ABC of clinical electrocardiography: Myocardial ischaemia

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Abstract
T wave changes Myocardial ischaemia can affect T wave morphology in a variety of ways: T waves may become tall, flattened, inverted, or biphasic. Tall T waves are one of the earliest changes seen in acute myocardial infarction, most often seen in the anterior chest leads. Isolated tall T waves in leads V1 to V3 may also be due to ischaemia of the posterior wall of the left ventricle (the mirror image of T wave inversion). Suggested criteria for size of T wave 1/8 size of the R wave <2/3 size of the R wave Height <10 mm As there are other causes of abnormally tall T waves and no commonly used criteria for the size of T waves, these changes are not always readily appreciated without comparison with a previous electrocardiogram. Flattened T waves are often seen in patients with myocardial ischaemia, but they are very non-specific. T wave inversion T wave inversion can be normal It occurs in leads III, aVR, and V1 (and in V2, but only in association with T wave inversion in lead V1) Myocardial ischaemia may also give rise to T wave inversion, but it must be remembered that inverted T waves are normal in leads III, aVR, and V1 in association with a predominantly negative QRS complex. T waves that are deep and symmetrically inverted (arrowhead) strongly suggest myocardial ischaemia. View larger version: In this window In a new window Arrowhead T wave inversion in patient with unstable angina View larger version: In this window In a new window Biphasic T waves in man aged 26 with unstable angina In some patients with partial thickness ischaemia the T waves show a biphasic pattern. This occurs particularly in the anterior chest leads and is an acute phenomenon. Biphasic T wave changes usually evolve and are often followed by symmetrical T wave inversion. These changes occur in patients with unstable or crescendo angina and strongly suggest myocardial ischaemia. View larger version: In this window In a new window ST changes with ischaemia showing normal wave form (A); flattening of ST segment (B), making T wave more obvious; horizontal (planar) ST segment depression (C); and downsloping ST segment depression (D)

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