Prediction of Intermittent Claudication, Ischemic Stroke, and Other Cardiovascular Disease by Detection of Abdominal Aortic Calcific Deposits by Plain Lumbar Radiographs

There has been little attention to vascular calcium testing for generalized assessment of cardiovascular disease (CVD) outcomes, such as intermittent claudication (IC) and ischemic stroke (IS). We hypothesize that aortic calcium is an important predictor of CVD outcomes. Lumbar x-rays were obtained in 848 men and 1,301 women (mean ages 59.7 and 60.1 years, respectively) from the original cohort of the Framingham Heart Study. Abdominal aortic calcium (AAC) deposits were graded using a previously validated scale. Participants were categorized according to a 10-year Framingham coronary heart disease (CHD) risk score. Multivariable Cox proportional hazards analyses were performed to relate AAC to CVD outcomes. There were 199 IC events, 201 IS events, 702 CHD events, and 1,121 CVD events during 32 years of follow-up. Multivariable adjusted hazard ratios for the third versus first AAC tertile in the combined cohort were 1.68 (95% confidence interval [CI] 1.12 to 2.50) for IC, 1.73 (95% CI 1.12 to 2.65) for IS, 1.59 (95% CI 1.26 to 2.00) for CHD, and 1.64 (95% CI 1.37 to 1.97) for CVD. Hazard ratios for IC and IS were similar in magnitude to those for CHD and CVD. A high AAC score was associated with significantly higher incidence of events in subjects at intermediate Framingham CHD risk for all end points. Risk prediction based on cardiovascular risk factors improved for most outcomes when AAC was added. In conclusion, there was a graded, increasing, and independent association of AAC with incident IC and IS, similar in magnitude to risks predicted for CHD and CVD. AAC appears to be useful for risk stratification in patients at intermediate CHD risk.