A 67-year-old man is hospitalized with cough, shortness of breath, orthopnea, and ankle swelling. He is treated with intravenous diuretics. He was diagnosed with non-ST segment elevation myocardial infarction 3 weeks ago and had a right coronary artery stent placed. On discharge, the patient's left ventricular ejection fraction was 40%. On the sixth day of his current hospitalization, he feels better but still complains of some shortness of breath. His platelet count is 62,000/µL, down from 210,000/µL on admission.
The other laboratory results are as follows:
Subcutaneous injections of unfractionated heparin for deep venous thrombosis prophylaxis are stopped and the nurses are instructed not to use heparin flushes. Appropriate laboratory workup is sent.
Which of the following should be used for preventing thromboembolism in this patient?

Question

A 67-year-old man is hospitalized with cough, shortness of breath, orthopnea, and ankle swelling.  He is treated with intravenous diuretics.  He was diagnosed with non-ST segment elevation myocardial infarction 3 weeks ago and had a right coronary artery stent placed.  On discharge, the patient's left ventricular ejection fraction was 40%.  On the sixth day of his current hospitalization, he feels better but still complains of some shortness of breath.  His platelet count is 62,000/µL, down from 210,000/µL on admission.
The other laboratory results are as follows:
 Subcutaneous injections of unfractionated heparin for deep venous thrombosis prophylaxis are stopped and the nurses are instructed not to use heparin flushes.  Appropriate laboratory workup is sent.
Which of the following should be used for preventing thromboembolism in this patient?

Quizplus · Accepted Answer

This patient's presentation suggests type 2 heparin-induced thrombocytopenia (HIT), an immune-mediated disorder that results in platelet aggregation and thrombosis. Type 2 HIT presents with thrombocytopenia 5-14 days after heparin therapy or within 24 hours of heparin re-exposure (rapid-onset HIT). Risk factors include type of heparin exposure (highest risk with unfractionated heparin), duration of treatment, gender (higher risk in women), and trauma severity (higher risk in surgical patients). HIT should be suspected in patients with decreased platelet counts > 50% from baseline 5-14 days after starting heparin, new-onset unexplained thrombocytopenia, or thrombosis after recent heparin treatment. The 4T's score (thrombocytopenia, timing, thrombosis, and other causes) can help assess HIT probability. This patient's score is 6, which suggests a high pretest probability. Diagnosis is confirmed with serotonin release assays (preferred), heparin-induced platelet aggregation assays, or solid-phase immunoassays with ELISA for heparin-PF4 complexes. All forms of heparin, including low molecular weight (eg, enoxaparin), must be stopped immediately (Choice D). Patients should receive an alternate rapidly acting anticoagulant as they are at high risk for thrombosis. Available agents include direct thrombin inhibitors (eg, argatroban, bivalirudin) or fondaparinux (synthetic pentasaccharide). 4T's score (Choices A and C) Clinical observation without alternate therapy is recommended only in patients with high bleeding risk as HIT increases the risk of thrombosis. Similarly, compression stockings do not treat the acute thrombus or effectively prevent future thrombus in patients with suspected HIT. (Choice E) Once the diagnosis of HIT is confirmed, treatment is transitioned to a vitamin K antagonist or alternate anticoagulant for 3 months. Initial treatment with warfarin is contraindicated as rapidly dropping protein C levels cause a prothrombotic state. Warfarin is usually started after the patient is treated with a non-heparin anticoagulant and recovers a platelet count to > 150,000/µL. Educational objective: Heparin-induced thrombocytopenia (HIT) should be suspected in patients treated (or recently treated) with heparin who develop unexplained thrombocytopenia (or a > 50% decrease in platelet count from baseline) or newly diagnosed thrombosis (venous or arterial). Once HIT is suspected, all forms of heparin must be stopped immediately, laboratory testing for HIT should be obtained, and alternate anticoagulants (eg, direct thrombin inhibitors) should be started even if thrombosis has not occurred. __________ References: Treatment and prevention of heparin-induced thrombocytopenia: antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians evidence-based clinical practice guidelines. (http://www.ncbi.nlm.nih.gov/pubmed/22315270)

A 67-Year-Old Man Is Hospitalized with Cough, Shortness of Breath