Electrocardiography Health Article

Risks

The EKG is a noninvasive procedure that is virtually risk-free for the patient. There is a slight risk of heart attack for individuals undergoing a stress test EKG, but patients are carefully screened for their suitability for this test before it is prescribed.

Risk factors for heart disease include obesity, hypertension (high blood pressure), high triglycerides and total blood cholesterol, low HDL ("good") cholesterol, tobacco smoking, and increased age. People who have diabetes mellitus (either type 1 or type 2) are also at increased risk for cardiovascular disease.

Normal results

When the heart is operating normally, each part contracts in a specific order. Contraction of the muscle is triggered by an electrical impulse. These electrical impulses travel through specialized cells that form a conduction system. Following this pathway ensures that contractions will occur in a coordinated manner.

When the presence of all waves is observed in the electrocardiogram, and these waves follow the order defined alphabetically, the heart is said to show a normal sinus rhythm, and impulses may be assumed to be following the regular conduction pathway.

In the normal heart, electrical impulses—at a rate of 60–100 times per minute—originate in the sinus node. The sinus node is located in the first chamber of the heart, known as the right atrium, where blood reenters the heart after circulating through the body. After traveling down to the junction between the upper and lower chambers, the signal stimulates the atrioventricular node. From here, after a delay, it passes by specialized routes through the lower chambers or ventricles. In many disease states, the passage of the electrical impulse can be interrupted in a variety of ways, causing the heart to perform less efficiently.

The heart is described as showing arrhythmia or dysrhythmia when time intervals between waves, or the order or the number of waves do not fit the normal pattern described above. Other features that may be altered include the direction of wave deflection and wave widths.

Morbidity and mortality rates

According to the American Heart Association, cardiovascular disease is the number one cause of death in the United States. It is also the leading cause of death among people with diabetes.

Alternatives

Electrocardiography is the gold standard for detecting heart conditions involving irregularities in electrical conduction and rhythm. Other tests that may be used in conjunction with an EKG include an echocardiogram (a sonogram of the heart's pumping action) and a stress test—an EKG that is done in conjunction with treadmill or other supervised exercise to observe the heart's function under stress—may also be performed.

BOOKS

Beasley, Brenda. Understanding EKGs: A Practical Approach. 2nd ed. Upper Saddle River, NJ: Prentice Hall, 2002.

PERIODICALS

Kadish, Alan, et al. "ACC/AHA Clinical Competence Statement on Electrocardiography and Ambulatory Electrocardiography." Journal of The American College of Cardiology 38, no. 7 (2001). <http://www.acc.org/clinical/competence/ECG/pdfs/ECG_pdf.pdf.>.

Fergusun, J. D., et al. "The Prehospital 12-Lead Electrocardiogram: Impact on Management of the Out-of-hospital Acute Coronary Syndrome Patient." American Journal of Emergency Medicine 21, no. 2 (March 2003): 136–42.

ORGANIZATIONS

The American College of Cardiology. Heart House, 9111 Old Georgetown Road, Bethesda, MD 20814-1699. (800) 253-4636. <http://www.acc.org>.

American Heart Association. 7272 Greenville Ave., Dallas, TX 75231. (800) 242-8721. <http://www.americanheart.org>.

Maggie Boleyn, R.N., B.S.N. Paula Ford-Martin

WHO PERFORMS THE PROCEDURE AND WHERE IS IT PERFORMED?

The electrocardiograph is conducted by a fully trained technologist and may be done in the cardiologist's office, a testing facility, or at a hospital patient's bedside. The technologist, or perhaps a nurse or nurse practitioner, will take the patient's medical history, educate them about the procedure they are about to undergo, and help them relax. The results of the electrocardiograph will be interpreted by a qualified physician, usually a cardiologist.

QUESTIONS TO ASK THE DOCTOR

• Why has an EKG been prescribed for me?
• When will I get the results of my EKG?
• Should I take my prescription and over-thecounter medications as normal before my EKG or stress test?
• Should I refrain from eating before my stress test?