Attention clinicians

The Clinical Practice Guideline on which this Quick Reference Guide for Clinicians is based was developed by an interdisciplinary, private-sector panel comprising health care professionals and two consumer representatives. Panel members were:

• Eugene Braunwald, MD (Chair)
• Jay Brown, MD
• Leslie Brown, MPH, JD
• Melvin D. Cheitlin, MD
• Craig A. Concannon, MD
• Marie Cowan, PhD, RN
• Conan Edwards, PhD
• Valentin Fuster, MD, PhD
• Lee Goldman, MD
• Lee A. Green, MD, MPH
• Cindy L. Grines, MD
• Bruce W. Lytle, MD
• Kathleen M. McCauley, PhD, RN, CS
• Alvin I. Mushlin, MD, ScM
• Gregory C. Rose, MD
• Earl E. Smith III, MD
• Julie A. Swain, MD
• Eric J. Topol, MD
• James T. Willerson, MD

• Douglass A. Morrison, MD

For a description of the guideline development process and information about the sponsoring agencies (Agency for Health Care Policy and Research and the National Heart, Lung, and Blood Institute), see the Clinical Practice Guideline, Unstable Angina: Diagnosis and Management (AHCPR Publication No. 94-0602). To receive a copy of the Clinical Practice Guideline, this Quick Reference Guide for Clinicians (AHCPR Publication No. 94-0603), or the Patient and Family Guide (AHCPR Publication No. 94-0604, English or 94-0605, Spanish), call toll free:

• (800) 358-9295 or write to:

• Unstable Angina Guideline
• AHCPR Publications Clearinghouse
• P.O. Box 8547
• Silver Spring, MD 20907

This guideline describes principles of patient care derived from systematic analysis of scientific literature and from opinions of the expert panel when evidence was lacking. Diagnostic and management strategies recommended are as reasonable and safe as possible, given the current state of medical knowledge. Descriptions of usual approaches to care are expected to provide starting points for management of individual patients. However, adherence to this or any other guideline will not ensure perfect medical outcomes. Even the most careful application of current medical knowledge and procedures cannot eliminate all risk in the management of patients with unstable angina.

Note: This Quick Reference Guide for Clinicians contains excerpts from the Clinical Practice Guideline. Practitioners should review the Clinical Practice Guideline carefully to become familiar with the diagnosis and treatment options for patients with unstable angina and then use the Quick Reference Guide to help them remember major decision points.

Purpose and Scope

Unstable angina is a transitory syndrome that causes significant disability and death in the United States. In 1991 alone, 570,000 hospitalizations for this principal diagnosis resulted in 3.1 million hospital days. Unstable angina most often results from disruption of an atherosclerotic plaque and the subsequent cascade of pathologic processes that critically decrease coronary blood flow. In most but not all patients presenting with angina, symptoms will be caused by significant coronary artery disease (CAD).

The Clinical Practice Guideline, Unstable Angina: Diagnosis and Management, provides recommendations and supporting evidence for all aspects of the diagnosis and treatment of unstable angina in both the inpatient and outpatient settings. The management of patients with acute myocardial infarction or stable angina is addressed only when these related conditions border indistinguishably with unstable angina.

Throughout this Quick Reference Guide, unstable angina is defined as a clinical syndrome falling between stable angina and myocardial infarction in the spectrum of patients with CAD.

See the back of this guide for a listing of information to be entered in the medical record during each phase of care.

Unstable angina presentations

• Rest angina within 1 week of presentation
• New onset angina of Canadian Cardiovascular Society Classification (CCSC) class III or IV within 2 months of presentation
• Angina increasing in CCSC class to at least CCSC III or IV
• Variant angina
• Non-Q-wave myocardial infarction
• Post-myocardial infarction angina (>24 hours)

Table

CCSC angina classification.

Initial Evaluation and Treatment

Initial Evaluation

Diagnosis of unstable angina depends on a careful clinical history, physical examination, and examination of a resting 12-lead electrocardiogram (ECG). Therefore, the initial evaluation of patients with symptoms consistent with ischemic pain usually should take place in a medical facility and not by telephone.

