S1Q3T3 Pattern on ECG in Pulmonary Embolism

S1Q3T3 pattern in ECG is seen in acute pulmonary embolism.
S1Q3T3 pattern means the presence of an S wave in lead I (indicating a rightward shift of QRS axis) with Q wave and T inversion in lead III. S1Q3T3 pattern is the classical ECG pattern of acute pulmonary embolism which is often taught in ECG classes, though it is not the commonest ECG finding in pulmonary embolism. The same pattern can also occur in other cases of acute cor pulmonale.