Novel Cardiac Magnetic Resonance Technique Detects Ischemia Without Gadolinium Contrast

At rest and during adenosine stress, T1 mapping, a novel cardiac magnetic resonance (CMR) technique, differentiated between normal, infarcted, ischemic, and remote myocardium with distinctive T1 profiles, concluded new data.

“Stress/rest T1 mapping on CMR holds promise for ischemia detection without the need for gadolinium contrast,” the researchers wrote.

The aim of the study was to test whether T1 mapping, which is highly sensitive to changes in myocardial water content, at rest and during adenosine vasodilatory stress could detect myocardial blood volume changes in normal and diseased myocardium.

The study involved 20 normal controls (n=10 at 1.5-Tesla; n=10 at 3-Tesla) and 10 patients with coronary artery disease (CAD; 1.5-Tesla). All patients received conventional CMR to evaluate for left ventricular function, infarction, and ischemia. Researchers compared these results with pre-contrast stress/rest T1 mapping using the heart rate-independent shortened modified look locker inversion recovery (ShMOLLI) technique, and determined T1 values in both controls and patients with CAD.

According to results, a normal resting T1 (954 ± 19 ms at 1.5-Tesla; 1189 ± 34 ms at 3-Tesla) was observed in the normal myocardium of controls, which consisted of normal wall motion and myocardial perfusion reserve index and no late gadolinium enhancement. Compared to baseline, there was a significant positive T1 reactivity during adenosine stress (6.2 ± 0.5% at 1.5-Tesla; 6.3 ± 1.1% at 3-Tesla; P for both <.0001).

Researchers also found that infarcted myocardium had the highest resting T1 of all tissue classes (1442 ± 84 ms), without evidence of significant T1 reactivity (0.2 ± 1.5%).

Furthermore, elevated resting T1 was detected in ischemic myocardium compared with normal myocardium (987 ± 17 ms; P<.001), with no significant T1 reactivity (0.2 ± 0.8%). Despite observing similar resting T1 between remote and normal myocardium, the former demonstrated blunted T1 reactivity (3.9 ± 0.6%; P<.001).

“This proof-of-principle study demonstrates for the first time that normal, remote, and ischemic myocardium have distinctive ranges of T1 reactivity to adenosine vasodilatory stress that can be detected by T1 mapping without gadolinium contrast administration,” the researchers wrote. “The finding that T1 reactivity is blunted in remote myocardium of CAD patients compared to normal controls may provide novel insights into disease characteristics of the remote myocardium. Significantly higher resting T1 in ischemic myocardium compared to normal controls and remote regions may potentiate detection of ischemia without vasodilatory stress, in the absence of other causes of T1 elevations at rest.”

Reference

Liu A, Wijesurendra RS, Francis JM, et al. Adenosine stress and rest T1-mapping can differentiate between ischemic, infarcted, remote and normal myocardium without the need for gadolinium contrast agents. JACC Cardiovasc Imaging. 2015. doi:10.1016/j.jcmg.2015.08.018.