This 58-year-old man was admitted after an accidental fall, and underwent urgent spinal surgery. This normal ECG was recorded during the pre-op assessment:

On postoperative day 5, the patient suddeny became severely hypotensive:

• Sinus tachycardia, 124/min
• Right bundle branch block
• S1Q3 pattern, with abnormal Q waves and ST elevation in III and aVF

This is an example of ECG changes associated with pulmonary embolism simulating acute inferior infarction. There are significant Q waves and slight elevation of the ST segment in III and aVF (however, not in II), which has been known to occur in cases of pulmonary embolism. The ECG computer program had diagnosed acute inferior infarction. The acute development of RBBB also favors the diagnosis of pulmonary embolism.

A CT scan demonstrated large emboli in both lungs. The patient was in profound shock, with marked elevation of his jugular venous pressure, and developed signs of a stroke.

He was transferred to the operating room, where the pulmonary artery was dilated with elevated PA pressure. The surgeon removed three large clots (about 10 cm each in length), saddled across the bifurcation of the pulmonary artery. The right atrium was opened and an atrial septal defect with a diameter of 2 cm was found and closed. A right-to-left shunt causing systemic embolism was suspected given the development of a stroke.

Surgery was successful and was followed by rapid marked improvement of the patient’s hemodynamic status. The following ECG was recorded in the surgical ICU four hours after the operation:

• Sinus tachycardia, 112/min
• S1Q3 pattern – Significant Q waves in III and aVF
• Right bundle branch block is no longer present
• ST elevation in III and aVF is no longer present

These findings reflect evolutionary changes of a treated acute pulmonary embolism.