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Elastography can help evaluate carotid plaque

By Erik L. Ridley, AuntMinnie staff writer

June 19, 2017 -- A shear-wave ultrasound elastography method can be used to evaluate the stability of carotid plaques, helping to identify those that are most vulnerable to rupturing and causing a stroke, according to a study published in the June issue of the Journal of Ultrasound in Medicine.

Researchers from the First Affiliated Hospital of China Medical University in Shenyang, China, used shear-wave elastography to calculate the Young's modulus -- a measure of stiffness -- of carotid plaques in more than 60 patients. After retrospectively evaluating patient outcomes after six months, they found that patients who went on to have a stroke or transient ischemic attack within that time period had a lower mean Young's modulus score, indicating a more vulnerable plaque. In addition, the group found that the combination of the Young's modulus with the plaque's stenosis rate yielded the best diagnostic performance for identifying the plaques that became symptomatic.

"The [shear-wave elastography] technique is a noninvasive, vascular elastography technique that can provide information regarding carotid plaque vulnerability, and could be of clinical benefit to help identify symptomatic carotid plaques more comprehensively and to predict cardiovascular risk," wrote the team led by Dr. Zhe Lou.

Carotid plaque stability

The presence of carotid atherosclerotic plaques is a strong predictor of cerebrovascular events, and investigators are searching for noninvasive imaging and biochemical parameters that can accurately identify vulnerable plaques to prevent stroke. While the rigidity of a plaque can be calculated on shear-wave elastography via the Young's modulus stiffness measure, few studies have assessed its use for evaluating the stability of carotid atherosclerotic plaque. As a result, the researchers set out to evaluate the feasibility and clinical value of the technique in assessing the rigidity and vulnerability of carotid plaque (J Ultrasound Med, June 2017, Vol. 36:6, pp. 1213-1223).

Lou and colleagues retrospectively studied a total of 61 subjects with carotid plaques who had received carotid ultrasound from January to November 2015. Patients were excluded from the study if they showed disabilities caused by stroke, bilateral focal neurological symptoms, atrial fibrillation, vascular lesions, recent myocardial infarction, or severe congestive heart failure that could be the cardioembolic cause of cerebrovascular stroke.

To ensure that culprit plaques originated from the external cranial carotid artery, the researchers also excluded patients with moderate to severe stenosis of the intracranial artery, or with moderate to severe stenosis before the initial part of the carotid. Patients with radiation injury-associated stenosis, restenosis after endarterectomy, Takayasu arteritis, carotid artery dissection, or total carotid occlusion were also left out of the study.

The patients -- 45 men and 16 women -- were separated into two groups depending on whether they showed unilateral focal neurological symptoms within six months or if they were asymptomatic over that time frame. Of the 61 patients, 31 were in the symptomatic group; 16 had a nondisabling stroke and 15 had a transient ischemic attack. The remaining 30 were asymptomatic.

All patients received a clinical carotid ultrasound examination in conjunction with shear-wave elastography using an Aixplorer (SuperSonic Imagine) ultrasound scanner with a L10-2 MHz linear array transducer. Shear-wave elastography analysis was successfully carried out in 271 (92%) of the 295 plaques evaluated in the study, and the scanner's built-in Q-Box-Trace software tool was used to quantify the maximum, mean, and minimum Young's modulus values.

Finding vulnerable plaques

When confounding factors such as gender and smoking history were controlled, the researchers found a significant correlation between Gray-Weale plaque classification and mean Young's modulus (r = 50.728, p < 0.01). In addition, the mean Young's modulus of representative plaques in the symptomatic group was 81 kPa, compared with 115 kPa in the asymptomatic group. The difference was statistically significant (p < 0.01).

The researchers noted that the vulnerability of the whole plaque can be determined by calculating its Young's modulus measure on shear-wave elastography.

"The lower mean Young's modulus indicates a greater proportion of lipid cores, which could imply greater vulnerability than plaques with a higher fibrous content," they wrote.

(A, above) Carotid plaque classified as Gray-Weale Type II shown with a B-mode and shear-wave elastography image. (B, below) The Young's modulus value of the plaque located in the anterior of the internal carotid artery was obtained using the Q-Box-Trace software tool. All images courtesy of the Journal of Ultrasound in Medicine.

What's more, logistic regression and receiver operating characteristic (ROC) analysis suggested that the combination of the mean Young's modulus with stenosis rate could yield increased sensitivity and specificity for identifying symptomatic carotid plaques, according to the researchers.

Diagnostic efficacy of ultrasound parameters for differentiating carotid plaque
	Area under the curve
Gray-Weale plaque classification	0.760
Mean Young's modulus	0.871
Stenosis rate	0.880
Gray-Weale classification and mean Young's modulus	0.872
Gray-Weale classification and stenosis rate	0.901
Stenosis rate and mean Young's modulus	0.933

"Further studies are required to prove our initial findings and to extend the study to the assessment of the different Young's modulus values against other noninvasive imaging techniques and pathological staining, which could further confirm the clinical potential and value of the carotid plaque evaluation via [shear-wave elastography]," the authors wrote.

Study questions use of FAST exam for kids with trauma

By Erik L. Ridley, AuntMinnie staff writer

June 14, 2017 -- Can a focused assessment with sonography for trauma (FAST) exam improve the clinical care of hemodynamically stable children who have blunt trauma to the torso? Apparently not, according to research published June 13 in the Journal of the American Medical Association.

