Correlation Study Comparing Electron Beam Angiogram and Coronary  Angiogram: Retrospective study Dr Ng Swee Choon, Dr Beh Chor Khim. Presented at the 14th ASEAN Congress of Cardiology, Kuala Lumpur

Objective – To evaluate the accuracy of non-invasive Coronary Artery Calcium Scan and Electron Beam Angiogram (EBA) by EBCT technology for the detection of significant obstructive disease as compared to coronary angiogram.

Methods – 56 patients who had undergone both EBA and conventional coronary angiogram were reviewed retrospectively. EBA findings were compared on a double-blinded basis with results of coronary angiogram read by an independent cardiologist. Criteria for significant lesion were: a) lesions of greater than 50% narrowing in the left main stem and b) lesions greater than 70% in left anterior descending(LAD),  right coronary (RCA)  and left circumflex (LCX) arteries.

Results:

Calcium score >zero  vs Coronary Angiogram for significant obstructive disease:

Calcium scan vs CAG	Sensitivity	Specificity	Positive Predictive Value	Negative  Predictive Value
	92.5%	12.5%	88 %	40%

 

Calcium score >75^th percentile vs Coronary Angiogram for significant obstructive disease:

Calcium scan vs CAG	Sensitivity	Specificity	Positive Predictive Value	Negative  Predictive Value
	67.5%	50%	77 %	38%

 

EBA vs Coronary Angiogram for significant obstructive disease:

EBA vs  CAG	Sensitivity	Specificity	Positive Predictive Value	Negative  Predictive Value
	100%	50%	83%	100%

Note: 8 coronary angiogram cases were read as non-significant lesions by the cardiologist.   However all 8 patients underwent coronary angioplasty and stenting by their respective cardiologists.  If these 8 cases were re-classified as having significant lesions then the PPV and Specificity of EBA  would be significantly higher.

Summary of results:

Coronary calcification is 100% specific for presence of atherosclerotic plaque in the coronary arteries. However, since coronary arteries remodel to maintain luminal integrity, significant plaque may be present before the development of luminal stenoses. This explains why the specificity of coronary calcification may be poor for predicting obstructive disease.  In this study cohort, a calcium score > zero was highly sensitive for predicting obstructive coronary artery disease but the specificity was only 12.5%.  A calcium score above the 75^th percentile increased the specificity to 50% but reduced the sensitivity of the test to 67.5%. On the other hand EBA showed excellent correlation with coronary angiogram. Further prospective study of a larger number of patients should be carried out to further evaluate the correlation between EBA and coronary angiogram.