Acute Heart Failure: Diagnosis and Risk Assessment in the Emergency Department

Transcription

1 Acute Heart Failure: Diagnosis and Risk Assessment in the Emergency Department J. Douglas Kirk, MD Professor and Vice Chairman, Department of Emergency Medicine Director, Chest Pain Evaluation Unit, University of California, Davis Health System, Sacramento, CA Objectives: 1. Describe the clinical and diagnostic test findings in patients with acute heart failure. 2. Relate the relative contribution to risk assessment of the clinical and diagnostic test variables available in the emergency department. 3. Review recently described acute heart failure risk models. INTRODUCTION Heart failure is a clinical syndrome of cardiovascular dysfunction resulting in elevated filling pressures and pulmonary and systemic congestion. Cardiac dysfunction can be related to systolic or diastolic dysfunction, to abnormalities in cardiac rhythm, or to preload and afterload mismatch. Acute heart failure (AHF) may present as a new diagnosis or from decompensation of chronic established heart failure, but irrespective of the origin, both typically result in presentation to the emergency department (ED) or hospital with symptoms that require urgent therapy. 1, 2 Heart failure is a leading cause of morbidity and mortality in the United States. Nearly five million patients in the United States have heart failure, with 1.1 million hospitalizations that represent 6.5 million hospital days. Heart failure is the most common Medicare discharge diagnosis (5.8% of all Medicare charges) and the most costly cardiac problem in the U.S., accounting for $34.8 billion in costs in More importantly, 57,120 deaths were attributed to heart failure in ,4 The problem is likely to worsen as the incidence of heart failure is expected to increase due to the aging of our population, as the vast majority of all heart failure patients are over the age of 65. In addition, the successes of cardiovascular disease management, particularly acute coronary syndrome (ACS), have resulted in increased survival in patients who frequently go on to develop heart failure. The ED may be the focal point of the issue as most heart failure admissions originate there and account for a majority of these subsequent expenditures. Some have suggested that up to half of these ED patients could be discharged home and managed as outpatients after initial therapy. 5-7 However, these same patients collectively have an in-hospital mortality of 4% to 7%, and a 60-day recidivism rate of 25%. 8,9 These data result in a conservative approach and one of risk aversion that may lead to unnecessary admission of some patients. Heart failure is a leading cause of morbidity and mortality in the United States. 45

2 ADVANCING THE STANDARD OF CARE: Cardiovascular and Neurovascular Emergencies Furthermore, current heart failure guidelines are sparse in their recommendations for ED management of AHF in general and provide little or no evidence based advice for disposition. 3,8 These challenges represent opportunities to improve patient care while more effectively utilizing our ever shrinking resources. Diagnosis Versus Risk Stratification Dyspnea is the most common chief complaint in patients with AHF and represents a broad spectrum of clinical presentations from acute flash pulmonary edema to gradual worsening of symptoms in a patient with established heart failure. Pathophysiological etiologies such as systolic and diastolic dysfunction are useful in management decisions but frequently these data are not available in the ED. A recently described classification system based upon hemodynamic characteristics at presentation (systolic blood pressure) in addition to a clinical symptom profile that suggest AHF (dyspnea, pulmonary congestion, peripheral edema, weight gain, fatigue, history of heart failure) may be more useful in triaging patients, determining risk, and tailoring appropriate therapy. 2,10 Patients with AHF associated with elevated systolic blood pressure at presentation (>160 mm Hg) are more often women, older, and more likely to have diastolic dysfunction with relatively preserved left ventricular function. Symptom onset is generally abrupt and severe, with dyspnea as the predominant complaint, although signs of end-organ hypoperfusion may be present. Acute pulmonary edema is the hallmark of this syndrome and is usually evident as rales on examination and pulmonary edema on chest radiograph (CXR). These patients are frequently critically ill upon presentation due to respiratory embarrassment and without prompt treatment have an increased risk of immediate morbidity and mortality. However, they typically respond quickly to aggressive therapy and subsequently are at low risk for short term adverse events. On the contrary, patients with normal systolic blood pressure at presentation ( mm Hg) typically have a progressive worsening of chronic symptoms and signs that develop gradually, over days to weeks, and not only pulmonary but also systemic congestion (jugular venous distension and peripheral edema) is present. The ejection fraction is usually reduced. In a number of patients the clinical and/or radiographic signs of pulmonary congestion are not evident, despite elevated left ventricular filling pressures, which pose an additional diagnostic challenge. While these patients immediate risk of morbidity and mortality are modest compared to the aforementioned group, their subsequent risk is substantially higher. This paradoxical relationship of clinical presentations and outcomes adds to the complexity of both management and disposition decisions in the ED. Because of the heterogeneity of these clinical presentations, the term acute heart failure syndromes has recently been advocated. 2 The diagnosis of AHF is based on clinical assessment of symptoms and physical findings, supported by appropriate diagnostic studies including the electrocardiogram (ECG), CXR, routine laboratory tests and cardiac biomarkers in the ED, although the ultimate diagnosis is typically confirmed later by echocardiography or less commonly by pulmonary artery catheterization (Table 1). The approach to the diagnostic work-up is critical, as establishing a correct diagnosis is critical for risk assessment. Further, the same investigations used to confirm the diagnosis are the very ones most integral to assessing an individual patient s risk of short term morbidity and mortality. Clinical Assessment A thorough history and physical examination should be performed in all patients with suspected AHF. While dyspnea is the chief complaint in the majority of patients, it is nonspecific and frequently present in a host of other conditions, most notably chronic obstructive pulmonary disease, which is a frequent confounder in the diagnosis of AHF. The presence of paroxysmal nocturnal dyspnea, orthopnea, or dyspnea on exertion increases the likelihood of AHF as does the presence of dyspnea in a patient with a previous history of heart failure. 11 Findings of an S3 gallop, jugular venous distension, pulmonary rales, and 46

