1164 Sleep Conversion of Atrial Bigeminy to Sinus Rhythm and Using Oximetry for Heart Rate

Abstract Introduction Patient presented for PSG with initial wake, N1 period showing bigeminy on ECG that converted to sinus rhythm during N2, N3, and REM. SR persisted despite periods of hypoxemia until the end of the study. Furthermore, the heart rate, as generated using oximetry and Polysmith, would not recognize the bigeminal beat underestimating heart rate by half. Report of case(s) A middle-aged female was referred to Sleep Medicine for difficulty falling asleep, staying asleep, snoring, witnessed apneas. Epworth Sleepiness Scale score (ESS) was 9/24. PSG was performed using Polysmith software. Epochs showed: Wake: bigeminy on EKG and corresponding plethysmography with one large peak (the visible P wave) and one small peak (where P is hidden in the preceding T wave). Only the first P wave is used to generate heart rate. A clear transition can be seen within a single epoch in N1: EKG changes from bigeminy to SR with corresponding plethysmography showing two peaks (as in wake) that convert to a single peak in sinus rhythm. Heart rate is then correctly accounted for midway through the epoch. N2 and REM: SR, single peak on plethysmography, accurate heart rate continue. ECG approximately one week prior to PSG showed sinus bradycardia. Conclusion While there has been no mention of atrial bigeminy and sleep in cardiovascular or sleep medicine literature, one hypothetical reason for its resolution in sleep is the reduction of sympathetic and cholinergic tone. As for the spurious heart rate on oximetry, software did not recognize the smaller plethysmography peak, underestimating heart rate by half during periods of bigeminy. Atrial bigeminy is associated with heart failure, alcohol, electrolyte derangement, caffeine and usually left untreated in asymptomatic patients. Patients with symptoms, such as palpitations, dizziness, near syncope, or syncope can be treated with β-blockers, calcium-channel blockers, or catheter ablation. While this patient did not complain of symptoms, recent labs did show hypomagnesemia and hypokalemia. Support (if any)