1051 Second Degree Heart Block in a Young Man

Introduction Episodes of sinus arrest and atrioventricular block occur in approximately 20% of patients with obstructive sleep apnea (OSA) in comparison to just 3% among the healthy population. Bradyarrhythmias more commonly occur during REM sleep and are associated with the severity of OSA and extent of hypoxemia. Here we present a case of a patient with second degree AV block discovered on diagnostic polysomnogram revealing severe obstructive sleep apnea (OSA). Report of Case A 28-year-old man referred to our center for hypersomnia, loud snoring, and morning headaches. He was diagnosed with OSA as a child which resolved after tonsillectomy and adenoidectomy. He denied any waking signs of cardiac arrhythmias. His medical history includes mild well controlled asthma, hypertension and non-insulin dependent diabetes mellitus. Physical examination was remarkable for BMI 51.22kg/m2, neck circumference 21.1inches, macroglossia, and a Mallampati Class IV. He underwent a nocturnal polysomnogram to evaluate for sleep disordered breathing. Hypnogram revealed decreased sleep onset latency, increased REM latency, and decreased REM sleep 11.3% TST. The overall apnea-hypopnea index (AHI) was 107.5 events/hour sleep during the first 115 minutes of sleep meeting the criteria to initiate positive airway pressure (PAP). During the diagnostic portion of the study, his oxygen saturation nadir was 75%. He was trialed on continuous PAP settings of 9-15cmH2O which was unsuccessful controlling his OSA. Bilevel PAP was initiated with inspiratory PAP 19cmH2O and expiratory PAP 13cmH2O effectively treating his OSA. The patient developed second degree atrioventricular heart block throughout the study, most notably in phasic REM sleep and persisted during the titration, although with improvement once on appropriate PAP settings. Consequently, a 24-hour Holter ECG was recorded showing sinus rhythm with intermittent nocturnal second degree atrioventricular (Mobitz I) block with the longest pause of 2.5yu seconds. Cardiology decided to continue to monitor the patient since he is asymptomatic and the heart block most likely is related to his untreated OSA. Conclusion Many patients with sleep related bradyarrhythmias present with non-specific symptoms and may remain undiagnosed. Once diagnosed, many patient’s bradyarrhythmias resolve with adequate PAP therapy. Currently, the appropriate treatment of REM related bradyarrhythmias remains a topic of discussion.