The American College of Cardiology (ACC)/American Heart Association (AHA) Task Force on Practice Guidelines recently issued a joint executive summary of guidelines for the management of ST-elevation myo-cardial infarction (STEMI). This “Practice Guideline” will focus on two sections of the guidelines: management before STEMI and initial recognition and management in the emergency department. In the November 15, 2004, issue of American Family Physician, a Practice Guideline will discuss the hospital and long-term management sections of this guideline. The ACC/AHA guidelines were published in the August 3, 2004, issue of Circulation and are available online athttp://www.acc.org/clinical/guidelines/stemi/index.htm.

This guideline focuses on advances in the diagnosis and management of STEMI since 1999. Recommendations for indications for a diagnostic procedure, a particular therapy, or an intervention in patients with STEMI are based on clinical evidence and expert opinion. Definitions of the evidence levels are as follows: Level A: Data derived from multiple randomized clinical trials or meta-analyses. Level B: Data derived from a single randomized trial, or nonrandomized studies. Level C: Only consensus opinion of experts, case studies, or standard-of-care.

Class I: Procedure or treatment should be performed or administered. Class IIa: It is reasonable to perform procedure or administer treatment (additional studies with focused objectives needed). Class IIb: Procedure or treatment may be considered (additional studies with broad objectives needed; additional registry data would be helpful). Class III: Procedure or treatment should not be performed or administered because it is not helpful and may be harmful (no additional studies needed).

Management Before STEMI

IDENTIFICATION OF PATIENTS AT RISK OF STEMI

Class I

1. Primary care providers should evaluate the presence and status of control of major risk factors for coronary heart disease (CHD) for all patients at regular intervals (approximately three to five years). (Level of Evidence: C)

2. Ten-year risk (National Cholesterol Education Program global risk) of developing symptomatic CHD should be calculated for all patients who have two or more major risk factors to assess the need for primary prevention strategies. (Level of Evidence: B)

3. Patients with established CHD should be identified for secondary prevention, and patients with a CHD risk equivalent (such as diabetes mellitus, chronic kidney disease, or 10-year risk greater than 20 percent as calculated by Framingham equations) should receive equally intensive risk factor intervention as those with clinically apparent CHD. (Level of Evidence: A)

PATIENT EDUCATION FOR EARLY RECOGNITION AND RESPONSE TO STEMI

Class I

1. Patients with symptoms of STEMI (chest discomfort with or without radiation to the arm[s], back, neck, jaw, or epigastrium; shortness of breath; weakness; diaphoresis; nausea; lightheadedness) should be transported to the hospital by ambulance rather than by friends or relatives. (Level of Evidence: B)

2. Health care providers should actively address the following issues regarding STEMI with patients and their families:

   The patient’s risk of myocardial infarction (Level of Evidence: C)

   How to recognize symptoms of STEMI (Level of Evidence: C)

   The advisability of calling 9-1-1 if symptoms are unimproved or worsening after five minutes, despite feelings of uncertainty about the symptoms and fear of potential embarrassment (Level of Evidence: C)

   A plan for appropriate recognition and response to a potential acute cardiac event that includes the telephone number to access emergency medical services (EMS), generally 9-1-1. (Level of Evidence: C)

3. Health care providers should instruct patients for whom nitroglycerin has been prescribed previously to take one nitroglycerin dose sublingually in response to chest discomfort or pain. If chest discomfort or pain is unimproved or worsening five minutes after one sublingual nitroglycerin dose has been taken, it is recommended that the patient or family member/friend call 9-1-1 immediately to access EMS. (Level of Evidence: C)

The authors state that the mortality and morbidity rates associated with STEMI can be reduced significantly if people recognize the symptoms early, activate the EMS system, and thereby reduce the time to definitive treatment. They recommend that patients with possible symptoms of STEMI be taken to the hospital in an ambulance rather than by friends or relatives.

