Marlene Busko

July 14, 2014

SAN DIEGO, CA — In a large study of patients in Korea with suspected CAD, those who were sent for coronary computed tomography angiography (CCTA) were more likely to survive and not be hospitalized with MI during follow-up compared with patients who were sent for myocardial single-photon-emission CT (SPECT)[1]. In this "real-world" study, patients were sent for either test at the discretion of the physician.

Moreover, patients who had a negative CCTA test (no coronary stenosis detected) were more likely to survive and not have an acute MI than patients who had a negative myocardial SPECT test (no ischemia detected), lead study author Dr Seung-Pyo Lee (Seoul National University Hospital, Seoul, Korea) said in a presentation here at the Society of Cardiovascular Computed Tomography (SCCT) 2014 Annual Scientific Meeting .

"I think the main message from this study is that it confirms what we know—if you have a negative [coronary] CT [angiography test] then your chance of survival is good," moderator Dr Mohamed Marwan (University of Erlangen, Germany) commented to heartwire . Study strengths include the very large sample size. However, there was a lot of selection bias, since the patients sent for SPECT were sicker, he noted.

Lee acknowledged the selection bias but added that their multivariate analysis adjusted for differences in baseline patient characteristics. Nevertheless, this was a hypothesis-generating, retrospective study, he said. More insights should come next year from the group's randomized, prospective CARE-CCTA trial, which aims to determine the cost-effectiveness of CCTA vs myocardial SPECT in patients with chest pain.

Looking at Anatomy vs Function

"To verify that a patient has clinically significant CAD, the patient must have significant stenosis in a given segment of the coronary artery plus evidence of ischemia due to that lesion," Lee said. To do this, CCTA (which looks at anatomy) and myocardial SPECT (which looks at function) are used, and they have comparable sensitivity and specificity of around 90% to 95%, he added.

However, it's not known whether the downstream rates of survival or invasive coronary angiography and revascularization (with PCI or CABG) differ among patients with suspected CAD who are assessed using myocardial SPECT vs CCTA.

To investigate this, the researchers examined data from about 25 000 consecutive patients who underwent CCTA or myocardial SPECT. They excluded about 1000 patients who underwent both CCTA and SPECT simultaneously, as well as patients who had cancer or known CAD.

This left 11 843 patients: 7376 patients who underwent CCTA and 4467 patients who underwent SPECT.

Around 1000 patients who had SPECT and around 1100 patients who had CCTA had findings that were positive for CAD.

Patients who underwent SPECT tended to be older and were more likely to have hypertension, diabetes, cerebrovascular disease, and chronic obstructive pulmonary disease (COPD) and to be receiving more medications related to these diseases compared with patients who underwent CCTA.

The primary outcome was all-cause mortality, and secondary outcomes were rates of coronary revascularization, invasive coronary angiography without revascularization, and hospitalization for acute MI, during a follow-up of up to about four years.

Compared with patients who underwent SPECT, those who underwent CCTA had about a 30% lower mortality rate (adjusted hazard ratio [aHR] 0.716), which was largely driven by patients who had negative test results.

Patients who had CCTA were about half as likely to be hospitalized for acute MI (aHR 0.475) compared with those who had SPECT.

Invasive coronary angiography without revascularization was more common in patients who had SPECT.

Perhaps surprisingly, patients who had CCTA tests were about 20% more likely to have coronary revascularization procedures compared with patients who had SPECT (aHR 1.191).

In Korea, "you do either a SPECT or CT, and if you have any abnormal findings, you refer the patient directly to the cath lab," Lee explained.

This differs from the US, where "if a patient has a positive CT, and you know there is a stenosis, normally you would want to have a functional test to determine ischemia," Marwan said.

Lee had no disclosures. Marwan receives honoraria from Edwards Lifesciences and Siemens Healthcare.

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