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In the United States, there are approximately 850,000 acute myocardial infarctions (AMI) annually. Of these, 500,000 are ST segment elevation MI’s (STEMI). AMI is the leading cause of sudden cardiac death and one of the major causes of congestive heart failure. The southeastern region of the United States has both the highest incidence and highest mortality for cardiovascular disease. The definition for AMI has recently been updated by a joint European-American statement for AMI, and must fulfill the following criteria:

Detection of the rise and fall of cardiac biomarkers with at least one value above the 99th percentile of the upper reference limit with at least one of the following: (1) Symptoms of myocardial ischemia; (2) ECG changes of new ischemia-either ST-T changes or a new LBBB; (3) New pathologic Q waves in the ECG; (4) Imaging study of new loss of viable myocardium.

When faced with a STEMI there are four cardinal issues to consider: (1) Reperfusion strategy; (2) Careful observation for common complications; (3) Administration of pharmacologic agents beneficial to patients; (4) Modification of cardiac risk factors (Secondary Prevention).

The goal of reperfusion is to minimize the total time of ischemia which begins at symptom onset. Reperfusion can be effected by either thrombolytic therapy or primary percutaneous coronary intervention (PCI). When PCI is available 24 hours a day, 7 days per week, this is the superior treatment. It is important that if PCI is chosen then the time from presentation to balloon inflation be less than 90 minutes. For thrombolytic therapy, the door to needle time should not exceed 30 minutes. The Vanderbilt Acute MI Network is designed to expedite the care of patients suffering an AMI by timely PCI for patients with AMI. We have organized participating regional ER’s and have implemented a system to achieve quick door to balloon times for patients that need transfer for PCI so that a door to balloon time of 90-120 minutes can be achieved for all patients that present to an ER within 100 miles of Vanderbilt University Hospital. Unless there is an obvious contraindication, almost all patients that receive thrombolytic therapy should be considered for coronary angiography. If thrombolysis has been successful, it is reasonable to wait 24-48 hours; for patients that receive thrombolysis but continue to have pain and ST changes immediate coronary angiography and rescue PCI are needed.

The use of IV, oral, or topical nitrates should be considered for management of ischemic pain. Morphine remains the drug of choice for STEMI patients that need analgesia. Because of adverse cardiac events all NSAIA’s should be discontinued immediately at the time of STEMI.

Patients hospitalized for acute MI care need to be observed for any potential complications. The most common are recurrent ischemia, congestive heart failure, or ventricular arrhythmias.

When managing patients with a STEMI, proper pharmacologic therapy is critical for best practice. As part of the initial reperfusion strategy, all patients should receive aspirin, clopidogrel, and an anticoagulant-either unfractionated heparin or low molecular weight heparin-enoxaparin. Aspirin doses should be 160-325 mg immediately and 81-160 mg daily. Clopidogrel loading dose of 600 mg should be administered. If the patient receives an intracoronary stent then a dose of 75 mg daily is needed post procedure. All patients should be started on anticoagulant therapy. Unfractionated heparin is given as a loading dose of 60 units/kg then infused at 12 units/kg/hr with a goal of keeping the aPTT 1.5-2.0 times normal. If low molecular weight heparin is administered the most commonly used regimen is 30 mg IV bolus followed by 1.0 mg/kg subcutaneously every 12 hours.

Beta-blocker use for AMI patients reduce the incidence of recurrent infarction and ischemia and have beneficial effects for ventricular arrhythmias. Unless there is an obvious contraindication, all patients should be administered a beta-blocker within 24 hours and continued indefinitely; those that have a contraindication should be reassessed for beta-blocker candidacy as secondary prevention. The use of ACE inhibitors or angiotensin receptor blockers is important for patients with an LV ejection fraction of 50% or less post MI and should be continued indefinitely.

Secondary preventative measures are critical for best practice. Patients are advised the following: (a) Cessation of all tobacco products; (b) Lipid management- dietary and pharmacologic therapy to achieve an LDL cholesterol < 70 mg/dL and triglycerides < 200 mg/dL; (c) Blood pressure control of 120/80 mmHg or less; (d) Aerobic physical activity at a minimum of 5 days/week for 30-60 minutes; (e) Weight management with BMI goal of 18-25 kg/m2; (f) Aggressive management of blood sugars in diabetics; (g) Daily aspirin therapy with doses of 81-325 mg; (h) Influenza vaccine yearly.



REFERENCES

Anbe DT et al. ACC/AHA Guidelines for the Management of Patients with ST-Elevation Myocardial Infarction. J Am Coll Cardiol 2004; 44:671-719.

Antman EM et al. 2007 Focused Update of the ACC/AHA 2004 Guidelines for the Management of Patients with ST-Elevation Myocardial Infarction. J Am Coll Cardiol 2008; 51: 210-247.




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