Table 1.

Myocardial injury grading scale

Myofiber Degeneration
0	Absent
1+	Single to multiple foci of vacuolated, shrunken, or fragmented, hypereosinophilic myofibers
2+	More frequent multifocal foci to larger zones of vacuolated, shrunken, or fragmented hypereosinophilic myofibers
3+	Large coalescing to regionally extensive zones of vacuolated, shrunken, or fragmented hypereosinophilic myofibers
Myocardial hemorrhage
0	Absent
1+	Focal to multifocal mild myocardial, epicardial, or endocardial hemorrhage
2+	Moderate multifocal to regionally extensive myocardial, epicardial, or endocardial hemorrhage
3+	Severe regionally extensive hemorrhage involving large portions of heart section
Interstitial edema
0	Absent
1+	Mild and multifocal separation of myofiber bundles or expansion of perivascular spaces
2+	Moderate and multifocal separation of myofiber bundles or expansion of perivascular spaces
3+	Marked regionally extensive or multifocal separation of myofiber bundles and perivascular spaces
Endothelial changes
0	Absent
1+	Plump endothelial cells, separation of endothelium from underlying basal lamina
2+	Cellular infiltration of vessel wall or disruption of layers of vessel wall
3+	Necrosis or severe vascular cellular infiltration