Practice Guidelines

ACC/AHA Release Guidelines on Management of Patients With STEMI: Hospital and Long-Term Management

matthew j. neff

The American College of Cardiology/American Heart Association (ACC/AHA) Task Force on Practice Guidelines recently issued a joint executive summary of guidelines for the management of ST-elevation myocardial infarction (STEMI). This "Practice Guideline" will focus on two sections of the guideline: hospital and long-term management. In the November 1, 2004, issue of American Family Physician, a Practice Guideline discussed management before STEMI and initial recognition and management in the emergency department sections of this guideline. The ACC/AHA guideline was published in the August 3, 2004, issue of Circulation and is available online at http://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).

Hospital Management

EARLY, GENERAL MEASURES

Level of Activity
Class IIa

1. After 12 to 24 hours, it is reasonable to allow patients with hemodynamic instability or continued ischemia to have bedside commode privileges. (Level of Evidence: C)

Class III

1. Patients with STEMI who are free of recurrent ischemic discomfort, symptoms of heart failure, or serious disturbances of heart rhythm should not be on bed rest for more than 12 to 24 hours. (Level of Evidence: C)

Diet
Class I

1. Patients with STEMI should be prescribed the diet of the National Cholesterol Education Program Adult Treatment Panel III Therapeutic Lifestyle Changes, which focuses on reduced intake of fats and cholesterol, less than 7 percent of total calories as saturated fats, less than 200 mg of cholesterol per day, increased consumption of omega-3 fatty acids, and appropriate caloric intake for energy needs. (Level of Evidence: C)
2. Patients with diabetes who have STEMI should have an appropriate food group balance and caloric intake. (Level of Evidence: B)
3. Sodium intake should be restricted in STEMI patients with hypertension or heart failure. (Level of Evidence: B)

Patient Education in the Hospital Setting

Class I

1. Patient counseling to maximize adherence to evidence-based post-STEMI treatments (such as compliance with taking medication, exercise prescription, and smoking cessation) should begin during the early phase of hospitalization, occur intensively at discharge, and continue at follow-up visits with providers and through cardiac rehabilitation programs and community support groups, as appropriate. (Level of Evidence: C)
2. Critical pathways and protocols and other quality-improvement tools (such as the ACC "Guidelines Applied in Practice" and the AHA's "Get with the Guidelines") should be used to improve the application of evidence-based treatments by patients with STEMI, caregivers, and institutions. (Level of Evidence: C)

Analgesia/Anxiolytics
Class IIa

1. It is reasonable to use anxiolytic medications in patients with STEMI to alleviate short-term anxiety or altered behavior related to hospitalization for STEMI. (Level of Evidence: C)
2. It is reasonable to routinely assess the patient's anxiety level and manage it with behavioral interventions and referral for counseling. (Level of Evidence: C)

RISK STRATIFICATION DURING EARLY HOSPITAL COURSE

Risk stratification requires the updating of initial assessments with data obtained during the course of the hospital stay. The recurrence of chest pain and persistence of electrocardiogram findings indicating infarction are indicators of failed reperfusion. These patients should undergo coronary angiography. Sudden onset of heart failure or presence of a new murmur herald increased risk and suggest the need for rapid intervention. For those who did not undergo primary reperfusion, changes in clinical status may herald a worsening clinical status and are an indication for coronary angiography. Patients with a low risk of complications may be considered for early discharge.

MEDICATION ASSESSMENT

Beta Blockers

There is overwhelming evidence for the benefits of early use of beta blockers in patients with STEMI and no contraindications to their use. Studies have demonstrated benefits of their use in patients with and without concomitant fibrinolytic therapy, both early and late after STEMI.

