ECG changes in pneumothorax. A unique finding and proposed mechanism.

A patient with anterior myocardial infarction had bilateral pneumothoraces. Left pneumothorax was associated with reappearance of precordial R waves, while right pneumothorax caused no ECG change. This previously undescribed finding suggests the importance of air insulating the chest wall, rather than cardiac rotation, dilatation, or displacement as a mechanism of the ECG change.