S1Q3T3 pattern in ECG is seen in acute pulmonary embolism. The commonest ECG finding in acute pulmonary embolism is sinus tachycardia, which is noted in this ECG as well. T wave inversion in anterior leads is another finding in pulmonary embolism. Incomplete right bundle branch block pattern can also be a manifestation sometimes noted in pulmonary embolism. Similar electrocardiographic findings can also occur in other causes of acute cor pulmonale with right ventricular overload.