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“How we do” CMR in acute myocardial infarction

“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

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“How we do” CMR in acute myocardial infarction

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  1. “How we do” CMR in acute myocardial infarction Derek J Hausenloy, Anna S Herrey, James C MoonUCLH 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.

  2. 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

  3. CMR and other Imaging Modalities in AMI Coronal Transverse 1 Transverse 2

  4. 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

  5. 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

  6. 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 thrombus20 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

  7. 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

  8. 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

  9. 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)

  10. 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

  11. 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

  12. 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

  13. 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,

  14. 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 LGE STIR imaging LGE T2* imaging Perfusion Ganame et al Eur Heart J 2009 Apr Epub O’Regan et al Radiology 2009;250:916-22.

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

  16. 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

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

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