Dataset for: Vascular narrowing in pulmonary arterial hypertension is heterogeneous: rethinking resistance

Background - In idiopathic pulmonary arterial hypertension (PAH), increased pulmonary vascular resistance is associated with structural narrowing of small (resistance) vessels and increased vascular tone. Current information on pulmonary vascular remodeling is mostly limited to averaged increases in wall thickness, but information on number of vessels affected and internal diameter decreases for vessels of different sizes is limited. Background – Our aim was to quantify numbers of affected vessels and their internal diameter decrease for differently sized vessels in PAH in comparison with non-PAH patients. Methods - Internal and external diameters of transversally cut vessels were measured in 5 control subjects and 6 PAH patients. Resistance vessels were classified in Strahler orders, internal diameters 13μm (order 1) to 500μm (order 8). The number fraction, i.e. % affected vessels, and the internal diameter fraction, i.e. % diameter of normal diameter, were calculated. Results - In PAH not all resistance vessels are affected. The number fraction is about 30%, i.e., 70% of vessels have diameters not different from vessels of control subjects. Within each order the decrease in diameter of affected vessels is variable with an averaged diameter fraction of 50-70%. Conclusions - Narrowing of resistance vessels is heterogeneous: not all vessels are narrowed, and the decrease in internal diameters, even within a single order, vary largely. This heterogeneous narrowing alone cannot explain the large resistance increase in PAH. We suggest rarefaction could be an important contributor to the hemodynamic changes.