Obstructive sleep apnea in heart failure patients: evidence for persistent conduction disturbances or sinus node dysfunction.

Bradycardia is a common finding in patients with obstructive sleep apnea and might be pronounced in heart failure patients. The aim of the present study was to determine the relationship between nocturnal hypoxemia, apnea-hypopnea index, and electrophysiological parameters of sinus node and atrioventricular conduction properties. Electrophysiological studies were performed in 12 patients with heart failure. Polygraphic studies were done in all of the patients. Patients with an AHI >10/h were classified as sleep apnea patients. Mild sleep apnea was diagnosed in 50% of the patients (AHI 17.8 +/- 4.4 vs. 5.1 +/- 3.6/h). There were no differences with respect to the resting heart rate, PQ interval, or QRS duration between the two groups. Sinus node recovery time was normal in all of the patients (993 +/-291 vs. 1099 +/-62 ms, P=0.45). There was no abnormal atrioventricular conduction. Nevertheless, sleep apnea patients showed decreased atrioventricular conduction time (AH) intervals (134 +/- 42 vs. 102 +/- 25 ms, P=0.1) and infranodal conduction time (HV) intervals (59 +/- 9 vs. 43 +/- 7 ms, P=0.01). We conclude that mild sleep apnea was not associated with abnormal findings in sinus node function or AV conduction properties in patients with heart failure. Decreased AH/HV intervals might be a consequence of apnea associated sympathetic activation.