Coronary artery calcification detected by a mobile helical computed tomography unit and future cardiovascular death: 4-year follow-up of 6120 asymptomatic Japanese

In the present study, we performed a prospective follow-up study in a population which underwent chest computed tomography (CT) screening. A total of 6 120 participants underwent a chest CT medical examination for lung cancer and tuberculosis in Nagano Prefecture, Japan, between 1996 and 1997. Computed tomography scanning was performed from the apex of the lung to the diaphragm at a tube voltage of 120 kV and a tube current of 50 mA. We measured the CT density of the coronary arteries in 5-7 slices where coronary arteries were detected. The CT density threshold for determining coronary artery calcification (CAC) was above +110 HU. In 2000, we investigated the number of deaths due to cardiac and noncardiac disease among the participants. Of the 6120 participants, 14 died of cardiac disease (9, myocardial infarction; 4, heart failure; and 1, angina pectoris) and 64 died of other diseases. Coronary artery calcification was detected in 10 of the patients who died of cardiac disease, and in 31 of those who died of other diseases. The prevalence of CAC was higher in the former than in the latter (71.4% vs 48.4%, P = 0.084). The relative risk of CAC for cardiac death was 2.66 (95% confidence interval: 0.76, 9.37). The findings of this study suggested that CAC detected in a mass chest CT screening by a mobile helical CT unit was predictive of future cardiovascular death.