Cardiac Stress Testing
For patients capable of performing an exercise test, exercise stress testing is preferred, as exercise capacity is a significant predictor of long-term outcomes. Nuclear Stress Testing, though widely used, is expensive and involves radiation exposure. As a more cost-effective and radiation-free alternative, Stress Echocardiography (Stress Echo) is recommended as a first-line diagnostic modality whenever possible. Stress echo provides diagnostic accuracy for detecting coronary artery disease (CAD) and offers valuable prognostic information comparable to Single Photon Emission Computed Tomography (SPECT) or nuclear stress test.
Stress Test or Stress Echocardiography?
Stress echocardiography has demonstrated significant value in detecting coronary artery disease (CAD) and has been shown to provide an excellent prognosis. It is also more sensitive than Exercise Treadmill Stress Testing (GXT) alone in identifying CAD and can provide detailed insights into the presence of multi-vessel disease.
Stress Echocardiography: A Well-Validated Diagnostic Tool
Stress echocardiography is a non-invasive imaging technique that plays a key role in the evaluation and management of patients with suspected coronary artery disease (CAD). Its accuracy and prognostic value have been well-documented in multiple large-scale studies across various populations, including both men and women. Importantly, Stress Echo is particularly useful in patients with intermediate risk for CAD, where other diagnostic tools may yield less conclusive results. By providing real-time imaging of the heart's functional response to stress, stress echo allows for the assessment of global and regional ventricular function, detecting ischemic areas that may otherwise go undiagnosed.
Benefits of Stress Echocardiography
Stress echo is often preferred for patients at intermediate risk for coronary artery disease, as it provides both high sensitivity and specificity in diagnosing CAD, especially when compared to Exercise Treadmill Testing. Additionally, stress echo offers the advantage of identifying multi-vessel disease and is associated with a lower false positive rate compared to nuclear tests. The higher specificity of stress echocardiography reduces the likelihood of over-diagnosing patients without CAD, making it a critical tool in risk stratification for patients with known or suspected CAD.
Further, stress echocardiography plays a crucial role in the evaluation of patient’s post-myocardial infarction (MI) or following revascularization procedures. When performed early after MI, it provides essential information not only about global and regional ventricular function, but also the presence and extent of residual ischemia. This critical data can guide clinical decision-making, helping to determine the need for further treatment or revascularization strategies.
Stress Echocardiography Accuracy
As established by the American Society of Echocardiography (ASE) in 1998, stress echocardiography has shown 88% sensitivity and 83% specificity for detecting coronary artery disease (CAD). More recent studies, such as those published in the Journal of the American Society of Echocardiography (2007), have reaffirmed that the diagnostic accuracy of stress echocardiography is comparable to SPECT imaging, with the notable advantage of higher specificity for CAD detection. These findings highlight stress echocardiography's effectiveness as a reliable non-invasive diagnostic tool in the assessment of CAD.
Versatility of Stress Echocardiography
In addition to evaluating myocardial ischemia, stress echocardiography provides a broad range of diagnostic benefits, including:
Assessment of left ventricular size, shape, and function
Identification of valvular and pericardial abnormalities
Detection of wall motion abnormalities and regional dysfunction
Evaluation of myocardial viability in patients with ischemic cardiomyopathy
Detection of myocardial hibernation, a condition in which the myocardium fails to contract normally but may recover following revascularization
This versatility makes stress echocardiography a highly valuable tool not only in the detection of CAD but also in broader cardiac assessment, aiding in decision-making regarding treatment strategies, especially in complex cases such as ischemic cardiomyopathy or myocardial hibernation (Tighe et al., 2003; Bonow et al., 2019).
Indications for Stress Echocardiography in Special ECG Conditions
Stress echocardiography is particularly valuable in patients with ECG conditions that may interfere with other diagnostic tests, such as:
Left Bundle Branch Block (LBBB)
Paced ventricular rhythm
Pre-excitation syndrome (e.g., Wolf-Parkinson-White syndrome)
Significant ST segment depression, which may be associated with left ventricular hypertrophy (LVH) or the digitalis effect
These ECG abnormalities can make it difficult to interpret results from other stress tests, such as treadmill electrocardiography or nuclear imaging, due to either baseline changes in the ECG or the inability to assess ischemia reliably. Stress echocardiography overcomes these limitations by offering a more direct evaluation of myocardial function and ischemia, regardless of the underlying ECG findings.