Class I

1. Patient receiving beta blockers within the first 24 hours of STEMI without adverse effects should continue to receive them during the early convalescent phase of STEMI. (Level of Evidence: A)
2. Patients without contraindications to beta blockers who did not receive them within the first 24 hours after STEMI should have them started in the early convalescent phase. (Level of Evidence: A)
3. Patients with early contraindications within the first 24 hours of STEMI should be reevaluated for candidacy for beta-blocker therapy. (Level of Evidence: C)

Nitroglycerin
Class I

1. Intravenous nitroglycerin is indicated in the first 48 hours after STEMI for treatment of persistent ischemia, congestive heart failure, or hypertension. The decision to administer intravenous nitroglycerin and the dosage used should not preclude therapy with other proven mortality-reducing interventions, such as beta blockers or angiotensin-converting enzyme (ACE) inhibitors. (Level of Evidence: B)
2. Intravenous, oral, or topical nitrates are useful beyond the first 48 hours after STEMI for treatment of recurrent angina or persistent congestive heart failure (CHF) if their use does not preclude therapy with beta blockers or ACE inhibitors. (Level of Evidence: B)

Class IIb

1. The continued use of nitrate therapy beyond the first 24 to 48 hours in the absence of continued or recurrent angina or CHF may be helpful, although the benefit is likely to be small and is not well established in contemporary practice. (Level of Evidence: B)

Class III

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

Inhibition of the Renin-Angiotensin-Aldosterone System

Class I

1. An ACE inhibitor should be administered orally during convalescence from STEMI in patients who tolerate this class of medication, and it should be continued over the long term. (Level of Evidence: A)
2. An angiotensin-receptor blocker (ARB) should be administered to STEMI patients who are intolerant of ACE inhibitors and have clinical or radiologic signs of heart failure or left ventricular ejection fraction (LVEF) less than 0.40. Valsartan and candesartan have demonstrated efficacy for this recommendation. (Level of Evidence: B)
3. Long-term aldosterone blockade should be prescribed for post-STEMI patients without significant renal dysfunction (creatinine should be less than or equal to 2.5 mg per dL [221.0 µmol per L] in men and less than or equal to 2.0 mg per dL [176.8 µmol per L] in women) or hyperkalemia (potassium should be less than or equal to 5.0 mEq per L [5.0 mmol per L]) who are already receiving therapeutic doses of an ACE inhibitor, have an LVEF less than or equal to 0.40, and have symptomatic heart failure or diabetes. (Level of Evidence: A)

Class IIa

1. In patients with STEMI who tolerate ACE inhibitors, an ARB can be useful as an alternative to ACE inhibitors provided there are either clinical or radiologic signs of heart failure or LVEF is less than 0.40. Valsartan and candesartan have established efficacy for this recommendation. (Level of Evidence: B)

Antiplatelets
Class I

1. Aspirin (162 to 325 mg) should be given on day 1 of STEMI and in the absence of contraindications should be continued indefinitely on a daily basis thereafter at a dosage of 75 to 162 mg. (Level of Evidence: A)
2. A thienopyridine (preferably clopidogrel) should be administered to patients who are unable to take aspirin because of hypersensitivity or major gastrointestinal intolerance. (Level of Evidence: C)
3. For patients taking clopidogrel for whom coronary artery bypass graft surgery is planned, if possible, the drug should be withheld for at least five days, and preferably seven, unless the urgency for revascularization outweighs the risk of bleeding. (Level of Evidence: B)
4. For patients who have undergone diagnostic cardiac catheterization and for whom percutaneous coronary intervention (PCI) is planned, clopidogrel should be started and continued for at least one month after bare metal stent implantation (three months for sirolimus, six months for paclitaxel) and up to 12 months in patients who are not at high risk for bleeding. (Level of Evidence: B)

Antithrombotics
Class I

1. Intravenous unfractionated heparin (bolus of 60 U per kg, maximum 4,000 U IV; initial infusion 12 U per kg per hour, maximum of 1,000 U per hour) or low-molecular-weight heparin (LMWH) should be used in patients after STEMI who are at high risk for systemic emboli (large or anterior myocardial infarction, atrial fibrillation, previous embolus, known left ventricular thrombus, or cardiogenic shock). (Level of Evidence: C)

Class IIa

1. It is reasonable that patients with STEMI who are not undergoing reperfusion therapy and do not have a contraindication to anticoagulation be treated with intravenous or subcutaneous unfractionated heparin or with subcutaneous LMWH for at least 48 hours. In patients whose clinical condition necessitates prolonged bed rest and/or minimized activities, it is reasonable that treatment be continued until the patient is ambulatory. (Level of Evidence: C)