3 Acute Heart Failure: Diagnosis and Risk Assessment in the Emergency Department Table 1. Diagnostic Assessments Supporting the Presence of Heart Failure pedal edema also increases the likelihood of AHF. However, these clinical findings are sorely lacking in combined sensitivity and specificity, limiting their usefulness. More importantly, persistent elevation in filling pressure indicated by orthopnea or elevated jugular venous distention is associated with adverse clinical outcomes and mortality. 12, 13 In a retrospective analysis of the ACTIV in CHF trial, patients with severe congestion, defined as presence of dyspnea, jugular venous distention, and edema after initial in-hospital therapy had a two fold increase in 60-day mortality compared to patients without congestion. 14 As previously described, systolic blood pressure at presentation helps characterize a patient s specific clinical profile and is also reflective of their short term risk. 15 As depicted in Figure 1, a relatively lownormal blood pressure portends an adverse effect on mortality. 47

4 ADVANCING THE STANDARD OF CARE: Cardiovascular and Neurovascular Emergencies Data from the Acute Decompensated Heart Failure National Registry (ADHERE) revealed that nearly 19% of patients with AHF had no signs of pulmonary congestion on the CXR. Subtle levels of hyponatremia (Na+ < 135mmol/L) are associated with an increased risk of inhospital mortality. Electrocardiogram An ECG should be performed in all patients with suspected AHF. While ECG changes are common in patients with AHF, it has poor predictive value to determine the presence of AHF. If the ECG is completely normal, AHF is less likely, particularly that due to systolic dysfunction. The ECG may however be helpful to determine an etiology of AHF if indeed present, in those cases precipitated by acute coronary syndromes (ACS) or atrial fibrillation. It may also suggest a hypertensive cardiomyopathy in patients with ECG evidence of left ventricular hypertrophy. Its implications for risk stratification, other than that obviously associated with the presence of ACS, are less clear. Chest Radiography Obtaining a CXR is routine in the evaluation of dyspneic patients in the ED. The presence of pulmonary venous congestion, interstitial edema, alveolar edema, and cardiomegaly increase the likelihood of AHF but their absence by no means excludes it. 11 Data from the Acute Decompensated Heart Failure National Registry (ADHERE) revealed that nearly 19% of patients with AHF had no signs of pulmonary congestion on the CXR. 16 Additional reports from the related ADHERE-EM database likewise reported normal CXRs in 20% of patients admitted with AHF, but it also described the prognostic importance of radiographic evidence of AHF. 17 After adjustment for known predictors of mortality, patients with a negative CXR were less likely to require mechanical ventilation (2.0% vs 3.9%, OR 0.60, 95% CI ) or ICU care (10.7% vs 16.8%, OR 0.69, 95% CI ), and in-hospital mortality was lower (1.6% vs 2.6%, OR 0.58, 95% CI ). Although these data are retrospective analyses and should be interpreted with caution, they do come from a rather large data set (~5,000 patients) and are thought provoking. Laboratory Tests Patients with suspected AHF typically have routine measurement of serum electrolytes, renal function, blood count and cardiac troponin. While these tests do not provide significant diagnostic accuracy to include or exclude AHF as a cause of acute symptoms, they are useful in assessment of comorbidities and may provide additional prognostic information. A number of recent retrospective analyses from registries or clinical trials of AHF patients have suggested that abnormalities in these routine tests confer increased risk. Renal dysfunction indicated by elevations of either creatinine or blood urea nitrogen (BUN) may be the strongest predictor of adverse events in AHF patients. 1,18,19 Patients with admission BUN categorized in quartiles ( 18, 19-26, 27-39, and 40 mg/dl) had 60-day mortality rates of 0%, 4.0%, 9.3%, and 14.3% respectively, p< Subtle levels of hyponatremia (Na+ < 135mmol/L) are associated with an increased risk of in-hospital mortality, 6.0% (95% CI ) versus 3.2% (95% CI ), p< and postdischarge mortality at days, 12.4% (95% CI ) versus 7.6% (95% CI ), p<

