What is a Holter monitor?

A Holter monitor is a 24-hour (or 48-hour) cardiac monitor that records the heart's rhythm continuously over a period of time. The monitor includes from 3 to 5 leads that are attached with stickers to the chest, which are connected to a recording device with a wire cable. The recording device may be an analog recorder (cassette tape) or a digital recording device. These are returned to the clinician's office and then downloaded onto a computer for processing and printing. The most common indications for performing Holter monitors are: (1) to diagnose rhythm disturbances which occur on a daily or near-daily basis, (2) to monitor the effectiveness of treatment for arrhythmias which have already been diagnosed, and (3) to assess the heart rate over 24 hours (especially with respect to children who have other types of heart disease).

What is an event monitor?

An event monitor is similar to a Holter monitor, with four important differences. One difference is that the event monitor is smaller and more portable, and therefore more convenient. A second difference is that the patient may keep the event monitor for up to one or two months. This way, rhythm disturbances (or palpitations) which occur less frequently may be captured and recorded. Third, rather than recording continuously, an event monitor is activated by the patient (or parent) during the event by pressing a button. Finally, rather than recording onto a cassette tape or digital device, the event monitor recording may be transmitted over the telephone directly for interpretation by the physician. Event monitors may come in different shapes and sizes. Some are worn on the wrist, some look like a smaller version of a Holter monitor, and some look like a credit card that is placed over the chest during the event. The most common indication for ordering an event monitor is to diagnose intermittent arrhythmias or palpitations that occur less than once a day in frequency.

What is an exercise test?

An exercise test is a test in which the patient exercises while thetechnician continuously records the heart rate and rhythm, breathing mechanics, oxygen level in the bloodstream, and blood pressure. The exercise performed usually takes the form of running on a treadmill, however some labs also have a bicycle ergometer. There are many indications for ordering exercise testing. Most commonly, exercise testing is ordered to evaluate symptoms that occur with exercise, for instance chest pain or tachycardia (rapid heartbeat). However, exercise testing is also indicated to assess the heart rate and rhythm response to exercise for patients with known rhythm disturbances, to assess exercise tolerance for patients with known heart or lung disease, and to assess pacemaker function for patients with implanted cardiac pacemakers.

What is an electrophysiology study (EP study)?

An electrophysiology study, or EP study, is a type of test in which the heart is paced artificially, and the heart rhythm recorded continuously, in order to evaluate and in many cases treat (see below) a known rhythm disturbance. EP studies are performed in a cardiac catheterization laboratory under very controlled conditions. The EP team, in addition to the electrophysiologist (a cardiologist who subspecializes in the management of rhythm disturbances), consists of nurses and EP lab technologists experienced in taking care of patients with rhythm disorders, as well as an anesthetist or anesthesiologist responsible for keeping the patient comfortable during the test. EP studies are most commonly performed invasively, with catheters that are placed from the vessels of the groin and neck into the heart using X-ray guidance. No incisions (cuts) are made, and no stitches are required. The catheters are then used to pace the heart, and to record the heart's own intrinsic activity and response to pacing. Occasionally, limited EP studies are performed noninvasively using a patient's own implanted pacemaker, and occasionally limited EP studies are performed transesophageally (with a catheter passed from the nose to the esophagus, or swallowing tube). EP studies are often indicated to make a definitive diagnosis of a rhythm disturbance prior to performing radiofrequency ablation to cure the arrhythmia using similar catheter techniques. Rhythm disturbances that are most amenable to radiofrequency ablation include supraventricular tachycardia (SVT), Wolff-Parkinson-White syndrome, atrial flutter, and certain types of ventricular tachycardia.