Class IIb

1. Prophylaxis for deep venous thrombosis (DVT) with subcutaneous LMWH (dosed appropriately for specific agent) or with subcutaneous unfractionated heparin, 7,500 U to 12,500 U twice per day until completely ambulatory, may be useful, but the effectiveness of such a strategy is not well established in the contemporary era of routine aspirin use and early mobilization. (Level of Evidence: C)

Oxygen
Class I

1. Supplemental oxygen therapy should be continued beyond the first six hours in STEMI patients with arterial oxygen desaturation (SaO2 less than 90 percent) or overt pulmonary congestion. (Level of Evidence: C)

ESTIMATION OF INFARCT SIZE

Measurement of infarct size is a vital element in the overall care of patients with STEMI. The guidelines discuss the five major modalities that apply to measuring myocardial infarction, including electrocardiographic techniques, cardiac biomarker methods, radionuclide imaging, echocardiography, and magnetic resonance imaging.

SECONDARY PREVENTION

Unless contraindicated, secondary prevention strategies are essential components of managing STEMI. The accompanying table provides recommended interventions for secondary prevention for patients with STEMI.

The hospital management section of the guidelines also includes guidelines for hemodynamic disturbances, arrhythmias after STEMI, recurrent chest pain after STEMI, other complications (including ischemic stroke, DVT, and pulmonary embolism), coronary artery bypass graft surgery after STEMI, and convalescence, discharge, and post-myocardial infarction care. It also includes an algorithm for the emergency management of complicated STEMI, cardiogenic shock, or acute pulmonary edema.

