Calculation of left ventricular volume using implanted tantalum markers: a method reproducible despite rotation of the heart.

Endocardial markers implanted by catheter have been used to estimate the left ventricular volume by outlining the ventricle in orthogonal planes. However, if the position of the ventricle with respect to the biplane radiographic system changes, the projected outlines formed by the markers will narrow and the calculated volume will decrease. Therefore, a mathematical technique to correct this error was developed. It was tested by extensively rotating silicone casts of the left ventricle to which markers were glued. Except for one position at which the volume deviated by 4.5 ml, all the calculated volumes of the casts were reproducible to within 2 ml.