Pivotal role of early and sustained infarct vessel patency in patients with acute myocardial infarction
Article Abstract:
Today clot-dissolving (thrombolytic) therapy is standard in the treatment of acute myocardial infarction, and several studies have demonstrated improved short- and long-term survival from thrombolysis over either placebo or conventional therapy. However, the relationship between restoring blood flow through the arteries (reperfusion) with clot-dissolving drugs and the outcome of the patient is not clear. There are five thrombolytic agents in current use: non-fibrin-selective agents (streptokinase, urokinase, and anisoylated plasminogen streptokinase activator complex; APSAC) and fibrin-selective agents, such as tissue-plasminogen activator (TPA) and single-chain urokinase plasminogen activator (scu-PA). Pooled data suggest that 90 minutes into therapy, APSAC provides the greatest effect, followed by urokinase, and then streptokinase. Fibrin-selective agents do not cause allergic reactions, and may work more quickly. Another method of opening up arteries is percutaneous transluminal coronary angiography (PTCA) to dilate the blood vessel mechanically by means of a catheter. PTCA has a success rate between 83 percent and 95 percent at highly experienced referral centers, with a 15 percent rate of closing up again (reocclusion) within 7 to 10 days. This technique is useful when drug therapy cannot be used or when the patient is at a medical facility versed in this technique. The reocclusion rate for drug therapy is thought to be 10 percent to 15 percent. It is possible that reperfusion and subsequent reocclusion may actually be worse than no reperfusion at all. At this time it seems clear that early and sustained blood flow restoration is fundamental in improving outcomes, and research will be directed at making drug therapy faster and prolonging its effectiveness. Amount of damage to the heart muscle and long-term outcome are no longer closely related, thanks to thrombolytic drugs, suggesting that treatment is beneficial even if started after damage has occurred. The complexity of this issue is only now being appreciated, including the potential negative effects of treatment. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Heart and Lung
Subject: Health
ISSN: 0147-9563
Year: 1990
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Intracranial hemorrhage after use of tissue plasminogen activator for coronary thrombolysis
Article Abstract:
A relatively recent advance in the treatment of acute myocardial infarction (MI, heart attack) is the use of thrombolytic drugs to dissolve the clot blocking the coronary artery. One thrombolytic agent is tissue plasminogen activator (tPA). While tPA is effective at dissolving the clot in 70 to 89 percent of patients, it can induce hemorrhage as a side effect. Clinical studies of tPA have noted bleeding in 15 to 33 percent of patients, with a serious form of bleeding, intracranial (brain) hemorrhage, occurring in 0.6 to 1.6 percent. The cases of six patients who were treated with tPA after an MI and developed intracranial hemorrhage are discussed. Hemorrhage began between two and 14 hours after the infusion of tPA was finished; all patients also received heparin, an anticoagulant drug. Four of the patients died from massive intracranial hemorrhage, and it was concluded that several factors may have contributed to this response. The medication tPA, or the combination of tPA and heparin, was considered a potential cause, as was a possible vascular abnormality at the site of the bleeding. Hypertension was not implicated as a contributing factor. In theory, tPA should be less likely to cause unintended bleeding than other thrombolytic agents due to its effects on blood components, yet these cases suggest that the risk may not be as small as expected. Continued reporting of intracranial hemorrhage in patients receiving tPA is needed so that the mechanism, and potential patient risk factors, can be identified. Use of heparin in combination with tPA may not be warranted if no benefit can be demonstrated and the risk for bleeding is shown to be enhanced. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: Annals of Internal Medicine
Subject: Health
ISSN: 0003-4819
Year: 1990
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