5 Acute Heart Failure: Diagnosis and Risk Assessment in the Emergency Department It is well known that an elevated troponin is associated with an increase in mortality in patients with ACS, independent of the presence of heart failure. A recent report from the ADHERE registry examined 67,924 patients with a serum creatinine < 2.0 mg/dl who had troponin routinely measured during their admission, of which 6.2% had an elevation of either troponin I or T. 21 Patients who were positive for troponin had a higher inhospital mortality (8.0% vs. 2.7%, p<0.001) than those who were negative for troponin. The adjusted odds ratio for death in the troponin positive group was 2.55 (95% CI 2.24 to 2.89, p<0.001) and was independent of an ischemic etiology of AHF. Natriuretic Peptides Natriuretic peptides (NP) are elevated in response to left ventricular stretch due to high filing pressures, and as such, both B-type natriuretic peptide (BNP) and N-terminal prohormone B-type natriuretic peptide (NT-pro BNP) are useful blood tests to help establish a diagnosis of AHF Both are commercially available and can be readily measured in the ED. Their use in conjunction with a standard clinical evaluation can help identify a majority of patients with AHF (Figure 2). This strategy does leave a grey zone in which the diagnosis is uncertain with BNP levels between pg/ml and NT-pro BNP levels between pg/ml. Clinical judgment is necessary to exclude other possible explanations of an elevated NP such as pulmonary hypertension, cor pulmonale, pulmonary embolism, ACS, female gender, advanced age, or renal insufficiency. On the contrary, obesity may falsely underestimate the NP value. Measurement of NPs has also been correlated with clinical outcome and elevations of both BNP and NTproBNP 26 and have important prognostic implications. BNP values obtained in dyspneic ED patients were able to successfully predict the occurrence of adverse events (death, repeat ED visit for AHF, or hospital admission with cardiac diagnosis) over a 6 month course of followup. Patients with BNP values of >480 and <230 pg/ml had event rates of 51% and 2.5%, respectively. 27 In a retrospective analysis from the ADHERE database, BNP values obtained within 24 hours of presentation were examined from 48,629 patient episodes. Quartiles of BNP (<430, 430 to 839, 840 to 1,729, and >1,730 pg/ml) demonstrated a near-linear relationship with in-hospital Figure 2. Flow Chart for the Diagnosis of Acute Heart Failure with Natriuretic Peptides in Patients with Suggestive Symptoms 49

