Asymptomatic Subjects with Zero Coronary Calcium Score: Coronary CT Angiographic Features of Plaques in Event-Prone Patients

A zero coronary calcium score is often interpreted as strong reassurance — the “warranty period” concept holds that CAC=0 predicts very low near-term cardiac event rates. This study examined whether that reassurance is always warranted.

Among 7,961 asymptomatic subjects with zero CACS, 441 had noncalcified plaques identified on CCTA and 48 had obstructive coronary disease. The subset who experienced cardiac events despite zero calcium had plaques with low CT density, high remodeling index, and greater stenosis degree — the classic imaging features of vulnerable, lipid-rich lesions prone to rupture.

The clinical significance is a necessary qualification of the zero-CAC warranty. Noncalcified plaque is invisible to calcium scanning by definition. A zero score cannot exclude early coronary atherosclerosis in patients who have soft, potentially vulnerable plaque — particularly younger patients or those with strong family histories of premature CAD. For these individuals, CCTA provides information that calcium scanning alone cannot.

We rate the evidence moderate. A large prospective study clarifying an important limitation of calcium scoring and supporting CCTA’s ability to identify noncalcified plaque risk beyond what the calcium score detects.