Clinical Indications for Stress Echocardiography
Typical or atypical chest pain or ischemic equivalent syndrome.
New or worsening chest pain or ischemic equivalent.
Evaluation of patients at intermediate (e.g., hypertension, diabetes, dyslipidemia, smoking history, or family history of premature CAD) or high global CAD risk.
Re-evaluation of patients at intermediate or high global CAD risk.
Post-MI and ACS for risk stratification.
Re-evaluation of stable patients with known CAD (e.g., previous coronary angiography, CTA, MI, ACS, or abnormal stress imaging).
Known left ventricular (LV) systolic dysfunction.
Assessment of myocardial viability in patients with significant LV dysfunction post-revascularization.
History of congestive heart failure (CHF).
Physiologic assessment and/or symptom correlation in patients with moderate aortic stenosis, mitral stenosis, mitral regurgitation, aortic regurgitation, or hypertrophic cardiomyopathy.
Ventricular arrhythmias.
Syncope of unclear etiology.
Assessment of established or latent pulmonary hypertension.
Limitations of Stress Echocardiography
It is estimated that up to 20% of resting transthoracic echocardiograms (including pre-exercise resting echo images taken as part of a stress echocardiography protocol) have suboptimal left ventricular endocardial visualization, defined as two or more segments not being adequately visualized. This limitation underscores the importance of high-quality visualization for accurate diagnostic results.
Contrast Stress echocardiography, using Definity as a contrast agent, enhances the sensitivity of standard transthoracic echocardiography by improving the visualization of cardiac structures and blood flow, particularly in patients with suboptimal baseline images.
For comprehensive information about contrast stress echocardiography, indications, and additional details about Definity, please visit our "For Doctors: Contrast Echocardiography" section.
Report Processing
The Stress echocardiography report is meticulously analyzed by a cardiologist. A detailed report, including conclusions and clinical recommendations, is sent directly to the referring physician. This ensures that patients receive timely and accurate follow-up care.
Next Steps
To refer a patient for Stress Echocardiography or any other diagnostic modality, please download the Requisition Form and fax it to our Requisition Processing Centre at 647-351-6648.
References
American Society of Echocardiography (ASE). (1998). Sensitivity and specificity of stress echocardiography. ASE Guidelines.
Cheitlin, M.D. (2003). Stress echocardiography: A valuable tool in the diagnosis of coronary artery disease. Journal of the American College of Cardiology.
CorHealth Ontario. (2021). Standards for Provision of Echocardiography in Ontario.
Fihn, S.D., et al. (2014). ACC/AHA guideline for the management of patients with coronary artery disease. Journal of the American College of Cardiology.
Frazier, D.T., et al. (2004). Non-invasive testing for coronary artery disease: A comparison of SPECT and stress echocardiography. Circulation.
Garcia, M., et al. (2013). Prognostic value of stress echocardiography. American Journal of Cardiology.
Krittayaphong, R., et al. (2010). Stress echocardiography for the evaluation of coronary artery disease. American Heart Journal, 159(2), 123-130.
Lanza, G.A., et al. (2007). Stress echocardiography and nuclear imaging for coronary artery disease detection: A comparative study. Journal of the American Society of Echocardiography, 20(9).
Lanza, G.A., et al. (2007). Stress echocardiography in the diagnosis and prognosis of coronary artery disease: A review of the literature. Journal of the American Society of Echocardiography, 20(9), 1101-1111.
Marwick, T.H., et al. (2009). Stress echocardiography: Role in the diagnosis of coronary artery disease. European Heart Journal.
Marwick, T.H., et al. (2014). Stress echocardiography: An overview. Journal of the American College of Cardiology, 64(5), 538-546.
Medical Advisory Secretariat. (2010). Use of contrast agents with echocardiography in patients with suboptimal images: An evidence-based analysis. Ontario Health Technology Assessment Series, 10(9), 1–44.