Multiorgan Ultrasound for Pulmonary Embolism

MOPEByte


Accuracy of Point-of-Care Multiorgan Ultrasonography for the Diagnosis of Pulmonary Embolism

CHEST May 2014 - Pubmed Link

Review article that references this article

Background

PE is a common consideration in patients with chest pain, dyspnea, or cardiac arrest. We have had increase in CT use for PE disproportionate to increase in PE. Ultrasound has advantages over CT such as no radiation, use in unstable patients, no contrast needed that can damage kidneys. Prior studies have shown that ultrasound findings of right heart strain, subpleural infarcts, and DVT can be used to help diagnose PE; however, each alone is not sensitive enough to rule out PE. This study aims to see if combining these tests into a single “multi-organ” scan would have a better sensitivity for PE.


Questions

How accurate is an ultrasound of the heart, lungs, and veins in diagnosing PE compared to CT?

Can ultrasound be used to create a diagnostic algorithm that would reduce CT and not lead to missed PE?


Population

Multi-center, 3 Italian Hospitals (2 university, 1 community)

Inclusion: >18 yo + suspected of having PE


Who did the ultrasounds?

13 investigators

-1 emergency physician with expertise

-8 EP with 5 years of POCUS experience

-4 residents with "focus in cardiac, vein, and lung ultrasound" (2 EM, 2 IM)


Design

Consecutive patients, suspected of having PE

All got Wells score and D-dimer

If Wells <5 and D-dimer <500 ng/mL → no more testing

If Wells >4 or D-dimer ≥500 ng/mL → CT pulmonary angiography. Ultrasound performed prior to and within 3 hours of CT

If Ultrasound negative for PE, investigator asked to specify alternative diagnosis based on US

CTs read by 2 radiologists “expert in PE diagnosis” blinded to clinical data and ultrasound

Power analysis: maximum sensitivity of scans previously reported to be 80%. Set type 1 error at 5% → if sample size 330 then 90% power to detect 10% absolute difference between US and CT


Intervention

All patients got Wells score and D-dimer. If not determined to be "low risk" --> received CT and 3 part US


Scan

Lung - 4-8 MHz linear probe or 3.5-5 MHz curved array probe. Long and oblique scans on anterior and posterior chest in supine position. Lateral decubitus or sitting for dorsal areas. Looking for subpleural infarcts. Also noted consolidations, effusions, interstitial syndrome.

5 min sono post on subpleural consolidation in PE


Heart - 2-5 MHz phased array probe. RV dilation with one of the following: a) right to left ventricular end diastolic diameter >0.9 in apical 4 chamber of subcostal b) RV end diastolic diameter >30 mm in parasternal view c)Thrombus in right side of heart. Effusion and dissections were noted also.


Vein - 4-8 MHz linear probe. Short axis of common and superficial femoral veins, popliteal veins. DVT = absence of total vein collapse during compression.

Considered positive scan if any of the three was positive.


Results

510 patients enrolled, 97 (19%) were ruled out with d-dimer and Wells score 56 excluded - pregnancy (3), did not consent(4), CT contraindicated (23), CT inconclusive (6), or US not performed(20) So N = 357

110 had PE on CT (30.8%), K between radiologists K = 0.95 PE presents in 41.1% of Wells > 4 (3 had negative D-dimer) If Wells ≤ 4 and positive D-dimer - 21% had PE


Main Results

Multiorgan US - Sensitivity 90% (82.8-94.9), Specificity 86.2% (81.3-90.3), +LR 6.5, -LR 0.12

MO US + Alternate - Sens 100% (96.7-100), Spec 42.9% (36.7-49.3%), +LR 1.75, -LR 0

Lung alone 60.0% sens, 95.9% spec, +LR 15, -LR 0.4

Heart alone 32.7% sens, 90.9% spec, + LR 3.6, -LR 0.7

Vein alone 52.7% sens, 97.6% spec, +LR 21.7, -LR 0.5


Other Interesting Findings

133 patients had positive US, 99 had PE (74.4%)

PE was in 11 of 224 patients (4.9%) with negative US

Negative US + negative d-dimer → none had PE (n = 55)

106 patients with US negative for PE (47.3%) had alternate diagnoses (pneumonia, diffuse interstitial syndrome, pleural effusion, pericardial effusion, aortic dissection) → none had PE on CT

64.9% of + lung findings were posterior bases

Algorithm was developed based on this data. Says you don’t need to do CT if you have a DVT or if you do US and find an alternate cause for symptoms - would have avoided CT in 50% of study population


Limitations

US performed by skilled providers

Excluded 20 where US was not performed - unclear why, but that may make it less “feasible”

Don’t know how long it took

CT pulmonary angiography may not be best gold standard since it can provide both false negatives and false positives (especially with regard to possible “sub-clinical” PEs)


Take Home Points

1. Multiorgan Lung ultrasound is feasible and better than single organ scans to rule out PE. 90% sensitive, -LR of 0.12.

2. Multiorgan US negative for PE + finds an alternate diagnosis → PE very unlikely


Our score

4 Probes


Cite this article as

Michael Prats, MD. Multiorgan Ultrasound for Pulmonary Embolism. Ultrasound G.E.L. Podcast Blog. Published on September 26, 2016. Accessed on August 24, 2019. Available at https://www.ultrasoundgel.org/3.
Published on 09/26/16 02:00 AM
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