Supine position enhanced both long-axis shortening (15.1 vs 9.3 mm, P<0.001) and short-axis shortening (16.3 vs 12.7 mm, P<0.001) compared to the upright position in healthy subjects.
Observational (n=10)
Does supine position compared to upright position affect left ventricular long- and short-axis shortening in healthy subjects?
Supine posture increases both long- and short-axis left ventricular shortening compared to upright posture, likely via Starling mechanisms.
Absolute Event Rate: 15.1% vs 9.3%
p-value: p=< 0.001
End-diastolic volume and left ventricular stroke volume are increased in the supine compared with upright position, but the contribution of long-axis (LAS) and short-axis shortening (SAS) to these changes with change in posture has not been established. We examined long- and short-axis motion and dimensions with echocardiography in 10 healthy subjects in the upright and supine position. Long-axis length at end diastole was almost identical, whereas the diastolic short-axis diameter was increased in the supine position. At end systole, there was a decreased long-axis length and increased short-axis length in the supine vs. upright position. Both LAS and SAS were enhanced in supine vs. upright positions LAS: 9.3 +/- 2.2 vs. 15.1 +/- 3.1 mm (P < 0.001); SAS: 12.7 +/- 3.2 vs. 16.3 +/- 2.8 mm (P < 0.001), presumably via Starling mechanisms. LAS increased more in the lateral part of the mitral annulus than in the septal part 7.7 +/- 2.6 vs. 4.0 +/- 2.8 mm (P < 0.006), which implies that the more spherical form, in the supine position, induces more stretch at the lateral free wall than in the ventricular septum. These findings support the notion that Starling mechanisms affect systolic LAS.
Sundblad et al. (Tue,) conducted a observational in Healthy subjects (n=10). Supine position vs. Upright position was evaluated on Long-axis shortening (LAS) (p=< 0.001). Supine position enhanced both long-axis shortening (15.1 vs 9.3 mm, P<0.001) and short-axis shortening (16.3 vs 12.7 mm, P<0.001) compared to the upright position in healthy subjects.