Right pneumothorax with the S1Q3T3 electrocardiogram pattern usually associated with pulmonary embolus.

An 18-year-old man presented with a spontaneous right pneumothorax. An initial electrocardiogram (ECG) showed an S wave in lead I, a Q wave in lead III, and an inverted T wave in lead III. This ECG pattern, S1Q3T3, has been most often associated with pulmonary embolus. These changes resolved with partial reexpansion of the lung. Both right and left pneumothorax have been associated with ECG changes, including changes that mimic myocardial ischemia. Because the clinical presentation of pneumothorax may be similar to angina or pulmonary embolus, ECG changes with pneumothorax may lead to confusion in the diagnosis.