In a randomized clinical trial involving nearly 1,000 hemodynamically stable pediatric patients being treated in the emergency department (ED) for blunt torso trauma, FAST failed to show any benefit over standard trauma evaluation in terms of reducing CT utilization, ED length of stay, missed intra-abdominal injuries, or hospital charges.

"These findings do not support the routine use of FAST in this setting," wrote the team led by Dr. James Holmes from University of California, Davis Medical Center.

Identifying hemoperitoneum

The FAST exam is used to evaluate injured patients with the goal of identifying hemoperitoneum associated with intra-abdominal injuries. Most research assessing the utility of FAST has involved adult patients, with randomized clinical trials finding that an initial FAST exam yielded lower utilization of abdominal CT, a shorter hospital length of stay, fewer complications, and fewer hospital charges.

The FAST exam isn't routinely used in the initial evaluation of injured children, however, perhaps reflecting the lack of randomized clinical trials involving children, according to the researchers.

To determine if pediatric patients would also benefit, the researchers set out to investigate whether a FAST exam performed during the initial evaluation of hemodynamically stable children with blunt torso trauma would lead to decreases in abdominal CT use, ED length of stay, and hospital charges without significantly increasing the number of missed intra-abdominal injuries (JAMA, June 13, 2017, Vol. 317:22, pp. 2290-2296).

"It was hypothesized that evaluating children with blunt torso trauma with the FAST examination would result in improved care and reduced costs," the authors wrote.

Randomized trial

The researchers performed a randomized, nonblinded trial at their large, urban, level I trauma center between April 2012 and May 2015, evaluating 925 hemodynamically stable children and adolescents younger than 18 years of age. The subjects had experienced blunt torso trauma and had presented to the ED within 24 hours of the traumatic event.

The children were placed into one of two cohorts: One group received standard trauma ED care, while another group received a FAST exam as an initial evaluation. The inclusion criteria aimed to select a study population with an approximate 5% risk of intra-abdominal injury. The baseline patient demographics were similar for each group.

All FAST exams were performed using a Zonare Z.One Ultra portable ultrasound scanner (Mindray Medical International) with 3.5-MHz and 5.0-MHz transducers. Patients received the standard FAST exam, including views of Morison's pouch, the splenorenal fossa, long and short axes of the pelvis, and subxiphoid.

The exams were performed and interpreted at the bedside by ED physicians who were certified in performing FAST exams based on guidelines from the American College of Emergency Physicians. The participating physicians -- 35 board-certified or eligible emergency physicians and five board-certified pediatric emergency physicians -- also recorded their suspicion of intra-abdominal injury, both before and after the FAST exam. In addition, they noted whether the FAST exam results had changed their decision to order an abdominal CT scan.

For the purposes of the study, all FAST exam results were also presented for later interpretation by one of two experienced ED ultrasonographers. These reviewers were blinded to all clinical data, according to the researchers.

No statistical benefit

Outcomes were similar for both groups of patients, the researchers found.

Effect of FAST exam on patient outcomes
	Control group	FAST group
No. of patients receiving abdominal CT exams	254 of 465 (54.6%)	241 of 460 (52.4%)
Mean length of ED stay	6.07 hours	6.03 hours
Median hospital charges	$47,759	$46,415

None of the differences were statistically significant. There was also one missed case of intra-abdominal injury in the FAST group, compared with no missed cases in the control group.

"Therefore, the study suggests that the routine use of the FAST examination in hemodynamically stable children with blunt torso trauma may not be useful," the authors wrote.

The group did find that the FAST examination was associated with a decrease in physician suspicion of intra-abdominal injury. However, this decrease was seen primarily in children initially suspected to have a 1% to 10% chance of intra-abdominal injury prior to the FAST exam.

"Changes in physician suspicion associated with the FAST examination, however, did not result in decreases in abdominal CT use," the authors wrote.

Changes in CT orders

There were 25 cases in which physicians changed plans to order CT studies after performing the FAST exam. In 12 of these cases, a physician elected to order an abdominal CT study that had not been planned prior to the FAST exam; one of these patients was diagnosed with an intra-abdominal injury. The physician decided not to order a planned abdominal CT following the FAST exam in 13 cases, and none of these patients were later diagnosed with intra-abdominal injuries.

In other findings, agreement between the FAST exam interpretations by the treating physicians and the expert ultrasound viewer was only moderate.

"However, the aim of the study was not to assess agreement between physicians in the performance of the FAST examination but rather to evaluate the effect of the use of the FAST examination on clinical outcomes and resource use," the authors wrote.

They pointed out that the study excluded certain high-risk patients for whom the FAST exam may have the potential to be beneficial.

"The FAST examination is considered the standard of care at the study site in hypotensive injured adults and has a reported sensitivity of 100% for hemoperitoneum in hypotensive injured children," the authors wrote. "Including these high-risk patients in the current study may have improved the sensitivity of the FAST examination."

Unresolved questions

In an accompanying editorial (pp. 2283-2285), Dr. David Kessler of the Columbia University College of Physicians and Surgeons said that rather than removing FAST examinations from pediatric trauma algorithms, the pediatric emergency medicine and ultrasound communities should be encouraged by these study results to further investigate the many unresolved questions about integrating FAST examinations into pediatric blunt abdominal protocols. He noted that the FAST exam is increasingly being used in pediatric trauma despite the lack of robust evidence for best practice.

"Quality improvement or implementation studies may be better suited to studying the desired behavior changes resulting from FAST algorithms," he wrote. "This is worth pursuing considering the potential to reduce exposure to ionizing radiation, the evolving technological advances, and the minimal risks associated with point-of-care ultrasound.