• The ECG provides crucial information in the diagnosis of unstable angina, and recordings taken both during periods of pain and after pain relief are useful.
• In patients with symptoms suggesting unstable angina, there are two complementary and equally important components to the initial assessment: (1) assessment of the likelihood of CAD (Table 1) and (2) assessment of the risk of adverse outcomes (Table 2).

Table

Table 1. Likelihood of significant CAD in patients with symptoms suggesting unstable angina.

Table

Table 2. Short-term risk of death or nonfatal myocardial infarction in patients with symptoms suggesting unstable angina.

At the conclusion of this initial evaluation, the patient can be assigned to one of four diagnostic categories: not coronary artery disease, stable angina, acute myocardial infarction (MI), or unstable angina (Figure 1).

Figure

Figure 1: Diagnosis and risk stratification.

Initial Medical Treatment

The certainty of diagnosis, severity of symptoms, hemodynamic state, and medication history will determine the choice and timing of drugs used in individual patients. Drugs to be considered for use at the time of initial evaluation and treatment of patients with unstable angina include aspirin, heparin, nitrates, and beta blockers (Table 3).

Table

Table 3. Drugs commonly used in intensive medical management of patients with unstable angina.

• Begin treatment with an indicated drug in the emergency department; pharmacologic treatment should not be delayed until hospital admission. The aggressiveness of drug dosage will depend on the severity of symptoms and, for many drugs, will require modification throughout the subsequent hospital course.
• Institute anti-ischemic therapy in the emergency department as soon as the working diagnosis of unstable angina is made.
• Give supplemental oxygen to patients with cyanosis, respiratory distress, or high-risk features. Monitor for adequate arterial oxygenation with finger pulse oximetry or blood gas determinations.
• Place patients with intermediate- or high-risk unstable angina on continuous ECG monitoring for ischemia and arrhythmia detection.
• Intravenous thrombolytic therapy is not indicated in patients who do not have evidence of acute ST-segment elevation or left bundle branch block on their 12-lead ECG.

Outpatient Care

Patients with unstable angina who are judged in the initial evaluation and treatment phase to be at low risk for adverse outcomes can, in many cases, be safely evaluated further as outpatients. Typically, these are patients who have experienced new onset or worsening symptoms that may be due to ischemia, but they have not had severe, prolonged, or rest episodes in the preceding 2 weeks.

• Schedule a followup evaluation as soon as possible, generally within 72 hours after the initial presentation.
• Conduct a systematic search for precipitating noncardiac causes that might explain the new development of unstable angina symptoms or the conversion from a stable to an unstable course. Thus, at the followup evaluation, each patient should have: a second ECG to look for asymptomatic ischemia or arrhythmias, measurement of body temperature and blood pressure, a hemoglobin or hematocrit determination, and a physical examination for evidence of other cardiac diseases (particularly aortic valve disease and hypertrophic cardiomyopathy) or hyperthyroidism.
• Review the patient's history to determine additional potential exacerbating factors, such as a recent increase in physical activity level (especially in combination with environmental temperature extremes), noncompliance with medical therapy, or a recent increase in psychological stress levels.
• Advise patients diagnosed with unstable angina to take aspirin, 80 to 324 mg per day, unless contraindications are present. For patients unable to take aspirin because of a history of true hypersensitivity or recent significant gastrointestinal bleeding, ticlopidine, 250 mg twice a day, may be used as a substitute.
• Begin therapy for newly diagnosed patients, generally with sublingual nitroglycerin as needed, followed by oral beta blockers and/or long-acting topical or oral nitrates. Review the medical regimen of patients with established coronary artery disease already on medical therapy, and increase dosages as appropriate for symptom management and as tolerated.
• Consider prescribing long-acting forms of antianginal drugs for enhanced patient compliance.

Intensive Medical Management

Intensive medical treatment should begin immediately in the emergency department in patients at high or intermediate risk of death or non-fatal MI. For high-risk patients, such as those with ongoing angina at rest and/or those who appear unstable, simultaneous evaluation and treatment assume an urgency greater than for intermediate-risk patients, such as those with prior discomfort who are asymptomatic during the initial evaluation.

