Table of Contents
Introduction
The heart's function is to supply blood throughout the body. Its functionality increases during various exercises, which is why researchers have used exercises as a tool to evaluate heart diseases.
What Are the Impacts of Exercise on the Heart?
Exercise increases the overall muscular activity in the body. The exercises are linked to alterations in the lungs and heart due to adaptation. While doing so, the respiratory system adapts by increasing both the rate and depth of breathing, resulting in enhanced ventilation to meet the increased oxygen demands of the active muscles. Moreover, vasodilation occurs in the blood vessels near the working muscles, leading to improved blood flow and enhancing gas exchange at the capillary level. These vasodilators are caused by substances like carbon dioxide, lactate, nitric oxide, and prostaglandins. Also, vascular contraction is observed in other parts of the body to maintain blood supply. As a result, the heart rate escalates to accommodate larger quantities of oxygenated blood circulation throughout the body. This leads to an increase in the cardiac output and stroke volume. Gradually, the body reaches its peak oxygen demand level. To compensate for this, a gradual increase in the heart rate is observed, which reaches its maximum level.
The heart plays a significant role during exercise, which is why cardiac patients may experience several complications. Exercise can also be used as a diagnostic tool to identify cardiac diseases.
What Is Exercise Stress Test?
Exercise stress tests are non-invasive and affordable exercises that are used to understand cardiac conditions. These tests are mostly used as diagnostic methods to identify underlying heart conditions. This test is performed on a treadmill, which is also known as treadmill stress testing. These tests are used to identify coronary artery diseases. The indications of these tests are;
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Conditions in which patients complain of chest pain and heaviness. Such symptoms can be felt both during resting and during exercises.
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Patients complain of breathing difficulties and fatigue.
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As a diagnostic test to identify myocardial infection.
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For the risk assessment after myocardial infarction.
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This is a good non-invasive procedure to evaluate the effectiveness of surgical and medicinal therapy.
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This can also be used to identify the presence of disorders like cardiac arrhythmia (rhythmic dysfunction of the heart), heart failure (complete failure of the heart muscles to pump blood), latent coronary disease, and congenital heart disease.
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It can be used to assess the functional capacity of the heart which can be used to determine exercise capacity.
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These exercises are also used as a tool to change lifestyle.
How to Perform Exercise Stress Test?
The goal of the exercise stress test is to assess exercise potency based on metabolic equivalents (MET). In this process, the uptake of the oxygen is determined and compared to the baseline value (one MET is equivalent to 3.5 millimeters of oxygen uptake per kilogram per minute). The Bruce protocol is the most commonly used protocol for exercise stress tests. It consists of seven stages, each lasting three minutes, totaling 21 minutes of exercise for a full test. In the first stage, the patient walks at 1.7 mph (2.7 km) up a 10 percent incline, with an estimated energy expenditure of 4.8 METs (metabolic equivalents). Subsequent stages involve an increase in both speed and incline. A modified Bruce protocol is employed for exercise testing within a week of a heart attack.
Procedure:
A day before exercise cardiac drugs like Digoxin and beta blockers are discontinued as these drugs may interfere with the exercise test results.
The initial step in the procedure involves connecting the patient to the exercise electrocardiogram machine. Resting electrocardiograms are then recorded in both sitting and standing positions, as changes in the electrocardiogram, particularly T wave inversion, may occur when the patient transitions from sitting to walking on the treadmill. Additionally, a brief period of electrocardiographic recording during hyperventilation is conducted to identify any changes that may be attributed to hyperventilation rather than coronary ischemia.
Throughout the test, the electrocardiogram machine provides a continuous record of the patient's heart rate, while the 12-lead electrocardiogram is recorded intermittently. Before commencing the exercise, blood pressure measurements are taken, and this process is repeated at the end of each exercise stage. It should be kept in mind that during the initial stage of exercise, blood pressure may either decrease or remain stable, which can be attributed to the patient's relaxation due to anxiety. However, as the test progresses and the intensity of exercise increases, systolic blood pressure should rise. In adults, it is considered normal for systolic blood pressure to reach levels up to 225 millimeters of Mercury. However, athletes may exhibit higher levels of blood pressure during exercise due to their adaptive capacity. On the other hand, diastolic blood pressure should decrease a bit.
Interpretation:
During the procedure, the blood pressure and the electrocardiogram are evaluated. Electrocardium changes like a depression in the ST segment are indicative of ischemic heart disease. Other abnormal changes, like the absence of Q wave and ST elevation, can also be observed. Such changes are indicative of severe coronary artery diseases. An Inversion of the U wave is an indicator of ischemia. However, due to the challenge of identifying U waves, particularly at elevated heart rates, this sign lacks sensitivity. An abnormal rise in blood pressure is indicative of an increased risk for future hypertension. Less than 5 MET indicates a low level of fitness, 5-8 MET indicates a moderate level, 9-11 MET indicates a good level and 12 METS or more signifies an excellent level of fitness. The inability to exercise for less than six minutes may be a sign of severe heart disease.
What Are the Contraindications of Exercise Stress Test?
Such exercises should not be performed in the following cases;
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If the patient is suffering from acute myocardial infarction within four to six days.
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If the patient is suffering from unstable angina or pain during the rest period for the last 48 hours.
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Patients having uncontrolled hypertension. Also, during exercise, if the uncontrolled elevation of the blood pressure is observed it should be stopped.
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Patients suffering from severe systemic infection.
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Presence of deep vein thrombosis.
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Recent history of cardiac surgery.
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Exercise should be stopped if a severe drop in the ST segment or severe elevation in the ST segment is observed.
It should be noted that such exercises are only can be used for diagnostic purposes. However, the specificity of this test is low, only 70 to 80 percent.
Conclusion
During physical activity, the heart plays a crucial role. Thus, the assessment of cardiac conditions is needed during physical activity. The exercise stress test is useful to provide information about cardiac conditions. Disorders like coronary artery disease, cardiac arrhythmia, and heart failure can be identified by this test.
