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Stress Echocardiography—State of the Art
indication, and results in estimated incremental savings of approximately
Figure 2: Case of a 64-year-old Male Who Underwent a
$238/patient.
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We also have evaluated the cost savings of using contrast
Pre-operative Dobutamine Stress Echocardiogram
agents with SE in a large single-center experience comprising 16,052
patients, of whom 3,637 (23%) received contrast. The adjusted odds ratio
(OR) for having a repeat test in patients receiving contrast was 0.38
(95% confidence interval [CI] 0.29–0.47), with 16% of patients in the
non-contrast group having additional testing compared with 5.8% in the
contrast group (p<0.001) at 21 days.
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Myocardial Contrast Echocardiography
Myocardial perfusion abnormalities occur as a result of limited coronary
A
flow reserve, with a consequent decrease in myocardial contractility.
Ultrasound contrast agents enhance the backscattered ultrasound
signal, permitting detection not only in the LV cavity, improving regional
wall motion assessment, but also in the myocardium. Indeed, improved
ultrasound imaging strategies for microbubble detection have resulted
in routine visualization of contrast within the myocardium, and
stimulated a proliferation of investigative work into the non-invasive
ultrasound assessment of myocardial perfusion. Image acquisition
techniques using reduced acoustic power (mechanical index 0.1–0.2),
B
while maintaining realtime imaging frame rates (20–30Hz), have allowed
realtime myocardial contrast echocardiography (MCE) and simultaneous
A: Apical two-chamber view at peak dobutamine stress showing inferior wall perfusion defect
assessment of both function and perfusion.
(arrows) at two beats after microbubble destruction (flash). Acoustic shadowing prevents
visualization of normal perfusion in the anterior wall in this view. No regional wall motion
abnormalities detected at peak dobutamine stress. B: Coronary angiography showed a normal
Stress Myocardial Contrast Perfusion Echocardiography
left anterior descending artery (LAD) and a 40% stenosis in the distal left circumflex coronary
artery (left panel). The proximal right coronary artery (RCA) shows a 60%, stenosis (arrow)
Destruction of microbubbles and observation (both qualitative and
(right panel).
quantitative) of gradual refill (replenishment) into the myocardial
microvasculature are the keys to accurately evaluating perfusion using sensitivity and specificity for Aβ reserve was 80% (75–84) and 81%
realtime MCE.
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A meta-analysis of eight studies comparing the sensitivity (77–84), respectively.
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The assessment of quantitative myocardial
and specificity of qualitative MCE with those of SPECT/dobutamine SE for perfusion during SE was shown to further improve the accuracy of SE
the detection of CAD showed at least equivalent (non-inferior) results.
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A over qualitative MCE alone.
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An example of a perfusion defect with
number of SE studies have employed coronary angiography as the gold realtime perfusion during dobutamine stress is shown in Figure 2.
standard (see Table 4) for CAD diagnosis, with reported sensitivities of
64–97% and specificities of 51–100%; MCE perfusion consistently Stress MCE also provides prognostic value in patients with stable CAD.
improved sensitivity for detection of CAD over wall motion analysis alone. Tsutsui and colleagues studied 788 patients with realtime MCE during
dobutamine SE during a median follow-up of 20 months. The authors
Quantification of myocardial blood flow (MBF) can be indirectly yet reported that patients with normal perfusion have a better outcome
accurately calculated by using the rate and volume of microbubble than patients with normal wall motion. Furthermore, abnormal
movement through the coronary microcirculation. With continuous myocardial perfusion had significant incremental value over clinical
microbubble infusion, steady-state microbubble concentration is factors, resting ejection fraction, and WM responses in prediction of
achieved in the blood pool. After a brief high-mechanical-index impulse cardiac events. Indeed, abnormal myocardial perfusion was an
to deplete the myocardium of microbubbles, replenishment is independent predictor of cardiac events (HR 5.2, 95% CI, 3.0–9.0;
characterized by a time–intensity curve, which is subsequently fitted to p<0.001).
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Similarly, in a recent study by Dawson and colleagues
89
the
the monoexponential function Y=A(1–e–
βt
), where β represents the incidence of non-fatal MI and cardiac death was determined in 261
rate of rise in signal intensity (microbubble velocity) and A is the peak patients with known or suspected CAD who underwent simultaneous
plateau of video intensity (myocardial blood volume). The product of A dipyridamole stress MCE and 99mTc-sestamibi SPECT during a mean
times β represents an index of MBF.
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We recently performed a follow-up period of 14 months. The authors reported that abnormal
systematic review and meta-analysis database search of the literature to results on MCE were found to be an independent predictor of an
identify 627 patients who had undergone quantitative stress (vasodilator adverse outcome (OR 23, 95% CI 6–201; p<0.001) and provided
or dobutamine) MCE for detection of CAD with comparative coronary incremental prognostic value over clinical variables, LV systolic function,
angiography and/or SPECT. We found a significantly lower weighted inducible wall thickening abnormalities, and SPECT results.
mean difference (95% CI) for each of the measured parameters—A, β,
and Aβ reserve parameters in those patients with CAD versus those 3D Stress Myocardial Contrast Perfusion Echocardiography
without: 0.12 (0.06–0.18), 1.38 (1.28–1.52), and 1.47 (1.18–1.76), Realtime 2D MCE is limited by the single cross-sectional 2D image,
respectively (all with p<0.001). Pooled sensitivity and specificity for β which cannot evaluate the 3D architecture of a perfusion defect. Recent
reserve was 81% (76–85) and 77% (73–80), respectively, while pooled improvements in 3D contrast technology include the incorporation of
US CARDIOLOGY 21