Prevalence of coronary artery calcification in patients undergoing SPECT/CT myocardial perfusion imaging.

Objectives: The presence of coronary artery calcification (CAC) may indicate plaque buildup within the arteries. CT scans are commonly used to detect CAC, and the results of these scans have been shown to have prognostic significance. Myocardial perfusion imaging (MPI) is utilized for the evaluation of patients with known or suspected coronary artery disease (CAD) by detecting areas of impaired myocardial perfusion. Some patients may have normal SPECT MPI studies, yet have calcium deposition in the coronary arteries. Thus, the objective of this study involved determining the prevalence of CAC in patients referred for SPECT MPI. Most importantly, the percentage of patients without known CAD who had CAC despite a normal SPECT MPI was determined. The early detection of CAC may affect patient treatment and minimize risk factors for CAD.

Methods: SPECT and CT images from patients who underwent clinically indicated stress MPI with SPECT/CT at Northwestern Memorial Hospital were reviewed between 1/21/2018 and 12/6/2018. Patients with known CAD were excluded from the analysis. The CT images were evaluated for the presence of CAC. In patients found to have coronary calcification, the severity of the calcification was rated as mild, moderate or severe. The SPECT images were evaluated for the presence of myocardial perfusion abnormalities.

Results: One hundred and one patients underwent MPI with SPECT/CT. Of these, 69 had no known CAD (41 females and 28 males, average age of 63.0 years). Coronary calcification was present in 35 patients (51%) with 19 rated as mild, 11 as moderate, and 5 as severe. Of these 69 patients, 52 had normal myocardial perfusion SPECT studies (29 females and 23 males, average age of 62.4 years). Of the patients without known CAD who had normal SPECT studies, coronary calcification was present in 26 patients (50%) with 16 rated as mild, 7 as moderate, and 3 as severe.

Conclusions: These results show that approximately half of the patients without known CAD who underwent clinically ordered SPECT MPI were found to have coronary calcification, indicating the presence of subclinical CAD. A similar percentage was found even in patients with normal myocardial perfusion SPECT studies. Thus, reviewing the CT scan for the presence of coronary calcification provided information that may impact patient treatment, such as more intensive risk factor modification.