Abstract
BackgroundIn humans, dynamic contrast CMR of the first pass of a bolus infusion of Gadolinium-based contrast agent has become a standard technique to identify under-perfused regions of the heart and can accurately demonstrate the severity of myocardial infarction. Despite the clinical importance of this method, it has rarely been applied in small animal models of cardiac disease. In order to identify perfusion delays in the infarcted rat heart, here we present a method in which a T1 weighted MR image has been acquired during each cardiac cycle.Methods and resultsIn isolated perfused rat hearts, contrast agent infusion gave uniform signal enhancement throughout the myocardium. Occlusion of the left anterior descending coronary artery significantly reduced the rate of signal enhancement in anterior regions of the heart, demonstrating that the first-pass method was sensitive to perfusion deficits. In vivo measurements of myocardial morphology, function, perfusion and viability were made at 2 and 8 days after infarction. Morphology and function were further assessed using cine-MRI at 42 days. The perfusion delay was larger in rat hearts that went on to develop greater functional impairment, demonstrating that first-pass CMR can be used as an early indicator of infarct severity. First-pass CMR at 2 and 8 days following infarction better predicted outcome than cardiac ejection fraction, end diastolic volume or end systolic volume.ConclusionFirst-pass CMR provides a predictive measure of the severity of myocardial impairment caused by infarction in a rodent model of heart failure.
Highlights
In humans, dynamic contrast CMR of the first pass of a bolus infusion of Gadolinium-based contrast agent has become a standard technique to identify under-perfused regions of the heart and can accurately demonstrate the severity of myocardial infarction
Clinical studies have demonstrated that the extent of myocardial perfusion deficit after infarction is a strong predictor of functional outcome, with patients who present with large microvascular obstructions (MVO) having poor prognosis [10]
First-pass MR imaging has only very recently been used in small animal models of myocardial infarction [24,25]
Summary
Dynamic contrast CMR of the first pass of a bolus infusion of Gadolinium-based contrast agent has become a standard technique to identify under-perfused regions of the heart and can accurately demonstrate the severity of myocardial infarction. In order to identify perfusion delays in the infarcted rat heart, here we present a method in which a T1 weighted MR image has been acquired during each cardiac cycle. Infarct size and transmurality, measured using CMR shortly after systemic infusion of the contrast agent gadolinium-diethylenetriaminepentaacetate (DTPA), strongly correlates with progression to Scaling down imaging techniques to study the ever increasing number of small animal disease models has been a formidable challenge [15]. The left ventricular mass of the rat heart (~500 mg) is approximately three hundred times smaller than the human left ventricle (~150 g), and contracts 5 to 10 times faster, making it necessary to use high field strengths, smaller voxel sizes and rapid gating strategies
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