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Stress Echocardiography in Diagnosis of Coronary Artery Disease
Several studies have shown that assessment of coronary flow reserve From experienced laboratories, DSE using visual wall motion assessment
(CFR) during vasodilator SEcho as a complement to wall motion analysis demonstrated a mean sensitivity of 85% and specificity of 79% in regional
increases acuity for diagnosing CAD and adds power of prognostication. functional recovery prediction.
20
Moreover, a linear relation was present
In fact, a normal CFR as evaluated by pulsed Doppler flowmetry of mid- between the number of viable segments and the likelihood of recovery
distal LAD artery increases the predicted value of a negative test for wall of overall  left ventricular  function after revascularization. The
motion criteria.
15
Reduced CFR, however, is an additional parameter of identification of four or more viable segments accurately predicted LVEF
severity in risk stratification.
16
The European Society of Echocardiography improvement (e.g. ≥5%) after revascularization (sensitivity 86%,
has  recommended assessment of CFR and  wall motion  during specificity 90%), improvement in heart failure symptoms, and
vasodilator SEcho as complementary strategies whenever suitable reduction in event rate.
21
technology and dedicated expertise are available.
5
Recently, TDI parameters have been used to better quantify regional
Myocardial contrast echocardiography (MCE) is a technique that uses myocardial function during DSE in patients undergoing revascularization.
microbubbles during echocardiography. These microbubbles remain Aggeli and co-workers
22
showed that pre-ejection longitudinal tissue
exclusively within the intravascular space and their presence within any velocity change and peak systolic longitudinal velocity change assessed
myocardial territory denotes the status of microvascular perfusion by pulsed-wave TDI during low-dose dobutamine are reliable parameters
within that region. Recently, several authors have shown that by adding of myocardial viability, predicting recovery after revascularization.
MCE analysis to wall motion assessment during SEcho, the sensitivity in
detecting relevant CAD increases, especially in patients who do not
reach the target heart rate during stress and in patients with multivessel
Stress echocardiography’s wide
disease.
17
Moreover, although analysis of MCE is commonly performed
on a visual subjective basis, it is less vulnerable to interobserver acceptance in clinical practice reflects
variability than wall motion assessment.
18
its safety and prognostic value, which
Assessment of Myocardial Viability has also been proved in several
Systolic left ventricular dysfunction due to CAD is the complex result of
large-scale multicenter trials.
necrosis and scarring, but also of functional and morphological adaptive
abnormalities of the viable myocardium. In the setting of chronic  left
ventricular  dysfunction, myocardium viability usually refers to the
downregulation of contractile function in surviving myocardium in Hanekom et al.
23
demonstrated that strain rate imaging as an adjunct to
response to periodic or sustained reduction in coronary blood flow, routine visual wall-motion scoring during conventional DSE provides
which may be reversed if normal blood flow is restored. Viable incremental value to predict regional and global functional recovery
myocardium exists as a spectrum, from complete transmural infarction following revascularization, increasing sensitivity from 73 to 83% without
with no viability to transmural hibernation or stunning with potential for affecting the specificity. Further experimental and clinical studies have
full recovery. As roughly 40% of myocardial segments with resting wall validated strain rate imaging for the assessment of myocardial viability
motion  abnormalities after acute myocardial infarction have viable and suggest that  strain rate is a better quantitative parameter for the
tissue that may recover contractile function if revascularized, detection prediction of functional recovery compared with strain.
24
of viable myocardium is clinically relevant.
Although 2D strain is considered a promising tool to improve DSE
A number of non-invasive imaging procedures have been developed to accuracy in the assessment of myocardial viability, there are not yet
evaluate myocardial viability and to identify markers of functional clinical studies published in this setting. Becker and co-workers
25
recovery, including DSE, MCE, SPECT, positron emission tomography, and showed recently, however,  that 2D strain in rest allows the
cardiovascular magnetic resonance imaging. assessment of transmurality, since radial and circumferential strain
impairment is proportional to the extent of transmural scarring.
SEcho is based on evaluation of contractile reserve, a characteristic Moreover, they also found that peak systolic radial strain identifies
feature of viable myocardium that may be elicited by catecholamine reversible myocardial dysfunction and predicts regional and global
stimulation. The underlying principle is that adrenoreceptor stimulation functional recovery at 9±2 months follow-up. Moreover, the predictive
by dobutamine will augment function before ischemia is engendered by value was similar to that achieved by contrast-enhanced cardiac
increased myocardial work and metabolic demands. Typically, primarily magnetic resonance.
inotropic response occurs at low doses. Tachycardia, potentially eliciting
ischemia, usually develops only at higher doses. Assessment of Coronary Artery Disease
Exercise ECG stress testing is the most widely used test for detection
Alternative protocols for echocardiographic assessment of of CAD and assessment of prognosis. Although relatively inexpensive,
myocardial viability include dipyridamole, low-level exercise, and, its use is limited by suboptimal sensitivity for detecting single-vessel
more recently, levosimendan. Among them DSE is the most disease and poor  specificity in the presence of resting ST
extensively studied and the only one that has class 1 indication for abnormalities. Exercise or pharmacological SPECT and SEcho compare
viability assessment in guidelines.
19,20
favorably with ECG stress testing since they provide enhanced
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