From the Guidelines
A positive exercise stress test is diagnosed when specific abnormalities occur during or after physical exertion, with the primary diagnostic criterion being ST-segment depression of at least 1 mm (0.1 mV) that is horizontal or downsloping, measured 80 milliseconds after the J point on the ECG, as stated in the 2005 American College of Cardiology/American Heart Association task force report 1.
Diagnostic Criteria
The diagnostic criteria for a positive exercise stress test include:
- ST-segment depression of at least 1 mm (0.1 mV) that is horizontal or downsloping, measured 80 milliseconds after the J point on the ECG
- New ST-segment depression greater than or equal to 2 mm (0.2 mV) (horizontal or downsloping) believed to represent ischemia even in the absence of ischemic discomfort
- Exercise-induced angina
- ST-segment elevation in leads without Q waves
- Sustained ventricular arrhythmias
- A drop in systolic blood pressure ≥10 mmHg during increasing workload
Test Interpretation
The test's diagnostic accuracy varies, with sensitivity around 68% and specificity about 77%, influenced by factors like the patient's pretest probability of disease, medications, and baseline ECG abnormalities, as reported in the 2006 European Society of Cardiology guidelines on the management of stable angina pectoris 1.
Additional Considerations
The Duke Treadmill Score can help quantify risk, incorporating exercise time, ST-segment deviation, and angina symptoms, and a test may also be considered positive if the patient cannot achieve 85% of their age-predicted maximum heart rate due to limiting symptoms, as discussed in the 2014 American Heart Association consensus statement on the role of noninvasive testing in the clinical evaluation of women with suspected ischemic heart disease 1.
Key Points
- The primary diagnostic criterion for a positive exercise stress test is ST-segment depression of at least 1 mm (0.1 mV) that is horizontal or downsloping
- Other criteria include exercise-induced angina, ST-segment elevation, sustained ventricular arrhythmias, and a drop in systolic blood pressure ≥10 mmHg during increasing workload
- The test's diagnostic accuracy varies, with sensitivity around 68% and specificity about 77%
From the Research
Diagnostic Criteria for a Positive Exercise Stress Test
The diagnostic criteria for a positive exercise stress test, also known as an Exercise Tolerance Test (ETT), are based on several factors, including:
- The magnitude of ST segment depression during exercise 2
- The persistence of ST segment depression after exercise 3, 4
- The presence of ST segment depression on the resting electrocardiogram 5
ST Segment Depression
ST segment depression is a key indicator of myocardial ischemia during exercise stress testing. The magnitude of ST segment depression can improve the predictive value of exercise tests and help recognize patients with more severe coronary heart disease 2. A study found that the predictive value of exercise testing improved progressively with increasing ST depression, and was most reliable in patients with normal electrocardiographic baseline who were not receiving digitalis 2.
Persistence of ST Segment Depression
The persistence of ST segment depression after exercise can also be an indicator of a positive exercise stress test. However, the duration of ST segment depression after exercise may not be a reliable indicator of more severe disease 4. A study found that patients with ST segment depression persisting for more than 5 minutes after exercise did not have significantly more severe ischemia or coronary artery disease than those with ST segment depression persisting for less than 5 minutes 4.
Resting Electrocardiogram
The presence of ST segment depression on the resting electrocardiogram can confound the results of exercise stress testing. However, a study found that the presence of ST segment depression on the resting electrocardiogram did not impair the detection of ischemia by exercise stress testing, but may be associated with a higher false-positive rate 5.
Other Factors
Other factors, such as the patient's symptoms, medical history, and physical condition, can also influence the interpretation of exercise stress test results. The Duke treadmill score has excellent prognostic value for exercise stress testing, and imaging is not necessary if patients are able to achieve more than 10 metabolic equivalents on exercise stress testing 6.