The Coronary Artery Calcium Score and Stress Myocardial Perfusion Imaging Provide Independent and Complementary Prediction of Cardiac Risk

Objectives This study sought to examine the relationship between coronary artery calcium score (CACS) and single-photon emission computed tomography (SPECT) results for predicting the short-and long-term risk of cardiac events. Background The CACS and SPECT results both provide important prognostic information. It is unclear whether integrating these tests will better predict patient outcome. Methods We followed-up 1,126 generally asymptomatic subjects without previous cardiovascular disease who had a CACS and stress SPECT scan performed within a close time period (median 56 days). The median follow-up was 6.9 years. End points analyzed were total cardiac events and all-cause death/myocardial infarction (MI). Results An abnormal SPECT result increased with increasing CACS from < 1% (CACS <= 10) to 29% (CACS > 400) (p < 0.001). Total cardiac events and death/MI also increased with increasing CACS and abnormal SPECT results (p < 0.001). In subjects with a normal SPECT result, CACS added incremental prognostic information, with a 3.55-fold relative increase for any cardiac event (2.75-fold for death/MI) when the CACS was severe (> 400) versus minimal (<= 10). Separation of the survival curves occurred at 3 years after initial testing for all cardiac events and at 5 years for death/MI. Conclusions The CACS and SPECT findings are independent and complementary predictors of short-and long-term cardiac events. Despite a normal SPECT result, a severe CACS identifies subjects at high long-term cardiac risk. After a normal SPECT result, our findings support performing a CACS in patients who are at intermediate or high clinical risk for coronary artery disease to better define those who will have a high long-term risk for adverse cardiac events. (J Am Coll Cardiol 2009; 54: 1872-82) (C) 2009 by the American College of Cardiology Foundation