ACI (Acta Cardiologia Indonesiana) Vol.5 No.1(P):47-51 47 Distinct Mechanism between Arterial and Venous Thrombosis: Impact for Clinical Manifestations M. Taufik Ismail Department of Cardiology and Vascular Medicine, Faculty of Medicine, Public Health and Nursing, Universitas Gadjah Mada – Dr. Sardjito General Hospital, Yogyakarta, Indonesia Corresponding author: M. Taufik Ismail, MD, - email: mutaufiq_is@yahoo.com Department of Cardiology and Vascular Medicine, Faculty of Medicine, Public Health and Nursing, Universitas Gadjah Mada – Dr. Sardjito Hospital Jalan Farmako Sekip Utara,Yogyakarta,Indonesia 55281 Introduction: basic mechanism of hemostasis and thrombosis Hemostasis is a complex physiological process aiming to keep the integrity of a closed circulatory system after an occurrence of vessel wall injury. Hemostasis involving the role of circulating platelets and coagulation cascade. 1 There are two major pathways that act independently to activate the platelet. The first pathway is mediated by collagen and the other by tissue factor. After intimal layer injury, platelets are recruited through the interaction between platelet’s surface glycoprotein (GPVI and GPIb/V/IX) with collagen and von Willebrand factor. This process results in adhesion of platelets in the site of injury. Further recruitment of platelets is achieved by secretion of aggregatory mediators such as thromboxane A2 and adenosine diphosphate. 1,2 The formation of three dimensional platelet clot involving the activation of GPIIb/IIIaintegrins. In the setting of deeper tissue damage, the activation of platelet is mediated by tissue factor released predominantly from medial and adventitial layer of vessel wall. This process generates thrombin from prothrombin and activates coagulation cascade resulting in fibrin generation. 1 In the physiologic condition, blood is maintained in the fluid state by certain mechanism. The endothelium of vessel wall plays a major role in this process by producing antithrombotic mediators such as nitric oxide, prostacyclin, and the ectonucleotidase CD39. 1 The balance of prothrombotic and antithrombotic properties of blood and vessel wall has to be regulated to maintain the closed circulatory system but prevent pathologic formation of thrombus at the same time. The alteration of this balance leads to some forms of disease entities. Thrombosis is a group of disease characterized by pathologic formation of thrombus resulting in occlusion of blood vessel. 1,3 Traditionally, the patho- genesis of thrombosis is originated from interdependent factors: blood stasis, vessel wall injury, and hypercoagulable state. 4 A. Mechanism of arterial thrombosis Arterial thrombosis frequently occurs in the setting of preexisting atherosclerotic plaque. 2,5,6 Although considered as different process, it is proposed that the mechanism responsible for the formation of atherosclerotic plaque is also responsible for arterial thrombogenesis and vice versa. The formation of atherosclerotic plaque is a result of interaction between endothelium,