Whatever the initiating cause, the final pathway involves the conversion of prothrombin to thrombin. Thrombin subsequently converts fibrinogen into fibrin which, together with red blood cells, platelets, and plasminogen, can produce a thrombus.
Describe the final common pathway in thrombolysis.
The endogenous thrombolytic system can be activated by thrombus and endogenous or exogenous plasminogen activators. The activation proceeds by converting plasminogen into plasmin. Plasmin, in turn, lyses stable fibrin clots and degrades circulating fibrinogen, both which result in the formation of fibrinogen split products which further inhibit fibrin formation. This process may also be termed fibrinolysis.
Why would lysing a thrombus potentially alleviate the effect of a myocardial infarction?
A myocardial infarction is not an all-or-nothing phenomenon. Instead, it is a dynamic process known as a wave-front phenomenon that generally progresses over several hours. Thus, there is a window of opportunity to lyse a thrombus and restore flow to the jeopardized myocardium and potentially limit infarct size.
Does the endogenous fibrinolytic system lay a role in spontaneous fibrinolysis to produce reperfusion?
Yes. This was demonstrated by DeWood and others who noted that the incidence of total occlusion of an infarct-related artery tends to decrease the longer the time from the development of a myocardial infarction to the time of catheterization. This spontaneous process generally appears to fall outside the window of opportunity for myocardial salvage. For this reason, activating agents have been developed to accelerate the course of thrombolysis.