“How we do” CMR in acute myocardial infarction Derek J Hausenloy, Anna S Herrey, James C Moon UCLH Heart Hospital and The Hatter Institute, University College London, UK. This presentation posted for members of SCMR as an educational guide – it represents the views and practicesof the author, and not necessarily those of SCMR.

CMR in acute myocardial infarction Established indications in AMI STEMI: Assess global and regional LV function. Detect LV thrombus. Detect and quantify microvascular obstruction. Detect and quantify acute myocardial infarct size Detect and quantify preserved myocardium. Potential future indications in STEMI: Detect and quantify the area at risk of infarction- myocardial oedema. Determine the myocardial salvage index (infarct size-area at risk/area at risk) Detect and quantify myocardial haemorrhage. Detect and quantify the peri-infarct ‘grey’ zone. Coronal Transverse 1 Transverse 2

CMR and other Imaging Modalities in AMI Function Infarct Thrombus MVO Radiation Dose Haem Area at risk Myocardial salvage Cardiac MRI +++ ++ Nuclear + Echo Cardiac CT Coronal Transverse 1 Transverse 2

Facilitating CMR in AMI Fine balance between time available and completeness of protocol. Need to optimize protocol to <45 min. Non breath-hold approaches to CMR: 3D whole heart navigated sequences Single-shot LGE Motion corrected averaging Coronal Transverse 1 Transverse 2

CMR in AMI – general considerations Aim to image on day 2-3 i.e. on day of discharge, although safe within 24 hours Phrommintikul et al Eur J Radiol. 2009 Apr 16. [Epub] Coronary stents are not a problem Patel et al Radiology. 2006;240(3):674-80. Patient may still be unwell Difficulty breath holding and tachycardia in patient Ensure resuscitation facilities nearby Check renal function. If eGFR<30, only rarely does the benefits of CMR outweigh risk of contrast (NSF) Aim to complete scan within 45 minutes Coronal Transverse 1 Transverse 2

Summary of CMR protocol for AMI Axial scouts. Time Multi-slice SSFP cine MRI in long and short axes for volumes and function. (see ‘How I do a volume study’) 10 min Early post-contrast T1-weighted 2D inversion- recovery GRE (or SSFP) with long TI. Multi-slice: a. MVO (presence and size) b. Acute thrombus 20 min 5-15 min post-contrast T1-weighted 2D inversion-recovery GRE (or SSFP). Multislice for: a. Infarct (presence and size) b. MVO (presence and size) 30 min Coronal Transverse 1 Transverse 2

Optional imaging for AMI Time 2a Optional – before giving contrast: Multi-slice T2 weighted TIRM or STIR for: a. Area at risk (size) b. Myocardial haemorrhage (presence and size). +15 min 2b Optional resting perfusion – minimum 3 SA slices – basal, mid, apical for: a. no-reflow (microvascular obstruction) +5 min Coronal Transverse 1

Early gadolinium enhancement - 1-3 min post-gadolinium, IR GRE or SSFP sequence, 2D or 3D set inversion time to ~440ms-480ms (higher if ↓HR or trigger 1) - To detect intra-cardiac thrombus (see arrow). RCA clip artefact

Late Gadolinium Enhancement (LGE) - 1 - Quantification of myocardial infarct size - T1 inversion recovery sequence (GRE or SSFP) - Usually image in diastole to reduce motion artefacts - Manually adjust TI (start depends on time, dose and trigger/HR)

Late gadolinium enhancement (2) Can also detect and quantify MVO (dark core –see arrow). presence of MVO linked to worse clinical outcomes preventing MVO is a viable target/mechanism for cardioprotection

Late gadolinium enhancement (3) Further LGE information: see AMI ‘Resources’ section of SCMR website (includes protocols, cases, standardized datasets, talks) 2D Inversion recovery sequence (GRE) - Alternatives: IR–SSFP, 3D sequences, PS-IR Image in diastole to reduce motion artefacts. Endocardial structures: systole (reduce segments) and later (blood pool down) Image technique Go and learn it. artefact recognition and reduction Manually adjust TI (260ms-480ms) Compulsory –even PS-IR sequences work better Gd dose: if not already given, use 0.1-0.2mmol/kg Image positions: Copy from cines, phase swaps, cross cuts

Optional imaging -T2 oedema imaging (1) - Myocardial oedema/inflammation appear as increased signal intensity on T2-weighted sequences (see AMI ‘Resources’ talks on T2W imaging) This can be used to detect an AMI, myocarditis, or delineate the ‘area at risk of infarction’. Several T2 weighted sequence e.g. TSE (black blood), STIR, TIRM, T2P-SSFP, ACUT2E. T2 TSE TIRM Area at Risk Area at Risk

Optional imaging -T2 oedema imaging (2) Problems with T2 oedema imaging Low SNR -therefore difficult to delineate and quantify. Surface coil sensitivity -T2 sequences are very prone to variations Bright subendocardial rims -due to stagnant blood. Posterior wall signal loss -due to cardiac movement,

Optional imaging –Myocardial hemorrhage The presence of myocardial hemorrhage within the infarct is associated with worse LV remodelling and clinical outcomes. It can be detected using either STIR or dual-inversion black-blood gradient multi-echo T2* imaging sequences. Hypointense region on T2 weighted imaging. Appears to correspond to area of MVO. Early Gd Ganame et al Eur Heart J 2009 Apr Epub LGE STIR imaging O’Regan et al Radiology 2009;250:916-22. LGE T2* imaging Perfusion

Optional imaging – Rest perfusion - Myocardial perfusion imaging (<1 min post-gadolinium). - To detect/quantify microvascular obstruction (see arrow). - See “How we do perfusion”

Optional imaging – Peri-infarct ‘grey’ zone Detecting and quantification of the peri-infarct ‘grey’ zone (intermediate contrast), which is associated with post-infarct sudden cardiac death, may be used for risk-stratification post-MI. Yan et al Circ 2006;114;32-39 Schmidt et al Circ 2007;115;2006-2014 Detect using LGE and quantify using thresholds (SD±2-3) or full-width half max. See ‘On-Line talks: (copy and paste these into your browser) http://www.scmr.org/Members/CMR-online-video-on-demand-lectures/scmr-2009/Sunday_Plenary/Sun_Plenary-2-Kwong.html http://www.scmr.org/Members/CMR-online-video-on-demand-lectures/scmr-2009/Sunday_Plenary/SunPlen-3-Lee.html From Schmidt et al, above

LGE Example- LAD infarct Cine TIRM Perfusion LGE Acknowledgement:: Derek Hausenloy