0276: Dynamics of the perfusion reserve during adenosine-induced stress in rats

Abstract

In clinical routine, myocardial perfusion MRI is generally performed with a stress/rest protocol using adenosine as a short living (10s half-life) stressor. Adenosine allows visualizing ischemic risk zones in the myocardium and is typically injected 3 to 4 minutes prior to stress imaging. To gain insight into perfusion dynamics under stress, we used a non-invasive and fast imaging procedure (cine-ASL) to study the longitudinal effect of a continuous injection of adenosine on myocardial blood flow (MBF) and MBF reserve in rats. MBF and MBF reserve were monitored every 5min following adenosine injection (140μg/kg/min) on 17 healthy Wistar rats at 4.7T. For the Stress group (N=6), adenosine was continuously injected for 40min. For the Stress/Recovery group (N=6), adenosine was injected for 25min and then stopped for the last 15min. Finally, for the Control group (N=7), a saline solution was injected for 40 min. Mean group MBF at rest was 5.4±0.5mL/g/min in a ROI covering the entire myocardium. Mean group MBF data are reported as a function of time after onset of adenosine (Fig). In every studied animal of the 2 first groups subjected to stress, an initial MBF increase was found within the first 5min following adenosine infusion. But, the maximum MBF response to adenosine was always obtained later, between 5-10min, followed by a continuous MBF decrease until 25min. Maximum stress perfusion was 10.8±1.4mL/g/min leading to a reserve of 2.1±0.3, consistent with previously reported study. This study focuses on MBF response dynamics to adenosine. In rats, maximum MBF response to adenosine was found between 5 to 10min. Such dynamic measurements give more detailed insight into rodent coronary reserve and coronary responses to infused vasodilators and may give complementary information on microvascular functional defects in non-ischemic heart disease models.