In patients with mechanical valve replacement, life-long oral anticoagulant therapy with vitamin K antagonists and an INR in the target range are crucial [
5]. Prosthetic valve thrombosis (PVT) is one of the main causes of valve dysfunction and can be a life-threatening event [
6]. The most common causes of PVT are insufficient anticoagulation, hypercoagulable states, such as pregnancy, atrial fibrillation and left ventricular dysfunction [
7]. In addition, thromboembolic events may be a common complication among patients with APL through several mechanisms, such as prolonged immobility and the administration of ATRA alone or in combination with antifibrinolytic agents, genetic predisposition or as a consequence of differentiation syndrome [
8]. The thrombotic events seem to be more common in APL than in other types of acute leukemia, with a reported prevalence rate ranging from 2 to 10–15% [
9]. One of the potential mechanisms involved in the pathogenesis of thrombosis in APL includes the interaction of leukemic cells with endothelial cells and activation of the clotting system and subsequent thrombus formation [
10]. There is an ongoing debate on the prophylaxis and treatment of thromboembolic events in patients with APL due to the high risk of bleeding resulting from DIC and thrombocytopenia [
1]. Although there is some evidence that heparin can be beneficial in the setting of DIC, the use of heparin is not recommended in patients with APL due to the lack of evidence from clinical studies and high risk of bleeding [
11]. To the best of our knowledge, no randomized controlled trial data are available on the dose and type of anticoagulant for the treatment of patients with APL.
Also, there has not been any specific recommendation on the safety and permissive duration of withholding anticoagulants in patients with mechanical valve replacement. Krittalak
et al. evaluated 26 patients with a mechanical heart valve who were hospitalized with intracranial haemorrhage (ICH) and found that withholding anticoagulation treatment for < 7 days was associated with a low risk of thromboembolic events [
12]. Results from other studies suggest restarting anticoagulation treatment not earlier than 2 weeks after ICH in patients with a prosthetic heart valve and reserving earlier restarting of anticoagulant treatment only for patients at high risk of thromboembolic events [
13,
14].
Given the complex situation of our patient in association with the risk of prosthetic valve thrombosis in a context of bleeding tendency (disseminated intravascular coagulation and thrombocytopenia), choosing the type and dose of anticoagulation was challenging. Ahrari
et al. conducted a systematic review to determine the choice, dose, duration, efficacy and safety of anticoagulation in patients with acute leukaemia and thrombosis [
15]. Conventional heparin and low-molecular-weight heparin were the most commonly used anticoagulants in all studies. These authors revealed that dose adjustment of anticoagulant was made according to the severity of thrombocytopenia [
15]. Our patient was placed on conventional heparin instead of warfarin due to the shorter half-life of heparin and the availability of an antidote to reverse the effect of anticoagulation rapidly following any sign of bleeding. Also, we adjusted the dose of heparin according to the platelet count to reduce the risk of bleeding. Additionally, the combination of ATRA and arsenic without chemotherapy was not only effective in inducing complete remission in our patient but it also reduced the risk of prolonged severe thrombocytopenia caused by chemotherapy.