The cornerstone of management of acute myocardial infarction is prompt emergency care. Initial therapy in the field should include oxygen, nitroglycerin, morphine (if hypotension is not present), rapid transport to an emergency department, and evaluation for thrombolytic therapy. On arrival at the hospital, assessment should focus on hemodynamic stability and eligibility for
Nonspecific ST or T-wave changes or ST depression 10-20% early total occlusion rate in infarct-related vessels Lower CK peaks Higher ejection fractions Less wall-motion abnormalities Higher early reinfarction rate (40%)
ST-segment elevation 90% early total occlusion rate in infarct-related vessels Higher CK peaks Lower ejection fractions Wall-motion abnormalities more frequent Higher early morbidity (1.5-2 times increased) thrombolytic therapy or emergency angioplasty. All patients should be given aspirin if there are no contraindications.
What forms of therapy can result in reperfusion?
Prompt use of thrombolytic agents
Percutaneous transluminal coronary angioplasty (PTCA)
Coronary artery bypass surgery (CABG)
Explain the recommendations for thrombolytic therapy.
Thrombolytic therapy should be considered in all patients with presumed acute myocardial infarction and ST elevation or new left bundle branch block. The benefit of thrombolytic therapy in these patients has been demonstrated in numerous studies, where it routinely decreased mortality, improved left ventricular function, was associated with fewer arrhythmias, and improved long-term survival. Thrombolytic therapy accelerates the conversion of plasminogen to plasmin, an enzyme which dissolves fibrin clots, enhancing endogenous fibrinolysis. Nearly 80% of thrombosed arteries can be opened with thrombolytic therapy; however, there is a 15-20% reocclusion rate. The choice of thrombolytic agents is controversial. Currently approved agents and regimes are shown in the accompanying table.
Timely use of thrombolytic therapy seems to be the most important factor in predicting who will benefit. The use of theombolytic agents within 6 hours of presentation confers the most survival benefit, although effectiveness has been shown up to 12 hours. More recent data suggest the accelerated tPA may provide some survival benefit over other regimens. Adjunctive therapy for thrombolysis includes aspirin and heparin to prevent reocclusion. Heparin is necessary in conjunction with tPA but is probably not necessary with streptokinase or APSAC. Better agents are being developed and include thrombin-specific inhibitors (hirudin) and other platelet inhibitors.
Heparin is generally recommended for both tPA regimens as a 5000-U bolus, followed by an IV (intravenous) infusion of 1000 U/hr (1200 U/hr in patients 80 kg), with dose adjustments to raise the activated partial thromboplastin time (aPTT) to 60-85 seconds.
What is the initial management of acute myocardial infarction? Photo Gallery
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