Changes in structure and function of the human left ventricle after acclimatization to high altitude

Summary

To analyse the role of changes in structure and function of the left ventricle in determining cardiac function at rest and during exercise, several two-dimensional and Doppler echocardiographic measurements were performed on 11 healthy subjects immediately before an Himalayan expedition (Nun, 7135 m), during acclimatization (3 weeks) and 14 days after the return. At rest decreases were found in cardiac index (CI) (3.23 l · min⁻¹ · m⁻², SD 0.4 vs 3.82 l · min⁻¹ · m⁻², SD 0.58,P < 0.01), left ventricular mass (55.3 g · m⁻², SD 9.4 vs 65.2 g · m⁻², SD 13.5,P < 0.005) and left ventricular end-diastolic volume (LVEDV) (53.9 ml · m⁻², SD 6.9 vs 64.8 ml · m⁻², SD 9.1,P < 0.001) after acclimatization; by contrast the coefficient of peak arterial pressure to left ventricular end-systolic volume (PAP/ESV) (7.8, SD 1.6 vs 6.0, SD 1.8,P < 0.005) and mean wall stress [286 kdyn · cm⁻², SD 31 vs 250 kdy · cm⁻², SD 21 (2.86 N · cm⁻², SD 0.31 vs 2.50 N · cm⁻², SD 0.21),P < 0.005] increased. After return to sea level, low values of CI and mass persisted despite a return to normal of LVEDV and preload. A reduction of PAP/ESV was also observed. At peak exercise, PAP/ESV (8.7, SD 2.4 vs 12.8, SD 2.0,P < 0.0025), CI (9.8 l · min⁻¹ m⁻², SD 2.5 vs 11.61 · min⁻¹ · m⁻², SD 1.6,P < 0.05) and the ejection fraction (69%, SD 6 vs 76%, SD 4,P < 0.05) were lower after return to sea level than before departure. The depressed left ventricular performance after prolonged exposure to hypoxia may be related to changes in structure and function including reduction in preload, loss of myocardial mass and depression of inotropic state.