Investigation of mechanical load on proximal left anterior descending of coronary artery

It is clinically recognized that percutaneous coronary intervention (PCI) treatment for proximal left anterior descending (LAD) artery disease is resulting in less satisfactory in comparison with other lesions. However, the reason has not yet clarified. The purpose of this study is to investigate the mechanical loading conditions in proximal LAD artery. This study hypothesized that the coronary artery is prestretched in the heart. In order to investigate the pre-stretched value, porcine heart was obtained from a local slauterhouse. Two points were marked at coronary artery and its distance was measured. Two-dimensional distances (L1) between the dots marked on vessel centerline were measured with digital microscope. The coronary artery was separated from the heart, the distance between the points was measured again (L2). Pre-stretched ratio was calculated as (L1-L2)/L2 ×100%. 101 consecutive patients of coronary CT were taken in Hokkaido Cardiovascular Hospital from September 2012 in order to investigate dynamic loads acting on coronary artery. The distance of proximal LAD artery was measured in diastolic phase (Ld) and systolic phase (Ls) from a stretch view taken from CT. Shortening ratio was defined as (Ld-Ls)/Ld ×100%. The twist angle was defined as a sum of the following two angles and mesured in end-systolic and end-diastolic phase. One is tha angle between the line connecting the centers of LAD and left circumflex (LCX), and the perpendicular line toward abdominal to dorsal. The other is the angle between the line connecting the centers of LAD and the first septal branch, and the perpendicular line. Twisting ratio was calculated as θ/Ld ×100%.Results showed that the pre-stretched ratio was calculated to be 7.6±2.9% (mean±SD) in porcine LAD artery. The length of proximal LAD artery of human coronary artery was 26.6 ± 9.3mm (mean±SD). Shortening ratio was calculated to be 6.1 ± 6.2% (mean±SD). And the mean twisting ratio was calculated to be 0.6 °/mm. This study revealed the pre-stretched value of proximal LAD artery due to restrain from the myocardium. Moreover shortening and twisting motions in proximal LAD artery were quantified.