Fig. 3. Distribution of the rib or intercostal space level on the parasternal border where RA or LA heights and AP diameter were respectively measured. AP diameter = the largest anteroposterior diameter of the thorax; ICS = intercostal space; LA height = the longest vertical distance from the skin on the back to the most anterior portion of the left atrium; RA height = the longest vertical distance from the skin on the back to the most anterior portion of the right atrium.