Hypoxemic load in sleep apnea is associated with acute changes in T-wave amplitude

Obstructive sleep apnea (OSA) imposes significant stress on the cardiovascular system and the heart. While long-term cardiac effects are understood, the immediate impact of hypoxemia on the heart’s electrophysiology lacks understanding. Our study aims to explore desaturation severity on cardiovascular repolarization.We retrospectively analyzed electrocardiograms from full diagnostic polysomnographies from 492 patients with suspected OSA. The analyses were conducted before, during, and after 9137 nocturnal apnea or hypopnea-related desaturations. The mean and standard deviation of T-wave amplitude change from the baseline level to the level during and after desaturations (ΔTamp_mean, ΔTamp_SD) was calculated. To investigate the modulatory effects of desaturation severity, the data were divided into subgroups based on the duration (10s≤Tdes<20 s, 20s≤Tdes<30 s, 30s≤Tdes<45 s, and Tdes≥45 s) and magnitude of blood oxygen saturation drop (3%≤ΔSpO2<4.5%, 4.5%≤ΔSpO2<6%, 6%≤ΔSpO2<7.5%, and ΔSpO2≥7.5%) for men and woman.Desaturations caused significant (p<0.01) changes in ΔTamp_meanduring and after desaturations. In men, the median ΔTamp_meanduring and after deep (ΔSpO2≥7.5%) desaturations were 21 µV and 24 µV, respectively. In women, the median ΔTamp_meanin deep desaturations was 15 µV during and 21 µV after desaturations. Similarly, the ΔTamp_SDincreased during and after deep desaturations. In regression analysis, the desaturation depth was an independent predictor for ventricular repolarization instability.We found an association between the severity of nocturnal desaturations and cardiac repolarization instability. These findings hold particular importance, as repolarization instability has been linked with cardiovascular morbidity and could potentially serve as a trigger for arrhythmias and sudden cardiac death.