A narrow QRS tachycardia is seen at a rate of around 150/min. ST segment depression is seen in inferior and lateral leads, with T wave inversion in leads I, aVl and V6. These ST – T changes during tachycardia need not indicate associated coronary artery disease. It is quite common in supraventricular tachycardia even in young individuals. It could be a manifestation of a prominent Ta wave which is the atrial repolarization wave. Another situation in which Ta wave becomes prominent and produces ST segment change is during exercise test. The upsloping ST segment depression seen during exercise test has low specificity for coronary artery disease due to this.
