Changes of heart rate and QT interval at high altitude in alpinists: Analysis by holter ambulatory electrocardiogram

Abstract

Summary:The purpose of this study is to record continuously electrocardiograms of alpinists during different activities practiced in mountaineering, compare heart rate and QT interval at high altitude with those at sea level, and compare alpinists with nonalpinists. Analysis was attempted on 14 alpinists (9 male, 5 female, ages 26-45) to determine changes in heart rate and QT interval using continuous ambulatory electrocardiograms recorded at sea level and high altitude. Between 1983 and 1984,9 of 14 alpinists (6 male, 3 female) were subjected to the study at high altitude, that is, at Mt. Kangchenjunga (Himalaya), Mt. Satopanth (Himalaya), and Mt. Jitudake (Butan), 4400 to 7800 m (mean 5710 m). The following were noted: (1) Heart rate at high altitude was significantly higher both in daytime and nighttime. The circadian rhythm of the heart rate disappeared at extremely high altitude in several alpinists. (2) A high correlation was noted between measured QT interval (QTm) and RR interval (r=0.81, p=0.005). Nighttime QT, at high altitude was prolonged in comparison with that of daytime so far as the RR interval remained the same. (3) At high altitude, the nighttime corrected QT interval (QT,) was also significantly prolonged in spite of shortened RR interval. The mechanism of QTc prolongation is not clear. Many factors may impact on the QT interval during mountaineering.

Electrocardiographic Changes During Exercise in Acute Hypoxia and Susceptibility to Severe High-Altitude Illnesses

“…Results are shown in Table 5. The decrease in the Sokolow index and T-wave amplitude in V 5 and V 6 in hypoxic conditions was correlated with desaturation at exercise. Moreover, trained status and low body mass index were correlated with a smaller hypoxia-induced Tables 6 and 7.…”

“…3 This activation results in tachycardia at rest and at a given level of exercise intensity. [3][4][5] In prolonged hypoxia, a desensitization of the adrenergic system, through a complex interaction of hypoxia with the G-proteincoupled cardiac receptors, leads to a decrease in resting and maximal heart rate (HR). 6 Contractile function, evaluated by echocardiography, is not altered up to the simulated altitude of 8000 m, at least at rest.…”

Hypoxic Challenge Testing (Fitness to Fly) in children with complex congenital heart disease

“…QTc was assessed as hypoxia prolongs cardiac repolarisation measured by QTc; for example, a small study of 11 healthy adults found that breathing 11% oxygen led to significant increases in QTc,18 and a study of nine mountaineers found significantly prolonged QTc when at high altitude (ranging 4400–7800 m) 19. However, a study in 101 adults with significant respiratory disease having a Hypoxic Challenge Testing showed that the QTc did not change during the test 20.…”

Effect of acute hypoxia on QTc interval in respiratory patients undergoing fitness to fly tests

“…Exposure to acute hypoxia (15% fractional inspired oxygen) is not associated with significant changes in cardiac QT c in patients with chronic respiratory disease, in contrast to the QT c prolongation seen in healthy subjects at altitude 2 4 5. The absence of response might be due to hypoxic preconditioning6 7 or drug effects upon autonomic efferent response (eg, salmeterol, ipratropium) or through other means (eg, renin-angiotensin system antagonists8).…”