Secondary Prevention for STEMI Patients Goals Intervention Recommendations Smoking: Goal is complete cessation. Assess tobacco use. Strongly encourage patient and family to stop smoking and to avoid secondhand smoke. Provide counseling, pharmacologic therapy (including nicotine replacement and bupropion), and formal smoking-cessation programs as appropriate. Blood pressure control: Goal is less than 140/90 mm Hg or less than 130/80 mm Hg if chronic kidney disease or diabetes. If blood pressure is 120/80 mm Hg or greater: • Initiate lifestyle modification (weight control, physical activity, alcohol moderation, moderate sodium restriction, and emphasis on fruits, vegetables, and low-fat dairy products) in all patients. If blood pressure is 140/90 mm Hg or greater or 130/80 mm Hg or greater for individuals with chronic kidney disease or diabetes: • Add blood pressure medications, emphasizing the use of beta blockers and inhibition of the renin-angiotensin-aldosterone system. Lipid management: (TG level less than 200 mg per dL [2.26 mmol per L]) Primary goal is LDL-C level substantially less than 100 mg per dL (2.60 mmol per L). Start dietary therapy in all patients (less than 7 percent of total calories as saturated fat and less than 200 mg per day cholesterol). Promote physical activity and weight management. Encourage increased consumption of omega-3 fatty acids. Assess fasting lipid profile in all patients, preferably within 24 hours of STEMI. Add drug therapy according to the following guide: LDL-C level substantially less than 100 mg per dL (baseline or on-treatment): • Statins should be used to lower LDL-C. LDL-C level substantially greater than 100 mg per dL (baseline or on-treatment): • Intensify LDL-C-lowering therapy with drug treatment, giving preference to statins. Lipid management: (TG 200 mg per dL or greater) Primary goal is non-HDL-C* substantially lower than 130 mg per dL (3.36 mmol per L). If TG is greater than or equal to 150 mg per dL (1.67 mmol per L) or HDL-C is less than 40 mg per dL (1.03 mmol per L): • Emphasize weight management and physical activity. Advise smoking cessation. If TG is 200 to 499 mg per dL (2.26 to 5.64 mmol per L): • After LDL-C-lowering therapy,† consider adding fibrate or niacin.‡ If TG is greater than or equal to 500 mg per dL (5.65 mmol per L): • Consider fibrate or niacin‡ before LDL-C-lowering therapy.† • Consider omega-3 fatty acids as adjunct for high TG. Physical activity: minimum goal is 30 minutes, three to four days per week; optimal is daily. Assess risk, preferably with exercise test, to guide prescription. Encourage minimum of 30 to 60 minutes of activity, preferably daily, or at least three to four times weekly (walking, jogging, cycling, or other aerobic activity) supplemented by an increase in daily lifestyle activities (such as walking breaks at work, gardening, household work). Cardiac rehabilitation/secondary prevention programs, when available, are recommended for patients with STEMI, particularly those with multiple modifiable risk factors and/or those moderate- to high-risk patients in whom supervised exercise training is warranted. Weight management: Goal is BMI 18.5 to 24.9 kg per m2; waist circumference less than 40 inches for men and less than 35 inches for women. Calculate BMI and measure waist circumference as part of evaluation. Monitor response of BMI and waist circumference to therapy. Start weight management and physical activity as appropriate. Desirable BMI range is 18.5 to 24.9 kg per m2. If waist circumference is greater than or equal to 35 inches in women or greater than or equal to 40 inches in men, initiate lifestyle changes and treatment strategies for metabolic syndrome. Diabetes management: Goal is A1C less than 7 percent. Appropriate hypoglycemic therapy to achieve near-normal fasting plasma glucose, as indicated by A1C. Treatment of other risks (such as physical activity, weight management, blood pressure, and cholesterol management). Antiplatelet agents/anticoagulants: Start and continue indefinitely aspirin 75 to 162 mg per day if not contraindicated. Consider clopidogrel 75 mg per day or warfarin if aspirin is contraindicated. Manage warfarin to INR of 2.5 to 3.5 in post-STEMI patients when clinically indicated or for those not able to take aspirin or clopidogrel. Renin-angiotensin-aldosterone system blockers: ACE inhibitors in all patients indefinitely; start early in stable high-risk patients (anterior MI, previous MI, Killip class greater than or equal to II [S3 gallop, rales, radiographic CHF], LVEF less than 0.40). ARBs in patients who are intolerant of ACE inhibitors and who have either clinical or radiologic signs of heart failure or LVEF less than 0.40. Aldosterone blockade in patients without significant renal dysfunction§ or hyperkalemia|| who are already receiving therapeutic doses of an ACE inhibitor, have an LVEF less than or equal to 0.40, and have either diabetes or heart failure. Beta-blockers: Start in all patients. Continue indefinitely. Observe usual contraindications. TG = triglyceride; LDL-C = low-density lipoprotein cholesterol; STEMI = ST-elevation myocardial infarction; HDL-C = high-density lipoprotein cholesterol; BMI = body mass index; A1C = hemoglobin A1C; INR = international normalized ratio; ACE = angiotensin-converting enzyme; MI = myocardial infarction; CHF = congestive heart failure; LVEF = left ventricular ejection fraction; ARB = angiotensin-receptor blocker. * - Non-HDL cholesterol equals total cholesterol minus HDL cholesterol. † - Treat to a goal of non-HDL-C substantially less than 130 mg per dL. ‡ - Dietary-supplement niacin must not be used as a substitute for prescription niacin, and over-the-counter niacin should be used only if approved and monitored by a physician. § - Creatinine should be less than or equal to 2.5 mg per dL in men or less than or equal to 2.0 mg per dL in women. || - Potassium should be less than or equal to 5.0 mEq per L. Adapted with permission from Smith SC, Blair SN, Bonow RO, Brass LM, Cerqueira MD, Dracup K, et al. AHA/ACC scientific statement: AHA/ACC guidelines for preventing heart attack and death in patients with atherosclerotic cardiovascular disease: 2001 update: a statement for health care professionals from the American Heart Association and the American College of Cardiology. Circulation 2001;104:1577-9.

