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Early post-operative thrombosis of the prosthetic mitral valve in patient with heparin-induced thrombocytopenia
© Cziráki et al; licensee BioMed Central Ltd. 2012
Received: 1 December 2011
Accepted: 13 March 2012
Published: 13 March 2012
Heparin-induced thrombocytopenia (HIT) is one of the most common immune-mediated adverse drug reactions, with frequencies as high as 2-3% for certain groups of post-cardiac surgery patients. We report on an 50-year-old woman with early post-operative thrombosis of the prosthetic mitral valve due to heparin-induced thrombocytopenia. Non-invasive imaging (two-dimensional transesophageal echocardiography; 2D-TEE) allowed the exact localisation of thrombotic masses and revealed the increase of the mean diastolic mitral gradient. The HIT diagnosis was proved by the clinical scoring system, and with the identification of heparin platelet factor 4-induced antibodies. After the withdrawal of LMWH therapy and the start of intravenous lepirudin treatment, the patient's medical condition improved continuously. Follow-up echocardiography showed a step-wise decrease in the severity of the mean diastolic mitral valve gradient and a complete resolution of thrombus formations. Perhaps we may remind ourselves that, whilst HIT is one of the most common immune-mediated adverse drug reactions for certain groups of post-cardiac surgery patients, it can be managed successfully. We would also stress the importance of serial 2D-TEE examinations in the early post-operative period.
Patients who are candidates for cardiac surgery require special care in respect of heparin-induced thrombocytopenia (HIT), as this patient population exhibits a relatively high risk for this antibody-mediated, prothrombotic adverse effect of heparin. However, monitoring the platelet count for HIT is a standard feature of post-operative care in cardiac surgery. Unfractionated heparin is remarkably immunogenic, as 25% - 50% of post-cardiac surgery patients develop heparin-dependent antibodies during the 5 - 10 days following surgery [1, 2]. Sometimes these antibodies strongly activate platelets and coagulation, thereby causing prothrombotic disorder , with the risk of heparin-induced thrombocytopenia at 1% - 3%.
A 50-year-old housewife with a history of paroxysmal supraventricular tachycardia and rapidly worsened dyspnea due to serious mitral regurgitation was referred to our hospital for the evaluation of valvular disease. The two-dimensional transesophageal echocardiography (2D-TEE) confirmed the diagnosis of severe MR and identified a prolapse of the P2 scallop of the posterior mitral leaflet. Severe MR was confirmed by a vena contracta of 7 mm, the effective regurgitant orifice of 0.9 cm2, and systolic reversal during Doppler investigation of the pulmonary venous flow. Because of the rapid progression of symptoms (orthopnea and threatening pulmonary edema) the patient was referred to the Cardio-surgery Department, where a prosthetic mitral valve was implanted (Sorin Allcarbon 27). During the first post-operative week the patient was on low-molecular-weight heparin (LMWH) treatment and she was examined by transthoracic echocardiography (TTE) every day.
At the same time we observed a rapid decrease in the platelet count from 178 G/l to 17 G/l. On the basis of the clinical symptoms, we used the '4 Ts' routine blood chemistry pre-test clinical scoring system to test for the possibility of HIT, and proved the high probability of heparin-induced thrombocytopenia . Consecutive anti-PF4 antibodies (Enzyme-Linked ImmunoSorbent Assay HPIA is Heparin Platelet Factor 4-Induced Antibodies [ELISA] Asserachrom HPIA Stago, Asnières France) were positive (optical density > 2), which confirmed the diagnosis of heparin-induced thrombocytopenia [6, 7].Anticoagulation with LMWH was immediately stopped and, after initial intravenous lepirudin bolus, continuous iv. infusion was started and maintained for an entire week. Thereafter, for five days combined lepirudin and warfarin therapy was applied until we reached the appropriate INR ratio . As a result of this treatment, the patient's platelet count returned to the preoperative level (213 G/l).
We present a case of early post-operative thrombosis of the prosthetic mitral valve in a patient with heparin-induced thrombocytopenia. We may remind ourselves that HIT is one of the most common immune-mediated adverse drug reactions, with frequencies as high as 2-3% for certain groups of post-cardiac surgery patients [8, 9]. Our case report is a good example that serious complications of HIT, such as early prosthetic mitral valve thrombosis, can be successfully managed by means of the clinical scoring system, with the identification of heparin platelet factor 4-induced antibodies and the timely initiation of appropriate drug treatment. We also emphasise the important role of repeated 2D-TEE examinations in the early post-operative period of cardiac surgery patients. Echocardiography also must be used for follow-up of patients with IE under antibiotic therapy, along with clinical follow-up. The number, type, and timing of repeat examinations depend on the clinical presentation, the type of microorganism, and the initial echographic findings . Weekly TTE may be sufficient in non-complicated streptococcal native IE, while more frequent TEE and TTE controls can be necessary in postoperative staphylococcal early PVE.
Written informed consent was obtained from the patient for publication of this Case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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