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 Doctors inject the harmless radioactive substance, called a tracer,
to help them diagnose or rule out coronary artery disease. Not every
patient needs the injection. But for those who do, not being able to
get it means the only other way for doctors to get the same
information is for the patient to undergo a cardiac catheterization.
In a cardiac catheterization, doctors thread a tube from an artery
in a patient’s wrist or groin all the way into the heart, to look
for blockages of the coronary vessels.
The current worldwide shortage of a radioisotope known as technetium
Tc 99m, which is commonly used during stress testing, appears to
have led to a nearly 10 percent increase in heart catheterizations
after stress tests, Dr. Venkatesh L. Murthy from the University of
Michigan in Ann Arbor told Reuters Health.
“Due to the complexities of the healthcare system, it isn’t that
often that we can tie supply chain issues such as this to direct
healthcare outcomes,” Murthy said.
Cardiac stress tests use technetium 99m to evaluate the blood supply
to the heart, but recent shutdowns of nuclear reactors have resulted
in significant shortages. Doctors have had to turn to other
radioactive tracers, like thallium 201, but it is associated with
higher radiation exposure and less accurate results.
Murthy’s team used information from Medicare to investigate how
these shortages affected cardiac stress testing and the use of
cardiac catheterization among individuals age 65 or older.
Between 2010 and 2012, technetium 99m use decreased by nearly 25
percent, while the rates of other tests used to evaluate coronary
artery disease remained stable.
However, cardiac catheterization rates within 90 days after testing
that would have used technetium 99m or thallium 201 increased by 9
percent. This translates into 5,715 extra cardiac catheterizations
among these Medicare patients.
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For a variety of reasons, the researchers note, shortages of
technetium are likely to continue.
“Shortages of important medical compounds can have substantial
clinical consequences,” Murthy said in an email. “In this particular
case, shifting to thallium-201 during future shortages of
technetium-99m may not be the optimum strategy, and greater use of
other tests, such as positron emission tomography (PET), magnetic
resonance imaging (MRI) and computed tomography (CT), may be a
better alternative.”
“There are efforts to address this issue by many groups,” he said.
“Several companies have developed technologies to produce the
technetium without using weapons-grade uranium. What is not
completely clear yet is whether they will be able to operationalize
these technologies and ramp up supply quickly enough.”
SOURCE: http://bit.ly/29xx50w JAMA Cardiology, online June 29, 2016.
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