Mechanical properties of porcine and human arteries: implications for coronary anastomotic connectors

Background To determine whether the pig is an appropriate experimental animal for studies on distal anastomotic connectors in coronary artery bypass surgery, the mechanical properties of young porcine and old human coronary and internal mammary arteries were compared within and beyond the physiologic range of strains. Methods Coronary arteries from 6 humans and 8 pigs were studied as well as internal mammary arteries of 3 humans and 6 pigs (human, aged 61 to 85 years; pig, 78.7 ± 5.8 kg [mean ± SD]). Pressure-diameter, pressure-axial force, circumferential and axial stress-strain relations, and dimensions were measured. Results The dimensions of the porcine and human coronary and internal mammary artery were generally similar but wall thickness was smaller in the porcine internal mammary artery (0.35 ± 0.07 mm versus 0.71 ± 0.06 mm, respectively, p = 0.002). The porcine internal mammary artery wall was less elastic than the coronary artery wall, whereas in humans both arteries displayed similar elasticity. Overall the porcine arteries were far more elastic in both circumferential and axial direction compared with the human arteries. Consequently the porcine arteries could be safely stretched by 60% to 70% compared with about 20% for the human arteries before reaching their maximum circumferential strain. Conclusions The three times greater elasticity of porcine compared with human coronary and internal mammary artery walls may result in underestimation of wall stress and the risk of wall injury when coronary connectors that involve overstretching of the wall are evaluated in the pig.