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 < or =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 (< or =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. 2009 by the American College of Cardiology Foundation