We present a case of a sixty-nine-year-old male admitted to the hospital because of an acute respiratory failure that needed intubation and mechanical ventilation. Shortly after several attempts of right and left (the last one successful) subclavian vein cannulation (the last one successful) he developed a bilateral tension pneumothorax with important hemodynamic repercussion, a critical hypoxia and an ST elevation in inferior leads. Other more typical electrocardiographic changes could be observed: decrease in QRS amplitude and diminishing of precordial R voltage. After removing the air of the right pleural space, all the electrocardiographic signs disappeared returning to normal without electric or enzymatic assay of myocardial necrosis.