Long-Term Management

PSYCHOSOCIAL IMPACT OF STEMI

Class I

1. The psychosocial status of the patient should be evaluated, including inquiries regarding symptoms of depression, anxiety, or sleep disorders and the social support environment. (Level of Evidence: C)

Class IIa

1. Treatment with cognitive-behavioral therapy and selective serotonin reuptake inhibitors can be useful for STEMI patients with depression that occurs in the year after hospital discharge. (Level of Evidence: A)

CARDIAC REHABILITATION

Class IIa

1. Cardiac rehabilitation/secondary prevention programs, when available, are recommended for patients with STEMI, particularly those with multiple modifiable risk factors and/or those moderate- to high-risk patients in whom supervised exercise training is warranted. (Level of Evidence: C)

FOLLOW-UP VISIT WITH MEDICAL PROVIDER

Class I

1. A follow-up visit should delineate the presence or absence of cardiovascular symptoms and functional class. (Level of Evidence: C)
2. The patient's list of current medications should be reevaluated in a follow-up visit, and appropriate titration of ACE inhibitors, beta blockers, and statins should be undertaken. (Level of Evidence: C)
3. 3The predischarge risk assessment and planned work-up should be reviewed and continued. This should include a check of left ventricular function and possibly Holter monitoring for those patients whose early post-STEMI ejection fraction was 0.31 to 0.40 or lower, in consideration of possible implantable cardioverter-defibrillator use. (Level of Evidence: C)
4. The health care provider should review and emphasize the principles of secondary prevention with the patient and family members. (Level of Evidence: C)
5. 5The psychosocial status of the patient should be evaluated in follow-up, including inquiries regarding symptoms of depression, anxiety, or sleep disorders and the social support environment. (Level of Evidence: C)
6. In a follow-up visit, the health care provider should discuss in detail issues of physical activity, return to work, resumption of sexual activity, and travel, including driving and flying. (Level of Evidence: C)
7. Patients and their families should be asked if they are interested in cardiopulmonary resuscitation training after the patient is discharged from the hospital. (Level of Evidence: C)
8. Clinicians should actively review the following issues with patients and their families:
   1. The patient's heart attack risk. (Level of Evidence: C)
   2. How to recognize symptoms of STEMI. (Level of Evidence: C)
   3. 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)
   4. A plan for appropriate recognition and response to a potential acute cardiac event, including the phone number to access emergency medical services, generally 9-1-1. (Level of Evidence: C)
9. Cardiac rehabilitation/secondary prevention programs, when available, are recommended for patients with STEMI, particularly those with multiple modifiable risk factors and/or those moderate- to high-risk patients in whom supervised exercising training is warranted. (Level of Evidence: C)

This guideline also discusses management before STEMI, out-of-hospital cardiac arrest, prehospital issues, and initial recognition and management in the emergency department.

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Practice Guideline Briefs

Carrie Morantz
Brian Torrey

Updated CDC Influenza Vaccination Recommendations

The Centers for Disease Control and Prevention (CDC) has updated its recommendations on who should be vaccinated against influenza this season because there is not enough influenza vaccine for everyone who may want it. The influenza vaccine should be given to protect people who are most likely to have serious health problems if they get influenza. These people should get the vaccine:

• Children ages six to 23 months.
• People who are 65 years and older.
• People two years or older who have an underlying, long-term illness (e.g, heart disease, lung disease, metabolic disease, kidney disease), a blood disorder, or are immunocompromised.
• Women who are or will be pregnant this influenza season.
• People who live in nursing homes or chronic-care residencies.
• People who are six months to 18 years of age and take aspirin daily.
• Health care workers directly involved with patient care.
• People who have or take care of an infant younger than six months of age.

Infants younger than six months of age should not receive the influenza vaccine.

Healthy people two to 64 years of age should wait to be vaccinated or skip getting a shot this season.

Healthy people ages five to 49 years of age may receive the nasal-spray vaccine. This is a good option for people in this age group who have or care for infants younger than six months of age or for health care workers who take care of sick patients. Pregnant women and people who care for or live with someone whose immune system is very weak should not use the nasal spray.

Additional information about the influenza vaccine is available online at http://www.cdc.gov/flu/protect/0405shortage.htm.

Strategy to Strengthen Safeguards for Children Treated with Antidepressants

The U.S. Food and Drug Administration (FDA) has issued a public health advisory announcing a multi-pronged strategy to warn the public about the increased risk of suicidal thoughts and behavior ("suicidality") in children and adolescents taking antidepressants. The advisory is available online at http://www.fda.gov/cder/drug/antidepressants/SSRIPHA200410.htm.

