ASNC: SPARC shows prognostic value of SPECT, PET, but CTA rises to top
SPECT, PET and CT angiography (CTA) all achieve significant risk stratification and add incremental value over pre-imaging data for the prediction of one-year adverse events. However, CTA eclipsed the other two modalities in low- and high-risk stratification, according to the preliminary data from the SPARC registry presented as a late-breaking clinical trial presented at the 2010 annual meeting of the American Society of Nuclear Cardiology (ASNC) in Philadelphia.

Although SPECT, PET and 64-slice CTA are widely used, their comparative incremental value and ability to risk stratify had been unclear, said Rory Hachamovitch, MD, from the department of cardiovascular medicine at the Cleveland Clinic, on behalf of the SPARC (Study of Myocardial Perfusion and Coronary Anatomy Imaging Roles in CAD) investigators.

The SPARC study is a prospective multicenter (41 sites) registry intended for two-year follow-up. These one-year data are preliminary. Researchers compared the incremental prognostic value of the imaging modalities in 3,019 patients with either prior coronary artery disease (CAD) (44 percent) or intermediate/high CAD likelihood. Close to 60 percent of patients were male and the average age of patients was 62.

The primary endpoint is a combination of hard adverse events—all-cause death and MI. The secondary endpoint is a combination of total events—all-cause death, MI and late revascularization.

CTA was performed in 30 percent of patients, PET in 39 percent and SPECT in 31 percent. All sites had to recruit for at least two of the three arms. A total of 2,919 patients were left for analysis after the exclusion of those lost to follow-up or early revascularization (195 early revascularizations). There was a balance between academic and practice settings, Hachamovitch said.

In total, 84 events occurred during the first year of follow-up (42 all-cause deaths, 16 MIs and 36 late revascularizations). Event rates were greater after a normal test with PET than with SPECT or CTA (2.6 vs. 1.6 vs. 0.5 percent, respectively). Event rates increased across test results for all modalities when tests were mildly abnormal (CTA, 5.5 percent; PET, 5.6 percent; and SPECT, 2.5 percent) or moderately/severely abnormal (CTA, 8.2 percent; PET 5.6 percent; and SPECT 4.4 percent).

Modeling analysis of pre-imaging data revealed that age, diabetes, prior MI and academic centers were most closely associated with the events. The addition of the imaging result and the modality used to this model was significant, Hachamovitch said.

A significant interaction between modality and test result identified CTA as having lower risk after a normal result and greater risk after an abnormal result.

He concluded that SPECT, PET and CTA all achieve significant risk stratification and add incremental value over pre-imaging data for the prediction of one-year adverse events.