A method for measuring the angle between left atrial and left ventricular long axes using 3D echocardiography

Left ventricle (LV) optimized views are routinely used for left atrial (LA) volume and strain measurements on 2D echocardiography. This might be a source of the error because of the variation of the angle between the left atrial and left ventricle long axes (LA-LV angle), leading to foreshortening of the LA.

We investigated two novel parameters: the angle between the left atrial and left ventricle long axes (LA-LV angle) and its deviation from the 4-chamber plane. To accurately measure the angles in 3D space, these measurements were performed using 3D echocardiography. We developed a method for the measurement based on marking anatomic points of reference in the 3D echocardiogram and measuring the angles between these points. We used three types of phantoms made of wood and agar-agar to investigate the repeatability and reproducibility of these measurements and performed measurements on human subjects.

The ultrasound measurements were in excellent agreement with the true angles of the phantoms: LA-LV angle bias was .5 degrees (95% CI -1.8 to +2.7) in the wooden phantoms and 1.2 degrees (-.7 to +3.1) in the agar-agar phantoms, while the angle deviation from the 4-chamber plane was -.9 degrees (-4.3 to +4.1) in the wooden phantoms and .0 degrees (-3.3 to +3.3) in the agar-agar phantoms. The measurements demonstrated good repeatability and reproducibility (Pearson correlation coefficients ranging from .91 to .99). The measurements from human hearts showed good repeatability (Pearson correlation was .81 for repeated LA-LV angle measurements and .97 for repeated measurements of the deviation from the 4-chamber plane).

The measurement of the LA-LV angle is a feasible tool to investigate one eventual error of 2D echocardiography.