HEART-BLOCK IN PATIENTS WITH OBSTRUCTIVE SLEEP-APNEA - PATHOGENETIC FACTORS AND EFFECTS OF TREATMENT

Heart block during sleep has been described in up to 10% of patients w ith obstructive sleep apnoea, The aim of this study was to determine t he relationship bet tr-een sleep stage, oxygen desaturation and apnoea -associated bradyarrhythmias as well as the effect of nasal continuous positive airway pressure (nCPAP)/nasal bilevel positive airway pressu re (nBiPAP) therapy on these arrhythmias in patients without electroph ysiological abnormalities. Sixteen patients (14 males and two females, mean age 49.6+/-10.4 yrs) with sleep apnoea and nocturnal heart block underwent polysomnography after exclusion of electrophysiological abn ormalities of the sinus node function and atrioventricular (AV) conduc tion system by invasive electrophysiological evaluation. During sleep, 651 episodes of heart block were recorded, 572 (87.9%) occurred durin g rapid eye movement (REM) sleep and 79 (12.1%) during nonrapid eye mo vement (NREM) sleep stages 1 and 2, During REM sleep, the frequency of heart block tr as significantly higher than during NREM sleep: 0.69+/ -0.99 versus 0.02+/-0.04 episodes of heart block min 1 of the respecti ve sleep stage (p<0.001). During apnoeas or hypopnoeas, 609 bradyarrhy thmias (93.5%) occurred with a desaturation of at least 4%. With nCPAP / nBiPAP therapy, apnoea/hypopnoea index (AHI) decreased from 75.5+/-3 9.6 . h(-1) to 3.0+/- 6.6 h(-1) (p<0.01) and the number of arrhythmias from 651 to 72 (p<0.01). We conclude that: 1) 87.9% of apnoea-associa ted bradyarrhythmias occur during rapid eye movement sleep; 2) the vas t majority of heart block episodes occur during a desaturation of at l east 4% without a previously described threshold value of 72%; and 3) nasal continuous positive airway pressure or nasal bi-level positive a irway pressure is the therapy of choice in patients with apnoea-associ ated bradyarrhythmias.