CC/AHA Guidelines for Ambulatory ECG - American College of Cardiology and the American Heart Association

American Family Physician,  Feb 1, 2000  by Sharon Scott Morey

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The American College of Cardiology (ACC) and the American Heart Association (AHA), in collaboration with the North American Society for Pacing and Electrophysiology, have developed guidelines for the use of ambulatory electrocardiography (ECG). The guidelines include recommendations for the evaluation of symptoms of cardiac arrhythmias; for risk assessment in patients who have sustained a myocardial infarction, have congestive heart failure (CHF) or have hypertrophic cardiomyopathy; for the evaluation of antiarrhythmic therapy, or pacemaker or implantable cardioverter-defibrillator function; and for the evaluation of possible myocardial ischemia. There is also a section on the use of ambulatory ECG for the evaluation of children with cardiac symptoms.

The eight-page executive summary of the guidelines appears in the August 24, 1999 issue of Circulation. It is also available on the ACC Web site (http://www.acc.org) and the AHA Web site (http://www.americanheart.org). The guidelines are published in their entirety in the September 1999 issue of the Journal of the American College of Cardiology. The complete guidelines are also available on the above-mentioned ACC and AHA Web sites. A single reprint of the executive summary (reprint no. 71-0171) can be obtained by calling 800- 242-8721 or writing the American Heart Association, Public Information, 7272 Greenville Ave., Dallas, TX 75231-4596. Reprints of the complete guidelines (reprint no. 71-0172) cost $5 and can be obtained by calling 800-253-4636 or writing the American College of Cardiology, Resource Center, 9111 Old Georgetown Rd., Bethesda, MD 20814-1699.

The recommendations are classified according to the system used by the ACC and AHA. The classification system is as follows:

Class I-Conditions for which there is evidence and/or general agreement that a given procedure or treatment is useful and effective.

Class II-Conditions for which there is conflicting evidence and/or a divergence of opinion about the usefulness/efficacy of a procedure or treatment. Class IIa-The weight of evidence/opinion is in favor of usefulness/efficacy. Class IIb-The usefulness/efficacy is less well established by evidence/opinion.

Class III-Conditions for which there is evidence and/or general agreement that the procedure/treatment is not useful/effective, and in some cases may be harmful.

The following is an excerpt from the executive summary, giving the recommendations for the use of ambulatory ECG for assessing symptoms of arrhythmia, the risk of arrhythmias, the efficacy of antiarrhythmic therapy, the function of pacemakers and implantable cardioverter defibrillators and monitoring myocardial ischemia.

Assessment of Symptoms of Cardiac Arrhythmias

The guidelines state that one of the primary and most widely accepted uses of ambulatory ECG is determining the association of a patient's transient symptoms to cardiac arrhythmias. The crucial information needed is the recording of an ECG during the precise time that the symptom is occurring. The recommendations note that the yield of ambulatory ECG monitoring in syncope is relatively low. However, because of the severity of symptoms, such testing is usually warranted. The yield of ambulatory monitoring that captures an episode of palpitation is higher than the yield in patients with syncope. Ambulatory ECG monitoring may also be indicated in the evaluation of other symptoms that may be related to cardiac abnormalities, such as intermittent shortness of breath, unexplained chest pain, episodic fatigue or diaphoresis.

The indications for ambulatory ECG monitoring for symptoms of arrhythmia are as follows:

Class I-(1) Patients with unexplained syncope, near syncope or episodic dizziness without obvious cause. (2) Patients with unexplained recurrent palpitation.

Class IIb-(1) Patients with episodic shortness of breath, chest pain or fatigue that is not otherwise explained. (2) Patients with neurologic events when transient atrial fibrillation or flutter is suspected. (3) Patients with symptoms such as syncope, near syncope, episodic dizziness or palpitation in whom a probable cause other than an arrhythmia has been identified but in whom symptoms persist despite treatment of this other cause.

Class III-(1) Patients with symptoms such as syncope, near syncope, episodic dizziness or palpitation in whom other causes have been identified by history, physical examination or laboratory tests. (2) Patients with cerebrovascular accidents, without other evidence of arrhythmia.

Assessment of Risk of Arrhythmias

According to the guidelines, ambulatory ECG monitoring is increasingly used to identify asymptomatic patients at risk of arrhythmias, such as after a myocardial infarction, in congestive heart failure and in hypertrophic cardiomyopathy. With myocardial infarction, 24-hour ECG monitoring is frequently performed before the patient is discharged from the hospital. Frequent premature ventricular contractions and high-grade ventricular ectopy are associated with a higher mortality rate among survivors of myocardial infarction.