Microvascular adaptation to coronary stenosis in the rat heart in vivo: a serial magnetic resonance imaging study

Abstract

Changes in the microcirculation may compensate for the reduction of perfusion supplied by the stenotic vessel. The objective of this study was to determine functional adaptive processes in the microcirculation by magnetic resonance imaging (MRI) during coronary stenosis in the rat heart. Left coronary artery (LAD) narrowing (cross-sectional area 49.8 ± 3.5%; n = 14) or sham operation ( n = 10) was induced in rats. Myocardial perfusion and relative intracapillary blood volume (RBV) at rest and during vasodilatation 1 and 2 weeks after surgery were quantified using MRI. Coronary stenosis in vivo was verified by 3D MR angiography. Foci of fibrosis were found in the poststenotic myocardium. In this area, perfusion at rest was significantly reduced (1.79 ± 0.11 ml/g/min, p < 0.001) despite a maintained perfusion reserve during adenosine (3.12 ± 0.20 ml/g/min compared to the remote myocardium (3.07 ± 0.12 and 5.24 ± 0.24 ml/g/min, respectively) and the sham operated group (3.22 ± 0.07 and 5.28 ± 0.24 ml/g/min, respectively). Poststenotic RBV at rest (12.63 ± 0.42 %) and during vasodilatation (22.42 ± 0.81 %) were not significantly different ( p > 0.05) from RBV of the remote myocardium (12.92 ± 0.33 and 23.32 ± 0.52 %, respectively). Coronary stenosis in the rat leads to foci of tissue injury with impaired perfusion at rest despite a partially maintained perfusion reserve distal to the stenosis. RBV remains constant in order to maintain blood supply. These functional changes reflect adaptive processes that may compensate for ischemic tissue loss.