6 ADVANCING THE STANDARD OF CARE: Cardiovascular and Neurovascular Emergencies mortality, 1.9%, 2.8%, 3.8%, and 6.0%, respectively (p<0.0001). After adjustment, BNP remained highly predictive of mortality between the highest and lowest quartiles (OR 2.23, 95% CI 1.91 to 2.62, p<0.0001). 29 In a multicenter trial of 1256 dyspneic patients, NT-pro BNP values correlated both with the presence of AHF and adverse outcomes. 26 Of the 723 (57%) patients with AHF, the median NT-proBNP level was considerably higher than those without AHF (4639 vs.108 pg/ml, p<0.001). In addition, among those with AHF, an NT-proBNP value >5180 pg/ml was strongly predictive of death by 76 days (OR 5.2, 95% CI , p<0.001). 26 Table 2. Modeling Studies With Reported Outcomes and Variables Found to be Significant Risk Indicators Author / Year N Subject Study Type a Type b Outcome c Significant Variables Filipatos / I P 60 day mortality, readmission BUN > 40 mg/dl Gheorghiade/ ,612 I R In-hospital mortality and 30 day mortality Sodium < 135 mmol/l Formiga/ I R In-hospital mortality Barthel index, creatinine, edema Diercks / E P LOS <24h, 30 day events SBP, troponin I Burkhardt / I R Observation Unit discharge BUN Felker / I R 60-day mortality/readmission Age, SBP, BUN, Na, Hgb, # Past admits, Class IV symptoms Lee / I R 30-day and 1 year mortality Age, SBP, RR, BUN, Sodium Harjai / I R 30-day readmission Sex, COPD, Prior admits Rame / E R 3-month readmission and mortality RR Cowie / I R 16-month mortality SBP, Creatinine, Rales Butler / I R Inpatient complications O 2 sat, Creatinine, Pulmonary edema Villacorta/ I R Inpatient and 6-month mortality Sodium, Sex Chin / I R, S 60-day readmission and mortality Marital status, Comorbidity Index Admit SBP, No ST-T changes Chin / R Inpatient complications Initial SBP, RR, Sodium, ST-T changes Selker / I PA, R Inpatient mortality Age, SBP, T-wave flattening, HR Brophy / E P 44-month mortality Prior HF admission, Sodium, IVCD, Amount furosemide given Brophy / E P LOS and 6-month mortality Left atrial size, Cardiac ischemia, Slow response to diuresis Esdaile / I PA, R Inpatient mortality Age, Chest pain, Cardiac ischemia, Valvular dz, Arrhythmia, New onset, Poor clinical response Katz / R 2-day complications 4-hour diuresis, History of pulmonary edema, T-wave abnormalities, JVD Plotnick / PA, R Inpatient and 1-year mortality Admit SBP, Dyspnea, Peak CPK a I = In-patients, E = emergency department patients b R = retrospective chart review, PA = patient assessment, S = survey, P = prospective c Complications include mortality, LOS = length of stay Adapted with permission from Collins SP, Gheorghiade M, Weintraub NL, et al. Society of Chest Pain Centers Recommendations for the Evaluation and Management of the Observation Stay Acute Heart Failure Patient: Risk Stratification. Critical Pathways in Cardiology, June 2008;7(2):

7 Acute Heart Failure: Diagnosis and Risk Assessment in the Emergency Department Risk Models A number of investigators have examined components of the clinical examination and laboratory data, including variables previously described here, to construct models that would predict a patient s risk of adverse events (Table 2). Most were constructed to identify high risk patients but some were aimed at identifying low risk patients. These models may have utility in determining disposition from the ED. A recently described model constructed retrospectively from the ADHERE database has received considerable attention. 1 Using classification and regression tree analysis with recursive partitioning, 45 variables were examined to predict in-hospital mortality. Serum creatinine, BUN, and systolic blood pressure were the strongest predictors of mortality. The algorithm can easily be used in the ED to assist with disposition decisions, including the appropriate level of inpatient care (Figure 3). Figure 3. In-Hospital Crude Mortality and Risk Stratification From the Acute Decompensated Heart Failure National Registry (ADHERE) Serum creatinine, BUN, and systolic blood pressure were the strongest predictors of mortality. Another model was created from a retrospective study of 4031 patients with AHF in Canada (2624 patients in the derivation cohort and 1407 patients in the validation cohort). 30 Multivariable predictors of mortality at both 30 days and 1 year included older 51

