Changes in Left Ventricular Function Assessed by 3D Echocardiography During Severe Central Hypovolemia in Healthy Humans.

Purpose: Central hypovolemia is considered to lead to a compensatory increase in cardiac contractility. From a physiological perspective, left ventricular (LV) twisting motion, which plays an important role in maintaining cardiac output, should be enhanced during central hypovolemia, but previous studies have shown inconsistent findings. Using 3D echocardiography, we tested the hypothesis that the LV twisting and untwisting motion would be enhanced during severe central hypovolemia.

Methods: Thirteen healthy men (25 ± 5 years old) underwent the maximal lower body negative pressure (LBNP) protocol; graded increase in LBNP loads up to presyncope. We evaluated the basic hemodynamics and LV function with 3D and Doppler echocardiography at each stage of LBNP. Indices were compared among baseline, half maximal LBNP (LBNP1/2max), and one stage before the presyncope (LBNPpre-max) to consider individual differences in orthostatic tolerance.

Results: In response to LBNP, ejection fraction (baseline: 62 ± 3, LBNP1/2max: 55 ± 5, LBNPpre-max: 43% ± 9%, mean ± SD, p < 0.01, ANOVA), global longitudinal strain (-20.5 ± 2.8, -17.6 ± 2.7, -13.6% ± 4.7%, p < 0.01), and global circumferential strain (-31.2 ± 3.7, -26.8 ± 3.3, -19.4% ± 5.3%, p < 0.01) were weakened. Twist (15.2 ± 5.1, 14.5 ± 5.4, 20.9° ± 7.7°, p = 0.012) and peak untwisting rate (-138 ± 42, -164 ± 50, -245°/cm ± 88°/cm, p < 0.01) were strengthened at the LBNPpre-max. e' (14.1 ± 2.0, 11.1 ± 1.5, 8.2° ± 2.2 cm/s, p < 0.01) decreased in response to LBNP, while E/e' (5.8 ± 0.8, 5.4 ± 1.0, 7.8 ± 2.3, p < 0.01) increased at LBNPpre-max.

Conclusion: The present findings indicate that LV twisting motion is enhanced during severe central hypovolemia. On the other hand, conventional echocardiographic indices appeared to deteriorate. Intriguingly, an index of LV filling (E/e') was paradoxically enhanced during severe central hypovolemia.