|CT perfusion of peri-infarct ischemia.
Image source: Journal of the American College of Cardiology
Adenosine stress CT can identify stress-induced myocardial perfusion defects with diagnostic accuracy comparable to SPECT, with similar radiation dose and the advantage of providing information on coronary stenosis, according to a study in the Sept. 15 issue of the Journal of American College of Cardiology.
Ron Blankstein, MD, from the Cardiac MR PET CT Program in the department of radiology and division of cardiology at Massachusetts General Hospital in Boston, and colleagues sought to determine the feasibility of performing a comprehensive cardiac CT exam incorporating stress and rest myocardial perfusion imaging (MPI) together with coronary CT angiography (CCTA). The authors noted that although cardiac CT can identify coronary stenosis, “very little data exist on the ability to detect stress-induced myocardial perfusion defects in humans.”
The researchers enrolled 34 patients who had a nuclear stress test and invasive angiography in the study. They performed dual-source CT as follows: 1) stress CT: contrast-enhanced scan during adenosine infusion; 2) rest CT: contrast-enhanced scan using prospective triggering; and 3) delayed scan: acquired seven minutes after rest CT. Two independent blinded readers each read images for CTA, CT perfusion and SPECT.
Blankstein and colleagues reported that the dual-source CT protocol was successfully completed for 33 of 34 subjects (average age 61.4; 82 percent male; body mass index 30.4 kg/m 2) with an average radiation dose of 12.7 mSv. On a per-vessel basis, CT alone had a sensitivity of 79 percent and a specificity of 80 percent for the detection of stenosis of at least 50 percent, whereas SPECT MPI had a sensitivity of 67 percent and a specificity of 83 percent.
For the detection of vessels with at least 50 percent stenosis with a corresponding SPECT perfusion abnormality, CT perfusion had a sensitivity of 93 percent and a specificity of 74 percent.
According to the researchers, the CCTA during adenosine infusion had a per-vessel sensitivity of 96 percent, specificity of 73 percent, and negative predictive value of 98 percent for the detection of stenosis of at least 70 percent.
Based on their results, the authors wrote that an “important advantage of CT perfusion is the ability to simultaneously visualize both coronary anatomy and myocardial perfusion. In comparison to SPECT, CT has improved spatial resolution and may be better at detecting small areas of ischemia or infarction. Furthermore, CT perfusion could offer improved accuracy for detecting multivessel disease because actual rather than relative blood flow patterns are assessed, thus avoiding false negatives that can occur in the setting of balanced myocardial ischemia.”
However, they also noted the limitations of CT perfusion, including radiation exposure—although in this study the effective dose was equivalent to SPECT—the requirement of a larger volume of iodinated contrast and the presence of artifacts.
The authors concluded that they hope that their “results will add myocardial perfusion to this list of important clinical uses of cardiac CT.”
The study was funded in part by Tokyo-based Astellas Pharma.