To assess the safety of bivalirudin as an alternative anticoagulant therapy for patients with new or previous heparin-induced thrombocytopenia (HIT) / heparin-induced thrombocytopenia and thrombosis syndrome (HITTS) undergoing percutaneous coronary intervention (PCI). This will be measured by the composite incidence of major bleeding events during administration or within 48 hours after stopping bivalirudin (or at hospital discharge, whichever occurs first). The components of the composite endpoint are: a) intracranial bleeding; b) retroperitoneal bleeding; c) bleeding that results in hemodynamic compromise; d) bleeding that requires transfusion of three or more units of whole blood or packed red cells; and e) a decrease in hemoglobin of greater than or equal to g/dL or in hematocrit of greater than or equal to 9%.