Chest
Volume 106, Issue 2, August 1994, Pages 466-471
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Clinical Investigations: Sleep
Cardiac Arrhythmias, Snoring, and Sleep Apnea

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We investigated the frequency of cardiac arrhythmias in patients suspected of having sleep apnea, and related them to the severity of apnea, snoring, and nocturnal hypoxemia. We prospectively studied 458 patients who had nocturnal polysomnography which included objective measurement of snoring (quantified by the number of snores per hour of sleep [snoring index (SI)] and maximum nocturnal sound intensity [(dBmax)], as well as examination of the electrocardiogram (modified lead 2). We found 58 percent prevalence of arrhythmias in patients with sleep apnea (apnea/hypopnea index=AHI >10), vs 42 percent in nonapneic controls (x2=16.7, p<0.0001). Patients with arrhythmias had more severe apnea and nocturnal hypoxemia, but not snoring, than patients without arrhythmias. To examine separately the relationship between the prevalence of arrhythmias and snoring, nocturnal oxygenation, and apnea—we selected subgroups of patients “at the opposite ends of the spectrum” with respect to the severity of snoring, hypoxemia, and apnea. We found that 38 percent of light snorers had arrhythmias vs 39 percent of heavy snorers, 82 percent of patients with mean nocturnal oxygen saturation <90 percent had arrhythmias vs 40 percent of patients with mean nocturnal oxygen saturation >90 percent (x2=7.4, p=0.006), and 70 percent of patients with AHI ≥40 had arrhythmias vs 42 percent with AHI 10 (X2=9.2, p=0.002). We conclude that patients with sleep apnea as a group have higher prevalence of cardiac arrhythmias than nonapneic patients and that snoring alone, without concomitant sleep apnea, is not associated with increased frequency of cardiac arrhythmias.

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Patients

We studied 458 consecutive and unselected patients referred to the sleep clinic at St. Michael's Hospital for evaluation of possible sleep apnea. Snoring was the chief complaint in the vast majority of patients, although daytime sleepiness and tiredness were also common.

Polysomnographic Measurements

In all 458 patients, we carried out nocturnal polysomnography, which included measurements of EEG, submental, and anterior tibial EMG, oronasal flow using thermistors, chest wall and abdominal excursions using inductance

Results

Table 1 summarizes the characteristics of the patient population examined in this study. There were 336 men and 122 women. Most patients (244/458) did not have obstructive sleep apnea (OSA) (AHI ≤10), 121/458 (26 percent) had AHI between 10 and 30, 41/458 (9 percent) had AHI between 30 and 50, and 52/458 patients (11 percent) had AHI >50.

There were 82 patients with history of cardiac disease (hypertension, 51; previous myocardial infarction, 6; angina pectoris, 5; congestive heart failure, 4;

Discussion

This study shows that (1) patients with obstructive sleep apnea have higher prevalence of arrhythmia than nonapneic patients, (2) patients without arrhythmias, as a group, have less severe apnea and nocturnal hypoxemia than patients with arrhythmias, and (3) prevalence of arrhythmias is independent of snoring, but it is linked to sleep apnea and nocturnal hypoxemia. The study design has certain limitations which could conceivably influence some of our conclusions.

One of the drawbacks is the use

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