Written by Chris Thom
Spoon Feed
In this single-center study investigating large vessel occlusion (LVO) ischemic stroke, the test characteristics of POCUS were promising.
POCUS for LVO?
This prospective study enrolled a convenience sample of ED patients presenting with a suspected stroke within 24 hours of symptom onset. Three medical students with extensive training performed POCUS of the bilateral common carotid arteries (CCAs). Spectral doppler evaluations were performed, which included measurement of the peak systolic velocity (PSV), end-diastolic velocity (EDV), resistance index (RI), and pulsatility index (PI). Patients were considered to have LVO if there was occlusion of the intracranial segments of the internal carotid and/or occlusion of the M1 branch of the middle cerebral artery. POCUS images were reviewed by two blinded neurologists with specialized ultrasound training to determine accuracy.
257 patients were enrolled, with 12% having LVO confirmed on CTA or MRA. Out of the studied variables, an EDV difference between sides (defined as greater than 2 cm/second) had the highest accuracy for detection of LVO. The area under the curve (AUC) was 0.9 (95%CI 0.85-0.93), with a specificity of 83% (95%CI 78-88) at a set sensitivity threshold of 80%. A qualitative “visual diagnosis” of presence or absence of LVO based on POCUS images had a sensitivity of 47% (95%CI 28-66) and specificity of 96% (95%CI 93-99).
How will this change my practice?
LVO in ischemic stroke is a fast-moving topic that we should keep up with. There is benefit of treatment up to 24 hours from symptom onset, which separates this disease entity from the traditional 3 to 4.5 hour thrombolytic window. Predicting LVO can be challenging, with clinical decision rules not always featuring high accuracy. This is particularly important for the prehospital environment, where the decision to transport directly to a stroke center may be prudent. The current study is thought provoking, and the POCUS findings make sense. The EDV in an LVO should go down, as the increased distal pressure from the LVO “dampens” diastolic forward flow in the cerebral vasculature. This is not ready for primetime, and further study with additional users are needed. But if I were a prehospital medical director, this may be a potential future application of POCUS in the prehospital environment.
POCUS pro-tips:
Spectral doppler does not have to be intimidating or require extensive training. The key to success in measuring arterial velocities is knowing that you want the doppler gate aimed in the direction of flow. If the gate is perpendicular to the blood flow, then the doppler shift will be minimal and not reflective of the actual velocities. You can “steer” the doppler gate in order to assist with aiming the doppler in the direction of flow. Find the CCA just proximal to the carotid bulb and apply the doppler gate over the center of the artery. You’ll then get a waveform similar to the above image, where the PSV and EDV can be easily measured.
Source
Point-of-care ultrasound of the common carotid arteries for detection of large vessel occlusion stroke: Results of the POCUS-LVO study. Eur Stroke J. 2025 Jan 30:23969873251315337. doi: 10.1177/23969873251315337. Epub ahead of print. PMID: 39882581
