This document discusses the diagnostic use of contrast agents in echocardiography. Contrast agents are injectable microbubble solutions that improve the visualization of the heart's structures when echocardiograms are suboptimal. They help delineate the left ventricular endocardial border to assess heart function. Two major types of contrast agents approved for use are those with air cores that dissipate quickly and those with heavy gas cores that are more persistent. Contrast agents enhance ultrasound imaging by improving organ edge delineation and evaluating blood volume and perfusion in the heart. This allows for more accurate diagnosis of conditions like valvular disease.

1. The Diagnostic Use for Contrast Agents in Echocardiography
Tobi Tamburrini
Diagnostic Medical Sonography Program–Long Island University
Objective
To examine the diagnostic purpose of using contrast agents as a tool
for echocardiograms and to compare different contrast agents that are
available.
Indication for Using Contrast Agents
A contrast agent is an injectable microbubble solution that is indicated
for use in patients with suboptimal echocardiograms.
Contrast agents help to opacify the left ventricular chamber and to
improve the delineation of the left ventricular endocardial border in
order to determine the function of the heart.
As defined by the American Society of Echocardiography (ASE), a
suboptimal image is one in which at least two out of six myocardial
segments of the left ventricle are not visualized in the apical views.
Segmental analysis of LV walls based on schematic views, in a parasternal short and
long axis orientation, at three different levels. The “apex segments” are usually
visualized from apical four-chamber, apical two- and three-chamber views.
Contrast Agents Approved by FDA for use in
USA
Advantages:
• Non-invasive
• Can be done at bedside
• Ultrasound allows for real time evaluation
• It is safe compared to alternative imaging modalities that use
radiation like MRI, PET and CT
• A very low dose of IV contrast agent is needed in ultrasound
compared to higher doses for MRI contrast studies
• No long term side effects known
Disadvantages:
• The microbubbles don’t last very long in circulation
• Microbubbles burst at low ultrasound frequencies and at high
mechanical index
• Since image quality increases with increasing mechanical index,
there is a trade off between image quality and destruction of
microbubbles
Conclusion
Contrast agents are of important diagnostic use especially helpful
when evaluating left ventricular function, delineating endocardial
boarders and diagnosing stenotic or insufficient heart valves.
Mechanism of Action
Organ Edge Delineation: contrast agents are used as a diagnostic tool
to enhance the contrast at the interface between the tissue and blood
within the heart. Tissue structure is crucial in echocardiograms, where
a thinning, thickening, or irregularity in the heart wall can indicate a
serious heart condition that requires either monitoring or treatment.
Blood Volume and Perfusion: contrast agents enhance ultrasound by
aiding in the evaluation of the degree of blood perfusion and blood
volume in the heart. When used in conjunction with Doppler
ultrasound, the microbubbles can also enhance the evaluation and
measurement of the myocardial flow rate to diagnose valvular disease.
Echocardiographic end-diastolic (top) and end-systolic (bottom) images of the
apical four-chamber view from a patient before (left) and after (right) intravenous
contrast.
Air Core Composition
• Highly soluble
• Low persistence and stability
• Rapid diffusion after disruption
Heavy Gases Core Composition
• High molecular weight
• Low solubility
• High persistence and stability
Microbubble size is fairly uniform regardless of the
composition of the microbubble shell or gas core
measuring 2-8 micrometers in diameter, which is smaller
than red blood cells.
Microbubble Size 2-8 μm Red Blood Cell Size 6-8 μm
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