Cardiac Stress Testing
For patients who are capable of performing an exercise test, an exercise stress rather than pharmacologic stress is recommended, as the exercise capacity is an important predictor of outcome. Nuclear Stress Testing is expensive and therefore other stress imaging modalities like stress echo should be considered as a first diagnostic modality when possible, providing accuracy for detection of CAD and prognostics information equivalent to SPECT perfusion imaging.
Stress Test or Stress Echocardiography?
In patients with suspected coronary artery disease, a Stress Echocardiogram confers an excellent prognosis and is more sensitive than Exercise Treadmill Stress Testing. Stress Echocardiography can also identify multi-vessel disease.
Stress Echocardiography is a well-validated tool for detection and assessment of CAD. Its prognostic value has been well documented in multiple large studies.
Stress Echocardiography (Cheitlin, 2003) is an imaging stress test alternative to a nuclear stress test. The sensitivity is slightly lower but the specificity is higher, making the overall accuracy of this test similar to that of stress nuclear imaging.
The prognostic value of stress echocardiography is well-established in both men and women. It is also as a useful non-invasive tool for the evaluation of CAD in elderly and when performed safely early after a myocardial infarction it provides not only an assessment of global and regional ventricular function, but can also detect the presence and extent of residual myocardial ischemia.
Stress Echocardiography Accuracy
Since 1998 when ASE (American Society of Echocardiography) reported on sensitivity (88%) and specificity (83%) of stress echocardiography, additional studies evaluating the accuracy have been performed. Studies comparing the accuracy of nuclear perfusion imaging and stress echocardiography in the same patient population have shown that the tests have similar sensitivities for the detection of CAD, but stress echocardiography has higher specificity (Journal of the American Society of Echocardiography- Volume 20, Issue 9 September 2007).
Clinical Indications for Cardiac Stress Testing
- Evaluation of chest pain (stable, unstable or stabilized by medical therapy)
- Evaluation of heaviness or burning in the chest, arms, neck, or jaw
- Evaluation of patients symptomatic with shortness of breath or heart palpitations
- Evaluation of patients with atypical or non-cardiac sounding chest pain
- To diagnose the presence or rule-out of coronary artery disease/ischemia
- Screening for silent CAD in selected high-risk asymptomatic patients
- Identification of known or suspected exercise-induced arrhythmia
- Risk assessment and follow up from a previous heart attack, angioplasty, bypass surgery or stent insertion
- Evaluationmultiple risk factors when screening for cardiac disease
- Evaluation of cardiac disease patients before the age of 60 withstrong family history of heart disease
- Risk stratification of patients with known or suspected CAD andpatients with diabetes mellitus
- Re-evaluation of medically managed patients in response to therapy
- As a part of an annual check up in patients with cardiac risk factors if clinically indicated
- Preoperative evaluation for non-cardiac surgery in high risk patients with valvular heart disease
- Ischemic cardiomyopathy, assessment of viability/ischemia
- Evaluation for exertional hypotension or exercise-induced hypertension
- Suitability to participate in competitive sports
Moreover, Stress Echo has great versatility, permitting assessment of global and regional left ventricular size, shape and function, site of coronary stenosis, valvular and pericardial abnormalities, chamber sizes, and wall thickness. It also predicts the presence of myocardial hibernation when the myocardium fails to contract normally but which may recover after revascularisation.
Stress Echo can be ordered when the baseline ECG shows the following:
- Paced ventricular rhythm
- Pre-excitation syndrome (Wolf-Parkinson-White syndrome)
- More than 1 mm ST segment depression (e.g. associated with LVH or digitalis effect)
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