The present case report describes the spontaneous formation of blood clots in the right and left sides of the circulation, despite good anticoagulation, in a patient undergoing coronary bypass surgery. The authors hypothesize that, because the patient turned out to have positive serology for heparin-induced thrombocytopenia that was not diagnosed preoperatively, heparin-induced thrombocytopenia thrombosis may account for all findings. The clinical scenario is described in detail and potential explanations and relevance are discussed.