ECG BASED (STANDARD) EXERCISE STRESS TESTING In the ED setting, exercise testing has been recommended for patients applied either as the final component of a chest pain observation protocol after the exclusion of AMI or, in selected low-risk patients, soon after presentation as an alternative to an extended observation period.
Many variations exist in the equipment, procedures, and interpretive algorithms used. Both treadmill and cycle ergometer devices are acceptable and commercially available. Cycle devices are smaller and less expensive, offering reduced motion artifact. However, treadmills are still more commonly used in the United States because many patients are unable to reach the desired point of maximum oxygen uptake on the cycle owing to quadriceps muscle fatigue. Other mandatory equipment includes a nearby crash cart with defibrillator and rhythm monitoring capability. Testing may be reliably performed by a trained technician or other allied health professional, although an experienced physician must be readily available. Dysrhythmia, AMI and death have been reported and can be expected to occur at rates of 4.8, 3.6 and 0.5 per 10,000 tests, respectively. 24
Several exercise and monitoring protocols are in use, differing in duration and level of exercise reached as well as testing end points. No consensus exists on the preferred protocol, although the Bruce protocol is the most common and best studied. At the time of testing, informed consent is obtained and the procedure is explained to the patient in detail. The patient's skin is prepared for electrode placement by trimming hair, use of a defatting agent, e.g., alcohol, and abrading the superficial skin layer. After electrode placement, baseline measures of heart rate, blood pressure, and 12-lead ECG are obtained at rest in both supine and standing positions. Exercise is then initiated, with exertion increased in a step-wise fashion predetermined by protocol with the desired endpoint ideally reached within 8 to 12 min of test initiation. Throughout the test and during recovery, ECG rhythm is monitored continuously and 12 lead ECGs are recorded at least once each min. Heart rate, blood pressure, patient symptoms, and perceived exertion (via a visual analog scale) is also recorded at each workload level. Depending on the protocol followed, exercise is terminated when the subject reaches a pre-determined percentage of predicted maximum heart rate (i.e., 85 percent) or when another defined end point is reached (T§ble,.45z5). The most commonly used definition of a positive exercise test result from an ECG standpoint is greater than or equal to 1 mm of horizontal or downsloping ST-segment depression or elevation for at least 60 to 80 ms after the end of the QRS complex.
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When it comes to pieces of aerobic equipment to buy, treadmills continue to be the most popular and the most valuable. And why not? They are simple to use and naturally intuitive. They burn calories effectively and offer a wide range of exercise options, whether walking, climbing, or jogging.