Contrast Enhanced Cardiac CT Detects Coronary Artery Disease In 44% Of Asymptomatic Long-Term Adult Allogeneic Stem Cell Transplant Survivors

Long term allogeneic stem cell transplantation (allo-SCT) survivors face a 2.3 fold increase risk of premature cardiovascular (CV) related death compared to the general population. A reliable screening strategy to identify allo-SCT survivors at risk for CV-related disease is therefore warranted to minimize future events. Cardiac CT is an emerging non-invasive imaging technology with high sensitivity for detecting coronary artery disease (CAD) and high negative predictive value to exclude the presence of CAD. We conducted the first prospective non-randomized single institution study to evaluate Agatston coronary calcium scoring by CT with concomitant coronary CT angiograms as a tool to identify the survivors at risk for CV disease. Sixteen asymptomatic post allo-SCT survivors (11 males; 5 females) with median age of 45 years (range 22-66) at transplant underwent coronary calcium scoring and contrast enhanced coronary CT angiograms at a median follow up of 5 years post transplant. 10-year Framingham cardiovascular risk scores (incorporating age, sex, total cholesterol, HDL cholesterol, systolic BP, HTN, smoking status) were also calculated at time of screening. Two were classified as high risk, 1 intermediate and 13 as low risk. Iodinated IV contrast was administered for coronary artery visualization and IV hydration given to patients with decreased creatinine clearance. Non-obstructive CAD was detected in seven (44%) patients. Additionally, four (25%) of these subjects had aortic root calcification. Lesion distributions by arterial territory were: left main 5.8%, left anterior descending 35.3%, left circumflex 29.4% and right coronary artery 29.4%. Characteristics of coronary plaques were: 47% calcified, 47% mixed calcified / non-calcified, and 6% non-calcified. In those with CAD, the median coronary calcium score was 55 (range: 0-992) (p<0.001), corresponding to the 75^th percentile (range: 33^rd to 97^th percentile) (p < 0.001) adjusted for age, gender, and ethnicity. In comparison, those without any CAD had a median coronary calcium score of 0, < 1 percentile. There was one patient with <1% Framingham cardiovascular risk score who had a zero coronary calcium score with non-obstructive CAD on the CT angiogram. The radiation exposure during the procedure was acceptable, at a median of 0.60 mSv (range 0.18 to 3.12 mSv) for the coronary calcium score and 0.85 mSv (range 0.34 to 8.01) for the coronary CT angiogram. There were no complications related to the procedure. Current (2010 AHA/ACC) guidelines suggest a role for coronary calcium scoring for screening asymptomatic non-transplant individuals with intermediate Framingham risk. However, we detected CAD in 4 of 13 (30.8%) low risk transplant survivors. Coronary calcium scoring alone (sensitivity of 85.7% and specificity of 100%) may be adequate for screening and avoids the use of IV contrast. In conclusion, coronary calcium score with or without CT angiogram is a safe, feasible, highly sensitive study in transplant survivors; even asymptomatic, low-risk survivors may benefit from screening.