Author + information
- Eric T. Chou,
- Pearl Zakroysky,
- Doug Hayden,
- Pamela Woodard,
- Stephen Wiviott,
- John Nagurney,
- Jerome Fleg,
- Hang Lee,
- David Schoenfeld,
- Udo Hoffmann and
- Quynh Truong
Whether a coronary artery calcium (CAC) study can be used alone to reliably exclude acute coronary syndrome (ACS) or provides added value to a coronary CT angiogram (CCTA) in emergency department (ED) patients with acute chest pain (ACP) remains unsettled.
In the multicenter ROMICAT II trial, we enrolled low to intermediate risk patients 40-74 years old with symptoms suggestive of ACS but without ischemic ECG changes or initial positive troponin. In this pre-specified subanalysis, we included 473 patients (54±8 years, 53% male) who underwent both CAC scanning and CCTA. The CAC study was not used in decision-making, while the CCTA was used to guide management. We evaluated the diagnostic accuracy of CAC=0 to exclude ACS and to meet safety threshold for missed ACS (defined as the upper bound 95% confidence interval [Ci] < 1%). The power was 92% to detect a missed ACS rate of >1% versus <0.01% at a 5% alpha by one-sided Exact binomial test. We also determined the radiation dose from CAC scanning and examined the relationship of high CAC scores and interpretability of CCTA.
Overall ACS (n=38) rate was 8%. There were 53% patients with CAC=0, while 7% had CAC>400. Among 253 patients with CAC=0, there were 2 patients with ACS (0.8%; 95% CI 0.1-2.8%). Specificity and negative predictive value of CAC=0 for determining ACS were 42% (95% CI 38-47%) and 84% (95% CI 78-88%), respectively. The discriminatory capacity of CAC=0 to exclude ACS was inferior to CCTA (c-statistic 0.76 vs. 0.91, p<0.001). The mean effective radiation dose from the CAC study was an additional 1.4 + 0.7 mSv. While the proportion of interpretable CCTAs decreased with increasing CAC score, the majority were deemed interpretable even among the highest CAC cutpoints (91% for CAC > 400, 87% for CAC > 600, 82% for CAC>800, 73% for CAC>1000).
In ED patients with ACP, a CAC score of zero cannot reliably exclude ACS with < 1% certainty and a high CAC score does not preclude reliable interpretation of CCTA in the vast majority of patients. Thus, CAC study prior to CCTA is not useful in this symptomatic cohort and confers unnecessary radiation exposure.
Moderated Poster Contributions
Poster Sessions, Expo North
Monday, March 11, 2013, 9:45 a.m.-10:30 a.m.
Session Title: Imaging: CT/Multimodality IX
Abstract Category: 20. Imaging: CT/Multimodality
Presentation Number: 1314M-355
- 2013 American College of Cardiology Foundation