Use of Coronary Computed Tomographic Angiography to Guide Management of Patients With Coronary Disease

Background In a prospective, multicenter, randomized controlled trial, 4,146 patients were randomized to receive standard care or standard care plus coronary computed tomography angiography (CCTA). Objectives The purpose of this study was to explore the consequences of CCTA-assisted diagnosis on invasive coronary angiography, preventive treatments, and clinical outcomes. Methods In post hoc analyses, we assessed changes in invasive coronary angiography, preventive treatments, and clinical outcomes using national electronic health records. Results Despite similar overall rates (409 vs. 401; p = 0.451), invasive angiography was less likely to demonstrate normal coronary arteries (20 vs. 56; hazard ratios [HRs]: 0.39 [95% confidence interval (CI): 0.23 to 0.68]; p < 0.001) but more likely to show obstructive coronary artery disease (283 vs. 230; HR: 1.29 [95% CI: 1.08 to 1.55]; p = 0.005) in those allocated to CCTA. More preventive therapies (283 vs. 74; HR: 4.03 [95% CI: 3.12 to 5.20]; p < 0.001) were initiated after CCTA, with each drug commencing at a median of 48 to 52 days after clinic attendance. From the median time for preventive therapy initiation (50 days), fatal and nonfatal myocardial infarction was halved in patients allocated to CCTA compared with those assigned to standard care (17 vs. 34; HR: 0.50 [95% CI: 0.28 to 0.88]; p = 0.020). Cumulative 6-month costs were slightly higher with CCTA: difference $462 (95% CI: $303 to $621). Conclusions In patients with suspected angina due to coronary heart disease, CCTA leads to more appropriate use of invasive angiography and alterations in preventive therapies that were associated with a halving of fatal and non-fatal myocardial infarction. (Scottish COmputed Tomography of the HEART Trial [SCOT-HEART]; NCT01149590)

The SCOT-HEART (Scottish COmputed Tomography of the HEART) trial showed that, when used in addition to standard care, CCTA markedly clarified the diagnosis for patients with suspected angina due to coronary heart disease (3). This diagnostic improvement was associated with alterations in downstream investigations and treatments and with potential improvements in clinical outcome. However, whether CCTA-guided changes in diagnosis led to appropriate improvements in invasive coronary angiography and initiation of preventive treatments, and whether these changes could be attributable to an improvement in clinical outcome, has not been explored.
It would be neither practical nor ethical to undertake invasive coronary angiography in all patients within a large trial of a noninvasive diagnostic test for angina pectoris due to coronary heart disease. However, a reasonable proxy for the assessment of diagnostic accuracy is to compare the rates of normal coronary arteries or obstructive coronary artery disease at the time of invasive coronary angiography.
To assess the appropriateness of therapy would again be inferential and requires the assessment of improvements in clinical outcomes directly attributable to coronary heart disease. For these clinical improvements to occur, the changes in management consequent on the diagnostic test have to be implemented and temporally associated with any observed benefits. Clearly, it is not sufficient for the test to be merely performed.
In this study, we aimed to assess the diagnostic utility of CCTA against the findings at invasive coronary angiography, and to investigate the timing and therapeutic implementation of CCTA-guided changes in preventive treatment. Finally, we explored the beneficial effects of these investigative and therapeutic implementations on coronary heart disease events.

METHODS
STUDY DESIGN. The SCOT-HEART study was a prospective, open-label, parallel group, multicenter, randomized controlled trial that assessed the role of CCTA in patients with suspected angina due to coronary heart disease who attended a cardiology clinic.
The study design has previously been described in detail (4)

DISCUSSION
We have previously reported that CCTA clarifies the diagnosis, changes treatments and investigations, and may improve outcomes in patients with suspected angina pectoris due to coronary heart disease.
However, whether these changes in management were appropriate and could be plausibly related to apparent improvements in outcomes remained to be  therapies (13,14) as well as lifestyle modification (14,15). A single-center registry of 8,372 patients with nonobstructive coronary artery disease identified by CCTA also showed that statin therapy was associated with lower mortality, but aspirin therapy was only associated with lower mortality in high-risk patients (16,17). However, all of these observational studies have many potential biases, including case selection bias and confounding by treatment allocation. Our study avoids these biases through the conduct of a randomized controlled trial of all patients attending the cardiology clinic for suspected angina pectoris due to coronary heart disease. Because the allocation of imaging was randomized, the subsequent downstream alterations in treatment can be attributable to the imaging intervention. In addition, although the SCOT-HEART trial event rates were relatively modest, the rates of fatal and nonfatal MI in trial participants were greater than those observed in asymptomatic individuals (9,16) and similar to those in symptomatic patients with stable disease (18,19).     Post hoc landmark analysis at 50 days to account for the implementation and treatment delay consequent on the conduct, reporting, and communication of the coronary computed tomography angiography (CCTA) findings. HR ¼ hazard ratio.
Williams et al. Clinical Effect of CCTA in Suspected Angina Pectoris A P R I L 1 9 , 2 0 1 6 : 1 7 5 9 -6 8 median of 5 years to allow the accrual of more events that will enable more precise estimates of benefit and facilitate the further exploration of our secondary endpoints.

CONCLUSIONS
We have demonstrated that CCTA facilitates the more appropriate and effective selection of invasive coronary angiography for patients with suspected angina due to coronary heart disease. CCTA also changed the downstream prescribing of preventive therapies and the application of coronary revascularization procedures that were associated with an apparent halving in the rates of fatal and nonfatal MI.