Transmission of radiowaves from a battery operated

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transmission of radiowaves from a battery-operated transmitter to a central bank of monitors. The primarybenefit of using telemetry is that the system is wireless, which allows patients to ambulate while one or twoECG leads are monitored..Ambulatory ElectrocardiographyAmbulatory electrocardiography is a form of continuous ECG monitoring used for diagnostic purposes in theoutpatient setting. Electrodes (number varies based on model used) are connected with lead wires to a cablethat is inserted into a portable recorder (ie, Holter monitor) that records the ECG onto a digital memory device.Cardiac Stress TestingNormally, the coronary arteries dilate to four times their usual diameter in response to increased metabolicdemands for oxygen and nutrients. However, coronary arteries affected by atherosclerosis dilate less,compromising blood flow to the myocardium and causing ischemia. Therefore, abnormalities in cardiovascularfunction are more likely to be detected during times of increased demand, orstress.Thecardiac stress testprocedures—the exercise stress test, the pharmacologic stress test, and the
mental or emotional stress test—are noninvasive ways to evaluate the response of the cardiovascularsystem to stress. The stress test helps determine the following:1.presence of CAD,2.cause of chest pain,3.functional capacity of the heart after an MI or heart surgery,4.effectiveness of antianginal or antiarrhythmic medications,5.dysrhythmias that occur during physical exercise, and6.specific goals for a physical fitness program.Contraindications to stress testing include severe aortic stenosis, acute myocarditis or pericarditis, severehypertension, suspected left main CAD, HF, and unstable angina. Because complications of stress testing canbe life-threatening (MI, cardiac arrest, HF, and severe dysrhythmias), testing facilities must have staff andequipment ready to provide treatment, including advanced cardiac life support.Stress testing is often combined with echocardiography or radionuclide imaging (discussed later). Thesetechniques are performed during the resting state and immediately after stress testing. The following are the 2types:Exercise Stress TestingPharmacologic Stress TestingEchocardiographyTraditional EchocardiographyEchocardiography is a noninvasive ultrasound test that is used tomeasure the ejection fraction and examine the size, shape, and motion of cardiac structures. It isparticularly useful for diagnosing pericardial effusions; determining chamber size and the etiology ofheart murmurs; evaluating the function of heart valves, including prosthetic heart valves; and evaluatingventricular wall motion.Transesophageal EchocardiographyA significant limitation of traditional echocardiography is thepoor quality of the images produced. Ultrasound loses its clarity as it passes through tissue, lung, andbone. An alternate technique involves threading a small transducer through the mouth and into theesophagus. This technique, called transesophageal echocardiography (TEE), provides clearer imagesbecause ultrasound waves pass through less tissue.

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