Asymptomatic pneumothorax mimicking pseudoaneurysm after the implantation of a dual-chamber pacemaker

An 80-year-old male, who had undergone dual-chamber pacemaker implantation through left subclavian approach, developed tension pneumothorax of the left side. It caused a pseudoaneurysm-like contracting mass image on the chest X-ray. The diagnosis of pneumothorax was verified by chest computed tomography. Tube thoracostomy drainage was performed immediately without any sequel.