T1 mapping and T2 mapping at 3T for quantifying the area-at-risk in reperfused STEMI patients.
BACKGROUND
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.


METHODS
18 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.


RESULTS
A 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 R(2) 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 (R(2) 0.95, P < 0.0001, bias 0.7 ± 5.1 %).


CONCLUSIONS
T1 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.
The Hatter Cardiovascular Institute, Institute of Cardiovascular Science, University College London, London, WC1E 6HX, UK. h.bulluck@gmail.com.|The National Institute of Health Research University College London Hospitals Biomedical Research Centre, London, UK. h.bulluck@gmail.com.|The Heart Hospital, University College London Hospital, London, UK. h.bulluck@gmail.com.
Heerajnarain
H
Bulluck
The Hatter Cardiovascular Institute, Institute of Cardiovascular Science, University College London, London, WC1E 6HX, UK. stevenkwhite@gmail.com.|The National Institute of Health Research University College London Hospitals Biomedical Research Centre, London, UK. stevenkwhite@gmail.com.|The Heart Hospital, University College London Hospital, London, UK. stevenkwhite@gmail.com.
Steven K
SK
White
The Heart Hospital, University College London Hospital, London, UK. sterosmini@gmail.com.
Stefania
S
Rosmini
The Heart Hospital, University College London Hospital, London, UK. anishbhuva@gmail.com.
Anish
A
Bhuva
The Heart Hospital, University College London Hospital, London, UK. thomas.treibel@gmail.com.
Thomas A
TA
Treibel
The Heart Hospital, University College London Hospital, London, UK. marianna_fontana@yahoo.it.
Marianna
M
Fontana
The Heart Hospital, University College London Hospital, London, UK. amnagadir@yahoo.co.uk.
Amna
A
Abdel-Gadir
The Heart Hospital, University College London Hospital, London, UK. anna.john@doctors.org.uk.
Anna
A
Herrey
The Heart Hospital, University College London Hospital, London, UK. cmanisty@gmail.com.
Charlotte
C
Manisty
UCL Institute of Nuclear Medicine, University College London Hospital, London, UK. mwan@nhs.net.
Simon M Y
SM
Wan
UCL Institute of Nuclear Medicine, University College London Hospital, London, UK. ashleygroves@nhs.net.
Ashley
A
Groves
UCL Institute of Nuclear Medicine, University College London Hospital, London, UK. leon.menezes@nhs.net.
Leon
L
Menezes
The National Institute of Health Research University College London Hospitals Biomedical Research Centre, London, UK. j.moon@ucl.ac.uk.|The Heart Hospital, University College London Hospital, London, UK. j.moon@ucl.ac.uk.
James C
JC
Moon
The Hatter Cardiovascular Institute, Institute of Cardiovascular Science, University College London, London, WC1E 6HX, UK. derek.hausenloy@duke-nus.edu.sg.|The National Institute of Health Research University College London Hospitals Biomedical Research Centre, London, UK. derek.hausenloy@duke-nus.edu.sg.|The Heart Hospital, University College London Hospital, London, UK. derek.hausenloy@duke-nus.edu.sg.|Cardiovascular and Metabolic Disorders Program, Duke-National University of Singapore, Singapore, Singapore. derek.hausenloy@duke-nus.edu.sg.|National Heart Research Institute Singapore, National Heart Centre Singapore, Singapore, Singapore. derek.hausenloy@duke-nus.edu.sg.
Derek J
DJ
Hausenloy
D000368:Aged; D019540:Area Under Curve; D016477:Artifacts; D003326:Coronary Circulation; D005260:Female; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D019028:Magnetic Resonance Imaging, Cine; D008297:Male; D008833:Microcirculation; D008875:Middle Aged; D009203:Myocardial Infarction / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D009206:Myocardium / Q000473:pathology*; D009336:Necrosis; D015588:Observer Variation; D062645:Percutaneous Coronary Intervention; D011237:Predictive Value of Tests; D012372:ROC Curve; D020127:Recovery of Function; D015203:Reproducibility of Results; D018570:Risk Assessment; D012307:Risk Factors; D013318:Stroke Volume; D013997:Time Factors; D016896:Treatment Outcome; D016277:Ventricular Function, Left