Risk of malignant arrhythmia in highlanders with high altitude pulmonary hypertension during wakefulness and sleep

Objective: High altitude pulmonary hypertension (HAPH) is a chronic altitude related illness associated with hypoxemia that may promote sympathetic excitation and cardiac arrhythmias. Therefore, we evaluated if the QT interval, a marker of malignant cardiac arrhythmia, is prolonged in highlanders with HAPH compared to healthy highlanders (HH) and lowlanders (LL) during wakefulness and sleep. Methods: We studied highlanders with HAPH and HH in Aksay, Kyrgyzstan, 3250m, and LL in Bishkek,760m (n=18 each group; matched for age, gender, body mass index). Heart rate, heart rate adjusted QT interval (QTc) and pulse oximetry were recorded during nocturnal polysomnography. Pulmonary artery pressure was estimated by echocardiography. Results: In highlanders with HAPH QTc during wakefulness was longer than in LL and increased further during sleep. QTc in HH was similar to that in HAPH had lower SpO 2 and more cyclic oxygen desaturations than HH and LL. Conclusions: Higher heart rate, lower SpO2 and prolonged QTc in highlanders with HAPH compared to HH and LL suggests that HAPH may predispose to malignant cardiac arrhythmia, particularly during sleep.