title: Innate collateral segments are predominantly present in the subendocardium without preferential connectivity within the left ventricular wall.
abstract: Functional collateral vessels often stem from outward remodelling of pre-existing connections between perfusion territories. Knowledge of the distribution and morphology of innate collateral connections may help in identifying myocardial areas with protection against risk for ischaemia. The coronary network of six healthy canine hearts was investigated with an imaging cryomicrotome. Innate collateral connections ranged from 286 to 1015 μm in diameter. Left ventricular collateral density (number per gram of tissue) was about five in the subendocardium vs. 2.5 in the mid-myocardium (P < 0.01) and 1.3 in the epicardium (P < 0.01). Subendocardial collateral connections were oriented parallel to the long axis of the heart. For the major coronary arteries, five times more intracoronary than intercoronary connections were found, while their median diameter and interquartile range were not significantly different, at 96.1 (16.9) vs. 94.7 (18.9) μm. Collateral vessels connecting crowns from sister branches from a stem are denoted intercrown connections and those within crowns intracrown connections. The number of intercrown connections was related to the mean tissue weight of the crowns (y = 0.73x - 0.33, r2 = 0.85, P < 0.0001). This relation was likewise found to describe intercoronary connections. The median collateral diameter and length were independent of the tissue volumes bridged. We conclude that connectivity and morphology of the innate collateral network are distributed with no preference for intra- or intercrown connections, independent of stem diameter, including epicardial arteries. This renders all sites of the myocardium equally protected in case of coronary artery disease. The orientation of subendocardial collateral vessels indicates the longitudinal direction of subendocardial collateral flow.
authors.affiliation: Department of Biomedical Engineering and Physics, Academic Medical Center - University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands. j.p.vandenwijngaard@amc.uva.nl.
authors.forename: Pepijn
authors.initials: P
authors.lastname: van Horssen
authors.forename: Maria
authors.initials: M
authors.lastname: Siebes
authors.forename: Jos A E
authors.initials: JA
authors.lastname: Spaan
authors.forename: Imo E
authors.initials: IE
authors.lastname: Hoefer
authors.forename: Jeroen P H M
authors.initials: JP
authors.lastname: van den Wijngaard
mesh_terms: D000818:Animals; D003097:Collateral Circulation; D003326:Coronary Circulation; D003331:Coronary Vessels / Q000033:anatomy & histology*; D004285:Dogs; D004699:Endocardium / Q000033:anatomy & histology*; D006352:Heart Ventricles / Q000033:anatomy & histology*; D066298:In Vitro Techniques; D008953:Models, Anatomic; D008955:Models, Cardiovascular