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Incremental prognostic utility of coronary CT angiography for asymptomatic patients based upon extent and severity of coronary artery calcium: results from the CONFIRM Study

Selected in European Heart Journal by G.G. Toth

References

Authors

Iksung Cho , Hyuk-Jae Chang , Bríain Ó Hartaigh , Sanghoon Shin , Ji Min Sung , Fay Y. Lin , Stephan Achenbach , Ran Heo , Daniel S. Berman , Matthew J. Budoff , Tracy Q. Callister , Mouaz H. Al-Mallah , Filippo Cademartiri , Kavitha Chinnaiyan , Benjamin J.W. Chow , Allison M. Dunning , Augustin DeLago , Todd C. Villines , Martin Hadamitzky , Joerg Hausleiter , Jonathon Leipsic , Leslee J. Shaw , Philipp A. Kaufmann , Ricardo C. Cury , Gudrun Feuchtner , Yong-Jin Kim , Erica Maffei , Gilbert Raff , Gianluca Pontone , Daniele Andreini , James K. Min

Published

February 2015

Link

Access the abstract

My Comment

Background

Coronary computed tomography angiography (CCTA) has become the standard non-invasive imaging modality for morphologic evaluation of coronary artery disease. CCTA enables visualisation of atherosclerotic plaques with high diagnostic performance in identifying or excluding luminal stenoses.

However, as recently reported CCTA adds no benefit for long term cardiovascular risk stratification for the global population beyond clinical risk factor scoring and coronary artery calcium score (CACS).­ This study investigated, whether the prognostic value of CCTA differs in different subgroups of population, grouped according to CACS severity.

Study

  • 3, 217 asymptomatic patients, who underwent CCTA, were enrolled in the study.
  • Coronary artery disease was defined as the presence of >1mm2 plaque tissue. Obstructive coronary artery disease was defined as the presence of coronary plaque causing >50% luminal diameter stenosis and specified as 1-, 2-, 3-vessel disease or left main stem disease.
  • Patients were followed prospectively for 2.5 years. End-point was defined as the composite of all-cause mortality and non-fatal myocardial infarction.
  • CACS was defined and patients were categorized in subgroups as follows: CACS 0-10; 11-100; 101-400; 401-1000; >1000.
  • Framingham risk score (FRS) was calculated and patients were categorised as follows: low- (<10%); low-intermediate- (10-15%); high-intermediate- (15-20%); high risk (>20%)

Findings

  • There were 58 composite end-points (1.8%) during 24 months of follow-up. The overall Kaplan-Meier 2.5-year cumulative event estimate was 2.3%. Specifically, it was 1.3% among individuals with CACS ≤100, increasing to 5.1% among individuals with CACS >100. Among the subgroups within CACS >100, the composite event estimates increased proportionally with increasing CACS categories.
  • Adding CCTA to a model including the FRS did not improve significantly the prediction of composite end-point for patients with CACS ≤100. But the incremental value of CCTA over FRS was significant in patients with CACS >100. The benefit of CCTA over FRS was particularly evident for those with a CACS between 101 and 400, but it was attenuated when CACS increased >400.

My comments

  • This study shows that for risk stratification of asymptomatic individuals,  CCTA can have an added prognostic value. However it can be observed only in a well specified subpopulation of patients with moderately elevated CACS.
  • Previous landmark studies confirmed the predictive value of proven ischemia over the pure presence of coronary stenosis. In this study obstructive coronary artery disease was defined using 50% luminal diameter stenosis as definition. The latter is known to correlate very purely with the presence of ischemia. Accordingly, added prognostic value was observed only for the minority of the population.

This finding is aligned with previous data showing, that marked improvement in risk stratification cannot be expected from adding more pure morphologic data, but maybe more from adding functional information about ischemia (non-invasively or invasively defined).

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