A new study from Duke shows that cardiac magnetic resonance testing can not only non-invasively diagnose coronary artery disease, but can also determine whether or not it is fatal.
Robert Judd, co-director of the Cardiac MRI Center in the department of medicine, and his team analyzed data from more than 9,000 patients who underwent CMR.
The team found that out of nearly 10,000 patients, there were about 1,500 deaths during a five year median follow-up time. Patients with abnormal CMR scans were 3.4 times more likely to die than those with normal CMR scans. Even after adjusting for age, sex and cardiac risk factors, researchers found a “strong association” between the abnormal CMR test and death.
“We’ve known for some time that CMR is effective at diagnosing coronary artery disease, but it’s still not commonly used and represents less than one percent of stress tests used in this country,” Judd said in a news release.
Judd noted that although CMR is a relatively new way to identify and diagnose coronary artery disease, Duke's CMR center is one of the largest in the world, which allowed for extensive testing.
With three CMR machines at Duke and collaborations with other hospitals, Judd’s team gathered around 10 years of follow-up data of screened patients. The team created a system which would allow for easy input of patient data, from health habits to test results.
At the conclusion of a visit or test, the doctor traditionally makes a report for the patient’s electronic medical records. The new software allowed for this report to also be put into a cloud server where it could later be analyzed.
“This became part of the routine clinical workflow,” Judd told The Chronicle. “It was a byproduct of them doing their everyday work.”
Since all reports were gathered, the study was not limited only to those with severe heart failure, but instead was a randomized and representative sample.
“Everybody that walked in the door was included,” Judd said.
At the conclusion of this 10-year study, the list was cross-referenced with the U.S. Social Security Death Index. Cases were sorted into groups of alive or dead, with abnormal or normal hearts. “Abnormal” meant that the patient either had previously had a heart attack or that the heart walls were not acting correctly.
Compared to other commonly used diagnostic tests, CMR is non-invasive and non-toxic. Right now, patients are commonly diagnosed using stress echocardiograms, catheterizations or stress nuclear exams. These procedures are “insensitive,” Judd said.
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“Any kind of intervention is invasive,” he explained.
A catheterization requires the injection of angioplasty and a stint, which pushes blood vessels that have constricted. If coronary artery disease is severe enough, patients then need bypass surgery.
In a stress echocardiogram, patients are given the drug Dobutamine, which causes heart rate to spike. Alternatively, patients run on a treadmill while their heart rate is monitored. In both of these tests, doctors are looking for any abnormalities in the heart, such as parts that are not contracting properly under the stress.
A nuclear cardiology test requires small amounts of radioactive tracer to be injected into the bloodstream, taken to the heart and then captured on a gamma camera. Judd said that this is dangerous when undergone every few years, and the image is so pixelated that the abnormal area cannot be examined in detail.
The next step to implementing nationwide CMR testing will be to establish comparative effectiveness between it and other tests.