0397: Age-related changes in rodent myocardial perfusion reserve in response to adenosine: longitudinal follow up with ASL-MRI

IntroductionIn clinical routine, myocardial perfusion MRI is generally performed with a stress/rest protocol using adenosine as a stressor to visualize ischemic risk zones in the myocardium. Changes in the vasodilator responses to adenosine with age have been reported in the rat thoracic aorta and the isolated- perfused rat heart. This study assesses the effect of maturation on the vascular relaxant action of adenosine in vivo on rats.MethodsWe used a fast imaging procedure (cine-ASL) to non-invasively quantify myocardial blood flow (MBF) and myocardial perfusion reserve (MPR) at rest and during adenosine-induced stress. Adenosine was injected via the tail vein at a rate of 420μg/kg/min. MBF and maximal MPR were monitored on 10 healthy Wistar rats at 4.7T, from young to mature rats at five different time points during growth (2, 8, 10, 13, and 15 months).ResultsMyocardial perfusion was measured in a region of interest covering the entire myocardium. No statistical differences in mean group MBF at rest were found across time (5.3±0.6mL/g/min). MPR, defined as the ration of stress MBF over rest MBF, was 2.3±0.3 at M2, 2.2±0.4 at M8, 2.0±0.5 at M10, 1.7±0.3 at M13, and 1.7±0.2 at M15 (Fig.1). In rats, maximum MPR to adenosine was found to be at early stage of growth, while a continuous decrease in coronary response was observed as the animals became mature (significantly different at M13 and M15).ConclusionThis study focuses on age-related changes in coronary response to adenosine as an infused vasodilator. These changes might be due to alterations in the adenosine receptor sites and a decrease in vascular elasticity. Such measurements give more detailed insight into changes of rodent coronary reserve occurring with growth and are of interest for studying myocardial stress response in rodent heart disease models across time