The Study Of Relationship Between The Change Of Ventricular Repolarization Phase And Acute Mountain Sickness

BackgroundChina has the largest high-altitude area (approximately26.8%of China’s total area)and the highest altitude (2.572×106km2is3000m above sea level or higher). With thedevelopment of society and the implementation of the western development, more and morepeople enter plateau area. About2million tourists travel by train or plane to high altitudesannually in China. In addition, there are more than100million such tourists worldwide. Butthe plateau environment has its own characteristics. Low atmospheric pressure and hypoxiaare the most important features.Acute high-altitude exposure can cause adverse effects on the body even to threateningthe life. Especially acute high-altitude exposure have enormous effects on thecardiovascular system. On the one hand, compensatory responses of the cardiovascularsystem help the body to adapt to high altitude environment. On the other hand,overcompensation responses of the cardiovascular system may cause impairment to thecardiovascular system, even resulting death. Epidemiological studies have indicated thatsudden cardiac death (SCD) is responsible for the death of up to30%of hikers and52%ofdownhill skiers at high altitude. In addition, epidemiological studies have found thatpatients with cardiovascular diseases are liable to appear SCD at altitude.Multiple studies have demonstrated that the extensions of QTc interval and TpTecinterval are associated with SCD and ventricular arrhythmia. Acute mountain sickness(AMS) is the most common disease after acute high-altitude exposure. Previous studieshave demonstrated that autonomic dysfunction is one of the important features of AMS.Clinical drug researches have demonstrated that beta and alpha receptor agonists caninfluence ventricular myocardial repolarization duration.Our study aimed to investigate the influence of high-altitude exposure on ventricularrepolarization time in healthy young men and to study the relationship between ventricularrepolarization time and AMS. Materials and methodsThe subjects in this study were92healthy young men who had lived at an altitude of3700m for1year and143healthy young male lowlanders rapidly ascending to highaltitude by air within two hours. In24hours the test were performed withsphygmomanometer；electrocardiogram in healthy young males and subjects were scoredaccordingly to the Lake Louise AMS scoring system by a self-reported questionnairerelated to the presence and severity of symptoms. AMS was defined by a score≧3and thesymptom of headache was required.Then143healthy young males live in the high altitued(4400m),after one week acclimatization and after50days acclimatization the test wereperformed with sphygmomanometer, electrocardiogram in healthy young males.Results1. After acute exposure to3700m,84of the143participants (58.74%) developedAMS, as indicated by Louise score≧3(range3-9). Acute high-altitude exposure headacheand dizziness were the most frequent symptoms (71.32%and74.83%, respectively),followed symtoms of gastrointestinal symptoms (18.88%), fatigue (59.44%) and difficultyin sleeping (52.44%).2. Compared with500m,heart rate (HR), systolic blood pressure (SBP), diastolic bloodpressure (DBP), QTc interval and TpTec interval significantly increased after acutehigh-altitude exposure (P<0.05). QT interval and TpTe interval significantly decreased(P<0.05). PR interval and QRS interval did not change significantly (P>0.05). Withacclimatization of the body, the above changes gradually returned to plain level.3. Compared with500m, after one year acclimatization at3700m, QT interval, TpTeinterval, QTc interval and TpTec interval were not significantly different (p>0.05).Compared with initial exposure to3700m, after one year acclimatization at3700m, QTinterval and TpTe interval significantly increased (p<0.05), while QTc interval and TpTecinterval significantly decreased (P<0.05).4. TpTe interval and QT interval in non-AMS participants were longer than those inAMS participants (p<0.05). Epinephrine (EPI), norepinephrine (NE) in AMS participantswere higher than those in non-AMS participants (p<0.05), TpTec interval and QTc intervalin AMS participants were longer than those in non-AMS participants (p<0.05).5. Simple regression analysis showed that EPI and NE correlated posively with QTc and TpTec interval, while EPI and NE correlated negatively with QT and TpTe interval.6. With acclimatization to altitude, prolonging ventricular repolarization timegradually returned to plain level.Conclusion1. After rapid ascent to high altitude, ventricular repolarization time decreased, whilethe heart rate-corrected ventricular repolarization time increased in healthy youngmen.These changes retured to plain level after acclimatization to high altitude.2. Ventricular repolarization time in non-AMS peoples was longer than in AMSpatients. But the heart rate-corrected ventricular repolarization time in AMS patients waslonger than in non-AMS.3. The heart rate-corrected ventricular repolarization time was positively correlatedwith catecholamine, while ventricular repolarization time was negatively correlated withcatecholamine. TpTec interval prolongation suggest that sympathetic excitement increasedventricular transmural dispersion of repolarization...