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[Significance of calcium detection with electron-beam tomography in coronary disease]
Insights
Electron beam tomography (EBT) precisely detects coronary calcium, a key indicator of arteriosclerosis. While valuable for assessing coronary artery disease (CAD), a minority of patients with severe CAD may show no calcification.
Area of Science:
- Cardiovascular Imaging
- Radiology
- Preventive Cardiology
Background:
- Coronary calcium is a strong marker for arteriosclerosis.
- Electron beam tomography (EBT) offers precise detection of coronary calcium.
- EBT is applicable to both symptomatic and asymptomatic individuals at risk.
Purpose of the Study:
- To evaluate the utility of EBT in detecting coronary calcium.
- To assess the correlation between calcium scores and the severity of coronary artery disease (CAD).
- To explore the role of EBT in both patients with known CAD and asymptomatic individuals.
Main Methods:
- Standard EBT protocol involves 30-40 slices (3mm thickness) with a 100 ms scan time, no contrast needed.
- Calcium score calculated using the Agatston method; radiation exposure is 0.8 mSv.
- Spiral CT with and without ECG gating was used as an alternative imaging modality.
Main Results:
- A strong correlation was observed between calcium scores, age, and gender.
- Higher calcium scores were associated with more severe coronary artery disease (stenoses >= 75%).
- A minority of patients (8.1%) with severe stenoses had a calcium score of 0, and 33% had a normal age-adjusted score. Spiral CT showed excellent correlation with EBT for calcium scoring.
Conclusions:
- Coronary calcium detected by EBT is a sensitive marker for CAD.
- EBT is indicated for prognosis in known CAD, for patients unable to stress test, or with atypical chest pain.
- The clinical value in asymptomatic patients requires further definition through randomized studies; EBT may aid selective primary prevention in high-risk individuals.
Purpose:
Coronary calcium is a powerful indicator of arteriosclerosis and can be detected very precisely with electron beam tomography. The method can be applied in patients with known coronary artery disease or in asymptomatic patients at risk of arteriosclerotic disease.
Methods:
The standard protocol of EBT consists of 30 to 40 slices of 3-mm thickness with a scan time of 100 ms, no overlap. No contrast medium is needed. The total scan can be performed within one breathhold. The calcium score is calculated as described by Agatston. Radiation exposure amounts to 0.8 mSv per total screen. We used spiral CT with and without ECG trigger as an alternative.
Results:
At the University of Munich we performed an EBT scan of the heart in 1100 patients within the last year. In 567 patients coronary angiography was performed also (+/- 3 days). Confirming previous reports in the literature, we found a correlation of the calcium score with the age and gender of the patients. Severe coronary artery disease (stenoses > or = 75%) was associated with significantly more calcium than less severe CAD. The calcium score did not discriminate between one-, two- and three-vessel disease. The site of calcification does not correlate with the localization of stenoses. Thirty-three percent of the patients with significant coronary artery disease showed a normal age-adjusted calcium score; a total of 8.1% of patients with severe stenoses did not reveal any coronary calcification (score = 0). With asymptomatic patients there are only a few studies available. Soft plaques cannot be detected with EBT, but in most patients soft plaques occur together with hard plaques. Our results show that spiral CT of the newest generation may also be used for calcium screening. There was an excellent correlation of the calcium scores of EBT and spiral CT at all levels of calcification.
Discussion:
Coronary calcium is a sensitive marker of coronary artery disease. In the clinical setting EBT is indicated in patients with known coronary artery disease (to evaluate prognosis), in patients who are unable to perform a stress test, and in patients with atypical chest pain. However, lack of calcification may be associated with severe stenoses in a minority of patients. The clinical value in asymptomatic patients needs to be defined: randomized studies are necessary. We see a possible indication in patients with known risk factors, in whom primary preventive strategies could be performed more selectively and cost-effectively.