Initial Recognition and Management in the Emergency Department

OPTIMAL STRATEGIES FOR EMERGENCY DEPARTMENT TRIAGE

Class I

1. Hospitals should establish multidisciplinary teams (including primary care physicians, emergency medicine physicians, cardiologists, nurses, and laboratorians) to develop guidelines-based, institution-specific written protocols for triaging and managing patients who are seen in the prehospital setting or present to the emergency department with symptoms suggestive of STEMI. (Level of Evidence: B)

INITIAL PATIENT EVALUATION

Class I

1. The delay from patient contact with the health care system (typically, arrival at the emergency department or contact with paramedics) to initiation of fibrinolytic therapy should be less than 30 minutes. Alternatively, if percutaneous coronary intervention (PCI) is chosen, the delay from patient contact with the health care system (typically, arrival at the emergency department or contact with paramedics) to balloon inflation should be less than 90 minutes. (Level of Evidence: B)

2. The choice of initial STEMI treatment should be made by the emergency medicine physician on duty based on a predetermined, institution-specific, written protocol that is a collaborative effort of cardiologists (both those involved in coronary care unit management and interventionalists), emergency physicians, primary care physicians, nurses, and other appropriate personnel. For cases in which the initial diagnosis and treatment plan is unclear to the emergency physicians or is not covered directly by the agreed-on protocol, immediate cardiology consultation is advisable. (Level of Evidence: C)

In the patient evaluation section, the authors discuss guidelines for taking a patient’s history, performing a physical examination, and obtaining an electrocardiogram, laboratory examinations, biomarkers of cardiac damage, and diagnostic imaging.

MANAGEMENT

A. Oxygen

Class I

1. Supplemental oxygen should be administered to patients with arterial oxygen desaturation(SaO₂ less than 90 percent). (Level of Evidence: B)

Class IIa

1. It is reasonable to administer supplemental oxygen to all patients with uncomplicated STEMI during the first six hours. (Level of Evidence: C) B. Nitroglycerin

B. Nitroglycerin

Class I

1. Patients with ongoing ischemic discomfort should receive sublingual nitroglycerin (0.4 mg) every five minutes for a total of three doses, after which an assessment should be made about the need for intravenous nitroglycerin. (Level of Evidence: C)

2. Intravenous nitroglycerin is indicated for relief of ongoing ischemic discomfort, control of hypertension, or management of pulmonary congestion. (Level of Evidence: C)

Class III

1. Nitrates should not be administered to patients with systolic blood pressure less than 90 mm Hg or greater than or equal to 30 mm Hg below baseline, severe bradycardia (less than 50 beats per minute), tachycardia (more than 100 beats per minute), or suspected right ventricular infarction. (Level of Evidence: C)

2. Nitrates should not be administrated to patients who have received a phosphodiesterase inhibitor for erectile dysfunction within the past 24 hours (48 hours after tadalafil). (Level of Evidence: B) C. Analgesia

C. Analgesia

Class I

1. Morphine sulfate (2 to 4 mg intravenously [IV] with increments of 2 to 8 mg IV at five- to 15-minute intervals) is the analgesic of choice for management of pain associated with STEMI. (Level of Evidence: C) D. Aspirin

D. Aspirin

Class I

1. Aspirin should be chewed by patients who have not taken aspirin before presentation with STEMI. The initial dose should be 162 mg (Level of Evidence: A) to 325 mg (Level of Evidence: C). Although some trials have used enteric-coated aspirin for initial dosing, more rapid buccal absorption occurs with non–enteric-coated aspirin formulations.

E. Beta blockers

Class I

1. Oral beta-blocker therapy should be administered promptly to those patients without a contraindication, irrespective of concomitant fibrinolytic therapy or performance of primary PCI. (Level of Evidence: A)

Class IIa

1. It is reasonable to administer IV beta blockers promptly to STEMI patients without contraindications, especially if a tachyarrhythmia or hypertension is present. (Level of Evidence: B)

The management section also discusses the issues that should be considered when selecting the type of reper-fusion therapy. The guidelines state that an assessment should include the following variables: time from onset of symptoms, patient’s risk of STEMI, risk of bleeding, and time required for transport to a skilled PCI laboratory. The accompanying figure details the assessment of reperfusion options for patients with STEMI.

This guideline also discusses out-of-hospital cardiac arrest, prehospital issues, hospital management of STEMI, and long-term management.