| Background and Objective:Chronic high altitude disease(CHAD)is an idiopathic disease involving multisystem organs due to maladaptation to the chronic hypoxic in high altitude population.The mechanisms of cardiac injury in CHAD,which often involve a variety of pathophysiological changes,are complex.Myocardial edema(ME)and myocardial fibrosis(MF)are the common pathological manifestation of different cardiovascular disease,and further lead to cardiac remodeling.CHAD patients usually show a different degree of ventricular remodeling due to synergy between hypobaric hypoxia and cardiovascular risk factors.In addition,high altitude pulmonary hypertension(HAPH)is one of classification of CHAD,which clinical manifestations are similar to those of idiopathic pulmonary arterial hypertension(IPAH).Then,it is important to make an accurate diagnosis on account of difference in progression and treatment.Therefore,this study prospectively recruited patients with CHAD underwent cardiac magnetic resonance(CMR)examinations to achieve the following purposes:1)To prospectively assess ventricular structure,function and myocardial strain in patients with CHAD,and further to explore possible risk factors related to ventricular remodeling.2)To evaluate left ventricular myocardial injury in patients with CHAD using native T1 mapping and T2 mapping combined with myocardial strain obtained from tissue tracking,and further to explore the relationship between left ventricular myocardial impairment and ventricular function and strain.3)To explore the value of CMR in identifying HAPH from IP AH based on the differences between these two disease in ventricular structure,function and myocardial strain parameters.Materials and Methods:From November 2019 to January 2021,this study prospectively recruited patients with CHAD in our hospital.Accordingly,age-and gender-matched high altitude(HA)healthy controls and sea level(SL)healthy controls were prospectively enrolled in our study.All subjects were underwent CMR examinations(Skyra,Seimens medical solutions,Erlangen,Germany).At the same time,the study included IPAH patients from the hospital database for analysis.The scanning sequences included:Cardiac cine sequence,axial black blood T2 sequence,native T1 mapping and T2 mapping sequence.CMR image analysis was performed on cardiac postprocessing software(cvi42).1)In the first part of this study,30 patients with CHAD,14 HA and 12 SL healthy controls were prospectively enrolled in.The left and right ventricular structural and functional parameters among three groups were measured and compared.The longitudinal peak strain(LPS),circumferential peak strain(CPS)and radial peak strain(RPS)of left and right ventricles obtained from CMR tissue tracking were compared among three groups.Binary logistics regression was used to evaluate the factors related to ventricular remodeling in patients with chronic high altitude disease.2)In the second part of this study,22 patients with CHAD,14 HA and 11 SL healthy controls were prospectively recruited.All the parameters from CMR,including native T1 values,T2 values and myocardial strain parameters were measured and compared.Bivariate correlation was used to analyze the relationship between the native T1 and T2 values and ventricular function and myocardial strain.3)In the third part of this study,14 patients with HAPH and 14 patients with idiopathic PAH were prospectively enrolled.The ventricular structural,functional parameters,as well as the global and regional LPS,CPS and RPS derived from CMR cine imaging between two groups were measured and compared.Results:The RVEF(39.51±13.41%,57.06±6.80%and 51.00±3.16,respectively)and LVEF(51.36±13.60%,65.62±4.75%and 61.26±2.43%,respectively)in patients with CHAD were lower than those in healthy controls,and those of HA healthy controls were the largest among three groups(all p<0.05).47%(14/30)of patients with CHAD were identified as having RVD according to the RVEF<40%as the threshold.The main pulmonary artery diameter in the patients with CHAD was larger than that in two control groups(p<0.05).Furthermore,the structural parameters of left and right ventricles in the patients with CHAD were significantly different from those in control groups.The LVMI and LVESV in patients with CHAD were significantly higher than those in two control groups,while LVEDV was larger than that in HA group(p<0.05).There was significantly difference between HA and SL groups in LVESV(p<0.05).The global LPS of RV in patients with CHAD was lower than that in two control groups(-8.68±5.44%,-13.07±3.52%and-12.90±3.60%,respectively;p<0.05),as well as the global RPS was lower than that in HA groups(p<0.05).For left ventricular myocardial strain,the global CPS in patients with CHAD(16.27±5.29%,-21.58±2.91%and-19.36±1.62%,respectively;p<0.05)was decreased compared with healthy controls,while global RPS and LPS were lower than those in HA group(p<0.05).Left and right ventricular ejection fractions were correlated with global and regional myocardial strain parameters to different extend.There were correlation between left and right ventricular function indexes in patients with CHAD(all p<0.05).Binary logistic regression found that gender is the factors related to RVH(OR=0.060,p=0.015)and LVD(OR=7.429,p=0.029),while TP(OR=1.249,p=0.019)was associated with RVD.In addition,LVD was also correlated with the presence of high altitude polycythemia(HAPC)(OR=5.500,p=0.033)and blood oxygen saturation(OR=1.637,p=0.041).The global native T1 value of patients with chronic high altitude disease was increased and the highest among three groups(p<0.05).There was no significant difference in native T1 of the apical segment among three groups(p=0.055).The T2 value of the myocardial basal segment in patients with CHAD was higher than that in two control groups(p<0.05),but there are no significant differences between HA and SL groups.In addition,there was a slightly negative correlation between LVEF and the myocardial native T1 value of the 3rd segment(r=-.50,p=0.019).Moreover,there was a negative correlation between RVEF and the native T1 value of basal segment(r=-0.43,p=0.045).Compared with HAPH patients,the main pulmonary artery diameter was significantly increased in idiopathic PAH patients(34.64±5.94mm vs.26.52±4.93mm,p=0.001),while no significant difference was observed in right ventricular outflow tract(p=0.099).There were no significant difference in RAESA,RAEDA,RVEDTD,RVESTD,RALRD and RAAPD between two groups(p>0.05).However,the tricuspid annular systolic forward displacement(TAPSE)in idiopathic PAH patients was significantly lower than that in HAPH patients(13.78±4.17mm vs.17.88±5.77mm,p<0.05).In addition,a significantly lower RV ejection fraction was observed in patients with idiopathic PAH than that in patients with HAPH(43.26±11.96%vs.31.95±11.71%,p<0.05).Furthermore,the proportion of RVD in patients with idiopathic PAH was approximately twice as common as this in patients with HAPH(71%vs.36%).There was a significant difference in RVESV between these two groups(p<0.05).Moreover,there were no significant differences in left ventricular function parameters between two groups(all p<0.05).Nevertheless,the LV global longitudinal strain(32.45±11.72%vs.28.74±5.73%),together with longitudinal strain of basal segment(-9.15±2.90%vs.-5.85±4.52%)in HAPH patients,were significantly higher than those in idiopathic PAH patients(all p<0.05).Conclusion:In patients with chronic high altitude disease,RV function was impaired due to chronic hypoxia and associated with the deterioration of LV function.Nearly half of the patients with chronic high altitude disease have right ventricular dysfunction.The multiple cardiac magnetic resonance sequence demonstrated diffuse myocardial fibrosis existed in patients with CHAD,accompanied by segmental myocardial edema.Hypoxia and hypoxia induced right ventricular injury together contributed to myocardial fibrosis,which is related to the left ventricular strain and function impairment.The patient with HAPH show a mild or moderate pulmonary hypertension with a better RV function,while idiopathic PAH is more likely to cause left ventricular longitudinal strain impairment suggesting the more severe left ventricular involvement.Furthermore,increased oxyhemoglobin saturation and decreased erythrocytes might mitigate against cardiovascular disease in patients with CHAD. |
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