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| Color-enhanced scanning electron micrograph of a partially occluded, atherosclerotic blood vessel. |
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Thrombolytic Agents
Thrombolytic agents, also called “clot busting drugs,” are given during a heart attack to break up or dissolve a clot in a coronary artery in order to restore blood flow. The sooner the thrombolytic agents are given following a heart attack, the more effective they are and the more myocardium that can be salvaged.1 |
Thrombolytic therapy for acute MI has been shown to reduce 35-day mortality when compared to controls. Further, this survival benefit can be maintained over a longer term from 6 months to at least 4 years.1
There has been a clear association with myocardial salvage and the time of administration of thrombolytics. To be most effective, they need to be given within one hour of the start of a heart attack. However, a reduction in mortality has been observed in patients treated up to at least 12 hours from onset of definitive symptoms, and some patients have benefited from treatment when presenting more than 12 to 24 hours after onset of persistent ischemic symptoms and ST elevation.1
Patients with left bundle branch blocks and anterior ST elevations have a greater inherent risk from an MI and achieve a greater benefit from thrombolytic therapy. However, the appropriate use of thrombolytic agents in eligible patients can save many additional lives. Younger patients achieve a greater relative reduction in mortality compared to older patients (> 75 years of age), and the older patient has a greater risk of stroke after an acute MI, whether they receive thrombolytic therapy or not. Patients should be considered at higher risk if they have any one of the following:1
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• Female
• Greater than 70 years of age
• Previous history of infarction
• Atrial fibrillation
• Anterior infarction
• Rales in more than one-third of the lung field
• Hypotension
• Sinus tachycardia
• Diabetes mellitus |
Clinicians must carefully weigh the risk-benefit ratio of thrombolysis for individual patients. The AHA has noted that hesitancy to prescribe thrombolytics arises from concerns about intracranial bleeding and uncertainty regarding the eligibility criteria. Based on the higher mortality rate among patients with an MI who do not receive thrombolytics, there are efforts underway to increase the awareness among physicians of the indications for thrombolysis.1 For more information on these activities, visit:
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