Abstract
In chronic myocardial infarction (MI), segments with a transmural extent of infarct (TEI) of ≤50% are defined as being viable. However, in the acute phase of an ST-segment elevation myocardial infarction (STEMI), late gadolinium enhancement (LGE) has been demonstrated to overestimate MI size and TEI. We aimed to identify the optimal cut-off of TEI by cardiovascular magnetic resonance (CMR) for defining viability during the acute phase of an MI, using ≤50% TEI at follow-up as the reference standard. 40 STEMI patients reperfused by primary percutaneous coronary intervention (PPCI) underwent a CMR at 4 ± 2 days and 5 ± 2 months. The large majority of segments with 1–25%TEI and 26–50%TEI that were viable acutely were also viable at follow-up (59/59, 100% and 75/82, 96% viable respectively). 56/84(67%) segments with 51–75%TEI but only 4/63(6%) segments with 76–100%TEI were reclassified as viable at follow-up. TEI on the acute CMR scan had an area-under-the-curve of 0.87 (95% confidence interval of 0.82 to 0.91) and ≤75%TEI had a sensitivity of 98% but a specificity of 66% to predict viability at follow-up. Therefore, the optimal cut-off by CMR during the acute phase of an MI to predict viability was ≤75% TEI and this would have important implications for patients undergoing viability testing prior to revascularization during the acute phase.
Highlights
Primary percutaneous coronary intervention (PPCI) is the revascularization strategy of choice for patients presenting with an acute ST-segment elevation myocardial infarction (STEMI)
The main findings from our study are that two thirds of segments with a transmural extent of infarct (TEI) of 51–75% on the acute cardiovascular magnetic resonance (CMR) scan were reclassified as having a TEI ≤50% and being viable at follow-up
A ≤50%TEI by late gadolinium enhancement (LGE) is the conventional cut-off used for defining viability in patients with stable coronary artery disease (CAD), and has been validated in the setting of revascularization by coronary artery bypass graft surgery (CABG) or PCI1,2
Summary
Primary percutaneous coronary intervention (PPCI) is the revascularization strategy of choice for patients presenting with an acute ST-segment elevation myocardial infarction (STEMI). An increasing number of patients with an acute myocardial infarction (MI), such as those presenting late, and for those patients with multi-vessel coronary artery disease, urgent in-patient revascularization by coronary artery bypass graft surgery (CABG) may be needed. In those cases viability assessment in the acute phase of MI is desirable prior to subjecting these high-risk patients to a major procedure. If a TEI of ≤50% is used to define viability by CMR in the acute phase of an MI, there is the possibility of over-estimating the number of non-viable segments, and missing potentially viable segments, when assessing patients prior to revascularization. The aim of the current study was to identify the optimal cut-off for TEI to define viability during the acute phase of an MI, which may be used when considering viability assessment for patients with recent acute MI requiring urgent in-patient revascularization
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