Transcript 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
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.
Coronal
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)
Transverse
Transverse
• Detect and quantify myocardial haemorrhage.
1
2
• Detect and quantify the peri-infarct ‘grey’ zone.
CMR and other Imaging Modalities in AMI
Function
Infarct
Thrombus
MVO
Radiation
Dose
Haem
Area
at risk
Myocardial
salvage
Cardiac MRI
+++
+++
+++
+++
0
++
++
+++
Nuclear
+
++
0
0
++
0
++
++
Echo
++
+
++
+
0
0
Cardiac CT
+
+
++
+
++
0
Transverse
1
+
Coronal
+
0
0
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
Coronal
Single-shot LGE
Motion corrected averaging
Transverse
1
Transverse
2
CMR in AMI – general considerations
1. 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]
2. Coronary stents are not a problem
Patel et al Radiology. 2006;240(3):674-80.
3. Patient may still be unwell
Coronal
4. Difficulty breath holding and tachycardia in patient
5. Ensure resuscitation facilities nearby
6. Transverse
Check renal function. If eGFR<30, only rarelyTransverse
does the
benefits 1of CMR outweigh risk of contrast (NSF)
2
7. Aim to complete scan within 45 minutes
Summary of CMR protocol for AMI
1. Axial scouts.
Time
2. Multi-slice SSFP cine MRI in long and short axes
for volumes and function.
(see ‘How I do a volume study’)
10 min
Coronal
3. Early post-contrast T1-weighted 2D inversionrecovery GRE (or SSFP) with long TI. Multi-slice:
a. MVO (presence and size)
b. Acute thrombus
20 min
Transverse
Transverse
5. 5-15 min
1 post-contrast T1-weighted 2D inversion2
recovery GRE (or SSFP). Multislice for:
a. Infarct (presence and size)
b. MVO (presence and size)
30 min
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
Coronal
2b Optional resting perfusion – minimum 3 SA slices
– basal, mid, apical for:
a. no-reflow (microvascular obstruction)
+5 min
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
Area at
Risk
TIRM
Area at
Risk
Optional imaging -T2 oedema imaging (2)
Problems with T2 oedema imaging
1. Low SNR
-therefore difficult to delineate and quantify.
2. Surface coil sensitivity
-T2 sequences are very prone to variations
3. Bright subendocardial rims
-due to stagnant blood.
4. Posterior wall signal loss
-due to cardiac movement,
Optional imaging –Myocardial hemorrhage
•
•
•
•
The presence of myocardial hemorrhage within the infarct is
Early Gd
associated with worse LV remodelling and clinical outcomes.
It can be detected using either STIR or dual-inversion blackblood gradient multi-echo T2* imaging sequences.
Hypointense region on T2 weighted imaging.
Appears to correspond to area of MVO.
STIR imaging
LGE
T2* imaging
Perfusion
LGE
Ganame et al Eur Heart J 2009 Apr Epub
O’Regan et al Radiology 2009;250:916-22.
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
Example- LAD infarct
Cine
TIRM
Perfusion
LGE
LGE
Acknowledgement:: Derek Hausenloy