axillary lines axillary lines the axillary lines are the anterior axillary line, midaxillary line and the posterior axillary line. axillary linesthe right side of the thorax with lines labeleddetailsidentifierslatinlineae axillaresanatomical terminology the anterior axillary line is a coronal line on the anterior torso marked by the anterior axillary fold. it's the imaginary line that runs down from the point midway between the middle of the clavicle and the lateral end of the clavicle. the v5 ecg lead is placed on the anterior axillary line, horizontally even with v4. the midaxillary line is a coronal line on the torso between the anterior and posterior axillary lines. it is a landmark used in thoracentesis, and the v6 electrode of the 10 electrode ecg. the posterior axillary line is a coronal line on the posterior torso marked by the posterior axillary fold. additional images the left side of the thorax with lines labeled