Assessment of cardiovascular risk status at CT colonography

Purpose: To retrospectively determine whether calcium scores of the abdominal aorta obtained during computed tomographic (CT) colonography relate to Framingham risk factors and clinical cardiac events. Materials and Methods: The institutional review board approved the current HIPAA-compliant retrospective study and waived informed consent. Between 1995 and 1998, 480 patients underwent CT colonography; 467 patients were available for assessment. Calcium scores with a threshold attenuation value of 130 HU or greater were recorded for abdominal aorta (suprarenal, infrarenal, and aortic bifurcation regions and total). Patient histories were abstracted for established cardiac risk factors and subsequent cardiac events. Associations between calcium measurements and binary risk factors were assessed with Wilcoxon rank sum test; those with continuous risk factors, with Spearman rank correlation coefficient; and those with combined end points, with Cox proportional hazards model. Results: Follow-up data were available for 467 patients with median age of 65 years (range, 34-83 years); 59% (275 of 467) were men. Nine patients had cardiac events subsequent to CT colonography. Results of proportional hazards regression analysis revealed a significant association between myocardial infarction or cardiac event-related death and calcium scores of the aortic bifurcation that exceeded 895, the value for the 75th percentile for this calcium variable (P < .01). Associations with established cardiac risk factors for all four calcium scores were significant (P < .05). Spearman rank correlation coefficients for associations between total calcium score and patient characteristics of age, number of pack-years of smoking, and systolic blood pressure were 0.51, 0.43, and 0.29, respectively (P < .001 for all). Conclusions: Aortic calcification scores at CT colonography are significantly associated with established cardiac risk factors and cardiac-related events. This screening information can be obtained without additional scanning or risk to the patient.