Non-contrast assessment of microvascular integrity using arterial spin labeled cardiovascular magnetic resonance in a porcine model of acute myocardial infarction

Abstract

BackgroundFollowing acute myocardial infarction (AMI), microvascular integrity and function may be compromised as a result of microvascular obstruction (MVO) and vasodilator dysfunction. It has been observed that both infarcted and remote myocardial territories may exhibit impaired myocardial blood flow (MBF) patterns associated with an abnormal vasodilator response. Arterial spin labeled (ASL) CMR is a novel non-contrast technique that can quantitatively measure MBF. This study investigates the feasibility of ASL-CMR to assess MVO and vasodilator response in swine.MethodsThirty-one swine were included in this study. Resting ASL-CMR was performed on 24 healthy swine (baseline group). A subset of 13 swine from the baseline group underwent stress ASL-CMR to assess vasodilator response. Fifteen swine were subjected to a 90-min left anterior descending (LAD) coronary artery occlusion followed by reperfusion. Resting ASL-CMR was performed post-AMI at 1–2 days (N = 9, of which 6 were from the baseline group), 1–2 weeks (N = 8, of which 4 were from the day 1–2 group), and 4 weeks (N = 4, of which 2 were from the week 1–2 group). Resting first-pass CMR and late gadolinium enhancement (LGE) were performed post-AMI for reference.ResultsAt rest, regional MBF and physiological noise measured from ASL-CMR were 1.08 ± 0.62 and 0.15 ± 0.10 ml/g/min, respectively. Regional MBF increased to 1.47 ± 0.62 ml/g/min with dipyridamole vasodilation (P < 0.001). Significant reduction in MBF was found in the infarcted region 1–2 days, 1–2 weeks, and 4 weeks post-AMI compared to baseline (P < 0.03). This was consistent with perfusion deficit seen on first-pass CMR and with MVO seen on LGE. There were no significant differences between measured MBF in the remote regions pre and post-AMI (P > 0.60).ConclusionsASL-CMR can assess vasodilator response in healthy swine and detect significant reduction in regional MBF at rest following AMI. ASL-CMR is an alternative to gadolinium-based techniques for assessment of MVO and microvascular integrity within infarcted, as well as salvageable and remote myocardium. This has the potential to provide early indications of adverse remodeling processes post-ischemia.

Adenosine stress CMR perfusion imaging of the temporal evolution of perfusion defects in a porcine model of progressive obstructive coronary artery occlusion

“…This may reflect differences in the prevalence and distribution of adenosine receptor subtypes between humans and swine . A recent study also saw a reduction in heart rate in Yorkshire pigs during dipyridamole stress, which further supports our evidence that the porcine stress response may differ from the human response …”

CMR for myocardial characterization in ischemic heart disease: state-of-the-art and future developments

“…It relies on the tracing of “labeled” water protons by changing their longitudinal magnetization using selective radiofrequency pulses and compare images with and without the inflow of labeled blood. This technique has been evaluated in various animal models of myocardial ischemia and infarction [ 82 , 83 ], and humans [ 84 ]. Currently, there are several drawbacks, such as low signal-to-noise ratio, limited reproducibility, and issues with motion correction and image registration [ 85 ], which limit its clinical implementation.…”

Molecular Imaging to Monitor Left Ventricular Remodeling in Heart Failure

“…Myocardial perfusion gives useful information about capillary blood flow in the myocardium. Myocardial perfusion can be measured without CA by techniques of arterial spin labeling [71] and blood oxygen level-dependent contrast [15]. CA is used in myocardial angiography, where blood flow inside coronary arteries can be measured since the blood flow is alternated in the area of MI compared to the surrounding heart muscle [72].…”

“…CA is used in myocardial angiography, where blood flow inside coronary arteries can be measured since the blood flow is alternated in the area of MI compared to the surrounding heart muscle [72]. CA-MRA has also been used to determine microvascular obstruction in swine acute MI model with high accuracy [22,71]. Increased ECV, loss of cardiomyocytes and therefore loss of orientational structure, increases water diffusion in MI compared to the rest of the myocardium [3] which can be imaged with the diffusion weighted MRI [73].…”