Oral Exam - Cardiac Flashcards
Multiple-gated cardiac blood pool acquisition (MUGA)
○ Low inter- and intra observer variability (<5%)
○ High reproducibility
○ Heart must be in regular rhythm for optimal imaging
– Ejection fraction results less reliable if ≥ 30%irregular
beats
○ If background drawn over spleen or aorta, ejection
fraction (EF) spuriously high
○ If background drawn over stomach or outside body, EF
spuriously low
• Evaluate raw images (cine) for study quality
○ Counts, labeling, gating, views
• Compare qualitative estimation of left ventricular ejection fraction with quantitative calculation
Things to evaluate on MUGA
○ Pericardial silhouette ○ Chambersizes ○ Hypo/akinesis ○ Filling defects ○ Aneurysm ○ Ejection fraction
MUGA protocol
Radiopharmaceutical: 15-25 mCi (555-925 MBq) Tc-99m
pertechnetate autologous labeled RBCs IV
○ Image acquisition
– Patient supine
– ECG gating
□ 16-32 frames per R-R interval
– Planar images: LEAP/high-resolution collimator
– Matrix: 64 x 64
– Each image acquired for 300K counts or 5 min
Anterior view - anterolateral and apical LV; right atrium and right ventricle
Best septal view LAO: Angle chosen that best shows septum between right and left ventricles; septal, anterolateral, posterolateral LV
Left lateral/LPO: 45° greater than best septal LAO
□ Shows inferior, apical, anterolateral LV
- Phase image: Shows equence of contraction of atria and ventricles
- Amplitude image: Shows magnitude of contraction of atria and ventricles
Artifacts myocardial perfusion imaging
Motion artifact
○ Hurricane sign: Counts outside epicardial border on short axis
○ Blurred endocardial border
○ Lateral wall blurring
Scatter artifact
○ Counts scatter into inferior wall due to high bowel
activity
Reconstruction artifact
○ Photopenia in inferior wall from high bowel activity
Attenuation
○ Soft tissue attenuation causing fixed defects
○ Misregistration of attenuation correction map and
perfusion data
• Normal apical thinning
• Left ventricular hypertrophy: Fixed lateral wall defect
• Soft tissue attenuation of photons: Breast (anteriorwall),
diaphragm (inferior wall)
• Septal hypokinesis common in absence of MI, especially
after coronary artery bypass graft surgery
Myocardial hibernation: Myocardium with little/no
perfusion, but viable due to anaerobic glycolysis
○ 25% of fixed defects are viable on viability studies
Conclusion of MPI study
Conclusion
○ Positive or negative for inducible ischemia
○ Positive or negative for myocardial infarction (± peri-
infarct ischemia)
– Consider possibility of hibernating myocardium, need
for viability study
○ LV function: EF and wall motion
R-L shunt protocol
○ Tc-99m MAA
○ Use reduced MAA particle count (100,000-200,000) in
case of suspected shunt, pulmonary hypertension, pregnancy, or pediatric patient
Imagea cquisition
○ LEAP collimator
○ In addition to anterior/posterior planar images of lungs,
posterior images of kidneys and anterior/posterior of brain
– Brain images: Most sensitive indicator of right-to-left
shunt
R-L shunt findings
○ Abnormal uptake within brain and kidneys confirms
shunting of Tc-99m MAA administered intravenously
○ Tc-99m MAA should localize only in brain and kidneys
with shunt
○ Must be differentiated from extrapulmonary uptake of
free Tc-99m pertechnetate
– Free Tc-99m pertechnetate is also visualized in thyroid gland, salivary glands and gastric mucosa
- Always scrutinize VQ scans for unexpected incidental uptake within brain or kidneys
- If uptake in kidneys, must look for brain or thyroid/salivary uptake (kidneys can be either due to free pertech or r-L shunt)
Ddx R-L shunt
Intracardiac shunt:
ASD/PFO/VSD
Extracardiac shunt:
Pulmonary AVM
Anamolous systemic venous return
Hepatopulmonary syndrome
Free pertechnetate - kidneys, thyroid, SG, gastric mucosa
FDG PET Normal perfusion decreased FDG
Reverse mismatch
Ddx: Revascularization early after MI LBBB RV pacing non-ischemic cardiomyopathy diabetes
FDG PET for sarcoid
Focal patchy FDG uptake in the myocardium can indicate active inflammation
Not specific for sarcoidosis
Other causes of myocardial inflammation – giant cell, viral myocarditis, pericarditis etc.
NPO x 12 hours
High risk scan features
SSS > 13 (regardless of reversability) SDS > 7 TID 1.22 with exercise; 1.35 with vasodilator Fall in EF > 5% with stress Post stress EF < 40% Multiple vascular territories
LBB?
If the QRS complex is widened and downwardly deflected in lead V1, a left bundle branch block is present.
Can get rabbit ears in V6
Criteria:
- QRS duration greater than 120 milliseconds
- Absence of Q wave in leads I, V5 and V6
- Monomorphic R wave in I, V5 and V6
- ST and T wave displacement opposite to the major deflection of the QRS complex
RBBB = RSR’ in V1; No rabbit ears in V6
Ventricular couplet
2 PVCs in a row
Premature beats
PAC = narrow complex QRS; unusual usually biphasic P wave
PJC - narrow complex QRS, sometimes no P wave
PVC = wide complex QRS
Ventricular tachycardia
3 PVCs in a row
A wide complex tachycardia without sinus P waves. Ddx BBB
