We describe the case of a 60-year-old man with unstable angina and a critical stenosis of an unprotected left main stem. The patient was also affected with oligophrenia and Paget's disease that contraindicated surgical revascularization. We performed a percutaneous transluminal coronary angioplasty in the cardiac surgery operating room, preparing a femoro-femoral cardiopulmonary bypass by means of a portable X-ray system. The final results were good and they were confirmed by an angiographic control performed three months later as well as during the six-month follow-up. Angioplasty of the unprotected left main stem is feasible and adequate technologic support can reduce the risks for the patient.