Electrocardiographic Changes During Exercise in Acute Hypoxia and Susceptibility to Severe High-Altitude Illnesses. Issue 9 (3rd March 2015)

• Record Type: Journal Article
• Authors: Coustet, Baptiste; Lhuissier, François J.; Vincent, Renaud; Richalet, Jean-Paul
• Is Part Of: Circulation. Volume 131:Issue 9(2015)
• Publication Date: 2015-03-03
• Subjects: Blood -- Circulation -- Periodicals; Cardiovascular system -- Periodicals; Cardiology -- Periodicals; Heart -- Diseases -- Periodicals; Blood Circulation; Cardiovascular System; Vascular Diseases; 616.1
• DOI: 10.1161/CIRCULATIONAHA.114.013144
• Languages: English
• ISSNs: 0009-7322

Abstract

<abstract> <title> <x xml:space="preserve">Abstract</x> </title> <sec> <title>Background—</title> <p>The goals of this study were to compare ECG at moderate exercise in normoxia and hypoxia at the same heart rate, to provide evidence of independent predictors of hypoxia-induced ECG changes, and to evaluate ECG risk factors of severe high-altitude illness.</p> </sec> <sec> <title>Methods and Results—</title> <p>A total of 456 subjects performed a 20-minute hypoxia exercise test with continuous recording of ECG and physiological measurements before a sojourn above 4000 m. Hypoxia did not induce any conduction disorder, arrhythmias, or change in QRS axis. The amplitude of the P wave in V<sub>1</sub> was lower in hypoxia than in normoxia. The amplitudes of the R, S, and T waves and the Sokolow index decreased in hypoxia. Under hypoxia, the amplitude of the ST segment decreased in II and V<sub>6</sub> and increased in V<sub>1</sub>, the ST slope rose in V<sub>5</sub> and V<sub>6</sub>, and the J point was lower in II, V<sub>5</sub>, and V<sub>6</sub>. Multivariate regression of hypoxic/normoxic ratios of electrophysiological parameters and clinical characteristics showed a correlation between the decrease in Sokolow index and T-wave amplitude in V<sub>5</sub> with desaturation at exercise. Trained status and low body mass index were associated with a smaller decrease in T-wave amplitude in V<sub>5</sub> and V<sub>6</sub>. Comparison of ECG between subjects suffering or not suffering from severe high-altitude illness failed to show any difference.</p> </sec> <sec> <title>Conclusions—</title> <p>During a hypoxia exercise test, a dose-dependent hypoxia-induced decrease in the amplitude of the P/QRS/T waves was observed. No standard ECG characteristic predicted the risk of developing severe high-altitude illness. Further studies are required to clarify the cause of these electric changes and their potential predictive role in cardiac events.</p> </sec> </abstract>