Fig 1.
Determining maximal anteroposterior diameter (APD) of the left ventricle (LV) using axial and scout images.
The skin above the maximal APD was searched to identify the sternum landmark representing the LV.
- The maximal APD of the LV was measured and aligned in the axial images from the full inspiration with the arms raised position. The centre of the line was defined as the location of the LV (a).
- The location of the LV was marked at the skin and a perpendicular line was drawn to the sternum for the sternum landmark of the LV.
- A perpendicular line was drawn at the margin of the right atrial contour, and the intersection between the perpendicular line and the right atrial contour was marked.
- A straight line was drawn from the heart’s apex to the intersection point at the right atrial contour.
- Another perpendicular line was drawn from the radio-opaque marker at the lowest palpable xiphoid process to the line that connected the apex and intersection point. This intersection was defined as the LV sternum landmark for the expiration with the arms down position, and the distance from the sternum landmark to the xiphoid process marker was defined as the XLVD. This method was also applied to the expiration with the arms down position scout images.
Fig 2.
Distances from the arbitrary sternum left ventricle (LV) landmark to the actual landmark using axial images from full inspiration.
The measured LV landmark was approximately 1.23 mm lower on the sternum, compared to the actual landmark (median: –1.23 mm, interquartile range: –15.58 mm, 10.56 mm, range: –19.35 mm, 14.52 mm).
Fig 3.
The distance from the xiphoid process to the point of the left ventricle’s maximal anteroposterior diameter of the left ventricle.
The perpendicular line between the point for the left ventricle (LV)’s maximal anteroposterior diameter (APD) and the xiphoid process marker was measured in the expiration with the arms down position and the inspiration with the arms raised position (XLVD) (a,b). From the upper side of the sternum, the 1/4 and 2/4 sections were defined as the upper half of the sternum, the 2/4 and 3/4 sections were defined as the middle of the sternum, and the 3/4 and 4/4 sections were defined as the lower half of the sternum, relative to the positions of the heart and liver (c,d). In the expiration with the arms down position, the land marks of LV at sternum were located beneath the middle of the sternum, and the liver was located beneath the lower half of the sternum. In the inspiration with the arms raised position, the land marks of LV at sternum were located beneath the lower half of the sternum.
Table 1.
Participant characteristics.
Table 2.
Comparing distances from the xiphoid process to the sternum landmark according to respiratory phase and arm position.
Table 3.
Locations of the heart and liver according to the three sternum divisions.
Table 4.
Univariable and multivariable analysis of factors associated with the location of the heart according to expiration and inspiration.