Redefining viability by cardiovascular magnetic resonance in acute ST-segment elevation myocardial infarction

Area of Science:

• Cardiology
• Medical Imaging
• Biomedical Engineering

Background:

• Chronic myocardial infarction (MI) defines myocardial viability using transmural extent of infarct (TEI) ≤50%.
• Late gadolinium enhancement (LGE) in acute ST-segment elevation MI (STEMI) can overestimate infarct size and TEI.
• Accurate assessment of myocardial viability in acute STEMI is crucial for guiding revascularization strategies.

Purpose of the Study:

• To determine the optimal TEI cut-off using cardiovascular magnetic resonance (CMR) for defining myocardial viability during the acute phase of STEMI.
• To use the ≤50% TEI at follow-up as the reference standard for myocardial viability.

Main Methods:

• 40 STEMI patients undergoing primary percutaneous coronary intervention (PPCI) were assessed using CMR acutely (4±2 days) and at follow-up (5±2 months).
• TEI was quantified using LGE on CMR scans.
• Sensitivity, specificity, and area under the curve (AUC) were calculated to evaluate TEI cut-offs for predicting viability.

Main Results:

• Segments with acute TEI of 1-25% and 26-50% showed high rates of sustained viability (100% and 96%, respectively).
• A significant proportion of segments with 51-75% TEI (67%) were reclassified as viable at follow-up, compared to only 6% of segments with 76-100% TEI.
• An acute TEI cut-off of ≤75% demonstrated high sensitivity (98%) and an AUC of 0.87 for predicting viability at follow-up.

Conclusions:

• The optimal cut-off for TEI by CMR in the acute phase of STEMI to predict myocardial viability is ≤75%.
• This finding has significant implications for selecting patients for viability testing and subsequent revascularization during the acute phase of MI.
• Utilizing a ≤75% TEI threshold in acute STEMI can improve the accuracy of viability assessment and treatment planning.