Thrombolytic therapy Flashcards
What process stops bleeding in a blood vessel?
Haemostasis
What type of factors are involved in normal haemostasis?
Extrinsic and intrinsic factors
What is the first step in primary haemostatic plug formation?
Platelets adhere to sub-endothelial regions
What do platelets stimulate to reinforce the platelet aggregate? What happens to the platelet aggregate and fibrin clot as wound healing occurs?
Local activation of plasma coagulation factors
They are degraded
What is the role of the coagulation cascade in haemostasis?
- Each activated factor acts as a catalyst
- Enhances the next reaction
- Results in a large collection of fibrin
- Fibrin forms a plug in the vessel
What must blood do within the vasculature? When must blood clot quickly?
Remain fluid
When exposed to non-endothelial surfaces
What insoluble protein is essential to clot formation? What is the formation of a clot called? Where can a thrombus form?
Fibrin
Thrombosis
Any vessel, artery or vein
What can a venous thrombus develop from? What components attach to a thrombus, increasing its size?
Venous stasis, vessel injury and altered coagulation
Fibrin, platelets and RBCs
What system is activated to restore fluidity when intravascular thrombi occur?
Fibrinolysis
What does a delicate balance prevent in the normal situation?
Thrombosis and haemorrhage
What model describes the primary factors that influence pathologic clot formation?
Virchow’s Triad
What are the three components of Virchow’s Triad?
- Abnormality in blood flow
(AF, left ventricular dysfunction) - Abnormalities of surface in contact with blood
(Vascular injuries, AMI, fracture, chemical irritation) - Abnormalities of clotting components
(Protein C & S deficiency, thrombocytosis)
Where is venous thrombosis mainly found?
Venous circulations
What is venous thrombosis mainly composed of? Where do venous thrombi most often occur? What condition is deep vein thrombosis (DVT) associated with?
Fibrin and erythrocytes
Lower extremities
Venous stasis
What is the most common type of venous thrombosis? Where does arterial thrombosis mainly occur? What conditions can cause arterial thrombosis? What are arterial thrombi primarily composed of?
DVT
Regions of rapid blood flow
Atherosclerosis or arrhythmias
Platelets, fibrin and leukocytes
What class of drug is Heparin?
What class of drug is Aspirin?
What class of drug is Streptokinase?
Anticoagulant
Platelets aggregation inhibitors
Fibrinolytic agents
What are anticoagulants (like UFH, LMWH, warfarin and DOACs) used for?
What are platelet aggregation inhibitors (like aspirin and clopidogrel) used for?
When are fibrinolytic agents (like Streptokinase) notably used?
Treatment and prevention of BOTH venous and arterial thrombi
Prevention of arterial thrombi
During MI
What is the purpose of thrombolytic therapy? What is the role of the fibrinolytic system? What is treatment with fibrinolytic drugs not a substitute for?
Rapid lysis of already formed clots
Restricting clot propagation and fibrin removal
Anticoagulant drugs
What converts plasminogen to plasmin?
Plasminogen activator (t-PA)
What inactivates t-PA in the plasma?
Plasminogen activator inhibitor-1 (PAI-1)
What can activation of the fibrinolytic system with thrombolytic drugs disturb? What does plasmin degrade due to its low substrate specificity?
Regulatory mechanisms and elevate plasmin
Fibrinogen, plasminogen, coagulation factors
What does systemic un-physiological activation of the fibrinolytic system cause?
Consumption of coagulation factors and bleeding
What do thrombolytic drugs cause? What are thrombolytic drugs?
Lysis of clots and reestablish perfusion
Plasminogen activators
What is an ideal fibrinolytic? How do older fibrinolytic (1st gen like Streptokinase) agents differ from newer agents (3rd gen)?
One which can provide clot-selective effects
Older agents are not clot selective, newer have improved fibrin specificity