8 ADVANCING THE STANDARD OF CARE: Cardiovascular and Neurovascular Emergencies age, lower systolic blood pressure, higher respiratory rate, elevated BUN and hyponatremia. Comorbid conditions associated with mortality included cerebrovascular disease, chronic obstructive pulmonary disease, hepatic cirrhosis, dementia, and cancer. Points were assigned each variable according to their respective predictive value and from that a risk index identified low and highrisk individuals. Patients with very low-risk scores (<60) had a mortality rate of 0.4% at 30 days and 7.8% at 1 year. Patients with very high-risk scores (>150) had a mortality rate of 59.0% at 30 days and 78.8% at 1 year. This validated model using variables available in the ED may also be useful in determining disposition. Others have described models that identified patients who were at low risk for complications or death. 31, 32 The former examined 20 variables among 499 patients with AHF to determine suitable candidates for observation unit care, which was defined as length of stay < 24 hours and no adverse events (death, myocardial infarction, arrhythmia, re-hospitalization) during 30 day follow-up. Using multivariate analysis, a systolic blood pressure > 160 mm Hg at presentation and a normal troponin I identified a low risk group. The latter examined a statewide database of 33,533 patients with AHF to create a model to identify patients with a low risk of death or serious complications. Within the entire cohort, 4.5% of patients died and 6.8% survived to hospital discharge but experienced a serious complication. The prediction rule used 21 prognostic variables to classify 17.2% of patients as low risk, of which only 0.3% died and 1.0% had a serious complication. Although effective in identifying a low risk cohort, its complicated scheme may limit its utility. SUMMARY The prevalence of heart failure is at epidemic proportions. Most AHF patients will present to an ED in need of urgent therapy. A correct diagnosis and assessment of risk for death or serious morbidity is critical to their appropriate management. Current guidelines lack significant evidence based recommendations regarding disposition. Emergency physician and hospitalist practice patterns entail a conservative approach based upon risk aversion which adds to the total economic burden. However, recent investigations have described a number of clinical and diagnostic variables that help secure the diagnosis and more importantly provide valuable prognostic data from which to determine a patient s disposition from the ED. Using these variables in algorithmic fashion as suggested by several risk models may help with management decisions and aid in more effective utilization of resources. REFERENCES 1. Fonarow GC, Adams KF Jr, Abraham WT, et al, for the ADHERE Scientific Advisory Committee, Study Group, and Investigators. Risk stratification for in-hospital mortality in acutely decompensated heart failure: classification and regression tree analysis. JAMA 2005;293: Gheorghiade M, Zannad F, Sopko G, et al. Acute heart failure syndromes: current state and framework for future research. Circulation 2005;112: Hunt S, Abraham W, Chin M, et al. ACC/AHA 2005 guideline update for the diagnosis and management of chronic heart failure in the adult: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation 2005;112:e American Heart Association. Heart Disease and Stroke Statistics 2008 Update. Available at: 52

