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Overview

Electrocardiographic procedures are non-invasive tests that are useful to obtain a great deal information about the heart. These procedures record the electrical activity of the heart and can tell a trained cardiologist a great deal of information about the heart under many different conditions. Following is a description of the various types of electrocardiographic procedures.

Electrocardiogram

The electrocardiogram (ECG; sometimes abbreviated EKG) is a non-invasive test which records the electrical activity generated by the heart. This electrical activity is recorded from the patient's body surface (limbs and chest) by 10 electrodes held snugly against the skin by elastic bands or suction cups. The test takes 5-10 minutes to complete and yields information about the heart rhythm and rate, hypertrophy (thickness of the heart muscle) and chamber enlargement, presence of an old or ongoing heart attack (myocardial infarction), or evidence of impaired blood supply (ischemia). This is one of the most informative tests performed upon the heart.

Exercise Electrocardiogram (Treadmill Testing)

The "treadmill test" obtains an electrocardiographic record from the patient at rest, during, and after graded exercise with the patient walking on a moving belt (treadmill). The test not only measures exercise tolerance objectively, but also is designed to elicit symptoms and/or electrocardiographic changes that are brought on by exercise. The test is valuable in the diagnosis and risk-stratification (assessment of the severity) of patients with known or suspected coronary artery occlusive disease (CAOD) and in selected asymptomatic patients who are being screened for possible CAOD. The test is also valuable in assessing the patient after recovery from a heart attack, and in patients with known CAOD on medical therapy, or after balloon angioplasty or coronary bypass surgery treatment.

Preparation for the Test

Do not eat or drink anything except water for three hours before taking the test. Your physician will instruct you about whether to take your routine medications. Either bring or wear clothing and shoes that will be comfortable for walking. Because you will have electrodes placed on your chest, it is best for women to avoid wearing a dress and for men to avoid wearing a jump suit.

The Procedure

A nurse or exercise technologist will place electrodes on your chest. For the clearest test results the skin will need to be lightly scraped. Men may need to have some of their chest hair shaved. A blood pressure cuff will also be placed on your arm. After a resting electrocardiogram is recorded, you will walk on the treadmill. The speed and elevation of the treadmill will be increased at three minute intervals. While you are walking, the technologist will monitor your heart rate, electrocardiogram, and blood pressure (BP). The test will be stopped when you have reached a predetermined heart rate, or at your request if you cannot walk any further, or feel chest pain or shortness of breath. Upon termination of exercise, you will rest on the examining table and your electrocardiogram and BP will be monitored for an additional 5 to 10 minute period.

Risk of the Precedure

The risk of treadmill exercise testing is very small and is equivalent to the risk of a similar degree of exercise experienced in the patient's daily life. The careful monitoring of the patient, his/her blood pressure, and the continuous electrocardiographic record, all serve to further minimize the small risk of the test.

Ambulatory Electrocardiographic Monitoring

(Holter Monitoring)

Patients with heart rhythm irregularities (palpitations) or slow (bradycardia) or rapid (tachycardia) heart rhythms, which are not documented on the routine electrocardiogram (ECG), will usually require some type of home (ambulatory) documentation. The holter monitor is a small compact magnetic tape electrocardiographic recorder. Electrodes are placed firmly on the skin of the chest beneath the patient's clothing and an ECG record of 12-24 hours is obtained. The recorder is returned the following day and the total ECG record is retrieved from the magnetic tape and interpreted by the physician. This technology is helpful in the diagnosis of paroxysmal (intermittent) rhythm disturbances and essential for selecting proper treatment and at times for evaluating the subsequent outcome on treatment.

Electrocardiographic Event Monitors

There are many circumstances wherein a rhythm disturbance, or symptoms presumed to be due to a rhythm disturbance, occur infrequently and cannot be documented during a single 24-hour record, such as that obtained with a holter monitor. These infrequent events require that electrocardiographic documentation be recorded at the time of the symptoms. An electrocardiographic event monitor is loaned to such patients for periods up to a month with instructions regarding its simple application to the chest wall at the time of symptoms. The electrocardiogram which is recorded is transmitted over the telephone to a central station, from which it is transferred to your physician for interpretation.

Signal-Average Electrocardiogram

The Signal Average Electrocardiogram (SAE) is a very specialized type of electrocardiogram which magnifies the heart muscle's signal (QRS) and searches for abnormal electrical activities (late-potentials) which have a unique relationship (perhaps a causative one) to the precipitation of rapid, runaway heart rhythms (ventricular tachycardia). This test takes 30 to 40 minutes and is of value in some patients with dizzy spells, arrhythmias and after heart attacks.