The shortage of technetium Tc 99m has led to physicians choosing to use stress echocardiography, computed tomography coronary angiography and positron emission tomography myocardial perfusion imaging instead of single-photon emission computed tomography myocardial perfusion imaging (SPECT-MPI), according to a study of Medicare beneficiaries.

Lead researcher Venkatesh L. Murthy, MD, PhD, of the University of Michigan, and colleagues published their results online June 29 in JAMA Cardiology.

They mentioned that nearly 15 million doses of technetium Tc 99m are used each year, typically for cardiac stress testing. However, they noted that none of the nuclear reactors that produce molybdenum Mo 99, the parent isotope of Tc 99m, are located in the U.S. and those that do are at least 50 years old.

For this analysis, the researchers evaluated the shortage of technetium Tc 99m from March to August 2010, when two major nuclear reactors shut down. They examined data on two million cardiac stress tests with SPECT-MPI performed from 2008 through 2012. They also calculated population-based rates of SPECT-MPI, stress echocardiography, computed tomography coronary angiography and positron emission tomography-MPI.

During the six-month shortage period, the use of technetium Tc 99m decreased from 64 percent of SPECT-MPI in February 2010 to 49 percent in May 2010. Although the usage gradually increased, it only accounted for 52 percent of SPECT-MPI in September 2012. The overall use of SPECT-MPI generally decreased throughout the study period.

Further, the researchers added that the adjusted odds of undergoing cardiac catheterization less than 90 days after SPECT-MPI increased during the shortage period. In fact, they noted that physicians might have performed 5,715 excess cardiac catheterizations on Medicare beneficiaries during the shortage.

If the shortage of technetium Tc 99m continues, the researchers noted that physicians could choose an older radiotracer, thallium TI201, which is associated with higher radiation exposure.

Congress authorized $143 million to encourage production of technetium Tc 99m from 2011 to 2014 from sources other than highly enriched uranium. However, the researchers said the funding has not been renewed. They added that the government plans on banning the exportation of highly enriched uranium fuel by 2020, which could significantly decrease the production of technetium Tc 99m.

“These converging pressures on the [technetium Tc 99m] supply chain have substantial clinical implications and underscore the importance of developing new production approaches and encouraging alternative testing approaches,” the researchers wrote.