Treadmill Stress Testing

Exercise testing is a form of cardiovascular stress testing that uses exercise with electrocardiography (ECG) and blood pressure monitoring. This form of stress testing is usually performed with exercise protocols using either a treadmill or bicycle. Patients who are unable to exercise may benefit from the administration of a pharmacologic agent that simulates the activity of the heart during exercise. This article will specifically focus on treadmill exercise stress testing.With exercise stress testing, we can determine a patient’s functional capacity, assess the probability and extent of coronary artery disease (CAD) as well as assess risks, prognosis and effects of therapy.Exercise PhysiologyExercise is associated with sympathetic stimulation and changes in coronary vasomotor tone which affects coronary blood flow. Several studies have reported that the coronaries dilate during exercise. Some reported mechanisms that may contribute to this dilatation include the release of vasoactive substances from the endothelium due to increased myocardial oxygen consumption, passive relaxation due to the increase in coronary arterial pressure and endothelium-mediated limitation of constrictor effects of catecholamine.During exercise, the increase in myocardial oxygen demand and coronary vasodilation allows for increased oxygen delivery which is crucial to myocardial perfusion thereby preventing ischemia. It is through this hyperemic effect that we can identify ischemia, as stenotic vessels do not vasodilate as well as normal vessels.Due to sympathetic stimulation and vagal inhibition, stroke volume, heart rate, and cardiac output increase. Alveolar ventilation and venous return also increase as a consequence of selective vasoconstriction. The hemodynamic response depends on the amount of muscle mass involved, exercise intensity, and overall conditioning. As exercise progresses, skeletal muscle blood flow increase and peripheral resistance decrease leading to an increase in systolic blood pressure (SBP), mean arterial pressure (MAP), and pulse pressure. Diastolic blood pressure (DBP) may remain unchanged, slightly increase or slightly decrease. The age-predicted maximum heart rate is a useful measurement for estimating the adequacy of stress on the heart to induce ischemia. The goal is usually 85% of the age-predicted maximum heart rate, which is calculated by subtracting the patient’s age from 220.