emDOCs Podcast – Episode 49: Acute Heart Failure Evaluation Misconceptions

Welcome back to emDOCs cast with Brit Long, MD (@long_brit). This is the first podcast in a series looking at acute heart failure. Today we look at the evaluation of acute heart failure in the ED and several misconceptions.


Episode 49: Acute Heart Failure Evaluation Misconceptions

Introduction

  • Acute heart failure (AHF) is a common syndrome. There are over 650,000 ED visits annually.
  • Patients may present in a variety of ways: gradual decline with worsening symptoms over several weeks, hypertensive pulmonary edema, or cardiogenic shock.

 

Misconception #1: Natriuretic peptide testing is always helpful in diagnosing or excluding AHF.

  • Natriuretic peptides include B-type natriuretic peptide (BNP) and NT-proBNP.
  • These molecules are cardiac neurohormones functioning in volume and sodium homeostasis produced in the cardiac musculature due to myocyte stretch, which may occur in AHF.
  • ACEP provides level B recommendations that with BNP < 100 pg/mL or NT-proBNP < 300 pg/mL, AHF is unlikely, while for BNP > 500 pg/mL or NT-proBNP > 1,000 pg/mL, AHF is likely.
  • The 2017 ACC/AHA/HFSA guidelines provide a Level IA recommendation that natriuretic peptides are useful to support the diagnosis or exclusion of AHF.

 

Pearl #1: Natriuretic peptides should only be used in conjunction with clinical evaluation, rather than using the test in isolation. There are other causes of elevated BNP.

  • Approximately one quarter of patients with dyspnea will fail to demonstrate definitive levels of the biomarker, creating difficulty in interpretation of the test
  • Multiple observational studies suggest BNP and NT-proBNP have high sensitivity but moderate or even poor specificity when compared to history and/or examination alone. When used in isolation, it can be sensitive, but the studies had poor gold standards (cardiologist opinion typically), and few looked at ED physician judgment. It does not outperform overall clinical judgment.
  • RCT data have found no difference in mortality, admission, or readmission, but there may be a controversial slight reduction in inpatient length of stay.
  • Cutoffs vary, and there is significant lack of blinding and spectrum bias present in studies evaluating BNP.
  • Other causes of BNP elevation: coronary syndromes, valvular heart disease, pericardial disease, atrial fibrillation, cardiac surgery, cardioversion, older age, anemia, renal failure, pulmonary hypertension, critical illness, sepsis, and burns.
  • Age, gender, body weight/body mass index can affect BNP levels. Due to less myocardial stress, obese patients may demonstrate lower BNP and NT-proBNP.
  • Other laboratory tests associated with AHF severity: decreased renal function, elevated troponin, increased LFT, electrolyte abnormalities (hyponatremia).

 

Misconception #2: Chest radiograph is the go-to imaging test in AHF.

  • Chest x-ray can be an important component of the overall assessment of patients, but chest X-ray findings are not definitive.
  • Kerley B-lines demonstrate a sensitivity of 9.2% and specificity 98.8%, interstitial edema sensitivity 31.1% and specificity 95.1%, cephalization sensitivity 44.7% and specificity 94.6%, alveolar edema sensitivity 5.7% and specificity 98.9%, pulmonary edema sensitivity 56.9% and specificity 89.2%, pleural effusion sensitivity 16.3% and specificity 92.8%, and cardiomegaly sensitivity 74.7% and specificity 61.7%.
  • Chest radiograph can be specific, but it is not sensitive, as close to 20% of chest X-rays demonstrate no findings.

 

Pearl #2: Point of care ultrasound (POCUS) is a reliable tool in assessing for pulmonary edema associated with heart failure

  • POCUS can provide clinicians with a means of more reliable and rapid diagnosis, while also considering potential etiologies and mimics of heart failure.
  • POCUS may include evaluation of several components, including the lungs, heart, and inferior vena cava (IVC), with several protocols available.
  • Lung US alone with the presence of > 3 B lines in > 2 bilateral thoracic lung zones possesses a positive likelihood ratio (+LR) of 7.4, sensitivity approaching over 90%, and specificity 92.7% for pulmonary edema, while the absence of B lines possesses a negative likelihood ratio (-LR) of 0.16.
  • IVC assessment is controversial. Dilated IVC with little to no respiratory variation may point to volume overload, but IVC assessment is complicated by other conditions like tricuspid regurgitation, pulmonary hypertension, PE, and right ventricular myocardial infarction.
  • Evaluating contractility can assist. A reduction in LV function on POCUS by emergency clinicians demonstrates a sensitivity for AHF 77-83% and specificity 74-90%.
  • A quantitative measure includes E-point septal separation (EPSS), which is the distance between the mitral valve and ventricular septum during systole. An EPSS measurement > 7 mm suggests ejection fraction (EF) < 50%.
  • Other findings: A diastolic filling restrictive pattern with pulsed Doppler analysis of mitral inflow demonstrates a +LR 8.3, sensitivity 80.6%, and specificity 80.6%.
  • Overall, lung US for the presence of > 3 B lines in > 2 bilateral thoracic lung zones is reliable and sensitive for pulmonary edema. Assessment of cardiac function with POCUS can also assist.

 

References and Further Reading:

 

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