Abstract O.71: Thrombosis and Thromboprophylaxis for Patients with Giant Coronary Artery Aneurysms after Kawasaki Disease

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Background: Children with giant coronary artery aneurysms (CAA) after Kawasaki disease (KD) are at substantial risk of thrombosis. There are currently no evidence-based guidelines for optimal thromboprophylactic therapy in these children.

Methods: The North American Kawasaki Disease Registry was queried to identify all patients with giant CAA (maximum coronary artery z-score >10) and their antithrombotic therapy. Freedom from thrombosis was modelled using the Kaplan-Meier method; thrombotic complication rate was calculated per patient-year/month of follow-up.

Results: n=202 patients with giant CAA were included, of whom 28 (14%) experienced either coronary artery thrombosis with or without myocardial infarction. Freedom from thrombotic complications was 92%, 85% and 79% at 3 months, 5 and 10 years after diagnosis, respectively. Non-pharmacological factors associated with increased risk of thrombotic complications included higher maximum coronary artery z-scores (HR: 1.7/+10 SD, p<0.001), higher number of coronary artery branches with giant CAA (HR: 2.6/branch, p<0.001), higher number of discrete CAA (HR: 1.4/aneurysm, p=0.001) and presence of complex CAA (involving the bifurcation or non-discrete; HR: 3.0, p=0.05). A total of 982 patient-years of follow-up were available for analysis (11% low molecular weight heparin (LMWH), 32% warfarin, 57% antiplatelet alone). All patients were maintained on ASA, with 47 patients (23%) also receiving clopidogrel. Patients while on LMWH had the highest event rate, at 1 event per 13 patient-years, compared to 1 per 39 on warfarin and 1 per 33 on no anticoagulant. However, LMWH was predominantly prescribed immediately after the acute phase, which is also the highest risk phase for thrombosis. When limiting analysis to events within 3 months of the acute phase, patients on LMWH had the lowest event rate at 1 per 46 patient-months, compared to 1 per 27 on warfarin and 1 per 33 on no anticoagulant (p=NS).

Conclusions: Current thromboprophylaxis strategies in patients with giant CAA have suboptimal efficacy, and residual thrombosis risk persists. New anticoagulants/antiplatelet agents should be assessed in this population to determine if they provide better, safer and more tolerable thromboprophylaxis.

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