VOL: 99, ISSUE: 02, PAGE NO: 29
- An electrocardiogram (ECG) is a quick, non-invasive method of acquiring data on the electrophysiology of the hea…
WHAT IS AN ECG?
An electrocardiogram (ECG) is a quick, non-invasive method of acquiring data on the electrophysiology of the heart as part of a cardiovascular assessment. It can identify potential or existing cardiovascular problems.
- Electrical changes, which take place as the cardiac muscle contracts and relaxes, are recorded on the ECG trace. The P-wave represents the atrial contraction and is followed by the QRS wave, which represents the ventricular contraction, and then the T-wave, which shows the repolarisation of the cardiac muscle.
- An ECG shows the rate and rhythm of the heartbeat indicating whether the rate is normal, fast (tachycardic) or slow (bradycardic).
WHY PERFORM AN ECG?
- Patients presenting with symptoms, which may be cardiac in origin, will have an ECG taken to contribute to the diagnosis.
- A baseline ECG is taken prior to surgery to ensure no abnormalities exist and so that the effects of anaesthetic drugs can be monitored.
- ECGs can be used to monitor the progress of patients known to have cardiac disease.
PERFORMING AN ECG
- Patients undergoing an ECG are usually anxious about their condition. Explanation and reassurance are essential to alleviate symptoms and ensure an accurate ECG trace is taken. The patient should be semirecumbent, encouraged to breathe normally and be asked not to speak or move while an ECG trace is being taken.
- To obtain an accurate ECG trace good conductivity must exist between the skin and the electrodes. The skin may need preparing and local policy may apply
- Limb leads should be placed on the upper or lower arms and legs, but it is helpful if staff adhere to a common policy. The six chest leads should be placed as seen on the diagram above.
V1: Right sternal edge to 4th intercostal space.
V2: Left sternal edge to 4th intercostal space.
V3: Between V2 and V4.
V4: Mid-clavicular line to 5th intercostal space.
V5: Anterior axillary line - horizontally in line with V4.
V6: Mid-axillary line - horizontally in line with V4.
- Electrodes may not stick to clammy skin. Wipe the skin with a gauze swab, rub in a little tincture of benzoin. Ensure the patient has no allergies to products used to prepare the skin.
- Patients whose shortness of breath or tremor interferes with the trace should be reassured and distracted while the trace is running.
- If a patient is only able to sit in a chair, because of difficulty with breathing, it is still possible to perform an accurate ECG trace.
- Limb leads can be placed more centrally to overcome peripheral interference. The lower limb leads can be placed on the lower abdomen and although this may alter the axis, significant abnormalities will still be detected.
ACTION AFTER THE ECG
- Ensure the patient’s name and the time and date of the recording are on the ECG and it is documented in the patient’s notes.
- Local policy will dictate who needs to see the ECG and how quickly.
- The patient’s history should be available with the ECG: a patient history is diagnostic in 80 per cent of cases.
- Ensure that the patient is comfortable and that the results of the ECG are discussed with the patient.
Clancy, J., McVicar, A.J. (2002)Physiology and Anatomy. A Homeostatic Approach. London: Arnold.
Mallet, J., Dougherty, L. (2000)The Royal Marsden Hospital Manual of Clinical Nursing Procedures. Oxford: Blackwell Science.
ECG library: www.ecglibrary.com/ecghome.html