What is the interpretation of exercise stress test (treadmill test) results?

From the Guidelines

The interpretation of exercise stress test results should primarily focus on the Duke treadmill score, which remains the most widely used method to assess risk and prognosis, as it provides a reliable estimate of annual mortality rate. The Duke treadmill score is calculated as the exercise time in minutes minus (5 × ST-segment deviation, during or after exercise, in millimeters) minus (0 if there is no angina, 4 if angina occurs, and 8 if angina is the reason for stopping the test) 1. This score works well for both inpatients and outpatients, and preliminary data suggest that it works equally well for men and women, although the evidence is limited for elderly patients.

Key Components of Treadmill Test Results

• Exercise capacity: measured by the duration of exercise in minutes
• Heart rate and blood pressure response: should increase appropriately with exercise
• Symptoms: presence of chest pain, shortness of breath, or other symptoms during exercise
• ECG changes: ST-segment deviation, arrhythmias, or other abnormalities
• Recovery patterns: return of heart rate and blood pressure to baseline after exercise

Abnormal Findings and Further Testing

Abnormal findings on the treadmill test, such as chest pain, shortness of breath, inadequate heart rate or blood pressure response, significant ECG changes, or arrhythmias, may suggest coronary artery disease, heart rhythm problems, or other cardiovascular issues 1. In such cases, further testing, such as stress nuclear myocardial perfusion imaging or stress echocardiography, may be indicated to provide prognostic information that is incremental to the clinical assessment. The addition of imaging is particularly useful for patients who have an uninterpretable result on baseline ECG or an equivocal exercise or intermediate Duke treadmill score 1.

Limitations and Clinical Context

It is essential to consider the results of the treadmill test in the context of individual clinical factors, including medical history, symptoms, and risk factors. The test's sensitivity is about 65-70%, meaning false negatives can occur, particularly in women 1. If patients have ongoing symptoms despite normal results, additional evaluation may be warranted. Therefore, it is crucial to discuss specific results with a healthcare provider, as interpretation depends on individual clinical context.

From the Research

Interpretation of Exercise Stress Test Results

The interpretation of exercise stress test (treadmill test) results is a complex process that involves considering various factors, including electrocardiographic response, blood pressure response, and workload achieved at peak exercise 2. The results can be categorized into normal, ischemic, nondiagnostic, and equivocal categories, with each category having different implications for patient outcomes 3.

Factors Affecting Interpretation

Several factors can affect the interpretation of exercise stress test results, including:

• Beta-blocker therapy: Beta-blockers can affect the interpretation of treadmill test results, and it is suggested that they be withdrawn in post-myocardial infarction patients before the test 4.
• Exercise capacity: Poor exercise capacity is associated with increased risk of mortality, and can be used as a prognostic indicator 5.
• Heart rate responses: Abnormal heart rate responses during exercise testing can also predict mortality 5.
• Electrocardiographic abnormalities: Electrocardiographic abnormalities, such as ST segment depression, can indicate the presence of coronary artery disease 2, 6.

Clinical Utility

The clinical utility of exercise stress test results depends on various factors, including the patient population and the presence of underlying cardiovascular disease 3, 5. The results can be used to risk-stratify patients and identify those who require further evaluation or treatment.

Key Findings

Some key findings related to the interpretation of exercise stress test results include:

• The natural language processing algorithm can accurately categorize ETT results into normal, ischemic, nondiagnostic, and equivocal categories, with a sensitivity of 96.4% and specificity of 94.8% 3.
• The rates of 30-day death or acute myocardial infarction vary significantly across different categories of ETT results, with normal results associated with the lowest risk 3.
• The presence of multiple exercise test abnormalities can constitute a "CVD risk equivalent" in patients without cardiovascular disease 5.
• Beta-blockers can affect the interpretation of stress test results, but do not compromise the overall sensitivity of the test to detect coronary disease 6.