1. How We Do CMR Perfusion Robert Manka, Rolf Gebker, Eike Nagel
German Heart Institute Berlin
and
Created October 2007 for SCMR
This presentation posted for members of scmr as an educational guide – it represents the views and practices of the author, and not necessarily those of SCMR.

2. Perfusion
The occurrence of myocardial perfusion deficits is a very sensitive indicator of ischemia in the presence of significant coronary artery stenoses.
Most perfusion defects occur during stress, such as pharmacological vasodilation.
Adenosine is a safe and well tolerated pharmacological stress agent.
In-plane resolution of 2-3 mm allows separate visualization of the endo- and epicardial layers of the left ventricle.

3. Pharmacological Agent
Stressor agent:
Adenosine: i.v. 140 mcg/kg/min (preferable concentration 5mg/ml)
- A potent vasodilator of most vascular beds, except for hepatic and renal arterioles. It exerts its pharmacological effect through the activation of purine A1 and A2 cell-surface adenosine receptors
- Half-life 4-10 seconds
Antidote:
Adenosine infusion should be discontinued
Aminophylline i.v (250mg slowly injected under ECG monitoring)
Patient instruction:
No caffeine (tea, coffee, chocolate)
No aminophyline or nitrates for 24 hours

4. Adenosine- Side-Effects
Mild-to-moderate reduction in systolic, diastolic and mean arterial blood pressure (< 10 mmHg) with a reflex increase in heart rate.
Some patients complain about chest pain, which is rather nonspecific and does not reliably indicate the presence of CAD.
Direct depressant effect on the SA and AV nodes transient first-, second- and third-degree AV block and sinus bradycardia have been reported in 2.8%, 4.1% and 0.8% of patients.
Increases in minute ventilation, reduction in arterial PCO2 and respiratory alkalosis.
Approximately 14% of patients complain of dyspnea.

5. Contraindications/Termination
Contraindication for Adenosine
Myocardial infarction <3 Days
Unstable angina pectoris
Asthma or severe obstruktive pulmonary disease
AV-block >IIa
Claustrophobia
Non compatible biometallic implants (pacemaker/AICD)
Caution
Stenotic valvular disease
Autonomic dysfunction
Cerebrovascular insufficiency
Termination criteria
Persistent or symptomatik AV-block
Significant drop in systolic pressure (>20 mmHg)
Persistent or symptomatic hypotension
Severe respiratory difficulty

6. Scanner environment The pts lies in the supine position
1.5 or 3 Tesla (T) whole body scanner
Gradient strength 30 mT/m, slew rate 150 mT/m/ms
5 element cardiac synergy coil
Multichannel ECG (Vector-ECG)

7. Contrast Agents and Injection Scheme
Bolus with a dosage of 0.05 mmol/kg bw of an extracellular Gd-based CA (dose may be lower with Gd-DTPA-BMA)
Injection speed of 4 ml/s is used at the German Heart Institute Berlin
The bolus is followed by a 20 ml saline flush using the same injection rate to facilitate a compact bolus passage
We recommend the use of an automatic infusion system
Two 18 gauge venflons for separate administration of the stress agent and CA

8. Imaging Procedure
Cine wall motion imaging of the heart at rest, perfusion imaging under vasodilator stress, and finally delayed enhancement imaging
Examination time may vary between minutes
Breathhold should be performed during expiration to ensure reproducible slice geometry
First is a about 6 to 10 seconds during baseline acquisition of myocardial signal intensity.
Then the patient is asked to inhale and exhale once more and to hold his breath as long as possible. Right before starting this breathhold command the contrast bolus is administered.
The patient should stop breathing at least for 15 to 20 seconds resulting in a fixed slice geometry during the first-pass of the contrast agent

9. Perfusion Flowchart RR, rhythm & respiratory monitoring Survey
Transversal
Single-angulated view
Double-angulated view
Resting wall motion
Short axis (apical, mid, basal slice)
4 chamber/3 chamber
2 chamber
Carefully exclude any wraparound
If necessary enlarge field of view
Perfusion test scan
Slice geometry identical to (4)
acquisition of 5 dynamic images
RR, rhythm & respiratory monitoring
Adenosine infusion (140 µg/kg/min)
over 4 minutes
Inject gadolinium
0.05 mmol/kg
Stress Perfusion
Start imaging (60 dynamics) after
4 minutes of adenosine infusion
Stop adenosine infusion
wait 10 min
Inject gadolinium
0.05 mmol/kg
Rest Perfusion
Repeat (8) without adenosine
infusion
Inject gadolinium
0.1 mmol/kg
wait 10 min
Delayed Enhancement
Determine optimal inversion time

10. Scanning procedure start scan contrast injection 2nd breathhold
1st breathhold
1 breathing cycle
2nd breathhold
free breathing
scanning interval
First pass myocardial contrast uptake
LV contrast uptake
RV contrast uptake: 2nd breath hold command
Second pass myocardial contrast uptake
Baseline 5 dyn,
start contrast injection

11. Pulse Sequences T1-weighted
In-plane resolution of 2-3 mm to separately visualize the endo- and epicardial layers.
We use a balanced SSFP-technique which shows a higher peak enhancement and superior image quality compared with other sequences (T1-GrE, GrE-EPI).

12. Monitoring requirements
Heart rate & rhythm: continuously
Blood pressure: every minute
Pulse oximetry: not required when the vector-ECG used
Symptoms: continuously
Defibrillator
All medications for emergency treatment

13. Analysis of MR Perfusion Studies cover 16 out of 17 myocardial segments
Visual Analysis
For routine clinical use, we do a qualitative analysis by visual comparison of the contrast enhancement in different myocardial regions (see next slide)
Quantitative
Absolute Tissue Perfusion (Unit: ml/g/min) (requires mathematical modeling)
Semiquantification (stress induced change of upslope)

14. Visual assessment of regional myocardial perfusion
Evaluate the equatorial slice first, then check whether the suspected perfusion defect
can be followed in corresponding segments of the apical or basal slice
Abnormalities:
Signal intensity Pattern and Location
Dark regions arising from the subendocardium with usually irregular intramyocardial border or with completely transmural extent.
Dynamic myocardial filling pattern
Initially, slow or missing enhancement persistent over a few dynamics with consecutive signal intensity increase starting from the defects epicardial border.
Comparison Stress vs. Rest
If a regional defect is found in the stress scan, but not in the rest scan, inducible ischemia is confirmed. Regional persistence of the perfusion deficit shows myocardial scar.

15. Report
Data is reported for 16/17 segments (segment 1 – 16). The apical segment (17) is not visualized with 3 short axis views.
Perfusion defects are reported with their transmurality (transmural defect vs. subendocardial defect).
Perfusion images are compared to cine and late enhancement images

16. Stress-Perfusion RV contrast uptake Early mycardial contrast uptake
Late myocardial
contrast uptake
Baseline

17. RV contrast
uptake
LV contrast
uptake
Myocardial
contrast uptake
Baseline
Stress-
Perfusion
Rest-
Perfusion
Viability and
coronary
angiography