Myocardial ischaemiaBMJ 2002; 324 doi: https://doi.org/10.1136/bmj.324.7344.1023 (Published 27 April 2002) Cite this as: BMJ 2002;324:1023
- Kevin Channer,
- Francis Morris
In clinical practice electrocardiography is most often used to evaluate patients with suspected ischaemic heart disease. When interpreted in the light of the clinical history, electrocardiograms can be invaluable in aiding selection of the most appropriate management.
Electrocardiography is not sufficiently specific or sensitive to be used without a patient's clinical history
Electrocardiography has limitations. A trace can suggest, for example, that a patient's heart is entirely normal when in fact he or she has severe and widespread coronary artery disease. In addition, less than half of patients presenting to hospital with an acute myocardial infarction will have the typical and diagnostic electrocardiographic changes present on their initial trace, and as many as 20% of patients will have a normal or near normal electrocardiogram.
Myocardial ischaemia causes changes in the ST-T wave, but unlike a full thickness myocardial infarction it has no direct effects on the QRS complex (although ischaemia may give rise to bundle branch blocks, which prolongs the QRS complex).
When electrocardiographic abnormalities occur in association with chest pain but in the absence of frank infarction, they confer prognostic significance. About 20% of patients with ST segment depression and 15% with T wave inversion will experience severe angina, myocardial infarction, or death within 12 months of their initial presentation, compared with 10% of patients with a normal trace.
Changes in the ST segment and T waves are not specific for ischaemia; they also occur in association with several other disease processes, such as left ventricular hypertrophy, hypokalaemia, and digoxin therapy.
T wave changes
Myocardial ischaemia can affect T wave morphology in a variety of ways: T waves may become tall, flattened, …