INTRODUCTION: It has been shown that coronary artery calcium (CAC)
can be accurately quantified using electron beam tomography (EBCT) and followed
over time. However, the significance of changing calcium scored (CS) is largely
unknown. In this study, the rate of change of the CS was correlated to the
occurrence of a cardiac event.
METHOD:
225 moderate to high-risk asymptomatic
individuals (81% male, mean age 60 +/- 9 years) with EBCT score >20 at
baseline were enrolled. Each had repeat EBCT scans at a minimum interval of 1
year and was interviewed at the time of the follow-up visit. Progression was
considered significant at > 20% per year.
RESULTS: The time between scans average 3 years with a
range of 1-7 years.
30 events
occurred in 23 patients: 8 myocardial infarction, 4 strokes, 13 angioplasties, 5
bypass surgeries. Of those patients that had events, the coronary calcium score
increase by a mean of 35% per year.
This
was significantly greater than those patients who did not have cardiac events
(mean annual change 22%, p=0.04). There was a larger proportion of patients with
significant percentage progression of CS (>20% per year) in the group
suffering events than in the without events (78 % vs 37%, p<0.001). No
patient who suffered a coronary event exhibited regression of lack of
progression of CAC.
The
relative risk of a cardiac event in patient with CS progression
(>20% per year) in the group was 5.1 fold greater than those with
<20% per year change in the CS (p<0.0010. A threshold of 10 % per year
yield a 13.4 fold greater risk of cardiac events than those with <10% per
year change in score (P<0.001).
CONCLUSION:
EBCT
can accurately predict the progression of CAD by measuring the change in CS.
This retrospective study reveals that EBCT measured progression of coronary
calcium correlates with a 5-13 fold greater risk of cardiac events. No patient
with lack of progression (same or
lower CAC scores on follow-up scan) suffered a cardiac.event.
