The commonest finding on electrocardiogram in pulmonary embolism is sinus tachycardia. Pulmonary embolism can occur without significant electrocardiographic abnormalities. ECG may show right ventricular ischemia, incomplete right bundle branch block pattern or S1Q3T3 pattern (S waves in lead I, Q waves and T wave inversion in lead III. T wave inversion in leads v1 to v3 may indicate right ventricular dysfunction in pulmonary embolism. T inversion in inferior leads can also occur in pulmonary embolism. Right axis deviation is another important feature of pulmonary embolism, which is also indicated by the S waves in lead I in the S1Q3T3 pattern. Read more about pulmonary embolism at Heart pearls!: http://www.heartpearls.com/?p=84