User:DiverDave/Bruce protocol

The Bruce protocol is a diagnostic test used in the evaluation of cardiac function, developed by Robert A. Bruce.

History
By the 1920s, it was generally recognized that patients with coronary artery disease could have resting normal electrocardiograms, but would demonstrate abnormalities under conditions of physical exertion. However, at that time there was no standardized method of reproducing and measuring this phenomenon. Different types of cardiac stress tests (typically involving some activity such as stair climbing, hopping, or dumbbell swinging) had been developed by different physicians. None of these tests, however, took critical variables such as age, sex, and body mass index into account. Consequently, the results were often inconsistent and misleading, producing a high rate of false-positive results. The first standardized cardiac stress test, the Master's Two-Step test, was developed in 1929 by Arthur Master and his colleague Enid T. Oppenheimer at Mount Sinai Hospital in New York City. This easy to follow test called for patients to ascend and descend two nine-inch steps for a specified amount of time, accompanied by calculations that took into account the patient’s age, sex, and weight.

While the Master's Two-Step test was a significant improvement over previous non-standardized tests, it was too strenuous for many patients, and inadequate for the assessment of respiratory function and coronary circulation during varying amounts of exercise. Most physicians relied upon patients' complaints about exertion, and examined them only at rest. To address these problems, Bruce and his colleagues began to develop a treadmill exercise test in the late 1940s. The test made extensive use of relatively new technological developments in electrocardiography and treadmills. Bruce's first reports on treadmill exercise tests, published in 1949, analyzed minute-by-minute changes in respiratory and circulatory function of normal adults and patients with heart or lung ailments.

In 1950 Bruce joined the University of Washington, where he continued research on the single-stage test, particularly as a predictor of the success of surgery for valvular or congenital heart disease. While at the University of Washington, Bruce teamed up with pioneering bioengineer Wayne Quinton to design a motorized treadmill that would be suitable for exercise tests; they produced their first prototype in 1952.

Bruce then developed the multistage test, consisting of several stages of progressively greater workloads. It was this multistage test, a description of which was first published in 1963, that became known as the Bruce protocol. In the initial paper, Bruce reported that the test could detect signs of such conditions as angina pectoris, a previous myocardial infarction, or a ventricular aneurysm. Bruce and colleagues also demonstrated that exercise testing was useful in screening apparently healthy people for early signs of coronary artery disease.

Clinical relevance
Exercise tolerance testing (also known as exercise testing or exercise stress testing) is used routinely in evaluating patients who present with chest pain, in patients who have chest pain on exertion, and in patients with known ischemic heart disease. Diagnostic indications for exercise testing include assessment of chest pain in patients with intermediate probability for coronary artery disease, provocation of dysrhythmias, and assessment of symptoms (for example, presyncope) occurring during or after exercise. Prognostic indications for exercise testing include risk stratification after myocardial infarction or in patients with hypertrophic cardiomyopathy, evaluation of the efficacy of revascularization or drug treatment, evaluation of exercise tolerance and cardiac function, assessment of cardiopulmonary function in patients with dilated cardiomyopathy or heart failure, assessment of treatment for cardiac dysrhythmia.

Procedure
A Bruce exercise test involves walking on a treadmill while the heart is monitored by an electrocardiograph with various electrodes attached to the body. Because the treadmill speed and inclination could be adjusted, this physical activity was tolerated by most patients. Initial experiments involved a single-stage test, in which subjects walked for 10 minutes on the treadmill at a fixed workload. Typically during a Bruce protocol heart rate and Rating of Perceived Exertion (RPE) are taken every minute and blood pressure is taken at the end of each stage (every three minutes). However institutions often vary this procedure slightly.

Modifications of the Bruce protocol
Ventilation volumes and respiratory gas exchange (oxygen uptake and delivery) can also be monitored before, during and after the exercise phase of the test. The test can also be combined with echocardiography (this is referred to as a stress echocardiogram).