How We Do CMR Perfusion

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How We Do CMR Perfusion
Robert Manka, Rolf Gebker, Eike Nagel German
Heart Institute Berlin and www.cmr-academy.com
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.
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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.

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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 (lt 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.

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Contraindications/Termination

• Contraindication for Adenosine
• Myocardial infarction lt3 Days
• Unstable angina pectoris
• Asthma or severe obstruktive pulmonary disease
• AV-block gtIIa
• 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 (gt20 mmHg)
• Persistent or symptomatic hypotension
• Severe respiratory difficulty

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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)

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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

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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 40-75 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

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Perfusion Flowchart

• 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

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Scanning procedure
start scan
contrast injection
2nd breathhold
1st breathhold
free breathing
1 breathing cycle
scanning interval
Baseline 5 dyn, start contrast injection
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Pulse Sequences

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

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Monitoring requirements

1. Heart rate rhythm continuously
2. Blood pressure every minute
3. Pulse oximetry not required when the vector-ECG
   used
4. Symptoms continuously
5. Defibrillator
6. All medications for emergency treatment

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Analysis of MR Perfusion Studiescover 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)

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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.

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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

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Stress-Perfusion
Early mycardial contrast uptake
RV contrast uptake
Late myocardial contrast uptake
Baseline
17
LV contrast uptake
RV contrast uptake
Myocardial contrast uptake
Baseline
Stress- Perfusion
Rest- Perfusion
Viability and coronary angiography