Electrocardiogram. The electrocardiogram (ECG; sometimes abbreviated EKG) is a non-invasive test that 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.
Stress Test. A stress test is a non-invasive test that gives important information about the exercise capacity and the presence or absence of blockages or narrowings in the coronary arteries (or blood vessels that supply blood to the heart). The "stress" portion of the test can be performed on a treadmill, or by injection of a medication. This test provides information about the presence underlying heart disease and how it has affected your general health.
Echocardiogram. Also referred to as an "echo," an echocardiogram is a non-invasive ultrasound test that uses sound waves emitted from a probe that is pressed against your chest wall or one that is swallowed to get a better view of the heart from the esophagus. The echoes or sound waves that bounce back from the emitted sound waves permit your doctors to see how your heart, heart valves and large blood vessels look and function. Electrophysiologists order an echo primarily to see if there is an underlying problem in any of the above structures that could explain, cause or complicate a rhythm disorder. An echo performed from your esophagus is very important in looking for blood clots if you have atrial fibrillation or atrial flutter and a cardioversion and/or radiofrequency ablation procedure is planned. If cardioversion is performed with blood clots present, there is much greater risk of suffering a stroke.
Signal-Averaged Electrocardiogram (SAECG). The Signal-Averaged Electrocardiogram (SAECG) is a non-invasive test that records the heart's electrical activity. It is like the electrocardiogram but uses specialized computer processing to magnify the heart muscle's signal (QRS) and search for abnormal electrical activities called late-potentials. These are not seen on the regular ECG. The presence of late-potentials helps identify individuals at risk for developing life-threatening arrhythmias, such as ventricular tachycardia or ventricular fibrillation. This test takes 30 to 40 minutes to perform. There are no restrictions on food, liquids or medications before this test.
T-Wave Alternans Test. A T-wave alternans test is another type of non-invasive test that measures the heart's electrical activity. It is a special type of ECG that requires additional accompanying computer processing to detect small changes in the heart's electrical activity that occur on a beat-to-beat basis. These changes are not readily seen on the regular ECG. The test specifically looks at the size of the T-wave.
The presence of alternating sizes of T-waves (or T-wave alternans) is abnormal and identifies individuals at a higher risk of life-threatening arrhythmias such ventricular tachycardia and fibrillation. A T-wave alternans test is usually done in conjunction with a stress test with the exception that some extra monitoring electrodes may be required. The preparation is the same as for the stress test.
Holter Monitor (Ambulatory ECG Monitoring). Arrhythmias that 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.
Long Term Event Monitor (External Loop Recorder). 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 or 48-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 from one and up to three months with instructions regarding its simple application to the chest wall at the time of symptoms. The electrocardiogram that is recorded is transmitted over the telephone to a central station, from which it is transferred to your physician for interpretation.
Tilt Table Test. A head upright tilt test (HUTT) is usually performed as part of the evaluation for syncope (passing out). It specifically screens for one of the more common causes of fainting called neurocardiogenic syncope. Individuals who suffer from this disorder usually pass out after being in the standing or sitting position for prolonged periods of time, although in some individuals the duration can certainly be brief). During a tilt test, the objective is provoke one of these spells by placing the patient in an upright position while constantly monitoring blood pressure and heart rate.
Preparation for the test:
- Nothing to eat or drink overnight or at least six hours prior to the test
- Make sure to ask your physician about taking your medications, particularly if you are diabetic and are on insulin.
- Wear comfortable clothes and shoes.
Procedure: You will be placed on a flat comfortable table. A nurse will place electrodes on your chest and a blood pressure cuff on your wrist and/or arm to monitor your heart rate (HR) and blood pressure (BP) continuously throughout the procedure. A recording of your blood pressure and heart rate will be done at baseline in the lying position, after which the table will be brought upright or tilted to a 70-degree inclination. Blood pressure and heart rate are then monitored continuously and values are recorded every 3 minutes. Unless the test is positive (your BP and/or HR fall and you faint or experience a near-faint), you will remain at 70-degrees for 30 minutes. At 30 minutes, additional maneuvers will be done to try to provoke an abnormal test. The first of these is massaging your upper neck on both the left and right sides (called carotid massage) and the second is giving a small dose of nitroglycerin under the tongue. After nitroglycerin is given, the tilt is continued for another 10-15 minutes. The test is terminated if you have a positive test or did not respond to any of the above.
After the test:
- You will be observed for 10-15 minutes.
- You can eat.
- You can go home on the same day.
Cardiac Magnetic Resonance Imaging (MRI) Test. A cardiac MRI is a non-invasive test that uses magnetic waves and the differing magnetic properties of our bodies to obtain high-resolution pictures of the heart and surrounding structures. It also permits assessment of heart valves and overall heart function. Electrophysiologists use cardiac MRIs generally to evaluate for the presence of underlying heart disease. More specific uses include evaluating the right ventricle (the right pumping chamber) when an arrhythmia is suspected of arising from there (the right ventricle is difficult to evaluate using other techniques), and ascertaining the origin and course of the coronary arteries when there is suspicion that this is abnormal. Certain individuals are born with abnormally coursing arteries that predispose them to arrhythmias. The test usually takes 45 minutes to an hour to perform.