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Study Objectives: To compare the frequency of daytime and nocturnal cardiac arrhythmias and ST-segment depression episodes among patients with obstructive sleep apnea-hypopnea syndrome (OSAHS), snoring subjects, and healthy subjects, and to analyze the relationship between the cardiac disturbances, sleep characteristics, and sympathetic tone in patients with OSAHS., Patients and Interventions: Twenty-one consecutive patients with OSAHS, 12 snorers without hypersomnolence, and 15 healthy subjects were selected. Polysomnography, 24-h Holter ECG recording, and urinary catecholamine determination were simultaneously performed on all subjects., Results: Patients with OSAHS had more daytime and nocturnal episodes of sinus and supraventricular arrhythmias and couplets than the snoring and control groups. Moreover, nocturnal ST-segment depression episodes were more frequent in the OSAHS group than in control subjects (0.565 +/- 0.826/h vs 0 +/- 0/h [mean +/- SD]). In patients with OSAHS, arousal index and daytime epinephrine levels were related to daytime and nocturnal ST-segment depression episodes, whereas minimum arterial oxygen saturation was related to nocturnal sinus bradycardia and supraventricular tachycardia. Epinephrine and norepinephrine urinary concentrations correlated with sinus and supraventricular arrhythmias., Conclusions: Patients with OSAHS have a higher frequency of cardiac rhythm disturbances and ST-segment depression episodes than snoring and control subjects. Moreover, ST-segment changes are related to sympathetic tone and sleep fragmentation, whereas most of the rhythm disturbances in patients with OSAHS are associated with sleep fragmentation, nocturnal hypoxemia, and sympathetic tone.

Objective: To determine the incidence of and risk factors for unexplained paroxysmal bradycardia in children treated with high-frequency oscillatory ventilation (HFOV)., Design: A nested case-control study., Setting: A university-affiliated children's hospital., Subjects: All children treated with HFOV for at least 3 days during a 2-year period and a randomly chosen comparison group of 50 children treated with only conventional mechanical ventilation (CMV) for at least 3 days during the same time period., Interventions: None., Measurements and Results: Unexplained paroxysmal sinus bradycardia occurred in six children (12%) receiving HFOV, and was significantly more common than in children treated with CMV (0%). The bradycardic events occurred after the lung disease started to improve, and the mean airway pressure (mPaw) at the time of the bradycardias was significantly decreased from the child's maximal mPaw. The bradycardic events were effectively treated acutely with manual ventilation or atropine sulfate, and resolved completely after the patient was changed to a regimen of CMV., Conclusion: Unexplained paroxysmal bradycardia associated with HFOV in children is not uncommon. It completely resolves with conversion to CMV and may be related to overdistention of alveoli as compliance improves.

In order to delineate the frequency of arrhythmias and conduction abnormalities in a group of apparently healthy elderly people, 24-hour ambulatory ECG recordings were obtained on subjects recruited from the Veterans Administration Voluntary Service. Their ages ranged from 60--84 (average 69). It is concluded from this preliminary study that complex supraventricular and ventricular arrhythmias occur in an apparently healthy elderly population. These findings must be taken into account in assessing the clinical significance of arrhythmias in an elderly population.