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Cardiovascular Applications of Ultrasound Contrast Agents
Figure 1: Apical Four-chamber View in a Figure 2: Apical Four- and Two-chamber Views
Patient with a Patent Foramen Ovale
A B
Contrast is seen in the right ventricular (RV) cavity after a peripheral A patient with a ‘good-quality’ echocardiographic study where it is obvious that in the absence of contrast (A) it is not possible to identify the left
injection of hand-agitated saline. A few bubbles are also seen in the left ventricular (LV) borders, while it is easy to identify them after the administration of contrast (B).
ventricuar (LV) cavity after a valsalva manoeuvre (arrow).
is one such example where a mass in the LV cavity (see arrow on panel A)
Figure 3: The Value of Using Ultrasound Contrast Agents to
was shown on myocardial perfusion imaging to have a ‘vascularity’ that was
Define the Absence or Presence of Left Ventricular Thrombus
greater than that of the surrounding myocardium (see arrow on panel B).
On angiography (see arrow on panel C) and histopathology (see panel D) it A B
was confirmed to be a cavernous haemangioma.
22
Similar results have been
reported for masses in other regions of the heart.
23
Another condition where CE has become the gold standard is in the
diagnosis of apical hypertrophic cardiomyopathy, since in many patients
with this condition the endocardium is not well visualised.
24
Figure 5
illustrates echocardiographic images before (panel A) and after (panel B) the
administration of US contrast in a patient with apical hypertrophic
In panel A there is suggestion of an apical thrombus (identified by the arrow) in a non-contrast-enhanced
image, while the contrast-enhanced image clearly rules out a thrombus. In panel B, the use of US contrast
cardiomyopathy. The endocardium was not clearly defined in the non-
clearly demarcates an apical thrombus (identified by the arrow).
contrast-enhanced images, while after administration of contrast better
endocardial definition led to the accurate diagnosis of the condition. Doppler Signal Enhancement
The clinical development of Levovist was initially for Doppler signal
The incidence of non-compaction of the LV has also markedly increased with enhancement.
31
Hand-agitated saline can be used successfully to enhance
the use of US contrast agents, since it is much easier to visualise the thinner the signal from the tricuspid regurgitation jet in patients with minimal
LV wall and the myocardial indentations and crevices seen in this condition.
25
tricuspid regurgitation so as to make the assessment of pulmonary artery
All patients with muscular dystrophy being referred to our laboratory to rule systolic pressure easier. However, the enhancement of left-sided signals
out cardiac involvement receive US contrast to rule out non-compaction or requires transpulmonary passage of microbubbles, and US contrast agents
other abnormalities. The endocardium is not clearly seen in many patients have been very helpful, especially in the case of mitral regurgitation,
32
with apical aneurysms or pseudo-aneurysms. US contrast can help prosthetic valves
33
and aortic stenosis.
34,35
Figure 6 illustrates how the
physicians to make the correct diagnosis and begin an appropriate presence of just a few microbubbles can enhance the pulsed-wave Doppler
therapy.
26
There also have been reports of the diagnosis of cardiac rupture signals from the pulmonary veins. US contrast-enhanced Doppler signals
with the use of US contrast agents.
27
have been reported to allow better non-invasive haemodynamic assessment
of heart failure patients.
36
These agents have been used for assessing
One of the biggest clinical applications for CE is stress echocardiography, pulmonary artery diastolic pressure from the pulmonary regurgitant jets that
where visualisation of every myocardial segment during stress is crucial to are present in almost all patients.
37
Despite the availability of hand-agitated
make the diagnosis of coronary artery disease (CAD).
28,29
In many cases the saline, US contrast agents have also become popular for enhancing the
endocardium may be visualised during rest and not during stress. tricuspid regurgitant Doppler velocity signals in order to measure pulmonary
Consequently, in our laboratory all patients are required to undergo CE artery systolic pressure.
38
during stress unless there is a specific contraindication or if the patient
declines. Our exercise stress tests are all performed using supine bicycle and Myocardial Perfusion Assessment
our pharmacological stress tests are all performed with dobutamine. In both By far the most research and greatest excitement has been generated in the
instances we administer contrast as a slow infusion using a pump and field of myocardial perfusion, and the reader is directed to in-depth reviews
acquire images at rest and recovery and during at least two exercise stages. elsewhere.
39–43
CE can be used to measure myocardial perfusion quite
As the presence of contrast does not often result in ambiguity regarding the precisely.
44
Microbubbles are administered as a constant infusion, and
occurrence of inducible wall motion abnormalities, we rarely if ever read a approximately two to three minutes later steady-state is achieved when
test as equivocal. Such an approach has shown to drastically reduce their concentration in any blood pool (LV cavity, myocardium, etc.)
downstream resource utilisation.
30
becomes constant and proportional to the blood volume fraction of that
ASIA-PACIFIC CARDIOLOGY 43
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