A blockage in an artery of the lungs caused by a substance from somewhere else in the body traveling through the bloodstream. Blood clots are the most common cause. Lung tissue is injured or dies (pulmonary infarction) which may cause the patient symptoms, and strain on the right heart.

•Possible ECG changes:

•S1, Q3, T3 pattern (S wave in lead 1, Q wave in lead 3, and T wave inversion in lead 3).

•Tachycardia (sinus tachycardia, possible atrial fibrillation).