Electrocardiographic Changes During Exercise in Acute Hypoxia and Susceptibility to Severe High Altitude Illnesses | Journal Scan
Can electrocardiographic (ECG) changes during hypoxic exercise predict the development of severe high altitude sickness?
A total of 456 subjects performed a 20-minute hypoxia exercise test with continuous recording of ECG and physiological measurements before traveling above 4000 m.
Hypoxia did not induce any conduction disorder, arrhythmias, or change in QRS axis. The amplitude of the P wave in V1 was lower during hypoxia than in normoxia. Amplitudes of S-, R-, and T-wave, as well as the Sokolow index (undefined, presumably the Sokolow-Lyon index, the sum of S-wave voltages in V1, and the greater of V5 or V6) decreased during hypoxia. During hypoxia, the amplitude of the ST-segment decreased in II and V6 and increased in V1; ST slope rose in V5 and V6, while the J point was lower in II, V5 and V6. Multivariate regression of hypoxic/normoxic ratios of electrophysiologic parameters and clinical characteristics showed a correlation between the decrease in the Sokolow index and the T-wave amplitudes in V5 and V6 with desaturation at exercise. Trained status and low body mass index were associated with a smaller decrease in the T-wave amplitude in V5 and V6. Comparison of ECG changes between subjects suffering or not suffering from severe high altitude illnesses failed to show any difference.
During a hypoxia exercise test, a dose-dependent hypoxia-induced decrease in the amplitude of P, QRS, and T waves was observed. However, no standard ECG characteristic predicted the risk of developing severe high altitude illnesses. The authors concluded that further studies are required to clarify the cause of the observed electrical changes and their potential predictive role in clinical cardiac events.
During exercise while breathing an inspired oxygen content of only 11.5% (equivalent to exercise at 4800 m altitude), there are changes in the ECG. These do not predict the clinical advent of severe high altitude illnesses.
Keywords: Altitude, Altitude Sickness, Arrhythmias, Cardiac, Body Mass Index, Electrocardiography, Exercise Test, Heart Conduction System, Oxygen, Rosa
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