Gadolinium chelate kinetics in cardiac MR imaging of myocarditis: comparison to acute myocardial infarction and impact on late gadolinium enhancement.

OBJECTIVES

To compare the kinetics of gadolinium in myocarditis and myocardial infarction and to establish the best interval between contrast injection and late gadolinium-enhanced (LGE) image acquisition for the diagnosis of acute myocarditis.

METHODS

Seventeen patients with acute myocarditis and 12 with acute myocardial infarction underwent Look-Locker sequences before and after administration of 0.2 mmol/kg gadolinium chelate for a period of 14 minutes. The apparent longitudinal relaxation rates (R'1) were calculated from left ventricular blood, enhanced and normal myocardium. LGE cardiac magnetic resonance images were acquired at 5, 10, and 15 minutes after contrast injection. The contrast between enhanced and normal myocardium (Contrastenhaced-normal) was measured, and the quality of the images was analyzed.

RESULTS

A faster decline in the R'1 values measured in the areas of myocardial enhancement was recorded in myocarditis than that in myocardial infarction. In myocarditis, the Contrastenhaced-normal values decreased over time (from 60.7 ± 35.1 at 5 minutes vs. 42.1 ± 26.7 at 15 minutes; P = 0.001). However, in myocardial infarction, the Contrastenhaced-normal value remained stable in time (60.7 ± 22.9 at 5 minutes vs. 68.8 ± 16.6 at 15 minutes; P = ns).

CONCLUSION

The gadolinium kinetics of acute myocarditis are different from those of acute myocardial infarction. In myocarditis, LGE images acquired 5 minutes after contrast injection provide higher Contrastenhaced-normal and better image quality compared with images taken at later points.