Electrocardiographic Changes in Pulmonary Collapse: Artificial and Spontaneous Left-Sided Pneumothorax Studied by Conventional and Unipolar Methods

1) Conventional and unipolar limb leads, and CF and unipolar chest lead electrocardiograms, and chest films were taken in four patients with spontaneous left-sided pneumothorax, and in two tuberculous patients in whom therapeutic pneumothorax was planned. In the first group the studies were made during pneumothorax and following the re-expansion of the lung. In the latter group the studies were made before and after institution of pneumothorax.

2) The characteristic electrocardiographic pattern for Leads I, II, III, and the CF precordial leads was repeated in all six cases. This pattern consisted of a small T₁, a T₃ larger than T₁, QRS small and inverted (or a QS complex), and low or inverted T waves in the chest leads, the chest lead changes being maximal in the more lateral precordial positions.

3) This previously described pattern can be explained on the basis of the "unipolar" lead findings. The standard limb lead changes are apparently produced by the heart assuming an extremely vertical position in the presence of left pneumothorax. The CF lead abnormalities in the recumbent position are related chiefly to the decreased voltage of the precordial V leads, resulting from the interposition of a non-conductor (air) between the heart and the chest wall.

4) The use of the CF precordial leads in the presence of left-sided pneumothorax might lead to a false electrocardiographic impression of coronary artery disease, or even of old myocardial infarction. In the same situation the V leads (Wilson terminal) show a tracing with a low amplitude but with a more normal contour. This would minimize the likelihood of erroneous interpretation.