Abstract
Byline: Soroosh Solhjoo, Johns Hopkins Univ Sch of Medicine, Baltimore, MD; Mark C Haigney, F. Edward HȨbert Sch of Medicine, Bethesda, MD; Trishul Siddharthan, Univ of Miami Miller Sch of Medicine, Miami, FL; Abigail L Koch, Univ of Miami Miller Sch of Medicine, Miami, FL; Ciprian M Crainiceanu, Johns Hopkins Bloomberg Sch of Public Health, Baltimore, MD; Naresh M Punjabi, Univ of Miami Miller Sch of Medicine, Miami, FL Introduction: Sleep-disordered breathing (SDB) is a common disorder in the general population that is associated with adverse cardiovascular events, such as sudden cardiac death, but the underlying mechanisms are unclear. Hypothesis: Ventricular repolarization instability is greater in those with severe SDB than those without SDB, independent of other risk factors. Methods: Among the participants of the Sleep Heart Health Study (SHHS), we identified those with SDB who had no diagnosed cardiovascular disease or other factors that could affect cardiac repolarization. Severe SDB was defined as having a respiratory disturbance index (RDI) > 33 events/hour (top 95%ile of the SHHS cohort). We also identified a group of participants matched to the severe SDB group on age, sex, BMI, and race and had RDI < 1.33 events/hour (bottom 25%ile; without SDB). Each group consisted of 61 (45 M and 16 F) participants. Oxygen saturation levels (SpO2) were used to measure hypoxemia burden as the percentage of sleep time with SpO2 < 90% (T90). Heart rate (HR), heart rate variability (SDNN), and QT variability index (QTVI, a measure of ventricular repolarization instability) were calculated from one-lead ECG recordings. Student's t-test was used to assess statistical associations. Results: The SDB group had a larger T90 than those without SDB (11.39 Ø 1.42% vs 1.32 Ø 0.61%, P < 0.001). Participants with SDB also had greater mean HR (P = 0.028), SDNN (P = 0.017), and QTVI (P = 0.027) than those without SDB. Based on a multivariable linear model that included hypoxemia burden, age, BMI, and smoking status, T90 was the only independent predictor of QTVI (P = 0.022). Conclusion: SDB is associated with higher HR, HRV, and QTVI, an indicator of increased instability in ventricular repolarization leading to increased risk for cardiac arrhythmias and sudden cardiac death. The severity of the destabilizing effect of SDB on ventricular repolarization appears to be modified by hypoxemia burden.