Lung and Cardiac Ultrasound Protocol for Acute Heart Failure

Podcast

LuCUS byte


A Modified Lung and Cardiac Ultrasound Protocol Saves Time and Rules in the Diagnosis of Acute Heart Failure

Journal of Emergency Medicine June 2017 - Pubmed Link


Take Home Points

1. A simple ultrasound protocol (bilateral B-lines and decreased EF) is specific for acute decompensated heart failure but not at all sensitive.

2. This may save time in making the diagnosis, but further studies are needed to confirm.


Background

Acute decompensated heart failure is a common cause for acute dyspnea. The accuracy of history, physical exam, blood tests, and chest xray are not spectacular. Ultrasound has been shown to be useful, but many people think it takes too long to perform. This study tries to simplify an existing formula to make an easy way to help diagnose this disease in undifferentiated patients.


Questions

How accurate is a simplified lung and cardiac ultrasound protocol in diagnosing patients with acute decompensated heart failure?


Population

Tertiary care hospital, December 2012 to July 2013


Inclusion

  • 18 years old

  • Primary complaint of undifferentiated dyspnea (defined as at least two possible etiologies in differential determined by treating physician)


Exclusion

  • Treating physician knew it was something else

  • STEMI

  • If treated for ADHF for >30 minutes prior to US

  • Refused to consent

  • Previously enrolled in this study


Design

Secondary analysis of previous study. Initial study was to determine accuracy of LuCUS protocol.

Previous study:

Prospective, observational, single center study

Patients enrolled in day time hours

Sonographers blinded to all other tests

Diagnosis of ADHF was determined by chart review for final diagnosis


Initial study included 12 views, modified one includes 3. Needed to have all three positive to diagnose as acute heart failure.


To determine timing, they used time stamps on images. Time stamp on right anterior lung to the end of PLAX clip.


Intervention

According to initial LuCUS (lung and cardiac ultrasound) protocol

All patients received history, physical exam, ECG

Treating physician ranked differential

Ultrasound was performed on all patients

Reported back to treating physician

Diagnosis was determined to be "heart failure" or "not heart failure" on LuCUS and was compared to chart review for final diagnosis


Who did the ultrasounds?

Three investigators: 1 emergency medicine ultrasound directors, two emergency medicine US fellows

  • All >1000 ultrasounds prior to study

  • 5 scans under direct supervision

  • 4 hours reviewing LV function in echocardiography reading room with cardiologist


The Scan

Curvilinear probe curvilinear

Full LuCUS (Lung and Cardiac Ultrasound) protocol =

  • 4 lung zones on each side of the chest, anterolateral

  • Costophrenic recess bilaterally

  • PLAX, PSAX

  • IVC

  • A4C, including diastology


This was pared down to the protocol used in this study

Modified LuCUS

Anterosuperieor lung zones bilaterally - needed 3 Blines per rib space

Parasternal long axis - estimate LVEF, qualitative

If EF not determined in PSLAX, then could do any other view

Positive LuCUS required all three:

  1. B lines on right

  2. B lines on left

  3. LVEF <45%


Learn how to ultrasound for B-lines and Cardiac Function at 5 Minute Sono


Results

104 patients enrolled

  • 5 excluding due to poor windows

  • 1 excluded by dropping out of study

N = 99

  • 36 had dx of ADHC (36.4%)

  • 9 (25% of 36), had positive modified LuCUS


Primary Outcome

Sensitivity 25%

Specificity 100%

+LR cannot calculate (because it is impossibly high)

-LR 0.75


Secondary Outcomes

Time to perform modified exam: mean of 1 min 32 seconds


Accuracy of Lung US alone

  • Sens 31%

  • Specifiicty 95%

  • +LR 6.4

  • -LR 0.73


Kappa .87 between coinvestiagtors

2 patients had preserved EF, these were missed by modified LuCUS


Limitations

Secondary analysis

Selection bias - convenience sample

Sonographer experience was high

Small sample size, only 36 positive patients

How accurate is the timing calculation? States that modified protocol had a mean of 1.5 minutes, but later states that the rest of the full LuCUS exam would be only 6 minutes, however total test in original study took 12 +/- 4 minutes on average so....something doesn't add up. Either way - we need a prospective evaluation of the time savings.


Discussion Points

Interestingly, original study had sensitivity of 83% (better as expected) but specificity of 83% (much worse). This shows that you are just making the cut off a little higher for diagnosis, thereby increasing specificity at expense of sensitivity.


Since this exam is specific but not sensitive for acute heart failure, authors surmise that you could do this modified protocol and if positive → done, if negative→ do more comprehensive ultrasound exam. Seems like a reasonable approach.


Take Home Points

1. A simple ultrasound protocol (bilateral B-lines and decreased EF) is specific for acute decompensated heart failure but not at all sensitive.

2. This may save time in making the diagnosis, but further studies are needed to confirm.


Our score

3 Probes


Published on 09/11/17 02:00 AM
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