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At the heart of general practice since 1960

Cardiac testing - ambulatory ECG recording

Cardiologists Dr Clive Handler and Dr Gerry Coghlan continue their series on tests commonly used in primary care

Cardiologists Dr Clive Handler and Dr Gerry Coghlan continue their series on tests commonly used in primary care

First described by the physician Norman Jeff Holter in 1949, this test records a patient's heart rhythm and rate, usually over a 24-hour period. It enables the effects of exercise, sleep, emotion and other daily activities to be evaluated in patients who complain of intermittent palpitations, giddy turns or loss of consciousness. The commonly recorded arrhythmias are ectopic beats and atrial fibrillation.

Patients are given a diary card to record the time, duration and nature of their symptoms, so that these may be correlated with arrhythmias timed on the recorder.

Ambulatory devices also record the ST segment, and are occasionally used in the evaluation of patients with coronary heart disease and ‘silent ischaemia'.

Magnetic tapes are still used in hospitals, and are the most widely used. They yield most information in patients with frequent daily symptoms. Recently, solid-state and neural-network technology devices have enabled GPs to perform and print their own recordings, and computer software provides a reliable diagnosis.

Long-term ECG recording devices

For patients with less frequent symptoms, event recorders enable the patient to trigger the recorder, which is placed against the chest wall during an attack. Some patients find these devices difficult to use. Loop recorders similar in size to a small pacemaker, which are implanted under the skin of the chest wall, record continuously for several months and are designed to capture arrhythmias responsible for elusive and occasional symptoms.

Arrhythmias in healthy people

41213712It is important for GPs to appreciate the range of arrhythmias that may be recorded in healthy people, so that they can explain and reassure patients not all arrhythmias indicate heart disease (see table below). Bradycardia and heart block are more common in young people. Ventricular ectopic beats and paroxysmal atrial fibrillation are not uncommon in older people, but may not result in symptoms.

Value and limitations of ambulatory ECG

The quality of the ECG depends on good skin preparation, no interference from cable movement and correct calibration. Reliable computer algorithms improve the diagnostic accuracy.

Symptoms and arrhythmias

A symptom occurring at the same time as a significant arrhythmia provides important diagnostic information that the patient's symptoms are caused by an arrhythmia. Conversely, a cardiac arrhythmia as a cause of symptoms is excluded if symptoms occur in the absence of an arrhythmia. It is difficult to reach a conclusive diagnosis

if the patient is symptom-free during recording, especially if symptoms are infrequent. However, patients may not always experience symptoms with ectopic beats and short runs of paroxysmal atrial fibrillation. Unsustained ventricular tachycardia is less common, but may not result in symptoms. If the history is consistent with these arrhythmias, it is likely that an arrhythmia is responsible.

Dr Clive Handler is consultant in pulmonary hypertension and Dr Gerry Coghlan is consultant cardiologist at the National Pulmonary Hypertension Unit, Royal Free Hospital, London.

This article is based on a chapter in Management of Cardiac Problems in Primary Care by Dr Clive Handler and Dr Gerry Coghlan, published by Radcliffe, which is offering a 20% discount on this book to Pulse readers (usual price £29.95+P&P, offer price £23.96+P&P). To claim, order via www.radcliffe-oxford.com or by telephone on 01235 528820. Please quote discount code ‘Pulse'. Offer expires 31 May 2009.

Smaller recorders have allowed 24 hour ECGs to be done outside hospital Normal

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