Innate collateral segments are predominantly present in the subendocardium without preferential connectivity within the left ventricular wall

Abstract

Key pointsr Innate collateral arteries provide the biophysical substrate for arteriogenesis. Their distribution and morphology predestine tissue areas salvageable by collateral flow.r Fluorescent episcopic cryomicrotome imaging resulted in a three-dimensional representation of the coronary network, in which collateral segments were automatically identified.r Innate collateral segments are predominantly present in the subendocardium without preferential connectivity within the left ventricular wall of the dog heart and are preferentially oriented perpendicular to the long axis of the heart in the outer layers and parallel to this axis at the subendocardium.r These results suggest that collateral segments are maintained without local hypoxia but because of heterogeneity in pressure gradients in the arterial tree.r The high density and long-axis orientation of collateral arteries in the subendocardial region provide the substrate for arterial plexus formation and indicate the need for three-dimensional perfusion assessment in clinical perfusion imaging.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, r 2 = 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.

Detection and quantification methods of monocyte homing in coronary vasculature with an imaging cryomicrotome

“…Coronary vasculature was segmented as described previously [13]. Briefly, vascular cast images derived from the imaging cryomicrotome were deconvolved with a system-specific point spread function (PSF).…”

“…This imaging modality has been successfully employed in the assessment of vascular adaptation due to cryoablation [14], and in the detection of coronary collateral vessels [10][11][12][13], but not in conjunction with monocyte detection. We utilized different animal models and examined various fluorescent probes for cellular imaging, with a focus on monocytes.…”

“…The objective of this study was to demonstrate the feasibility of the imaging cryomicrotome [10][11][12][13] to visualize monocytes at μm resolution on a 3D level, in conjunction with the coronary microvascular network. This imaging modality has been successfully employed in the assessment of vascular adaptation due to cryoablation [14], and in the detection of coronary collateral vessels [10][11][12][13], but not in conjunction with monocyte detection.…”

Influence of segmented vessel size due to limited imaging resolution on coronary hyperemic flow prediction from arterial crown volume

“…Five healthy canine hearts were obtained from a series of physiological experiments carried out according to a protocol that was approved by the Institutional Animal Care and Use Committee of the University of Utrecht Medical Center. Details on experimental procedures and animal handling are described elsewhere (22,23). After premedication (medetomidine 0.03 mg/kg im, ketamine 0.03 mg/kg im, and atropine 0.5 mg im), the animals were anesthetized (sufentanil 10 g·kg Ϫ1 ·h Ϫ1 iv), intubated, and mechanically ventilated with supplemental oxygen.…”

“…Tree segmentation was visually checked by overlaying the segmented tree and the 3D images of the vascular cast in 3D. The segmented tree represented the 3D topological vascular network (22).…”