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CT Alone Noninferior to CT Plus MRI for Stroke Outcomes

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In a new study among patients with acute ischemic stroke, diagnostic imaging using CT alone was non-inferior to baseline CT plus MRI for discharge and clinical outcomes at 1 year.

Mortality or addiction rates at hospital discharge and recurrent stroke or death within 1 year were not higher in patients who underwent brain CT alone.

Thus, “the value of MRI added to CT for these patients should not be underestimated,” write Heitor Cabral Freud, MD, University of Texas at Galveston, and colleagues in their study, published July 21 in the JAMA Network Open.

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The addition of MRI to CT has increased significantly, but it is unclear whether the added MRI, which is more expensive, improves outcomes, senior author William J. Powers, MD, University of North Carolina, Chapel Hill, explained to theheart.org. | Medscape Cardiology.

The researchers note that from 1999 to 2008, the use of MRI to evaluate patients with ischemic stroke in the United States increased from 28% to 66%, and more than 90% of patients who underwent brain MRI first underwent CT. Unnecessary medical imaging is a major cause of preventable waste in the American healthcare system.

“Many clinicians believe that more data means better patient outcomes, but that’s not always the case,” Powers said. With an MRI, “you see more things and make decisions based on that, but does that mean people are doing better? It’s an implicit assumption, but it’s not always true.”

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When you come up with a new diagnostic test, he continued, unlike a new drug, you don’t have to show the US Food and Drug Administration (FDA) that using it improves patient outcomes.

“May be [this study] will make people think that we really need more data and more research to determine which patients hospitalized with acute ischemic stroke benefit from MRI in addition to initial CT,” he said.

“Pause and Rethink”

“Given the prevalence of routine MRI in addition to CT in the clinical practice of stroke, the implications” of this study are “significant,” write Michael Teitcher, MD, and José Billar, MD, of Loyola University Chicago in an accompanying editorial.

“As stewards of healthcare resources, clinicians should be asking whether the additional information provided by diagnostic tests affects patient outcomes,” they advise, “and the answer should be based on data, not anecdotal evidence.”

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There are circumstances in which an additional MRI is still warranted, Teitcher and Billard admit. “But at a minimum, these results should give practitioners a reason to pause and reconsider the routine use of CT plus MRI.”

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“Hopefully, the present study will pave the way for future prospective studies that provide additional data on this common clinical question,” the authors write, echoing Powers.

Current American Heart Association/American Stroke Association guidelines state that it is prudent to obtain an additional MRI after initial imaging of the head in cases where initial imaging did not demonstrate infarction.

Some researchers and practitioners are recommending that all hospitalized patients with acute ischemic stroke have a brain MRI, Billard said theheart.org | Medscape Cardiology via email. This “may help differentiate subtypes of ischemic stroke (eg, extracranial and intracranial large artery atherosclerotic disease, cardioembolic disease, lacunar disease, and small vessel disease) within the continuum of ischemic cerebrovascular syndromes.”

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However, whether this imaging paradigm is associated with improved patient outcomes, he continues, remains unsupported by either consensus or evidence review.

The routine use of brain MRI in addition to CT among hospitalized patients with acute ischemic stroke “requires validation in well-designed clinical trials,” Biller said, adding, “Let the data speak for itself!”

“In the meantime,” he said, “it would be timely and prudent to rethink when to order MRI of the brain in hospitalized patients with acute ischemic stroke.”

Patients with relevant tendencies

In a propensity-matching study, 246 patients with acute ischemic stroke were admitted to the Comprehensive Stroke Center at the University of North Carolina Hospital between January 2015 and December 2017 and underwent either baseline CT or CT plus MRI.

Patients were classified as addicted at discharge from the hospital if they had a Modified Rankin score from 3 to 6 (where 3 indicates they need some help but can walk without assistance, and 5 indicates the need for constant medical care and attention, as well as bedridden and urinary incontinence). . The average age of study participants was 68 years, 53% of them were men.

Among the 123 patients with additional MRI, 42.3% of the studies were ordered under the supervision of the attending neurologists, 33.3% under the supervision of the attending emergency physicians, and 24.4% by nurse practitioners or neurocritical care physicians.

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Of the six treating neurologists who treated people with stroke during the study period, one never requested an MRI, another always requested one, and the rest were in between.

For 111 out of 123 MRIs, there was no specific indication other than stroke or neurological symptoms.

Death or addiction at hospital discharge was more common in patients who had MRI added to CT than in patients who had CT alone (48.0% vs 42.3%), consistent with the non-inferiority margin of -7 ,5%.

Similarly, stroke or death within a year of discharge was more common in patients who underwent both types of imaging than in patients who underwent only CT (19% vs. 13%), corresponding to a margin of non-inferiority of 0.725.

“Think about the value it will add”

Bruce C.W. Campbell, PhD, Royal Melbourne Hospital, Australia, told theheart.org | Medscape Cardiology, that at its center “we selectively prescribe an MRI, perhaps 20% to 30% of patients.”

“We also frequently do diffusion-only MRI to characterize infarction,” said Campbell, author of the second editorial accompanying the article.

“We regularly do CT, CT perfusion and CT angiography from the aortic arch to the apex of the brain, so we already have a lot of information about the vessels,” he continued.

“Diffusion MRI,” he explained, “confirms the diagnosis, indicates the size of the infarct (which is useful when considering the timing of anticoagulant therapy), gives indications of the mechanism [such as] small vessel disease, cardioembolism in multifocal infarcts, watershed patterns, and confirms the likelihood of symptomatic carotid stenosis.”

“As with any investigation, it is good practice to consider how much value it will add. [patient] decision making,” Campbell concluded. “In many situations, an MRI is necessary after a stroke, but not everyone needs it.”

Authors and editors report that they do not have relevant financial information.

JAMA The network is open. 2022;5:e2219416, e2223077, e2223074. Full text, Teitcher and Billard editorial, Campbell editorial

Read more at theheart.org | Medscape Cardiology, follow us on Twitter and Facebook.

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