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Gadolinium-Free Cardiac MR Stress T1-Mapping
Study Questions:
Can T1-mapping, an emerging cardiac magnetic resonance imaging (MRI) technique, be used to detect myocardial ischemia without the use of gadolinium-containing contrast?
Methods:
Ninety subjects (2:1 ratio of patients with angina to healthy controls) prospectively underwent cardiac MRI including assessment of left ventricular function and ischemia during adenosine stress and at rest using both T1-mapping and standard contrast perfusion techniques. Angina patients underwent coronary angiography including measurement of fractional flow reserve (FFR) and the index of microcirculatory resistance (IMR) in all three coronary arteries whenever feasible. Change in T1 was the primary predictor of interest. Qualitative and quantitative measures of stress perfusion using gadolinium-enhanced imaging was also measured.
Results:
Overall, 70% of angina patients had angiographic disease (≥50% visual narrowing); 30% had multivessel angiographic disease. 41 of 125 viable coronary artery territories were supplied by obstructive vessels (FFR <0.8). Myocardial perfusion reserve by stress perfusion MRI was lower downstream of obstructed vessels (1.4 ± 0.4 vs. 2.3 ± 0.6, p < 0.001). Similarly, change in T1 was lower downstream of obstructed vessels (0.7 ± -0.7% vs. 4.1 ± 1.3%, p < 0.001). A change in T1 cutoff of 1.5% had a c-statistic of 0.97 for distinguishing vessels with FFR <0.8 with sensitivity of 93%, specificity of 95%, positive predictive value of 91%, and negative predictive value of 96%. Discrimination was greater than visual interpretation of stress perfusion (c-statistic 0.85), semiquantitative perfusion assessment (c-statistic 0.87), and quantitative assessment of perfusion (c-statistic 0.91). In vessels with normal FFR, those with impaired microvascular function (IMR ≥25) had lower change in T1 than those with preserved microvascular function (p < 0.001).
Conclusions:
Noncontrast T1-mapping at rest and during vasodilator stress can accurately identify obstructive coronary artery disease.
Perspective:
These early data suggest that T1 mapping at rest and during vasodilator stress may be a gadolinium-free alternative to standard perfusion methodologies. The accuracy in this early study was exceptionally high and may be lower in larger studies and in clinical practice. Nonetheless, this is an area that warrants further investigation.
Keywords: Adenosine, Angina Pectoris, Coronary Angiography, Coronary Artery Disease, Diagnostic Imaging, Fractional Flow Reserve, Myocardial, Gadolinium, Magnetic Resonance Imaging, Microcirculation, Myocardial Ischemia, Vasodilator Agents
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