Two dimensions describe left ventricular volume change during hemodynamic transients.

Area of Science:

• Cardiovascular Physiology
• Echocardiography and Imaging
• Hemodynamics

Background:

• Left ventricular (LV) volume estimation is crucial for assessing cardiac function.
• Current methods often rely on complex three-dimensional measurements.
• Simpler indices are sometimes used but their validity under varying conditions is debated.

Purpose of the Study:

• To determine if LV cross-sectional area, derived from two dimensions, consistently correlates with LV three-dimensional volume.
• To assess the stability of the area-volume relationship during transient alterations in preload and afterload.
• To evaluate the feasibility of using LV cross-sectional area as a surrogate for LV volume in dynamic physiological states.

Main Methods:

• Sonomicrometry was used to measure three orthogonal dimensions of the LV in six dogs.
• LV cross-sectional area was calculated as the product of minor axis dimensions.
• Vena caval, pulmonary artery, and aortic occlusions were applied to induce transient hemodynamic changes over ~30 beats.

Main Results:

• A highly linear relationship was observed between LV cross-sectional area and LV volume (average correlation r=0.98).
• The standard error of the estimate for volume was small (0.9 ml), indicating precise estimation.
• Differences in the area-volume relationship intercepts among interventions were minimal (average 0.5 ml), with aortic occlusion showing a slight upward shift (0.8 ml).

Conclusions:

• LV cross-sectional area serves as a valid and consistent substitute for LV three-dimensional volume during acute changes in external load.
• This finding simplifies volume estimation in dynamic cardiovascular research.
• The study validates the use of 2D-derived area for 3D volume assessment under transient hemodynamic stress.