Background: Neither clinical prediction models nor noninvasive imaging tests that detect coronary artery calcification identify all patients who experience acute coronary events. Variations in culprit plaque morphology may account for these inaccuracies.
Methods and results: We compared the 10-year Framingham risk index, histologic coronary calcification, and culprit plaque morphology in 79 consecutive adults with sudden cardiac death. There was a modest relationship between the Framingham risk index and the extent of histologic coronary calcification (r=0.35, P=0.002). Agreement in risk classification between the histologic calcification score and the Framingham risk index occurred in 50 of 79 cases (63.3%, P=0. 039). Either a focus of coronary artery calcification >/=40 micromol/L (62% of cases) or a Framingham risk index score >/= average risk for age (62% of cases) were present in 66 of 79 (83.5%) cases. Cases with plaque erosion (n=22) had significantly less coronary calcification (P=0.003) and lower Framingham risk index (P=0.001) scores than stable (n=27) or ruptured (n=30) plaques. Fourteen of 22 (63.6%) cases of plaque erosion were classified as low risk by both the Framingham risk index and the histologic calcification score.
Conclusions: The prediction of sudden cardiac death using the Framingham risk index and the measurement of coronary calcification are distinct methods of assessing risk for sudden cardiac death. Excessive reliance on either method alone will produce errors in risk classification, particularly for patients at risk of plaque erosion, but their combination may be complementary.