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Arterial spin labeled MRI detects increase in myocardial blood flow with adenosine

Introduction

Myocardial arterial spin labeling (ASL) is an emerging technique for the assessment of myocardial perfusion. ASL does not require any contrast agents, and therefore can be used in patients with renal failure. We recently demonstrated feasibility of myocardial ASL [1]. In this study, we applied myocardial ASL to measure increased MBF during adenosine infusion.

Methods

Eleven patients were recruited, among those scheduled for routine cardiac MRI. All experiments were performed on a GE Signa 3 T scanner. Myocardial ASL measurements were obtained from a single mid short-axis slice, using flow-sensitive alternating inversion recovery (FAIR) tagging and balanced steady-state free precession (SSFP) imaging [1]. In each patient, one or two scans were performed at rest, and one scan was performed during adenosine infusion (dosage: 0.14 mg/kg/min). All patients also underwent first-pass perfusion imaging before adenosine infusion stopped (Table 1).

Table 1 Excerpt from the imaging protocol

Results

CMR first-pass images were read by two experienced cardiologists, and resulted in seven of the eleven subjects classified as "normal", based on having no visible perfusion defects. Fig. 1 contains the average MBF measurements of six myocardial segments (each segment size = 1.5 ± 1.0 cm3) from ASL in these "normal" subjects. The average MBF across subjects was 1.09 ± 0.53 ml/g/min at rest and 3.75 ± 1.06 ml/g/min during adenosine infusion, showing 4.97 ± 4.64 times increase. The increase in MBF was statistically significant (P < 0.001, t-test).

Figure 1
figure1

MBF measurements using ASL and heart rates (HR, in bpm) at rest and during adenosine infusion, from "normal" patients.

Discussion

The adenosine-induced MBF increase in normal myocardium has been documented to be 4.00 ± 1.10 times based on 15O-H2O PET [2]. The present study has demonstrated that myocardial ASL is able to capture these dramatic MBF changes. This study is on-going, and as we obtain more subjects with angiographically-significant disease and/or perfusion defects on first-pass imaging, we will be able to evaluate the ability of rest-stress myocardial ASL to detect perfusion defects. Fig. 2 contains segment-based MBF measurements using ASL and coronary angiogram from our first patient with single-vessel disease. Lowered MBF increase on anterior wall may be due to total occlusion of left anterior descending (LAD) artery.

Figure 2
figure2

Left: MBF measurements using ASL for each myocardial segment. Right: Coronary angiogram with total LAD occlusion (arrow) from the same patient.

References

  1. 1.

    Zun, et al: MRM. 2009,http://www3.interscience.wiley.com/journal/122543374/abstract

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  2. 2.

    Kaufmann, et al: Am J Physiol Heart Circ Physiol. 2007, 293 (4): H2178-82. 10.1152/ajpheart.01292.2006.

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Correspondence to Zungho Zun.

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Open Access This article is published under license to BioMed Central Ltd. This is an Open Access article is distributed under the terms of the Creative Commons Attribution 2.0 International License (https://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Zun, Z., Varadarajan, P., Pai, R.G. et al. Arterial spin labeled MRI detects increase in myocardial blood flow with adenosine. J Cardiovasc Magn Reson 12, P209 (2010). https://doi.org/10.1186/1532-429X-12-S1-P209

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Keywords

  • Left Anterior Descend
  • Myocardial Blood Flow
  • Perfusion Defect
  • Arterial Spin Label
  • Adenosine Infusion