(2)) and respirato ry disturbance index (90 +/- 36 per hour vs 24 +/- 24 per hour) were signif icantly different (P < .01) between patients with (n = 17) and without brad yarrhythmia (n = 222). Bradyarrhythmia occurred significantly more often du ring REM than non-REM sleep (P < .01). There was a significant difference i n end-apneic oxygen saturation in apnea/hypopnea episodes with and without bradyarrhythmia (71% + 9% vs 75% +/- 10%; P < .01). A linear relation betwe en end-apneic oxygen saturation and number of sinus arrests and heart block s could not be found. Conclusions Patients with apnea-associated bradyarrhythmia are more overwei ght than patients without bradyarrhythmia. The higher respiratory disturban ce index measurements found in these patients may be caused by this differe nce. Bradyarrhythmia occurs predominantly during REM sleep and occurred ind ependently from decrease in oxygen saturation; a threshold value as an uppe r limit could not be found.