Risk Factors Screening Of Pulmonary Hypertension And Its Impact On Right Ventricular Function After Exposure To High Altitude

Background and ObjectivesHigh altitude exposure can not only cause elevation of pulmonary artery pressure, butalso decrease physical activity, which depends on manner of arrive in high altitude and howlong after exposure to high altitude. Some staff may suffer from pulmonary hypertension（PH）or high altitude pulmonary edema(HAPE) upon acute high altitude exposure; Someone may suffer from right heart diseases upon chronic high altitude exposure.The previous studies have shown that only some staff suffered from PH after exposureto high altitude, and there were a considerable variation between them. Therefore, thestudies on risk factors of pulmonary hypertension after exposure to high altitude becomesvery important. There have been many studies on the risk factors of PH in rencent years.The results were inconsistent, which may be related to different studies background ordesign scheme. In oder to clarify the risk factors of PH caused by exposure to high altitude,we collect demographic data, clinical information and analysis risk factors of PH by carringout cohort study.In addition, PH often leads to changes in right ventricular(RV) structure and function.However, the RV owns a complex geometry chamber and special anatomical structure,which makes it difficult to precisely assess its function. Currently, there is a lack oflarge-scale, multi-center prospective cohort study, uniform testing standards on theevaluation of RV function, as well as evidence based medicine about how to conductclinical intervention. The relationship between pulmonary artery pressure and RV functionright under exposure to high altitude has been unclear. We carried out clinical trials researchto explore the relationship between PH and RV function and its impact on RV function uponhigh altitude exposure.Study designThe study consists of two parts. Firstly, we selected552cases of non-native Tibetan plains healthy young men assubjects, which spent2hours reached above sea level3700metres region from plain byplane rapidly from September in2011to September in2013. We collected demographicdata which were height，weight，age，high altitude exposure history, smoking, alcoholconsumption, measured oxygen saturation(SaO2), blood pressure, heart rate, pulmonaryartery systolic pressure measured by color doppler echocardiography and analysised riskfactors of PH by logistic regression finally.Secondly, we selected114cases of non-native Tibetan healthy young men as thecontrol group,91cases of non-native Tibetan healthy young men who spent2hours arrivedin3700m region from Chengdu by air as a acute high altitude exposure group,94cases ofnon-native Tibetan healthy young men who settled in3700m region at least one year as achronic high altitude exposure group. We collected demographic data, clinical information,examined subjects by color doppler echocardiography. We divided acute and chronic highaltitude exposure group into normal group, the borderline pulmonary hypertension（BPH）group and PH group according to mean pulmonary artery pressure. We analysised the databy one-way ANOVA and linear regression in oder to explore the relationship between PHand RV function.ResμltsThe first part1.Non-native Tibetan healthy young men who suffered from acute high altitudeexposure, whose incidence of tricuspid regurgitation was71.38%(394/552)，prevalence ofPH was23.10%(91/394), smoking ratio was73.74%(264/358, including once and currentsmokers), alcohol consumption ratio was66.76%(239/358, including the once and currentdrinking), and high altitude exposure history ratio was22.35%(80/358).2.The SaO2of PASP elevated group significantly decreased from89.09±2.65%to86.10±3.44%compared with the control group(P<0.01). There were no differrencesbetween two groups about smoking, alcohol consumption, high altitude exposure history,body mass index (BMI)21.48±2.34kg/m2versus to21.55±2.21kg/m2, age22.45±4.08years versus to22.78±4.00years, systolic blood pressure(SBP)118.70±10.28mmHgversus to118.21±11.17mmHg, diastolic blood pressure(DBP)78.68±9.17mmHg versusto78.15±9.87mmHg and heart rate(HR)85.66±15.40beats/min versus to85.41±12.61 beats/min (P>0.05).3. The lower SaO2was a risk factor of PH by logistic regression analysis, and the oddsratio(OR) was0.711, and the95%confidence interval(CI) was from0.647to0.782.The second part1.The subjects’HR, blood pressure(BP), left ventricular ejection fraction(LVEF),cardiac output(CO), mean pulmonary arterial pressure(mPAP), RV tei index(RVtei)increased significantly (P<0.05), SaO2, tricuspid E peak velocity(TEV), tricuspid E/Aratio(TE/A) decreased significantly(P<0.05) upon acute high altitude exposure. Withprolonged high altitude exposure, the subjects’ SaO2, TE/A increased significantly (P <0.05),while CO, mPAP, RV tei, tricuspid A peak velocity (TAV) decreased significantly (P <0.05).2.There was a significant positive correlation between the RV function and pulmonaryartery pressure in acute and chronic high altitude exposure group (r=0.512,r=0.409,P<0.001).3.The proportion of each subgroup were39.56%(mPAP<20mmHg)，28.57%(mPAP20-25mmHg),31.87%(mPAP≥25mmHg) in acute high altitude exposure group; Theproportion of each subgroup were52.13%(mPAP<20mmHg),37.23%(mPAP20-25mmHg),10.64%(mPAP≥25mmHg) in chronic high altitude exposure group. The proportions of twogroups were significantly different(P<0.01).4.The subgroup′s RVtei was0.24±0.05(mPAP normal group),0.27±0.04(BPH group)0.31±0.07(PH group) in acute high altitude exposure group, and there were significantdifferences between the three subgroup by pairwise comparison (P<0.01); The subgroup′sRVtei was0.20±0.04(mPAP normal group),0.23±0.04(BPH group),0.29±0.03(PH group)in acute high altitude exposure group, and there were significant differences between thethree subgroup by pairwise comparison (P<0.01).Conclusion1.The low SaO2is an important risk factor of PH after non-native Tibetan healthyyoung men suffering from acute high altitude exposure.2.The changes on RV function is related to pulmonary arterial pressure at theconditions of high altitude exposure.3.Borderline pulmonary hypertension resulted from exposure to high altitude onlycaused changes on right ventricular function，did not effect on the structure of the right heart whether acute or chronic altitude exposure to high altitude exposure conditions.