Restoration of infarct vessel patency has become one of the cornerstones of treatment for acute ST elevation myocardial infarction (STEMI). Intravenous fibrinolytic agents are the most widely used means for acute reestablishment of vessel patency, and their use has become routine as large clinical trials have shown their unequivocal benefit. In comparison, there is no apparent benefit in patients with non-ST elevation (non-Q wave) MI. (See "Characteristics of fibrinolytic (thrombolytic) agents and clinical trials in acute ST elevation myocardial infarction" and "Fibrinolytic (thrombolytic) agents in unstable angina and acute non-ST elevation myocardial infarction".)
The various markers that are used for establishing the efficacy of fibrinolysis are discussed here. The major issues in fibrinolytic therapy of acute STEMI including efficacy, choice of agent, indications and contraindications, the concurrent use of other agents, and the role of primary angioplasty as an alternative to fibrinolysis are addressed elsewhere. (See "Fibrinolytic therapy in acute ST elevation myocardial infarction: Initiation of therapy".)
TIMI flow grade — Fibrinolytic efficacy has been assessed using the TIMI (Thrombolysis in Myocardial Infarction trial) flow grade classification. This classification characterizes coronary blood flow in the infarct-related artery, which is usually measured at 60 to 90 minutes after the administration of fibrinolytic therapy .
- TIMI 0 refers to the absence of any antegrade flow beyond a coronary occlusion
- TIMI 1 flow is faint antegrade coronary flow beyond the occlusion, although filling of the distal coronary bed is incomplete
- TIMI 2 flow is delayed or sluggish antegrade flow with complete filling of the distal territory
- TIMI 3 flow is normal flow which fills the distal coronary bed completely
There are a number of factors that can influence TIMI flow grade after fibrinolysis, including hemodynamics, local anatomy, amount of residual thrombus, and cellular factors (figure 1) [2,3].