Holter Electrocardiography

Study Description

1. Depending on the device, electrographic (ECG) signals from 2, 3, or less commonly 12 leads are recorded.

2. The patient wears the monitor for 24 to 72 hours and keeps a diary of symptoms (time of occurrence and description) to facilitate interpretation of the results. Of note, an increasing variety of devices are capable of monitoring the heart rhythm for weeks or months, which is useful in patients with infrequent symptoms. These are patch monitors, which monitor the patient for up to 2 weeks and do not require leads; event (loop) monitors, which are activated by the patient during symptoms and may be used for over a month; or insertable cardiac monitors, which could be used for well over a year.

Result Interpretation

1. Criterion of sinus rhythm: Positive P waves in lead CM5 (positive electrode over the fifth intercostal space at the left anterior axillary line; negative electrode over the manubrium); assessment of the less frequently used 12-lead Holter ECG is the same as for standard ECG.

2. Automated assessment of continuous ambulatory ECG recording performed by an automatic analyzer requires the additional verification of:

1) Maximum and minimum sinus rates and maximum and minimum ventricular rates (in cases of atrial fibrillation or flutter).

2) Pauses. Holter systems analyze RR intervals, not PP intervals, and therefore pauses (aside from artifacts) may be caused by dropped P waves and QRS complexes (sinus arrest, sinoatrial block), or dropped QRS complexes only (second-degree or third-degree atrioventricular block).

3) The origin of tachycardia (the analyzer does not distinguish between narrow and wide QRS tachycardias) as well as heart rate, which may be significantly underestimated in ventricular tachycardia (the analyzer may not count all QRS complexes during ventricular tachycardia).

3. Assessment of clinical significance of the recorded rhythm abnormalities should take into account the severity of arrhythmia, age, as well as the type of activity (sleep vs awake) and overall health of the patient, because supraventricular and ventricular arrhythmias may sometimes be present in otherwise healthy individuals (Table 1).

4. Assessment of ST-segment changes:

1) ST-segment depressions are considered significant if they are horizontal or downsloping, ≥1 mm deep, and last ≥1 minute. ST-segment depressions confirm the diagnosis of coronary artery disease in men aged ≥35 years and women >55 years with typical angina. In men ≥35 years with atypical angina, men >55 years with a nonanginal chest pain, and women >45 years with atypical angina, the diagnosis of coronary artery disease established on the basis of ST-segment depressions must be confirmed by imaging studies (perfusion scintigraphy or stress echocardiography).

2) Asymptomatic long-lasting ST-segment elevations during sleep associated with sinus bradycardia and increased T-wave amplitudes are generally caused by increased parasympathetic tone.

3) ST-segment elevations associated with angina or ventricular arrhythmia lasting several minutes at a time and not accompanied by bradycardia are typical of Prinzmetal angina.

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