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← Section V · Cardiac Masses, Pericardial Disease, Contrast and New Applications
V.C

Contrast Echocardiography

7 cards

Notes

Types of contrast agents

  • Agitated saline - produces macrobubbles (large, quickly filtered by the lungs). Cannot cross pulmonary capillary bed → RA/RV opacification only. Used for shunt detection (bubble study).
  • Ultrasound contrast agents (UCA) - perfluorocarbon microbubbles (Definity, Optison, Lumason/SonoVue). Smaller, gas-stabilized microbubbles that cross the pulmonary bed → LA/LV opacification. Some UCAs are also used for myocardial perfusion.

LV opacification (LVO) - indications

  • ≥ 2 of 6 basal or mid LV segments not adequately visualized on standard imaging → give UCA.
  • Endocardial border definition in poor windows.
  • Detection of apical thrombus, apical HCM, LV non-compaction, aneurysm/pseudoaneurysm.
  • Stress echocardiography - improves regional wall motion assessment.

Right-heart bubble study (agitated saline)

  • Inject 5–10 mL agitated saline into a peripheral IV.
  • Watch for bubbles crossing to LA.
  • Intracardiac shunt (PFO/ASD): bubbles in LA within ≤ 3 cardiac cycles.
  • Intrapulmonary shunt (pulmonary AVM): bubbles appear later (4–8 beats).
  • Valsalva release increases sensitivity for right-to-left shunts.

Mechanical index (MI) considerations for contrast

  • Lower MI (0.1–0.3) for imaging: preserves microbubbles, allows longer observation.
  • Higher MI (~1.0) transiently destroys microbubbles - used in flash-replenishment perfusion imaging.

Safety

  • Adverse reactions rare (< 1 in 10,000).
  • Contraindication: known hypersensitivity. Previously included pulmonary hypertension and unstable cardiopulmonary status; current labeling relaxed but caution advised.
  • Injection technique matters: bolus injection avoiding excessive turbulence; flush with saline.

Myocardial contrast echocardiography (MCE)

  • Detects myocardial perfusion using microbubbles as an intravascular tracer.
  • Real-time MCE at rest and during stress can identify areas of hypoperfusion (ischemia) and viability (contrast replenishment kinetics).
  • Not routinely used clinically outside specialized centers.

Cards

  • basicV.C-001
    Why does agitated saline NOT opacify the LV/LA in a structurally normal heart?
    → The macrobubbles of agitated saline are too large to cross the pulmonary capillary bed — they are filtered out in the lungs and never reach the left heart.
  • basicV.C-002
    How many cardiac cycles suggest an intracardiac vs intrapulmonary shunt on a bubble study?
    → Bubbles in the LA within ≤ 3 cardiac cycles of RA opacification suggest an intracardiac shunt (PFO/ASD). Bubbles appearing after 4+ beats suggest an intrapulmonary shunt (pulmonary AVM as in hereditary hemorrhagic telangiectasia).
  • basicV.C-003
    Name three FDA-approved ultrasound contrast agents for LV opacification.
    → Definity (perflutren lipid microspheres), Optison (perflutren protein-type A), Lumason / SonoVue (sulfur hexafluoride microspheres). All contain gas-stabilized microbubbles that can cross the pulmonary capillary bed.
  • basicV.C-004
    When should LV contrast be used per ASE guidelines?
    → When ≥ 2 of 6 basal or mid LV segments cannot be adequately visualized on standard imaging. Also to detect apical thrombus, apical HCM, LV noncompaction, aneurysm/pseudoaneurysm, and to improve wall-motion assessment during stress.
  • basicV.C-005
    What mechanical index (MI) is used for LV opacification vs myocardial perfusion imaging?
    → Low MI (0.1–0.3) preserves microbubbles for opacification. Higher MI (~1.0) can be used to transiently destroy microbubbles during flash-replenishment for myocardial perfusion imaging.
  • basicV.C-006
    Why does Valsalva release increase sensitivity of a bubble study for PFO?
    → During the release (strain) phase, RA pressure transiently exceeds LA pressure, promoting right-to-left shunting across a small PFO that might not be evident at rest.
  • basicV.C-007
    What is a contraindication to intravenous ultrasound contrast?
    → Known hypersensitivity to the agent. Historically pulmonary hypertension and unstable cardiopulmonary status were contraindications; current labeling is relaxed but caution is advised in these patients.