OBJECTIVES: The aim of this study was to evaluate the potential of T1 mapping at rest and during adenosine stress as a novel method for ischemia detection without the use of gadolinium contrast. In chronic coronary artery disease (CAD), accurate detection of ischemia is important because targeted revascularization improves clinical outcomes. Myocardial blood volume (MBV) may be a more comprehensive marker of ischemia than myocardial blood flow. T1 mapping using cardiac magnetic resonance (CMR) is highly sensitive to changes in myocardial water content, including MBV. We propose that T1 mapping at rest and during adenosine vasodilatory stress can detect MBV changes in normal and diseased myocardium in CAD.
METHODS: Twenty normal controls (10 at 1.5-T; 10 at 3.0-T) and 10 CAD patients (1.5-T) underwent conventional CMR to assess for left ventricular function (cine), infarction (late gadolinium enhancement [LGE]) and ischemia (myocardial perfusion reserve index [MPRI] on first-pass perfusion imaging during adenosine stress). These were compared to novel pre-contrast stress/rest T1 mapping using the Shortened Modified Look-Locker Inversion recovery technique, which is heart rate independent. T1 values were derived for normal myocardium in controls and for infarcted, ischemic, and remote myocardium in CAD patients.
RESULTS: Normal myocardium in controls (normal wall motion, MPRI, no LGE) showed normal resting T1 (954 Â± 19 ms at 1.5-T; 1,189 Â± 34 ms at 3.0-T) and significant positive T1 reactivity during adenosine stress compared to baseline (6.2 Â± 0.5% at 1.5-T; 6.3 Â± 1.1% at 3.0-T; all p < 0.0001). Infarcted myocardium showed the highest resting T1 of all tissue classes (1,442 Â± 84 ms), without significant T1 reactivity (0.2 Â± 1.5%). Ischemic myocardium showed elevated resting T1 compared to normal (987 Â± 17 ms; p < 0.001) without significant T1 reactivity (0.2 Â± 0.8%). Remote myocardium, although having comparable resting T1 to normal (955 Â± 17 ms; p = 0.92), showed blunted T1 reactivity (3.9 Â± 0.6%; p < 0.001).
CONCLUSIONS: T1 mapping at rest and during adenosine stress can differentiate between normal, infarcted, ischemic, and remote myocardium with distinctive T1 profiles. Stress/rest T1 mapping holds promise for ischemia detection without the need for gadolinium contrast.