OBJECTIVES: This study sought to systematically assess the relationship between the magnitude of coronary artery calcium (CAC) and presence of myocardial ischemia. The likelihood of myocardial ischemia rises with increasing CAC score. However, the likelihood of ischemia according to different CAC abnormality cutoffs has not been systematically evaluated.
METHODS: A comprehensive systematic search was undertaken to identify all relevant studies that compared CAC with myocardial perfusion imaging and reported ischemia rates by CAC categories. The following thresholds of CAC scores were analyzed and correlated with rates of ischemia: scores of 0, 1 to 100, 101 to 399, and â‰¥400.
RESULTS: Overall, 20 studies reported frequencies of stress-induced myocardial ischemia by various CAC categories. Six studies (n = 2,123 patients) reported ischemia rates for all 4 CAC categories. A stepwise increase in the frequency of ischemia according to CAC abnormality was noted. The frequency of ischemia was low among patients with zero or very low CAC score. However, among the patients with CAC scores â‰¥400, the reported frequencies of ischemia varied widely among studies. Notably, most studies involved small sample sizes; only 5 of 20 studies included >500 patients and very few studies examined clinical parameters that may potentially modify the relationship between CAC score and ischemia.
CONCLUSIONS: Our meta-analysis indicates the presence of a quantitative relationship between the magnitude of CAC abnormality and the likelihood of inducible myocardial ischemia. Zero to low CAC scores were infrequently associated with ischemia, but there was a wide variance in the frequency of ischemia among patients with intermediate to high CAC scores. Thus, there is a need for prospective study involving larger patient samples to better define the clinical factors that influence the relationship between CAC scores and inducible myocardial ischemia.