title: Model combining hydrodynamics and fractal theory for analysis of in vivo peripheral pulmonary and systemic resistance of shunt cardiac defects.
abstract: The fractal state of the arterial vascular tree is considered to have a universal dimension related to the principle of minimum work rate, but can demonstrate the capacity to adapt to other dimensions in disease states such as congenital high-flow pulmonary hypertension (PH) by a process that is incompletely understood. To document and interpret fractal adaptation in patients with different degrees of PH, pulmonary and systemic vascular resistance was analyzed by a model that evaluated the fractal dimension, x, of the Poiseuille resistance contribution of the arterial vessel radius between 10 and 100μm, via the proportionality Q∝(R(peri)/BL)(-x/4), with Q, R(peri), and BL clinically observed variables representing total pulmonary or systemic blood flow, its peripheral arterial resistance, and body length, respectively. Identification of x in the pulmonary (P) and systemic (S) beds was evaluated from hemodynamic data of 213 patients, categorized into 7 groups by PH grade. In controls without PH, x(P)=2.2 while the dimension increased to 3.0, with the systemic dimension constant at x(S)=3.1. Our model predicts that severe grades of PH are associated with: a more elongated and hindered vessel in the periphery, and reductions in vessel numbers, as unit pulmonary resistive arterial trees (N(1)) and their component intra-acinar arteries (N(W)). These model network changes suggest a complex adaptive process of arterial network reorganization in the pulmonary circulation to minimize the work rate of high-flow congenital heart defects.
authors.affiliation: Department of Pediatrics, Graduate School of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan. yonakamura-tky@umin.ac.jp
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Nakamura
authors.forename: Shoichi
authors.initials: S
authors.lastname: Awa
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kato
authors.forename: Yoichi M
authors.initials: YM
authors.lastname: Ito
authors.forename: Akira
authors.initials: A
authors.lastname: Kamiya
authors.forename: Takashi
authors.initials: T
authors.lastname: Igarashi
mesh_terms: D000293:Adolescent; D000328:Adult; D006328:Cardiac Catheterization; D002648:Child; D002675:Child, Preschool; D005260:Female; D017709:Fractals; D006330:Heart Defects, Congenital / Q000150:complications / Q000503:physiopathology*; D006801:Humans; D006976:Hypertension, Pulmonary / Q000209:etiology / Q000503:physiopathology; D007223:Infant; D008297:Male; D008955:Models, Cardiovascular; D011652:Pulmonary Circulation / Q000502:physiology*; D014655:Vascular Resistance / Q000502:physiology*; D055815:Young Adult