Proximal pressure reducing effect of wave reflection in the pulmonary circulation disappear in obstructive disease: insight from a rabbit model.

Locating the site of increased resistance within the vascular tree in pulmonary arterial hypertension (PAH), could assist in both patient diagnosis and tailoring treatment. Wave intensity analysis (WIA) is a wave analysis method that may be capable of localizing the major site of reflection within a vascular system. We investigated the contribution of WIA to the analysis of the pulmonary circulation in a rabbit model with animals subjected to variable occlusive pulmonary disease. Animals were embolized with different sized microspheres for 6 weeks (N = 10) or underwent pulmonary artery (PA) ligation for 6 weeks (N = 3). These animals were compared to a control group (N = 6) and acutely embolized animals (N = 4). WIA was performed and compared with impedance based methods to analyze wave reflections. The control group showed a relatively high extent of reflected waves (15.7 ± 10.6%): reflections had a net effect of pressure reduction during systole suggesting an open-end reflector. The pattern of wave reflection was not different in the group with partial PA ligation (12.4 ± 4.1%). In the chronically embolized group, wave reflection was not observed (3.6 ± 1.5%). In the acute embolization group, wave reflection was more prominent (37.3 ± 12.6%), with the appearance of a novel wave increasing pressure suggesting the appearance of a closed-end reflector. Wave reflections of an open end type are present in the normal rabbit pulmonary circulation. However, the pattern and nature of reflections vary according to the extent of pulmonary vascular occlusion.