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May 16, 2019

Brain MRI may be overrated in deciding about valve surgery

By Advancing the Science contributor

By Jay Furst

Blood clots moving to the brain are a frequent -- and dangerous -- complication for patients with endocarditis. Endocarditis is an infection of the heart's inner lining that can damage heart valves and contribute to the formation of blood clots. As many as 80 percent of endocarditis patients who undergo magnetic resonance imaging (MRI) have strokes, though they may not show overt symptoms.

Three medical professionals examine MRI results on a bank of computer screens
Examining MRI results

Because of the risk of blood clots and strokes, it's common for patients to have an MRI prior to decision-making about whether heart valve surgery should be delayed or avoided out of concern that it could lead to greater risk of intracerebral hemorrhage (bleeding in the brain) due to blood thinners given during the surgery.

A team of Mayo Clinic physicians wanted to know more about how brain MRI findings affect cardiac surgical decisions, so they reviewed data from 361 patients treated at Mayo from a seven-year period and made some surprising discoveries.

"We were somewhat surprised that only four of 361 patients who underwent valve surgery had new postoperative intracerebral hemorrhage afterward," says Tia Chakraborty, M.D., a Mayo Clinic fellow in Neurocritical Care. One of the four patients who had postoperative hemorrhage also had preoperative hemorrhages, according to MRI results; the other three did not have an MRI.

Among them: postoperative hemorrhage may be a less common complication of valve surgery than is commonly believed.

"We do not recommend brain MRI as screening for patients with infective endocarditis, as its findings should not delay surgery in the absence of hemorrhage or large territorial stroke visible on a CT scan."


Tia Chakraborty. M.D., a Mayo Clinic fellow in Neurocritical Care

"It appears that perioperative intracerebral hemorrhage may be a less common complication of valve surgery than previously thought," says Dr. Chakraborty, lead author of the study, which will be published in Mayo Clinic Proceedings in June.

MRI shouldn't be allowed to delay surgery

That finding leads to the study's main takeaway: "We do not recommend brain MRI as screening for patients with infective endocarditis, as its findings should not delay surgery in the absence of hemorrhage or large territorial stroke visible on a CT scan," Dr. Chakraborty says.

The study recommends a CT scan of the head for patients having neurological symptoms. "CT scans should suffice to evaluate for territorial infarction or hemorrhage before valve surgery in patients with neurologic symptoms," says Dr. Chakraborty.

That's a significant change, says Larry Baddour, M.D., an infectious disease consultant and co-author of the study. "Further study is needed to fully define the subgroup of patients who may benefit from MRI," Dr. Baddour says, but the research defines indications for valve surgery, "which should improve outcomes in patients with heart valve infections."

A nurse and a patient (lying down) use a CT scanner
A nurse and a patient use a CT scanner

The study reviewed records for patients hospitalized at Mayo for infective endocarditis from January 2007 through December 2014. Of the 361 cases reviewed, 127 patients had MRI prior to valve surgery, and the imaging showed acute or subacute neurological abnormalities in most cases. But patients who underwent valve surgery despite these abnormalities had lower mortality and better functional outcomes overall, the study says.

Even incidental MRI findings tend to confound case management and potentially delay valve surgery for weeks, or even prevent surgery altogether, says Daniel DeSimone, M.D., a Mayo Clinic infectious disease consultant and also a co-author. "Valve surgery is often performed for control of the infection, worsening heart failure that is not responding to therapy, and/or preventing further embolic events to the brain and body," Dr. DeSimone says. Delaying or foregoing that surgery can affect patient outcomes.

The study found that most of the infective endocarditis patients had cerebral lesions on MRI, but it's unclear how these abnormalities impacted decisions regarding valve surgery. "Therefore, it is reasonable to conclude that the use of MRI is equivocal," the study says. "Although the risk of postoperative hemorrhage must always be weighed against the benefit of valve surgery, brain MRI should not be considered indispensable for surgical clearance."

Fewer hassles for patients, and less expense

To provide guidance to clinicians and patients, the study group developed an algorithm using data from this study and a previous one to approach the consideration of valve surgery based on CT findings. "We offer a way for providers to stratify the risk of perioperative hemorrhage based on specific findings on the CT, so as not to withhold surgery from patients who need it, while delaying or avoiding it in others who may be at higher risk of hemorrhage," she says.

Even incidental MRI findings tend to confound case management and potentially delay valve surgery for weeks, or even prevent surgery altogether.


Daniel DeSimone, M.D., a Mayo Clinic infectious disease consultant.

A potential next step for the researchers is to create a surgical risk-assessment scoring system based on the algorithm and predictors that the study found.

If a patient has neurological symptoms and certain findings on the initial CT, MRI remains an important next step, says Dr. Chakraborty, who completed her neurology residency at Mayo and has a bachelor’s and master’s degrees in biomedical engineering. For others, however, "our recommendation is that brain MRI should not be considered indispensable for surgical clearance."

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Tags: brain, CT, Daniel DeSimone, endocarditis, Findings, Larry Baddour, Mayo Clinic Proceedings, MRI, neurology, radiology, Tia Chakraborty

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