Altered Left Ventricular Geometry and Torsional Mechanics in High Altitude-Induced Pulmonary Hypertension: A Three-Dimensional Echocardiographic Study.

BACKGROUND: Changes in left ventricular (LV) torsion have been related to LV geometry in patients with concomitant long-standing myocardial disease or pulmonary hypertension (PH). We evaluated the effect of acute high altitude-induced isolated PH on LV geometry, volumes, systolic function, and torsional mechanics.

METHODS: Twenty-three volunteers were prospectively studied at low altitude and after the second (D3) and third night (D4) at high altitude (4,559 m). LV ejection fraction, multidirectional strains and torsion, LV volumes, sphericity, and eccentricity were derived by speckle-tracking on three-dimensional echocardiographic data sets. Pulmonary pressure was estimated from the transtricuspid pressure gradient (TRPG), LV preload from end-diastolic LV volume, and transmitral over mitral annular E velocity (E/e').

RESULTS: At high altitude, oxygen saturation decreased by 15%-20%, heart rate and cardiac index increased by 15%-20%, and TRPG increased from 21 ± 2 to 37 ± 9 mm Hg (P < .01). LV volumes, preload, ejection fraction, multidirectional strains, and sphericity remained unaffected, but diastolic (1.04 ± 0.07 to 1.09 ± 0.09 on D3/D4, P < .05) and systolic (1.00 ± 0.06 to 1.08 ± 0.1 [D3] and 1.06 ± 0.07 [D4], P < .05) eccentricity slightly increased, indicating mild septal flattening. LV torsion decreased from 2.14 ± 0.85 to 1.34 ± 0.68 (P < .05) and 1.65 ± 0.54 (P = .08) degrees/cm on D3/D4, respectively. Changes in torsion showed a weak inverse relationship to changes in systolic (r = -0.369, P = .013) and diastolic (r = -0.329, P = .032) eccentricity but not to changes in TRPG, heart rate or preload.

CONCLUSIONS: High-altitude exposure was associated with mild septal flattening of the LV and reduced ventricular torsion at unchanged global LV function and preload, suggesting a relation between LV geometry and torsional mechanics.