• Establish intravenous access while simultaneously obtaining a brief cardiovascular history, physical examination, and ECG.
• Institute daily aspirin and intravenous heparin plus nitrates and beta blockers (Table 3).
• Consider adding calcium channel blockers in the subset of patients who have significant hypertension (systolic blood pressure >=150 mmHg), in patients who have refractory ischemia on beta blockers, and in those with variant angina.

Recurrent symptoms after the initial hemodynamic goals of therapy have been achieved may be regarded as a failure of medical therapy and should prompt consideration of urgent cardiac catheterization. Although it is theoretically desirable to have the maximal medical regimen in place for >=24 hours before declaring any patient a failure of medical therapy, to do so in all cases may be inappropriate or even dangerous.

• Assign patients who have one or more recurrent severe, prolonged (>20 minutes) ischemic episodes, particularly when accompanied by pulmonary edema, a new or worsening mitral regurgitation murmur, hypotension, or new ST- or T-wave changes, to the high-risk category regardless of the level of medical therapy and triage them to early cardiac catheterization.
• Assign patients with shorter, less severe ischemic episodes without accompanying hemodynamic or ECG changes to a substantially lower risk category and continue medical therapy.

Selection of Further Therapy in Stabilized Patients

For patients who stabilize after initial treatment, this guideline proposes two alternative strategies for definitive treatment of unstable angina termed, "early invasive" and "early conservative."

Patients who prefer continued intensive medical management and patients who are not candidates for revascularization will continue to receive care at a level and duration dictated by the level of their disease activity.

Figure 3 describes the cardiac catheterization and myocardial revascularization phase.

Figure

Figure 3: Cardiac catheterization and myocardial revascularization.

Nonintensive Medical Management

Patients with unstable angina judged to be at moderate risk may be admitted initially to a monitored intermediate care unit until the diagnosis of myocardial infarction can be excluded and it is clear that the patient's symptoms are adequately controlled on medical therapy. These patients then enter the nonintensive phase of management.

Other moderate-risk and some low-risk patients may be admitted directly to a regular hospital bed with telemetry capabilities, thereby proceeding directly to the nonintensive phase. High-risk unstable angina patients will be moved to the nonintensive phase after 1 or more days of intensive management and stabilization.

Once patients reach the nonintensive phase of management, reasons for continued hospitalization include optimization of medical therapy, evaluation of the propensity for recurrent ischemia or ischemic complications, and risk stratification to determine the need for catheterization and revascularization.

• Discontinue continuous monitoring of the ECG in this phase for most patients.
• Instruct all patients to notify nursing personnel immediately if chest discomfort recurs.
• Recurrent ischemic episodes should prompt a brief nursing assessment and an emergent ECG and should be brought to the attention of a physician.
• Reevaluate the patient's medical regimen and adjust doses of anti-ischemic agents as tolerated.
• Encourage the patient to progress gradually to a level of activity, under the observation of the health care team, commensurate with that required to perform activities of daily living.
• Advise the patient and his or her family regarding risk-factor modification and have them work with the health care team to set appropriate goals.

Many patients reaching this phase will be referred within 1 to 2 days for either noninvasive functional testing or cardiac catheterization.

Noninvasive Testing

The goals of noninvasive testing in a recently stabilized patient with unstable angina are to estimate the subsequent prognosis, especially for the next 3 to 6 months, decide which additional tests and adjustments in therapy are required based on this prognosis, and provide the patient with the information and reassurances necessary to return to a lifestyle as full and productive as possible (Figure 2).

• Conduct exercise or pharmacologic stress testing of low-risk patients with unstable angina who are to be managed as outpatients, unless contraindicated.
• Perform noninvasive testing within 72 hours of presentation (in most cases) in low-risk patients who are to be managed as outpatients.
• Perform noninvasive exercise or pharmacologic stress testing in low- or intermediate-risk patients hospitalized with unstable angina who have been stabilized and free of angina and congestive heart failure for a minimum of 48 hours, unless cardiac catheterization is indicated.

