Aspirin infarction

There has been a rebirth of interest in a spirin between the 1970s and 1990s as evidence accumulated from a number of clinical trials that aspirin ingestion lowers the incidence of myocardial infarction (39,40), unstable angina (41,42), and stroke (43). 

In a more extensive international trial, 17,187 patients were treated intravenously with streptokinase alone, aspirin alone, a combination of streptokinase and aspirin, or placebo (78). Streptokinase and aspirin were equally effective in treating acute myocardial infarction, each decreasing mortahty by 25% their combination further reduced mortahty by 42%. A significant reduction in mortahty was seen even in those patients treated up to 24 hours after the onset of symptoms. 

Reduction of the risk of myocardial infarction in those with unstable angina or previous myocardial infarction (aspirin only) and... 

The GP Ilb-IIIa complex inhibitor Tirofiban has been used as an adjunct to thrombolysis in a number of small case series reports." A small transcranial Doppler (TCD) study suggests that it reduces microembolization from unstable carotid plaque." In an open pilot smdy, Tirohban administered within 9 hours after stroke onset blocked the conversion of ischemic penumbra to mature infarction." A phase III study (SETIS) has started recruiting patients to investigate its efficacy versus aspirin within the 6-hour window. 

Prior to myocardial infarction, coronary artery bypass graft (CABG), peripheral artery disease, cerebrovascular accident, or aspirin use... 

Administered to achieve an INR of 2.5 (range 2-3) in combination with low-dose aspirin pharmacotherapy (<100 mg daily [Chest guidelines] or 75-162 mg daily [Circulation guidelines]) for 3 mo postmyocardial infarction. Repeat echocardiogram before discontinuing warfarin pharmacotherapy... 

Antiplatelet therapy with aspirin should be considered for all patients without contraindications, particularly in patients with a history of myocardial infarction. Clopidogrel may be considered in patients with allergies or intolerance to aspirin. In some patients, combination antiplatelet therapy with aspirin and clopidogrel may be used. 

Aspirin decreases the risk of death, recurrent infarction, and stroke following myocardial infarction. Aspirin prescription at hospital discharge is a quality care indicator in MI patients.3 All patients should receive aspirin indefinitely those patients with a contraindication to aspirin should receive clopidogrel.2,3... 

Randomized trials have been completed assessing the role of antiplatelet therapy with aspirin for primary stroke prevention. The use of aspirin in patients with no history of stroke or ischemic heart disease reduced the incidence of non-fatal myocardial infarction (MI) but not of stroke. A meta-analysis of eight trials found that the risk of stroke was slightly increased with aspirin use, especially hemorrhagic stroke. Major bleeding risk was also increased with aspirin use.4 Aspirin is beneficial in the primary prevention of MI, but not for primary stroke prevention. 

COX-2 inhibitors such as celecoxib are associated with adverse effects such as nephrotoxicity and a potential increased risk of myocardial infarction (see Chaps. 55 and 15 for additional information). Combination of COX-2 inhibitors with alcohol may increase GI adverse effects. All NSAIDs should be used with caution in patients with aspirin-induced asthma.31... 

Another vasoactive substance produced by the endothelium is thromboxane A2 (TxA2). Normally, small amounts of TxA2 are released continuously however, increased synthesis appears to be associated with some cardiac diseases. Synthesized from arachidonic acid, a plasma membrane phospholipid, TxA2 is a potent vasoconstrictor. Furthermore, this substance stimulates platelet aggregation, suggesting that it plays a role in thrombotic events such as myocardial infarction (heart attack). Nonsteroidal anti-inflammatory drugs such as aspirin and ibuprofen block formation of TxA2 and reduce formation of blood clots. 

Aspirin is maximally effective as an antithrombotic agent at the comparatively low dose of 81 to 325 mg per day. (The antipyretic dose of aspirin in adults is 325 to 650 mg every 4 h.) Higher doses of aspirin are actually contraindicated in patients prone to thromboembolism. At higher doses, aspirin also reduces synthesis of prostacyclin, another arachidonic acid metabolite. Prostacyclin normally inhibits platelet aggregation. The prophylactic administration of low-dose aspirin has been shown to increase survival following myocardial infarction, decrease incidence of stroke, and assist in maintenance of patency of coronary bypass grafts. 

The AHA/ASA guidelines recommend that antiplatelet therapy as the cornerstone of antithrombotic therapy for the secondary prevention of ischemic stroke and should be used in noncardioembolic strokes. Aspirin, dopidogrel, and extended-release dipyridamole plus aspirin are all considered first-line antiplatelet agents (see Table 13-1). The combination of aspirin and clopido-grel can only be recommended in patients with ischemic stroke and a recent history of myocardial infarction or coronary stent placement and then only with ultra-low-dose aspirin to minimize bleeding risk. 

CAPRIE was a 19,185-patient, 304-center, international, randomized, double-blind, parallel-group trial comparing Plavix (75mg daily) with aspirin (325mg daily). The outcome was to compare the first occurrence of new ischemic stroke, new myocardial infarction, or other vascular death. The following are tabulated results ... 

The CURE study involved 12,562 patients randomized to receive Plavix (300 mg loading dose followed by 75 mg daily) or placebo and were treated for up to a year. Patients also received aspirin or other standard treatment such as heparin. The results showed that Plavix had a 20% relative risk reduction compared with placebo (582 cases of cardiovascular death, myocardial infarction, or stroke) versus 719 cases for placebo. 

During the early-to-moderate stages of vascular dementia, an aspirin a day can provide some protection from additional infarcts. However, daily aspirin does carry risks of bleeding and stomach irritation and should only be used under the supervision of a physician. 

ISIS-3. ISIS-3 a randomised comparison of streptokinase vs tissue plasminogen activator vs anistreplase and of aspirin plus heparin vs aspirin alone among 41299 cases of suspected acute myocardial infarction. Lancet 1992 339 753-70. 

ISIS-2 (Second International Study of Infarct Survival) Collaborative Group. Randomized trial of intravenous streptokinase, oral aspirin, both, or neither among 17,187 cases of suspected acute myocardial infarction ISIS-2. Lancet 1988 2 349-360. 

Collen, D. (1998). Staphylokinase a potent, uniquely fibrin-selective thrombolytic agent. Nature Med. 4(3), 279-284. Collins, R. et al. (1997). Drug therapy—aspirin, heparin and fibrinolytic therapy in suspected acute myocardial infarction. N. Engl. J. Med. 336(12), 847-860. 

Drug therapy of acute coronary syndromes including unstable angina and non-Q-wave myocardial infarction includes use of aspirin, heparin and anti-ischaemic drugs and is similar in older patients to other age groups. Activation of platelet thromboxane production in the coronary circulation has been demonstrated in unstable angina. The risk of myocardial infarction or death is reduced by approximately 50% by early aspirin therapy in recommended doses of 160-325 mg per day and continued... 

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