Accuracy of a diagnostic test (stress echocardiography) is the proportion of people correctly classified by the test. For stress echocardiography accuracy, along with other measures of diagnostic techniques, is mainly estimated for detection of coronary artery disease and myocardial viability.
Standard terminology used in diagnostic testing
The following standard terminology is used in diagnostic testing :
- True positive = Abnormal test result in individual with disease
- False positive = Abnormal test result in individual without disease
- True negative = Normal test result in individual without disease
- False negative = Normal test result in individual with disease
- Sensitivity = True positives/(True positives + False negatives)
- Specificity = True negatives/(True negatives + False positives)
- Accuracy = (True positives + True negatives)/Total number of tests performed
- Positive predictive value = True positives/(True positives + False positives)
- Negative predictive value = True negatives/(True negatives + False negatives)
- Likelihood ratio positive = sensitivity /(1 − specificity)
- Likelihood ratio negative = (1 − sensitivity)/ specificity
Diagnostic accuracy of the different stress echocardiograpy techniques for detection of Coronary Artery Disease
According to EAE expert consensus statement exercise, high-dose dobutamine, and high-dose (accelerated or with atropine) dipyridamole have not only similar accuracies, but also similar sensitivities (Tables 1 and 2) . It should be noted that diagnostic accuracy of any test varies according to the pre-test likelihood of CAD in the population tested.
Table 1. Dipyridamole-stress vs dobutamine-stress echocardiography for detection of coronary artery disease
Table 2. Dipyridamole vs exercise stress echocardiography for detection of coronary artery disease -
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In a recently performed meta-analysis  assessing diagnostic accuracy of exercise stress testing for coronary artery disease it was shown that discriminatory abilities of stress echocardiography and SPECT are significantly better than exercise testing with ECG alone. Overall, treadmill echo testing (LR+ = 7.94) performed better than treadmill ECG testing (LR+ = 3.57) for ruling in CAD and was similarly better at ruling out CAD (echo LR) = 0.19 vs. ECG LR) = 0.38). Bicycle echo testing (LR+ = 11.34) performed better than treadmill echo testing (LR+ = 7.94), which both outperformed treadmill ECG (LR+ = 3.57) or bicycle ECG (LR+ = 2.94).
Pharmacological Stress Echocardiography
In meta-analysis by E. Picano et al.  it was shown that dipyridamole and dobutamine have similar accuracy (87%, 95% confidence intervals, CI, 83–90, vs. 84%, CI, 80–88, p = 0.48), sensitivity (85%, CI 80–89, vs. 86%, CI 78–91, p = 0.81) and specificity (89%, CI 82–94 vs. 86%, CI 75–89, p = 0.15). It should be noted that in this meta-analysis only studies with state-of-the art protocols were considered.
Diagnostic accuracy of stress echocardiography for detection of myocardial viability
The concept of myocardial hibernation was introduced by Rahimtoola to describe a condition of chronically, dysfunctional myocardium due to chronic underperfusion in patients who have coronary artery disease and in whom revascularization causes the recovery of LV function. Despite clinical relevance of viability was questioned after STICH trial, several noninvasive techniques are readily available to detect signs of viability, such as an intact cell membrane, residual glucose metabolism, or contractile reserve. Dobutamine stress echocardiography is by far the most widely used echo method for assessing viable myocardium based on presence of contractile reserve. Because hibernating myocardium represents a balance among flow and function it is possible that contractility reserve is lost while more basal characteristics, such as glucose metabolism and cell membrane integrity are preserved. This situation may explain, in part, differences in sensitivity and specificity of imaging techniques focusing on contractile reserve in comparison with perfusion imaging. Analysis of viability studies by Bax et al. (Table 3) showed reduced sensitivity and higher specificity of dobutamine stress echocardiography in comparison with PET and SPECT .
|Technique||No. of studies||% Sensitivity||% Specificity||% NPV||% PPV|
Diagnostic accuracy of new stress echocardiograpy techniques
Contrast stress echocardiography
As with most imaging techniques patient dependant factors can limit image quality in stress echocardiography, which can adversely affect accuracy. Ultrasound contrast agents for LV opacification are recommended by EAE consensus statement to enhance endocardial border detection when suboptimal imaging is present. Myocardial contrast echocardiography also allows qualitative and quantitative assessment of myocardial perfusion. In meta-analysis by S. Abdelmoneim et al.  pooled LRs for positive test were 1.33 (1.13–1.57), 3.76 (2.43–5.80), and 3.64 (2.87–4.78) and LRs for negative test were 0.68 (0.55–0.83), 0.30 (0.24–0.38), and 0.27 (0.22–0.34) for A, b, and Ab reserves, respectively. Existing data support a moderate diagnostic accuracy of quantitative myocardial contrast echocardiography in the detection of coronary artery disease.
3D stress echocardiography
Real time 3D stress echocardiography is a promising technique allowing simultaneous assessment of overall motion of the entire ventricle in different planes. Several studies showed feasibility of real time 3D stress echocardiography both in pharmacological and exercise-induced stress (Table 4) .
|Ahmad, 2001||58||DSE||Coronary angiography||79||−||88||−|
|Aggeli, 2007||56||DSE||Coronary angiography||73||78||93||89|
|Yoshitani, 2009||71||DSE-3D Multiplane||Coronary angiography||−||−||72||72|
|DSE-3D Multislice||Coronary angiography||−||−||77||95|
|Jenkins, 2009||90||Treadmill exercise-2D||Coronary angiography||83||65|
|Treadmill exercise-3D||Coronary angiography||−||−||40||84|
|Treadmill exercise-3D +CFM||Coronary angiography||−||−||55||78|
|Abdelmoneim, 2010||30||Adenosine 2D||Tc 99m Sestamibi SPECT||92||75||−||−|
|Adenosine Live 3D||Tc 99m Sestamibi SPECT||−||−||91||69|
|Adenosine Full volume 3D||Tc 99m Sestamibi SPECT||−||−||90||79|
But several limitations of real time 3D stress echocardiography including low spatial and resolution, image artifacts due to respiration, patient motion have to be overcome to meet the clinical requirements.