Heparin-induced type II thrombocytopenia: response to renewed heparin administration

History and admission findings: At the age of 55 years a now 70-year-old ma n had his aortic valve replaced by a prosthetic (Bjork-Shiley) valve, and 1 1 years later a VDD pacemaker had been implanted. 18 months before the late st admission he had been hospitalized for treatment of staphylococcal endoc arditis involving the aortic prothesis. At that time thrombocytopenia devel oped during heparin administration, diagnosed clinically and with the hepar in-induced platelet activity (HIPA) test as type II heparin induced thrombo cytopenia. His latest admission was for the diagnosis and treatment of peri pheral arterial disease of the right leg (Fontaine stage IIb). Investigations: Right popliteal and pedal pulses were not palpable. He was able to walk pain-free for only 70 m. Doppler sonography demonstrated an ar m-leg index on the right of 0.7. Angiography revealed marked stenosis in th e right superficial femoral artery and a filiform stenosis in the right pop liteal artery. Treatment and course: Both stenoses were relieved by percutaneous translumi nal balloon angioplasty, in the course of which 5000 IU heparin were admini stered as a bolus intraarterially. Postoperative anticoagulation was mainta ined for 2 days with recombinant hirudin. There was no evidence of platelet reduction or heparin-induced antibodies despite the renewed infusion of he parin. Conclusion: Single re-administration of heparin in a patient who had develo ped a type II heparin-induced thrombocytopenia several years before does no t necessarily lead to a booster of antibodies and thus to a reduction of pl atelets in the peripheral blood. It is a moot point whether the course in t his case was an exception or the rule.