Microcirculation of the epimyocardial layer of the heart

Abstract

To study microcirculation of the heart in vivo, we developed a new technique of epi-illumination of the beating rat ventricular myocardium. Five tiny needles connected to the operation table were horizontally inserted into the ventricular myocardium just beneath the epicardium in order to restrict cardiac movement during contraction and to enhance the amount of light reflected from the structures under study. The in vivo light and fluorescent microscopy were performed with the Ultropak and the Fluopak systems (Leitz) combined with a highly sensitive television camera and recording system. In 142 individual in vivo measurements (6 animals) the mean capillary diameter amounted to 6.0 +/- 1.0 mu. In the same experiments, the mean intercapillary distance was 18.7 +/- 1.7 mu. In agreement with the literature, the capillaries of the epimyocardial layer of the rat heart demonstrate a mixed countercurrent flow pattern. In contrast to other authors, we observed no recruitment of resting capillaries after hypoxia.

Use of the perfused rat heart to study cardiac metabolism: retrospective and prospective views

“…The most significant observations are that the NADH distributions, and hence tissue oxygen tensions, are very heterogeneous, and that the border zone between aerobic and anoxic tissue occurs over only a few cells indicating very steep localized tissue oxygen gradients. These major findings have been confirmed by computer aided densitometric analysis of the negatives taken by fluorenscence flash photography (68), and are in accordance with observations of heterogeneous tissue flow distributions (69)(70)(71)(72). The implication of these findings is that hypoxic hearts (whether induced by high-flow hypoxia or by ischemia) represent a heterogeneous distribution of aerobic and anoxic cells, hence total tissue metabolite contents will reflect the statistical distribution between the different cell populations (67).…”

Coronary Circulation in the Presence of Vascular Disease

“…As can be seen, variations in both the magnitude of the flow and its direction are evident. The broad features of this distribution pattern are consistent with those observed in the living heart (15,16). Now consider an arbitrary arteriole winding its way through this maze and eventually partly perfusing the capillary bed.…”

Cardiac tissue engineering

“…Natural myocardium obviates this difficulty through a rich vasculature, with average capillary-to-capillary distances in rat heart of only 17 -19 mm, approximately the width of an individual cardiac myocyte. [31][32][33][34] Oxygen supply to cardiac cells is provided by hemoglobin an oxygen carrier (please note that hemoglobin increases the amount of oxygen in blood by two orders of magnitude, Table I). In engineered cardiac muscle, one can mimic blood flow through the capillary network by culturing cells on scaffolds that contain an array of channels that are perfused with culture medium.…”