Effect of strenuous physical activitat at high-altitude on cardiac structure and function and changes after return to lower altitude

AIM:To assess the effect of high-altitude strenuous physical activity on cardiac structure and function and to explore the changes after return to a lower altitude. METHODS: Ninety-six officers and soldiers leaving low-altitude areas (1 500 m) and moving directly to high-altitude areas (3 700 m) to undertake strenuous physical activities were enrolled in the study. The subjects (all male, aged 18-35 years) were divided into three groups according to the symptomatic scores of acute high-altitude reaction (AHAR): non-AHAR (group B, n=25), mild to moderate AHAR (group C, n=47) and severe AHAR (group D, n=24). Mean pulmonary arterial pressure (mPAP), right ventricular internal dimension (RVID), outflow tract of right ventricle (RVOT), left ventricular internal dimension (LVID), cardiac muscle work index (Tei index), and left ventricular ejection fraction (LVEF) were measured by echocardiograph after 50 days at high altitude area and 12 h, 15 days and 30 days after return to lower altitude (1500 m). Fifty healthy volunteers (group A) at 1500 m altitude served as control. RESULTS: Levels of mPAP, RVID, RVOT, RVID/LVID ratio and Tei index were higher and LVEF was lower in group B than those in group A (all P<0.01). The value of all the parameters further changed with increasing severity of AHAR, and significant differences were found between groups C and D (all P<0.01). After 50 days at an altitude of 3700 m, mPAP was positively correlated with RVID, RVOT, RVID/LVID ratio and Tei index (r=0.613, 0.647, 0.585, 0.647, respectively, all P<0.01), but negatively correlated with LVEF (r=-0.620, P<0.01). Compared with those in group A, levels of mPAP, RVID, RVOT, RVID/LVID ratio and Tei index significantly increased, whereas LVEF significantly decreased in the 96 officers and soldiers after 50 days at an altitude of 3 700 m (all P<0.01). Levels of mPAP, RVID, RVOT, RVID/LVID ratio and Tei index significantly decreased but LVEF significantly increased 12 h and 15 days after return to lower altitude, with significant difference between 12 h and 15 days (both P<0.01). The levels of mPAP, Tei index and LVEF 15 days after return to lower altitude showed no significant difference compared with those in group A (all P>0.05) and the levels of RVID, RVOT and RVID/LVID ratio 30 days after return to a lower altitude showed no significant difference compared with those of group A (all P>0.05). CONCLUSION: In the case of strenuous physical work following direct migration from a lower altitude (1500 m) to a higher altitude (3700 m), the more serious AHAR becomes, the more obvious right ventricular enlargement and decrease of left ventricular functions would be. These changes would be alleviated 12 h after returning to a lower altitude. Left ventricular function would be restored to normal 15 days after returning to lower altitude and right ventricular enlargement would restore to normal 30 days after returning to lower altitude.