Treadmill exercise test under 12-lead electrocardiographic (ECG) monitoring is a useful diagnostic tool because of its simplicity and widespread availability.
During this test, the patient initially walks and then runs on a treadmill, whose speed and angle gradually increase, under continuous ECG monitoring. As the workload increases, the patient’s heart rate increases, too. The test is completed when a target heart rate is reached. The test may also be stopped earlier for several reasons for example, if blood pressure drops, or if symptoms such as chest pain or shortness of breath occur. Any symptoms or ECG changes are assessed.
The test is particularly useful in the investigation for obstructive coronary artery disease. This disease refers to the narrowing of the coronary arteries (the arteries that supply the heart muscle with blood) due to chronic build-up of lipids, inflammatory cells, calcium etc. in the wall of the vessels (atheromatosis). This process is affected by age, gender, family history, smoking habits, hypertension, high blood sugar, diet and other factors called “cardiovascular risk factors”.
The doctor should evaluate the patient’s medical history, the clinical characteristics like what triggers the symptoms, if any, the nature and duration of symptoms, the ECG at rest, findings from the Echocardiogram (assessment of the heart using ultrasound), as well as the cardiovascular risk factors, to estimate how probable it is for a coronary artery disease to exist. The Guidelines of the European Society of Cardiology recommend the use of an ECG exercise test in people with moderate suspicion for coronary artery disease, since it is in those people that the test will add information to help the doctor to set or exclude the diagnosis. People with low probability should have other causes of symptoms investigated and no specific stress testing is indicated. This is because, since no tests in medicine are 100% accurate, the probability of a mistaken diagnosis due to the test, would be greater than the actual probability of having coronary artery disease. So, in the case of low probability, it is advisable to exclude the disease clinically. People with high probability, would not benefit from the test either, since the diagnosis of coronary artery disease may be set clinically (i.e. further testing will not improve accuracy).
Other reasons to use the treadmill exercise test with ECG will be explained in upcoming posts!
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