Table 3

Consensus Related to CMR Endpoints in Myocardial Infarction Experimental and Clinical Studies

It is recommended that the index CMR scan be performed 5 ± 2 days after reperfusion. At this time point, several key parameters have been shown to be relatively stable.
LGE extent, expressed both in absolute (grams) and relative (percentage of LV mass) terms, is the recommended CMR primary endpoint (106,107).
In experimental studies, if LGE extent is expressed as a ratio to AAR, the latter should not rely on edema and ideally both AAR and LGE have to be obtained at the same day post-MI (e.g., perfusion imaging during coronary occlusion by MDCT) and LGE by CMR) (15,89,90).
LVEF (%) and MVO (areas of hypoenhancement within LGE, in grams or as % of LV) are recommended as main secondary endpoints (105,108).
Edema extent (T2 mapping) may be used as secondary endpoint to assess the effect of cardioprotective therapies (89).
LV volumes (ml; ml/m2), RVEF (%), RV LGE (presence), and IMH (% of LV) can be included as secondary endpoints (111–114).
Myocardial mapping indexes (T1 [ms]; T2 [ms]; ECV [percentage of LV mass]), and strain (feature tracking) may be considered as exploratory endpoints (15,65,88,117–119).
The use of edema-sensitive CMR sequences as a surrogate for AAR (as well as edema-based MSI) is not recommended because edema is not stable in the days following MI, and is potentially affected by duration of ischemia, and by cardioprotective strategies (15,45,89).
Due to its easy implementation, ESL-based salvage index may be used as an exploratory outcome but not in cases with small amounts of LGE or aborted infarction, i.e., when a high degree of cardioprotection is expected (11,67,68,77,78).

For LGE post-processing, automated techniques using signal-intensity thresholding, manual delineation, and visual scoring (the 2 latter at intermediate signal-intensities) have similar good accuracy and reproducibility (129). For delineation of edema, T2 mapping (automated >2SD thresholding with manual correction) showed greater intraobserver and interobserver agreement (57). For MVO quantification, the most widely used is the manual delineation of dark areas within LGE region. Extended information is provided in the Online Appendix.

AAR = area at risk; ECV = extracellular volume; ESL = endocardial surface length; LVEF = left ventricular ejection fraction; MSI = myocardial salvage index; RV = right ventricle/ventricular; other abbreviations as in Table 1.

  • Controversial topic (majority but not all panelists in agreement).