The FDA is directing antidepressant manufacturers to add a "black box" warning to the health professional labeling of all antidepressants to describe this risk and emphasize the need for close monitoring of patients started on these medications.

This direction is based on a pooled analysis of 24 studies of antidepressants (selective serotonin reuptake inhibitors [SSRIs] and others) in more than 4,400 children and adolescents with major depression, obsessive-compulsive disorder, and other psychiatric disorders. These studies found a 4 percent risk of suicidal thinking or behavior in patients taking antidepressants compared with a 2 percent risk in patients taking placebo (number needed to treat for one to four months: 50).

The black box warning also notes what uses the antidepressants have been approved or not approved for in these patients. The FDA also has addressed other labeling changes designed to include additional information about studies of these drugs in children. These labeling changes are applicable to the entire category of antidepressant medications because the currently available data are not adequate to exclude any single medication from the increased risk of suicidality.

Fluoxetine (Prozac) is the only medication approved to treat depression in children and adolescents. The analyses of the placebo-controlled trials in children and adolescents summarized in the revised labeling are based on studies of five SSRIs (citalopram [Celexa], fluvoxamine [Luvox], paroxetine [Paxil], fluoxetine, and sertraline [Zoloft]) and four "atypical" antidepressants (bupropion [Wellbutrin], mirtazapine [Remeron], nefazodone [Serzone], and venlafaxine [Effexor]). In these studies, there was no reported suicide.

A black box warning is the most serious warning placed in the labeling of a prescription medication. Advertisements that serve to remind health care professionals of a product's availability (so-called "reminder ads") are not allowed for products with black box warnings. The new warning language does not prohibit the use of antidepressants in children and adolescents. Rather, it warns of the risk of suicidality and encourages prescribers to balance this risk with clinical need.

The FDA recognizes that depression and other psychiatric disorders in children and adolescents can have significant consequences if not appropriately treated. The new warning language recognizes this need but advises close monitoring of patients as a way of managing the suicidality risk.

The FDA is developing a Patient Medication Guide which needs to be given by pharmacists to patients taking antidepressants to advise them of the suicidality risk and precautions that can be taken. In addition, the FDA intends to work with manufacturers to implement "Unit-of-Use" packaging for all antidepressants as a means of ensuring that patients receive a medication guide with every prescription or refill. Unit-of-use packaging is a method of preparing a medication in an original container, sealed and labeled by the manufacturer, and containing sufficient medication for one normal course of therapy.

Risk of Recurrent Stroke with Patent Foramen Ovale and Atrial Septal Aneurysm

The Quality Standards Subcommittee of the American Academy of Neurology has released a new guideline entitled, "Practice Parameter: Recurrent Stroke with Patent Foramen Ovale and Atrial Septal Aneurysm." The guideline is available online at http://www.neurology.org/cgi/content/full/62/7/1042.

A patent foramen ovale (PFO) is a small opening between the two upper chambers of the heart, or the atria. The opening normally closes shortly after birth, but does not close in up to 25 percent of people. Current thinking is that patients with a PFO who have had a stroke with no known cause and received treatment are at greater risk of having a second stroke than those patients who had a stroke and did not have a PFO. However, this is not true according to the guideline. Having a PFO does not place the patient at increased risk for a recurrent stroke.

There has been some debate within the medical community about whether PFOs should be closed or managed with medication. According to the guideline, there is no evidence to support or refute the role of closing a PFO for stroke prevention. More research is needed to answer this question.

Persons younger than 55 years with both a PFO and an atrial septal aneurysm (ASA) may have an increased risk of a second stroke. An ASA is a bulge in the wall between the atria and occurs in an estimated 5 percent of people. Up to 70 percent of people with an ASA also have a PFO.

Both aspirin and warfarin reduce the risk of blood clots that can cause stroke. According to the guideline, there is inadequate evidence to determine whether aspirin or warfarin is the better medication to prevent subsequent stroke and death. However, the side effect of minor bleeding is more common with warfarin than aspirin.