Figure

Figure 2: Noninvasive testing.

Choice of Test

• Base the choice of the stress testing modality on an evaluation of the patient's resting ECG, ability to perform exercise, and the local expertise and technologies available.
• Employ the exercise treadmill test as the standard mode of stress testing in patients with a normal ECG who are not taking digoxin.
• Test patients with widespread resting ST depression (>1mm), ST changes secondary to digoxin, left ventricular hypertrophy, left bundle branch block/significant intraventricular conduction deficit, or pre-excitation using an imaging modality.
• Use pharmacologic stress testing in combination with an imaging modality for patients unable to exercise due to physical limitations (e.g., arthritis, amputation, severe peripheral vascular disease, general debility).

An exercise treadmill is the most commonly used stress test and has the largest reported experience for use in patients with unstable angina. A nomogram useful to convert results from this test into an assessment of risk has been derived on a large sample of patients with coronary artery disease exclusively (not in patients presenting with unstable angina) (See the Clinical Practice Guideline, Unstable Angina: Diagnosis and Management). Use of this nomogram to quantitate risk from results of treadmill examinations provides more clinically useful information than a simple normal/abnormal reading.

Interpreting Noninvasive Test Results

Implications and appropriate followup for the exercise treadmill tests are outlined in Table 4.

Table

Table 4. Implications of stress test results.

Cardiac Catheterization and Myocardial Revascularization

Hospital Discharge and Postdischarge Care

The need for continued hospitalization of the patient with unstable angina is determined by whether the inpatient objectives of that hospital admission have been achieved. Patients who have undergone successful revascularization will usually have the remainder of their hospitalization defined by the standard protocol for the given procedure (e.g., 1 to 2 days for angioplasty, 5 to 7 days for coronary artery bypass graft surgery).

Patients opting medical treatment after a cardiac catheterization or functional study include both a low-risk group that can be rapidly discharged (e.g., 1 to 2 days after testing) and high-risk group unsuitable for or unwilling to have coronary revascularization. These patients may require a prolonged hospitalization to ensure adequate (or as adequate as possible) symptom control.

The goal during the hospital discharge phase is to prepare the patient for normal activities to the extent possible.

Abstract

This Quick Reference Guide for Clinicians contains recommendations on the care of patients with unstable angina based on a combination of evidence obtained through extensive literature reviews and consensus among members of a private-sector, expert panel. Principal conclusions include:

• Many patients suspected of having unstable angina can be discharged home after adequate initial evaluation.
• Further outpatient evaluation may be scheduled for up to 72 hours after initial presentation for patients with clinical symptoms of unstable angina judged at initial evaluation to be at low risk for complications.
• Patients with acute ischemic heart disease judged to be at intermediate or high risk of complications should be hospitalized for careful monitoring of their clinical course.
• Intravenous thrombolytic therapy should not be administered to patients without evidence of acute myocardial infarction.
• Assessment of prognosis by noninvasive testing often aids selection of appropriate therapy.
• Coronary angiography is appropriate for patients judged to be at high risk for cardiac complications or death based on their clinical course or results of noninvasive testing.
• Coronary artery bypass surgery should be recommended for almost all patients with left main disease and many patients with three-vessel disease, especially those with left ventricular dysfunction.
• The discharge care plan should include continued monitoring of symptoms; appropriate drug therapy, including aspirin; risk-factor modification; and counseling.

This document is in the public domain and may be used and reprinted without special permission, except for those copyrighted materials noted for which further reproduction is prohibited without the specific permission of copyright holders.

AHCPR and NHLBI appreciate citation as to source, and the suggested format is as follows:

Braunwald E, Mark DB, Jones RH et al. Diagnosing and Managing Unstable Angina. Quick Reference Guide for Clinicians, Number 10. AHCPR Publication No. 94-0603. Rockville, MD. U.S. Department of Health and Human Services, Public Health Service, Agency for Health Care Policy and Research and National Heart, Lung, and Blood Institute. May 1994 (amended).

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AHCPR Publication No. 94-0603.

National Library of Medicine DOCLINE Information: MED/94163198