What is an echo with contrast (echocardiogram)?

Echo with Contrast: An Advanced Echocardiographic Technique

An echo with contrast is an ultrasound imaging technique that uses specialized contrast agents (microbubbles) to enhance visualization of cardiac structures, particularly the left ventricular chamber and endocardial borders, resulting in improved diagnostic accuracy for patients with suboptimal standard echocardiograms. 1

What is Contrast Echocardiography?

Contrast echocardiography utilizes the unique properties of ultrasound contrast agents to significantly improve image quality during an echocardiogram. These agents consist of:

• Microbubbles with specific shell compositions (lipid or albumin)
• Gas-filled cores with high molecular weight (less soluble/diffusible, more stable)
• Size small enough to pass through pulmonary circulation but large enough for optimal ultrasound reflection 1

How It Works

Contrast agents work through a process involving:

1. Non-linear oscillation: Microbubbles oscillate within the ultrasound beam, reflecting sound at both fundamental and higher harmonic frequencies
2. Specialized imaging modalities: Uses lower mechanical index (MI) settings (0.2-0.5) to prevent bubble destruction
3. Enhanced visualization: Creates sharp demarcation between contrast-enhanced cardiac chambers and surrounding tissue 1

Contrast Imaging Techniques

Several specialized imaging techniques are employed:

• Power pulse inversion
• Power modulation
• Cadence (coherent) contrast imaging

These techniques rely on the fact that tissue is a linear ultrasound scatterer, while contrast microbubbles are non-linear, allowing for clear differentiation between them. 1

Clinical Applications

Contrast echocardiography has several important applications:

1. Left ventricular opacification (LVO):

   • Improves endocardial border definition
   • Enhances assessment of global and regional wall motion
   • Increases accuracy of ejection fraction measurements 1, 2

2. Detection of structural abnormalities:

   • Left ventricular thrombi
   • Pseudoaneurysms
   • Apical hypertrophy
   • Left ventricular non-compaction 1, 3

3. Myocardial perfusion assessment:

   • Evaluates blood flow at the tissue level
   • Helps detect coronary artery disease 1, 4

4. Left atrial appendage visualization:

   • Helps detect thrombi when images are inconclusive 1

5. Aortic disease assessment:

   • Improves detection of aortic dissection
   • Helps identify entry tears and true lumen 1

Clinical Impact

Contrast echocardiography has significant impact on patient management:

• Changes clinical management in approximately 51% of patients with suboptimal acoustic windows
• Particularly beneficial in patients with heart failure, cardiomyopathy, and arrhythmias
• Most impactful in patients with reduced ejection fraction 2

Administration

For adult patients, contrast agents like DEFINITY (perflutren) can be administered as:

• Bolus dosing: 10 microL/kg intravenously over 30-60 seconds followed by saline flush
• Infusion dosing: 1.3 mL added to 50 mL saline, administered at 4-10 mL/minute 5

For pediatric patients:

• Bolus dosing: 3 microL/kg intravenously over 30-60 seconds followed by saline flush 5

Important Considerations

• Safety: While generally safe, serious cardiopulmonary reactions can occur (uncommon)
• Mechanical index settings: Must be adjusted appropriately (0.8 or below for adults, 0.3 or below for pediatrics)
• Timing: Contrast must be used immediately after activation for optimal results
• Contraindications: Known hypersensitivity to perflutren or components like polyethylene glycol 5

Advantages Over Standard Echocardiography

Contrast echocardiography offers significant advantages:

• Enables biplane LV ejection fraction measurement in 97.2% of technically difficult studies
• Allows interpretation of regional wall motion in 95% of difficult studies
• Provides definitive assessment of LV thrombus in 99% of cases
• Improves correlation with gold standard techniques like cardiac MRI 1, 2

Contrast echocardiography represents an important advancement in cardiac imaging, providing crucial diagnostic information when standard echocardiography is suboptimal or inconclusive.