General Description: Holter monitoring involves recording the electrocardiogram (ECG) from an ambulatory subject over extended periods of time. Holter monitoring is among the best means of detecting and evaluating supraventricular and ventricular arrhythmias. The conventional Holter recording obtains ECG data comparable to leads V1 through V5 positions of the standard 12-lead ECG. The electrical signal normally is recorded onto a cassette magnetic tape. The usual recording time for Holter monitoring is 24 hours, but newer recorders allow for up to 5 days of continuous recording. Using a light portable recorder, prolonged recordings can be made while the patient engages in usual daily activities and records these activities as well as any symptoms in a diary.
Indications: The clinical indications for Holter electrocardiography include:
Patient Preparation: No specified patient preparation is required. Patients are instructed to perform their normal daily activities and to record these activities as well as any symptoms in a diary. On scheduling Holter monitoring, the request should specify if the monitoring should be continuous, intermittent, or patient activated or event recording. Routine Holter monitoriing is continuous, but some laboratories offer any of these three choices, and if that is the case the specific type of request should be noted.
Technique: When the patient arrives at the clinic, they should be provided with a detailed explanation of the procedure. Previous history of allergic reaction to tape or electrode gel should be obtained. The chest is prepared and the electrodes are firmly put in place. The electrodes are looped and securely taped to minimize movement and artifact. The operation of the recorder and event marker is explained to the patient and information on how to complete the diary is provided. The patient is given instructions on continuing their normal daily activities, except they should avoid taking a bath while carrying the Holter monitor. Instructions on how to turn off the instrument, how to change batteries, and how to disconnect the monitor are provided.
Interpretation: The interpretation of Holter monitoring is done with the aid of a computer analysis system. Modern systems have an analog-to-digital converter and electronic storage capacity, allowing for the ECG to be saved to memory and played back at any time to provide documentation. The system normally provides information regarding duration of recording, amount of time deleted from analysis because of artifact, maximal and minimal heart rate, number of ventricular and supraventricular complexes, and number of runs if present. The clincican can then select strips of areas of interest for further analysis and interpretation. Most recorders have dual channel ECG monitoring to facilitate arrhythmic and ST displacement interpretation. Some systems provide "full disclosure" capability in which every complex occurring during the recording is plotted on compressed time and voltage scale. This is particularly helpful to detect sequence of premature ventricular complex and runs of ventricular tachycardia. Since the patient keeps a diary of activities, symptoms and time of medication, and the analysis system can determine the time of occurrence of any given arrhythmia, it is possible to associate symptoms with the presence or absence of rhythm abnormalities.
For Further Information:
DiMarco JP and Philbrick JT, "Use of Ambulatory Electrocardiographic (Holter) Monitoring,"Ann Intern Med, 1990, 113(1):53-68.
Knoebel SB, Crawford MH, Dunn MI, et al, "Guidelines for Ambulatory Electrocardiography,"Circulation, 1989, 79(1):206-15.
Sheffield LT, Berson A, Bragg-Rehmschel D, et al, "Recommendations for Standards of Instrumentation and Practice in the Use of Ambulatory Electrocardiography,"Circulation, 1985, 71:626A-636A.