It is increasingly appreciated that changes in the compliance properties of large blood vessels are critical determinants of ventricular afterload and ultimately dysfunction. Little is known of the mechanical properties of large vessels in the setting of pulmonary hypertension. We thus initiated a study to investigate the influence of chronic hypoxic pulmonary hypertension on the mechanical properties of the extrapulmonary arteries of rats. One group of animals was housed at the equivalent of 5000 m for 3 weeks and the other held at ambient conditions of ~1600 m. The two groups were age and gender matched. The animals exposed to hypobaric hypoxia exhibited signs of pulmonary hypertension as evidenced by an increase in the RV/(LV+S) heart weight ratio. The extrapulmonary arteries of the hypoxic animals were also thicker than those of the control population (P<0.05). Histological examination revealed decreased areal fraction of elastin and additional deposits of collagen in the adventitia. The mechanical properties of the trunk, and the right and left main pulmonary arteries were assessed by measuring the deformation of the artery with respect to pressure. Qualitatively, the pulmonary arteries from the rats treated with hypoxia were stiffer than those from the control animals - even at higher pressures we noted less deformation among the arteries from the hypoxic animals. Quantitatively, a four-parameter constitutive model was employed to analyze the data and it was found that a/c, the resistance to inflation, was best at detecting the stiffening of the artery wall (P<0.05) that was observed by plotting the strain as a function of pressure. Chronic hypoxic pulmonary hypertension is associated with a stiffening of all the extrapulmonary arteries.
Citation: American Journal of Physiology: Heart and Circulation Physiology
Pub Type: Journals
extrapulmonary arteries, main arteries, mechanical properties, pulmonary hypertension, rat, remodeling, stiffening, trunk