artery disease or three-vessel disease (blockage of all three major branches of coronary arteries). ST segment depression most prominent from V1 to V3 is suggestive of posterior infarction. Furthermore, tall or wide QRS complex with an upright T wave is further suggestive of the posterior infarction. Wellens' syndrome is caused by the injury or blockage of the left anterior descending artery, therefore resulting in symmetrical T wave inversions from V2 to V4 with depth more than 5 mm in 75% of the cases. Meanwhile, the remaining 25% of the cases shows biphasic T wave morphology. ST segments remains neutral in this syndrome. Those who were treated without angiography will develop anterior wall myocardial infarction in a mean period of 9 days. An episode of chest pain in Wellens' syndrome is associated with ST elevation or depression and later progressed to T wave abnormality after chest pain subsided. T wave inversion less than 5 mm may still represents myocardial ischaemia, but is less severe than Wellens' syndrome. Hypertrophic cardiomyopathy is the thickening of the left ventricle, occasionally right ventricle. It may be associated with left ventricular outflow tract obstruction or may not be associated with it in 75% of the cases. ECG would be abnormal in 75 to 95% of the patients. Characteristic ECG changes would be large QRS complex associated with giant T wave inversion in lateral leads I, aVL, V5, and V6, together with ST segment depression in left ventricular thickening. For right ventricular thickening, T waves are inverted from V2 to V3 leads. ST and T waves changes may not be apparent in hypertrophic cardiomyopathy, but if there is presence of ST and T waves changes indicates severe hypertrophy or ventricular systolic dysfunction. According to Sokolow-Lyon criterion, the height of R wave in V5 or V6 + the height of S wave in V1 more than 35 mm would be suggestive of left ventricular hypertrophy. Both right and left bundle branch blocks are associated with similar ST and T wave changes as in hypertrophic cardiomyopathy, but are opposite to the direction of the QRS complex. In pulmonary embolism, T wave can be symmetrically inverted at V2 to V4 leads but sinus tachycardia is usually the more common finding. T wave inversion is only present in 19% of mild pulmonary embolism, but the T inversion can be present in 85% of the cases in severe pulmonary embolism. Besides, T