SPECT beats CT for detection of stable CAD

Some clinicians maintain that cardiac-computed tomography angiography (CCTA) bests SPECT/CT for the detection of CAD, but two expert nuclear cardiologists suggest the opposite and presented data to demonstrate their case, in a study published April 10 in the Journal of Nuclear Cardiology.

Zachary J. Trzaska, MD, from the Maine Medical Center, department of cardiac cervices, Tufts University School of Medicine, South Portland, Maine, and colleagues compared SPECT/CT and CT for their respective power to diagnose CAD, and SPECT/CT was deemed the go-to treatment for the growing number of patients with coronary heart disease. 

“We contend that SPECT retains its superiority over CCTA as the first line imaging modality for establishing the diagnosis and prognosis in stable CAD,” wrote the authors.

CCTA utilization has grown recently to 1.21 patients out of 1,000. That is up from 0.31 patients in 2005. Still, many studies suggest SPECT is the better choice for CAD detection, especially in terms of the ability to image functional stenosis. CCTA’s negative predictive value was noted at 99 percent, yet its positive predictive value was 36 percent for patients who had 70 or greater percent stenosis.

More than 13,000 SPECT systems are estimated to be in use across the U.S.--accounting for more than 50 percent of the market. Cadmium zinc telluride (CZT) SPECT cameras provide 3-5 minute scan times and a 57 percent dip in radiation dose, at a lower cost than other molecular imaging systems.

SPECT’s prognostic value was also considered high. For patients in one study, 28 percent of patients found by SPECT to have 10 percent or greater ischemic myocardium were seen as likely to suffer a cardiac event.

“It is not only the presence of ischemia but also the reduction of ischemic burden after medical intervention that may lead to improved outcomes,” the researchers wrote.

The authors included two meta-analyses of the diagnostic effectiveness of SPECT for CAD. One asserted that SPECT was 82 percent sensitive, 76 percent specific, and 83 percent accurate at detecting coronary disease, and another meta-analysis of a total of 114 SPECT studies collectively indicated a sensitivity of 88 percent, specificity at 61 percent and a 15.31 diagnostic odds ratio.

“When compared to SPECT, the diagnostic accuracy of CCTA for the detection of myocardial ischemia is relatively poor,” wrote the authors.

Another study showed that CCTA signaled significant numbers of false positive readings for CAD. Results suggested fewer than half of patients who had 50 percent or greater cardiac lesion by CCTA showed any actual functional ischemia.

“The key difference between SPECT and CCTA lies in the ability of SPECT to detect myocardial ischemia,” wrote the authors. “It is this ability that allows clinicians to make meaningful changes in management, which in turn leads to better patient outcomes, an essential component of value in health care. Because of this, SPECT continues to be the first line imaging modality for establishing the diagnosis and prognosis in stable CAD,” wrote the authors.