Cardiopulmonary exercise test

At the initial phases of atherosclerosis in patients with stable angina, usually there is no problem in the resting condition and symptoms of coronary artery disease often appear during the patient's activity, and therefore, it is better to examine the heart during activity and under stress to see the condition of the blood supply to the heart muscle more accurately and realistically, so a region with Ischemia which has happened due to the atherosclerosis, emerge itself. In this way, by timely treatment of dyspnea, progression of the disease and subsequent risks will be prevented. When someone has a heart pain during activity, the ECG may not show any change in the resting condition. In these cases this vagueness will largely be eliminated by performing the exercise test. In other words, exercise test is a test that reveals the hidden resting ECG changes through inflicting stress, and exercise and physical activity to the heart of the individual.

Preparation of the patient for exercise test

It is necessary to abstain from smoking and any or at least heavy food from 3 hours before the test. It is better to wear a comfortable dress and shoe, and warm up before the test; but do not do intense physical activity. Also, if you have diabetes one hour of fasting after a light meal would be enough and there is no need to change the amount of insulin, but definitely inform your doctor. You have to abstain from taking any cardiovascular drugs that prevent the increase of heart rate during exercise (such as digoxin, propranolol, metoprolol, atenolol, diltiazem and ....) within a predetermined interval before exercise test, under the supervision of your doctor.

technique of cardiopulmonary exercise test

 First, the pulse and blood pressure are measured and recorded, the electrodes of the electrocardiography are connected to the patient and the initial electrocardiogram is produced, then the patient is placed on the treadmill to do the exercise (running). This machine includes a rolling and mobile rubber plane (like a conveyor belt) on which the patient stands and he should walk or run with a speed matched with its speed. Every 3 minutes the slope and speed of the plane will increase according to a planned schedule. The device first moves slowly, but gradually it speeds up, and the person must catch up and run at the speed of the conveyor belt. Gradually the device is slanted more, and the person runs up high- pitched slope.

The vital signs and the patient's electrocardiogram are controlled in different conditions to detect changes in parts and waves in exercise condition. Based on age and sex, a certain amount of exercise and the maximum heart rate are considered for each patient, before the start of the exercise and running will continue till reaching that particular values. If the heart rate test reaches at least 85% of the maximum heart rate expected for that age and sex, test results can be interpreted.

 The best and most reliable result is when the patient reaches the maximum of (100%) predicted activity without having any chest pain, shortness of breath, or ECG changes; This requires about 12 to 10 minutes of exercise. Nevertheless, whenever the patient really feels unable to continue his exercise, or if he has some clinical signs such as chest pain, excessive shortness of breath, dizziness and severe headache, abnormal changes in the electrocardiography or drop in blood pressure, test should be discontinued sooner than that time. Some people who are elderly or who have joint or muscular pain and are unable to perform the exercise test, and people who have no possibility of interpreting changes in the new ECG due to changes in the baseline ECG should experience other methods, such as nuclear scanning of the heart with medical stress (thallium test), or stress echocardiography instead of exercise. Heart scan and stress echocardiography are easier and more accurate than the exercise test, but they are costly.

 Application of exercise test

In general, an exercise test can show coronary artery stenoses (stenosis of more than 60%) and guide the physician in deciding whether to take more invasive methods (such as angiography). Another application of this test is associated with evaluating the functional strength (physical activity tolerance) of the people who experienced myocardial infarction or heart failure and to determine the level of permissible activity for them. Exercise testing disadvantages: In up to 25% of the cases (depending the involved artery) exercise test is falsely negative (i.e., negative results despite the narrowing of coronary) and vice versa; exercise test is sometimes falsely positive (ie, a positive result in a healthy person). Exercise test can also not detect mild atherosclerosis. However, these plaques of atherosclerosis are of less clinically importance, but sometimes they rupture and cause a heart attack.

Prohibition of the use of exercise tests

An active Ischemia or a new heart attack, or some changes in the electrocardiogram, which impedes the interpretation of the results, are of conditions in which exercise test is prohibited. Also, when the patient is not able to exercise for any reason or if the exercise is harmful to him; the injection of certain to cause the stress and subsequent cardiac imaging techniques (stress echocardiography or nuclear scan) are used.

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