Abstract
BackgroundWhether T1-mapping cardiovascular magnetic resonance (CMR) can accurately quantify the area-at-risk (AAR) as delineated by T2 mapping and assess myocardial salvage at 3T in reperfused ST-segment elevation myocardial infarction (STEMI) patients is not known and was investigated in this study.Methods18 STEMI patients underwent CMR at 3T (Siemens Bio-graph mMR) at a median of 5 (4–6) days post primary percutaneous coronary intervention using native T1 (MOLLI) and T2 mapping (WIP #699; Siemens Healthcare, UK). Matching short-axis T1 and T2 maps covering the entire left ventricle (LV) were assessed by two independent observers using manual, Otsu and 2 standard deviation thresholds. Inter- and intra-observer variability, correlation and agreement between the T1 and T2 mapping techniques on a per-slice and per patient basis were assessed.ResultsA total of 125 matching T1 and T2 mapping short-axis slices were available for analysis from 18 patients. The acquisition times were identical for the T1 maps and T2 maps. 18 slices were excluded due to suboptimal image quality. Both mapping sequences were equally prone to susceptibility artifacts in the lateral wall and were equally likely to be affected by microvascular obstruction requiring manual correction. The Otsu thresholding technique performed best in terms of inter- and intra-observer variability for both T1 and T2 mapping CMR. The mean myocardial infarct size was 18.8 ± 9.4 % of the LV. There was no difference in either the mean AAR (32.3 ± 11.5 % of the LV versus 31.6 ± 11.2 % of the LV, P = 0.25) or myocardial salvage index (0.40 ± 0.26 versus 0.39 ± 0.27, P = 0.20) between the T1 and T2 mapping techniques. On a per-slice analysis, there was an excellent correlation between T1 mapping and T2 mapping in the quantification of the AAR with an R2 of 0.95 (P < 0.001), with no bias (mean ± 2SD: bias 0.0 ± 9.6 %). On a per-patient analysis, the correlation and agreement remained excellent with no bias (R2 0.95, P < 0.0001, bias 0.7 ± 5.1 %).ConclusionsT1 mapping CMR at 3T performed as well as T2 mapping in quantifying the AAR and assessing myocardial salvage in reperfused STEMI patients, thereby providing an alternative CMR measure of the the AAR.
Highlights
Whether T1-mapping cardiovascular magnetic resonance (CMR) can accurately quantify the area-at-risk (AAR) as delineated by T2 mapping and assess myocardial salvage at 3T in reperfused ST-segment elevation myocardial infarction (STEMI) patients is not known and was investigated in this study
Despite timely myocardial reperfusion by primary percutaneous coronary intervention (PPCI), patients presenting with an acute ST-segment elevation myocardial infarction (STEMI) still experience significant morbidity and mortality [1,2,3]
The assessment of the efficacy of novel cardioprotective therapies requires the accurate quantification of the area-at-risk (AAR), as this enables the measurement of the myocardial salvage index (AAR subtract MI size/AAR), a more sensitive measure of cardioprotective effectiveness than a reduction in absolute MI size or MI size as a percentage of the left ventricular (LV) alone [4, 5]
Summary
Whether T1-mapping cardiovascular magnetic resonance (CMR) can accurately quantify the area-at-risk (AAR) as delineated by T2 mapping and assess myocardial salvage at 3T in reperfused ST-segment elevation myocardial infarction (STEMI) patients is not known and was investigated in this study. The assessment of the efficacy of novel cardioprotective therapies requires the accurate quantification of the area-at-risk (AAR), as this enables the measurement of the myocardial salvage index (AAR subtract MI size/AAR), a more sensitive measure of cardioprotective effectiveness than a reduction in absolute MI size or MI size as a percentage of the LV alone [4, 5] In this regard, T2-weighted (short tau inversion recovery) cardiovascular magnetic resonance (CMR) of myocardial edema in the first few days following PPCI has emerged as a promising technique for retrospectively quantifying the AAR in reperfused STEMI patients [6, 7]. Recent studies have found that in addition to reducing MI size, certain cardioprotective therapies such as ischemic postconditioning [10] and remote ischemic conditioning [11, 12] decreased the extent of myocardial edema as delineated by T2 mapping and T2-weighted CMR, resulting in an underestimation of the AAR with this approach
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