The authors of the guideline call for more research on the effects of an ASA on stroke risk and how ASAs should be managed. They also encourage physicians to communicate with patients who have had a stroke and are on aspirin or warfarin therapies about their future health risks. Patients should know that the presence of a PFO does not necessarily signify an increased risk for subsequent stroke, however these patients should consider participating in research studies to further address this condition.

Norovirus Gastroenteritis Outbreak at a Swimming Club

John Snow's historic investigation in London, England, of a severe epidemic of cholera traced the cause of infection to a common water source. Today, 150 years later, waterborne diseases remain a public health problem, and similar investigations are used to identify the source of infection. On February 3, 2004, the Vermont Department of Health (VDH) was notified of an outbreak of acute gastroenteritis among children whose only common exposure was attendance at a swimming club the previous weekend.

The VDH and the Centers for Disease Control and Prevention (CDC) determined the cause of the outbreak to be a combination of stool contamination, a blocked chlorine feed tube, and multiple lapses of pool-maintenance procedures.

Attendance records indicated that seven private groups used the pool, including three mother-infant swimming classes, two groups from a local girls' organization, a birthday party of children five to 10 years of age, and a preschool class. In addition, members of the club used the pool during two defined open-swim sessions. Of the 189 persons for whom information was collected and who visited the pool during the outbreak period,
53 (28 percent) reported an illness consistent with the case definition of gastroenteritis. Among these 53 persons, onset of symptoms began a median of 30 hours after attending an event at the club and included vomiting, diarrhea, nausea, stomach cramps, chills, and a fever higher than 38°C (100.4°F).

No obvious source of contamination was identified: all infants were reported to have worn swim diapers while in the pool, no vomiting or fecal incidents were reported, and no persons, when questioned, reported gastrointestinal illness in the two weeks before visiting the pool. Interviews with swimmers and staff indicated that the water was visibly cloudy throughout the weekend, when the regular maintenance person was not on duty and pool usage was the highest. A kink in the tube that supplies chlorine to the pool was subsequently identified and repaired by the pool's maintenance manager.

150th Anniversary of John Snow and the Pump Handle John Snow, M.D. (1813-1858), a legendary figure in epidemiology, provided one of the earliest examples of using epidemiologic methods to identify risk for disease and recommend preventive action. Best known for his work in anesthesiology, Snow also had an interest in cholera and supported the unpopular theory that cholera was transmitted by water rather than through miasma (i.e., bad air). On August 31, 1854, London experienced a recurrent epidemic of cholera. Snow suspected water from the Broad Street pump as the source of disease. To test his theory, Snow reviewed death records of area residents who died from cholera and interviewed household members, documenting that most deceased persons had lived near and had drunk water from the pump. Snow presented his findings to community leaders, and the pump handle was removed on September 8, 1854. Removal of the handle prevented additional cholera deaths, supporting Snow's theory that cholera was a waterborne, contagious disease. Snow's studies and the removal of the pump handle became a model for modern epidemiology.

At the time of the review, although disinfection equipment was working properly and pool chlorine and pH levels, and temperature were consistent with recommended national standards, multiple lapses and inadequacies in pool management were identified. Of these, most remarkable were a lack of staff training and response policies, and the absence of records of the pool's chemistry-monitoring results or pool maintenance.

Although waterborne outbreaks of norovirus gastroenteritis are much less commonly reported than foodborne outbreaks, the recorded incidence of norovirus-associated waterborne disease is likely an underestimate because of the lack of simple diagnostic technology. However, norovirus outbreaks associated with swimming pools rarely are reported.

Although prevention of norovirus outbreaks is difficult, this outbreak investigation suggests that staff training, pool-chemistry monitoring, and maintenance of appropriate disinfectant levels are important prevention strategies. As with John Snow's Broad Street cholera outbreak (see accompanying box), a series of environmental health failures occurred, creating conditions that could convey almost any waterborne pathogen.

Answers to This Issue's Clinical Quiz Q1. C Q2. A Q3. B Q4. B Q5. D Q6. D Q7. E Q8. A, B Q9. A, B, C, D Q10. A, B, D Q11. A, B, C Q12. B, D

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