Holter "To Go"
Edition: May 2003 - Vol 11 Number 05
There isn’t much we can’t do while “on the go.” We can eat, schedule appointments, even check for voice mails. And, while we’re at it, how about monitoring the heart?
Holter monitoring, also referred to as ambulatory electrocardiography, ambulatory ECG or ambulatory EKG, is a process in which a person’s heart is monitored during normal activity. When a cardiac patient wears a Holter monitor, the device provides a graphic record of the heart’s electrical currents. Compared to a standard EKG, which reportedly monitors 40 or 50 heartbeats while the patient is connected to it, a Holter monitor records as many as 100,000 heartbeats in a 24-hour period.
With Holter monitoring, the heart is assessed during normal activity, increasing the likelihood that irregular heartbeats, or arrhythmias, are detected. The battery-powered Holter monitor rests in a protective case with straps and can be carried at the waist or over the shoulder. The unit, which essentially is a tape recorder, is connected by wires –or “leads” – to two electrodes attached to the patient’s chest. The electrical activity of the heartbeats runs through the electrode wires and is continuously recorded on tape for up to 24 hours.
An electrocardiogram is referred to as a 12-lead ECG because it provides the physician with 12 simultaneous, but different, recordings. Each lead records the same electrical impulse, according to the American Heart Association (AHA). But each impulse is recorded from a different position relative to the heart.
While it’s not uncommon for people to have arrhythmias every now and then, it’s important to know the patterns they produce and the frequency with which they occur. Day-to-day activities -even those as basic as eating – can affect test results. To provide physicians with the most complete record of heart activity, the patient keeps a log of all activities and symptoms he or she experiences. The physician, in turn, can compare the timing of the patient’s activities and symptoms with the heart’s activity.
After the Holter recording is complete, the monitor and electrodes are detached from the patient. A technician reviews the recording using a computer, and the heart rate and rhythm are printed out.
Holter monitoring provides the following data, according to the AHA:
• Detection of poor blood flow to the heart muscle, indicating possible coronary artery disease or a heart attack.
• Evaluation of treatments (such as medication, a pacemaker or automatic defibrillator) for irregular heartbeats.
• Assessment of cardiac function when the patient takes medication that might adversely affect the heart.
Different types of physicians – such as cardiologists, internists and family practitioners – interpret electrocardiograms. Because interpretation skills vary from one doctor to the next, the Institute for Clinical Evaluation offers certification exams in clinical interpretation skills. Physicians and technicians responsible for interpreting EKG results should be able to recognize and understand a range of electrocardiographic standards and abnormalities, including the following, according to Alan H. Kadish, M.D. (“ACC/ AHA Clinical Competence Statement on Electrocardiography and Ambulatory Electrocardiography,” Journal of the American College of Cardiology, Vol. 38, No. 7, 2001.):
• Normal ECG
• Technical problems
• Sinus node rhythms and arrhythmias
• Other supraventricular rhythms
• Ventricular arrhythmias
• Atrial ventricular conduction
• Intraventricular conduction
• QRS Axis and voltage
• Chamber hypertrophy or enlargement
• Repolarization abnormalities
• Myocardial infarction
• Clinical disorders
• Pacemaker failures
There are no risks with Holter monitoring. Although the test measures electricity on the surface of the skin, it doesn’t actually produce any electricity or shocks to the patient. Electrode sites may itch a bit during the monitoring process, and the patient’s skin may become somewhat irritated when the electrodes are removed.
There is no preparation required for the test, but the patient may wish to bathe prior to having the leads attached, since he or she may not do so while wearing the Holter monitor. Sometimes physicians instruct patients to temporarily abstain from certain medications during the testing period.
While wearing a Holter monitor, the patient should avoid magnets, metal detectors, high-voltage areas, garage door openers, microwaves and electric blankets. The signals emitted from any of these can potentially interfere with the EKG recording.
The patient is best off sleeping on his or her back to help prevent the leads from detaching. A light on the monitor should blink if a wire becomes loose. By pressing on the center of an electrode, a patient may be able to reconnect it.
Simple and unobtrusive, Holter monitoring allows doctors to check up on their patients, without forcing patients to check in for extended periods of time.