Evidence-Based Medicine
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Clinical Bottom Line:
While a relatively simple tool like the Acute Heart Failure Index (AHFI) could be a useful aid to the challenging disposition decisions in the management of acute heart failure, the current tool requires broader testing before general use.

The Case:
A 65-year-old male presents to your ED complaining of increasing exertional dyspnea and orthopnea limiting daily activity. He has previously been diagnosed with congestive heart failure secondary to hypertensive cardiomyopathy, but has no history of diabetes or ischemic events. He reports some edema of the lower extremities but no chest discomfort or recent changes in medication, and the remainder of the review of systems is unremarkable.

Physical examination revealed rales and bilateral pedal edema. The electrocardiogram was unremarkable and the blood work including troponin was normal. Following 1.5L diuresis, your patient’s symptoms improve significantly so he wants to go home. Is it safe to discharge him?

Question:
Can we consistently identify acute decompensated Congestive Heart Failure patients appropriate for outpatient management?
The Study:
Validation of the Acute Heart Failure Index. Hsieh M, Auble TE, Yealy DM. Ann Emerg Med. 2008; 51(1):37-44.

Background:
The burden of illness associated with heart failure is enormous, resulting in over a million US ED visits and costs measured in the billions annually. The reported mortality and adverse rates vary significantly, leaving the clinician with little consistent direction in determining those patients requiring admission. Current EM guidelines offer little disposition guidance for CHF patients. Clinical decision rules (CDR) have been shown to enhance physician diagnostic and prognostic decision-making in scenarios of high frequency (Ottawa Ankle Rules) or high risk (Well’s DVT Score). Acute heart failure is both common and high risk so a reliable decision aid could be of great benefit.

The authors attempt to validate their previously derived AHFI by applying it to a computer generated random sample of 5000 patients from each of 2003/2004 in the Pennsylvania Hospitals (~10000 out of over 100000 ED visits for acute heart failure). With such a large and detailed database the authors have been able to derive a rule and test it on a large cohort of patients, something that would be challenging to do prospectively. The rule uses a rather complicated algorithm containing a number of predictors (Figure 1). All branches in the algorithm identify low-risk patients, while all others are high-risk.

The Results:
Application of the AHFI separated patients into two groups (high or low risk) and the primary and secondary outcomes for each are presented in Table 1. From the derivation cohort, the AHFI classified just 17% of subjects as low-risk. The AHFI had a poor positive-Likelihood Ratio for inpatient deaths or complications (1.21), but had a reasonable negative-Likelihood Ratio (0.11) for these outcomes. Even in the low risk group the event rate for death or serious outcomes ranges from 1-3%. Although this equates to a negative-LR of 0.31 (95% CI 0.24-0.41) for 30-day mortality this may not be sufficiently low for many clinicians.

Click on image to view high-res PDF
altFigure 1. Heart failure clinical prediction rule
All branches identify low-risk patients; all other patients are at higher risk.

*Test result also applies to patients for whom the test was not ordered. ECG, Electrocardiography; MI, myocardial infarction; BUN, blood urea nitrogen; WBC, white blood cell count; PTCA, percutaneous transluminal coronary angiography; SBP, systolic blood pressure; AMI, myocardial infarction.

 
 
 
 
 
Case Review:
After reviewing the article and collecting the patient’s data you look at the rule; any path that leads to the far right is considered low risk. Your patient, with no ECG evidence of myocardial ischemia or infarction, fairly normal vital signs (HR 90, BP 160/80, RR 20, SpO2 96%), unremarkable labs (BUN 34 WBC 9 Sodium 140) and no plural effusion, matches the path second to the bottom and is therefore classified as low risk by the AHFI. You explain to your patient this still probably means a 1-3% risk of death, MI, or V-fib. Nonetheless, with informed consent he chooses to go home.

In Summary:
Heart failure is a major cause of morbidity, mortality and increasing health care expenses. Any tool with the potential to improve a clinician’s decision making can have a major impact.  The AHFI is the best currently available evidence, but prospective validation in different patient populations would be needed before it is considered sufficiently reliable to be used routinely.

John Crossley, MD, FRCPC, is the Emergency Medicine Residency Program Director at McMaster University

 
 

Comments   

# Complicated RuleChris Carpenter 2009-07-09 22:27
This rule is really complex! The original article offered a link to a calculator, but the link never seems to work. Would anybody use this rule despite the complexity? If an automated calculator could be devised (PDA, Excel sheet, etc.) would anybody use it?
Reply
# Thanks from an author....D M Yealy 2009-07-12 16:35
Actually, the rule is often easy - done in a step or two (by intent - we knew EM MDs know that hypotensive folks, or those with altered mental status, etc... DO NOT NEED COMPLEXITY.)

AHRQ had a calculator up and on line - search there - they funded the work and we wanted that unbiquitous repository (rather than one man's server.)

We also agree - almost NO RULE is reliably remembered and applied, and tools need to be at bedside.

Finally, we have not done large scale 'real time use' studies - so recognize that limit. No one lse has done so with other rules either.

DMY
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# Senior Process Improvement Coordinator Kaleida Health SystemHeidi Mix RN MS 2010-03-02 16:20
Have you taken this information and developed any criteria for clincal care throughout the hospital stay and d/c placement (home, SNF)
we want to create a planning guide for high and low risk CHF patients coming through our ED which would help us classify the patient earlier for services they will need across the cont. Would greatly appreciate any feedback
Reply
# causes of congestive heart failuresyra 2010-12-06 19:14
Congestive heart failure (www.insideheart.com/causes-of-congestive-heart-failure.html) is a condition in which the function of the heart as a pump is insufficient to supply oxygen-rich blood to the body. Congestive heart failure can be caused by diseases that weaken the heart muscle, diseases that cause the stiffness of the heart muscles or diseases that increase oxygen demand by tissues of the body beyond the capacity of the heart to provide blood adequate oxygen-rich.
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