Sleep Circulation Time from Pulse Oximetry and Polysomnography: Predictive Value in Patients with Heart Failure with Reduced Ejection Fraction

Background: This study evaluated the use of circulation time (Tcirc) calculated from polysomnogram (PSG) with pulse oximetry to identify poor cardiac function with low left ventricular ejection fraction (EF). Methods: Subjects over 18 years with sleep apnea (apnea-hypopnea index (AHI) >5/hr) diagnosed by PSG who had transthoracic echocardiography (TTE) within 1 year of PSG were included in this retrospective study. Tcirc of each sleep stage (N2, N3, and REM) were measured and averaged and EF was recorded. Statistical analysis was done using Wilcoxon rank sum test, logistic regression and Youden index. Results: There were 89 sub-jects who met inclusion criteria, 14 with EF ≤45% (Group A) and 75 with EF ≥ 50% (Group B). All 14 Group A subjects had prolonged overall Tcirc with a median time of 27.8 seconds (range 14.1 - 39.6 sec), compared to Group B subjects with median Tcirc of 23.5 seconds (range 14.3 – 37.6 sec), p = 0.311. The op-timal cut-point for overall sleep Tcirc with moderate discrimination (AUC = 0.6) was 28.6 sec. Those with to-tal sleep Tcirc > 28.6 sec were 2.5 x more likely to have low EF with OR =2.56 (95% CI, 0.55-11.16). Con-clusions: In sleep apnea patients, total sleep Tcirc > 28.6 seconds is associated with low ejection fraction with specificity = 0.78.