9 Acute Heart Failure: Diagnosis and Risk Assessment in the Emergency Department 5. Graff L, Orledge J, Radford MJ, et al. Correlation of the agency for health care policy and research congestive heart failure admission guideline with mortality: peer review organization voluntary hospital association initiative to decrease events (PROVIDE) for congestive heart failure. Ann Emerg Med 1999;34: Smith WR, Poses RM, McClish DK, et al. Prognostic judgments and triage decisions for patients with acute congestive heart failure. Chest 2002;121: Polanczyk CA, Rohde LE, Philbin EA, et al. A new casemix adjustment index for hospital mortality among patients with congestive heart failure. Med Care 1998;36: Adams KF Jr, Fonarow GC, Emerman CL, et al. Characteristics and outcomes of patients hospitalized for heart failure in the United States: rationale, design, and preliminary observations from the first 100,000 cases in the Acute Decompensated Heart Failure National Registry (ADHERE). Am Heart J 2005;149: Cleland JG, Swedberg K, Follath F, et al. The EuroHeart Failure survey programme a survey on the quality of care among patients with heart failure in Europe. Part 1: patient characteristics and diagnosis. EurHeart J 2003;24: Filippatos G, Zannad F. An introduction to acute heart failure syndromes: definition and classification. Heart Fail Rev 2007;12: Wang CS, FitzGerald JM, Schulzer M, et al. Does this dyspneic patient in the emergency department have congestive heart failure? JAMA 2005;294: Lucas C, Johnson W, Hamilton M, et al. Freedom from congestion predicts good survival despite previous class IV symptoms of heart failure. Am Heart J 2000;140: Drazner MH, Rame JE, Phil M, et al. Prognostic importance of elevated jugular venous pressure and a third heart sound in patients with heart failure. N Engl J Med 2001;345: Gheorghiade M, Gattis WA, O Connor CM, et al. Effects of Tolvaptan, a vasopressin antagonist, in patients hospitalized with worsening heart failure, a randomized controlled trial. JAMA 2004;291: Gheorghiade M, Abraham WT, Albert NM, et al.; for the OPTIMIZE- HF Organized Program to Initiate Lifesaving Treatment in Hospitalized Patients with Heart Failure Investigators and Coordinators. Systolic blood pressure at admission, clinical characteristics, and outcomes in patients hospitalized with acute heart failure. JAMA 2006;296: Collins SP, Lindsell CJ, Storrow AB, et al.; and the Adhere Scientific Advisory Committee IaSG. Prevalence of negative chest radiography results in the emergency department patient with decompensated heart failure. Ann Emerg Med 2006;47: Kirk JD, Diercks DB, Peacock WF, Char DE, Summers R, Emerman C, Wynne J, Heywood JT. Positive versus negative chest radiography in heart failure: association with clinical characteristics, therapy, and outcome. Acad Emerg Med (5 Supplement 1): S Filippatos G, Rossi J, Lloyd-Jones DM, et al. Prognostic value of blood urea nitrogen in patients hospitalized with worsening heart failure: insights from the Acute and Chronic Therapeutic Impact of a Vasopressin Antagonist in Chronic Heart Failure (ACTIV in CHF) study. J Card Fail 2007;13: Formiga F, Chivite D, Manito N, et al. Predictors of in-hospital mortality present at admission among patients hospitalized because of decompensated heart failure. Cardiology 2007;108: Gheorghiade M, Abraham WT, Albert NM, et al. Relationship between admission serum sodium concentration and clinical outcomes in patients hospitalized for heart failure: an analysis from the OPTIMIZE-HF registry. Eur Heart J 2007;28: Peacock WF, De Marco T, Fonarow GC, et al. Cardiac Troponin and outcome in acute heart failure N Engl J Med 2008;358: Maisel AS, Krishnaswamy P, Nowak RM, et al. Rapid measurement of B-type natriuretic peptide in the emergency diagnosis of heart failure. N Engl J Med 2002;347: Dao Q, Krishnaswamy P, Kazanegra R, et al. Utility of B-type natriuretic peptide in the diagnosis of congestive heart failure in an urgent care setting. J Am Coll Cardiol 2001;37: McCullough PA, Nowak RM, McCord J, et al. B-type natriuretic peptide and clinical judgment in emergency diagnosis of heart failure: analysis from Breathing Not Properly (BNP) Multinational Study. Circulation 2002;106: Januzzi JL, van Kimmenade R, Lainchbury J, et al. NT-proBNP testing for diagnosis and short-term prognosis in acute destabilized heart failure: an international pooled analysis of 1256 patients: the International Collaborative of NT-proBNP Study. Eur Heart J 2006;27: Januzzi JL Jr, Camargo CA, Anwaruddin S, et al. The N-terminal Pro- BNP investigation of dyspnea in the emergency department (PRIDE) study. Am J Cardiol 2005;95:

10 ADVANCING THE STANDARD OF CARE: Cardiovascular and Neurovascular Emergencies 27. Harrison A, Morrison LK, Krishnaswamy P, et al. B-type natriuretic peptide predicts future cardiac events in patients presenting to the emergency department with dyspnea. Ann Emerg Med. 2002;39: Maisel A, Hollander JE, Guss D, et al. Primary results of the Rapid Emergency Department Heart Failure Outpatient Trial (REDHOT). A multicenter study of B-type natriuretic peptide levels, emergency department decision making, and outcomes in patients presenting with shortness of breath. J Am Coll Cardiol 2004;44: Fonarow GC, Peacock WF, Phillips CO, et al. Admission B-type natriuretic peptide levels and in-hospital mortality in acute decompensated heart failure. J Am Coll Cardiol. 2007;49: Lee DS, Austin PC, Rouleau JL, Liu PP, Naimark D, Tu JV. Predicting mortality among patients hospitalized for heart failure: derivation and validation of a clinical model. JAMA 2003; 290: Diercks DB, Peacock WF, Kirk JD, et al. ED patients with heart failure: identification of an observational unit-appropriate cohort. Am J Emerg Med 2006;24: Auble TE, Hsieh M, Gardner W, et al. A prediction rule to identify lowrisk patients with heart failure. Acad Emerg Med 2005;12: