The guidelines recommend coronary CT only in the subset of patients with low to intermediate risk of coronary artery disease (CAD) due to its limited positive predictive value and lack of functional information resulting in a lower cost effectiveness, and they state that patients with intermediate to high risk should undergo a stress imaging–based strategy.
Stress computed tomography myocardial perfusion (CTP) recently emerged as a potential strategy to combine the anatomic and functional evaluation of CAD in a single scan. But in most cases, these trials were performed with previous-generation scanners, did not include patients at intermediate to high risk for CAD, and typically compared coronary CTA versus invasive coronary angiography (ICA) alone or versus the combination of ICA plus non invasive stress testing.
Recently, a newer coronary CTA technology was introduced (Revolution CT), featuring 16-cm wide coverage, 0.23 mm of spatial resolution, faster gantry rotation time with an intracycle motion-correction algorithm, and the latest generation iterative reconstruction.
A new study by Monzino,1 – whose preliminary results were presented at the 12th Annual Meeting of the Society of Cardiovascular Computer Tomography (SCCT), held in Washington on July 2017, – shows in consecutive patients at intermediate to high risk for CAD that the addition of stress CTP to coronary CTA with a novel generation of a whole heart coverage CT scanner significantly increased overall specificity, positive predictive value, and accuracy in vessel-based and patient-based models. It is noteworthy that stress CTP correctly reclassified 18 of 23 patients with coronary CTA false-positive findings, suggesting a potential reduction of 78% of unnecessary invasive evaluation among patients with positive coronary CTA. See a representative case example in Figure 1.
About the effective radiation exposure, for stress CTP, the cumulative mean effective dose was lower than 3 mSv thanks to the new technology that is half of effective dose of ICA plus invasive FFR.
“To the best of our knowledge, – state Dr Andrea Baggiano, study investigator and staff member of OU Cardiac MR of Centro Cardiologico Monzino, – this is the first study that prospectively evaluated the incremental value of a combined protocol of coronary CTA plus stress CTP using the latest generation whole-heart coverage CT scanner and ICA plus invasive FFR as the reference standard in consecutive patients at intermediate to high risk for CAD”.
From a translational point of view, the use of stress CTP in patients at intermediate to high risk for CAD is a feasible and effective strategy for improving the diagnostic accuracy of coronary CTA. If obstructive CAD is not detected by coronary CTA, stress CTP is not needed. However, if an obstructive or non evaluable coronary artery segment is detected, stress myocardial CTP may be considered as a useful tool to improve diagnostic accuracy. Further studies are warranted to evaluate the prognostic value and cost-effectiveness of the promising technique used in our study.
- Pontone G, Andreini D, Guaricci AI, Baggiano A, Fazzari F, Guglielmo M, Muscogiuri G, Berzovini CM, Pasquini A, Mushtaq S, Conte E, Calligaris G, De Martini S, Ferrari C, Galli S, Grancini L, Ravagnani P, Teruzzi G, Trabattoni D, Fabbiocchi F, Lualdi A, Montorsi P, Rabbat MG, Bartorelli AL, Pepi M. Incremental Diagnostic Value of Stress Computed Tomography Myocardial Perfusion With Whole-Heart Coverage CT Scanner in Intermediate- to High-Risk Symptomatic Patients Suspected of Coronary Artery Disease. JACC Cardiovasc Imaging. 2018 Feb 9. pii: S1936-878X(17)31149-X. doi: 10.1016/j.jcmg.2017.10.025. [Epub ahead of print]