An ECG/EKG (the k stands for karida, which in Greek means heart) graphically records the electrical activity of the heart beating with characteristics of up and down patterns labeled consecutively as P waves, QRS complexes, T waves, and U waves. Any irregularities in the patterns may indicate a problem with the heart.
How does it work?
The ECG picks up impulses from electrodes which are attached to the chest, arms, and legs. This is so different views of the electrical activity can be monitored. A portable ECG is called a Holter Monitor, which will be discussed later.
The heart cycles start with the sinoatrial node (SA), the heart's natural pacemaker. It sends an electrical impulse, which travels along a nerve pathway and stimulates the muscles to contract. These contractions allow blood to pass through the heart's chambers and into the blood vessels. When the muscles relax, the heart refills with blood and the process starts all over.
What do the results show?
Doctors can identify causes of abnormal heart rhythms and heart muscle damage. Signs of a recent or prior heart attack can be detected and sometimes an evolving heart attack is identified. The effects of medications and the function of a pacemaker or internal cardioverter defibrillator (ICD) can also be assessed. Any abnormalities may cause changes in the flow of electrical impulses.
2005 Take It To Heart screening event at the
Susquehanna Township High School gymnasium
Image courtesy of The Patriot-News
A Holter Monitor is a portable ECG machine which can help detect problems that may not be observed on a resting ECG.
How does it work?
As with an ECG, there are electrodes connected to the chest that record the heartbeats over a 24 to 48 hour period. It is battery-operated and worn in a shoulder harness around the neck, in a pocket, or on a belt. Patients are told to keep a journal of their activities during the day.
References
Heart Care Health Monitor. "What is an electrocardiogram." 2003. Data Centrum Communications, Inc. 6 September 2004. www.healthmonitor.com
Heart1.com. "Holter Electrocardiogram." 3 June 2004. Body1, Inc. 6 September 2004. www.heart1.com
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