Emergency medicine clinicians propose a new, ultrasound-based diagnostic algorithm that could reduce the use of computed tomography pulmonary angiography (CTPA) by 28% to 58% in patients suspected of having a pulmonary embolism.
The approach, outlined by experts in Switzerland, prioritizes point-of-care ultrasound to streamline triage for both stable and unstable patients.
- FoCUS (Focused Cardiac Ultrasound): A bedside scan used to evaluate heart function and identify signs of right ventricular dilation (RVD) in unstable patients.
- CUS (Compression Ultrasonography): A test of the lower extremities to detect deep vein thrombosis; if positive, it eliminates the need for further radiation-heavy imaging.
- LUS (Lung Ultrasound): A secondary scan used when initial tests are inconclusive to help confirm or rule out pulmonary vascular obstruction.
The reliance on CTPA—a gold-standard diagnostic tool that uses ionizing radiation and intravenous contrast—has come under scrutiny due to concerns regarding over-testing and resource allocation.
For patients who are haemodynamically unstable, the protocol dictates an immediate FoCUS. If the scan is positive and shows no signs of chronic RVD, clinicians can initiate treatment immediately. If signs of chronic RVD are present, the team proceeds to CUS of the lower extremities.
In haemodynamically stable patients, the algorithm reverses the priority. Clinicians begin with CUS; a positive result confirms the diagnosis, rendering further imaging unnecessary, though a FoCUS scan is recommended for risk stratification. If the CUS is negative, the protocol moves to LUS. If LUS is positive, a FoCUS scan follows for risk assessment.
“If all three ultrasound modalities are negative or the findings remain inconclusive, proceed to CTPA.”
Osterwalder noted, cautioning that ultrasound is a supportive tool rather than a wholesale replacement for CTPA when diagnostic uncertainty persists.
| Patient Status | Primary Diagnostic Step | Secondary Step (if negative) | Tertiary Step (if negative) |
|---|---|---|---|
| Unstable | FoCUS | CUS | Clinical Judgement |
| Stable | CUS | LUS | FoCUS |
If all three ultrasound modalities are negative or the findings remain inconclusive, proceed to CTPA. This protocol is not intended for patients who are unable to undergo ultrasound due to anatomical limitations or severe obesity, which can degrade image quality.
