By Jeffrey Zimmet, MD, PhD
Associate Professor of Medicine, University of California, San Francisco; Director, Cardiac Catheterization Laboratory, San Francisco VA Medical Center
SYNOPSIS: Among those undergoing evaluation for transcatheter aortic valve replacement, coronary CT angiography and CT-derived fractional flow reserve demonstrated good diagnostic performance, potentially preventing invasive coronary angiography for many patients.
SOURCE: Peper J, Becker LM, van den Berg H, et al. Diagnostic performance of CCTA and CT-FFR for the detection of CAD in TAVR work-up. JACC Cardiovasc Interv 2022;15:1140-1149.
Assessment for obstructive coronary disease is part of the standard medical work-up before performing transcatheter aortic valve replacement (TAVR). Significant coronary artery disease (CAD) often is seen in patients with severe aortic stenosis (AS), with the prevalence affected by age and other comorbidities. Unrecognized obstructive disease in the proximal coronary vessels could negatively affect some patients during the TAVR procedure. As TAVR has moved into lower-risk and younger patients, the prevalence of CAD has decreased but remains significant. In younger and healthier patients, diagnosis of significant CAD before valve replacement becomes important in the context of potential issues with coronary access after TAVR. Thus, recognizing obstructive CAD may alter the timing of coronary intervention, the choice of TAVR valve, or (in some cases) lead to a preference for surgical AVR and coronary bypass grafting (CABG) over TAVR.
The standard approach in most centers has been to perform invasive coronary angiography in all patients considered for TAVR. Virtually all potential TAVR patients undergo ECG-gated coronary CT angiography (CCTA), which provides essential information about annulus sizing, vascular access, and tortuosity, as well as an assessment of the relationship of the coronary arteries to the valve apparatus. The same gated CT scan can, in most cases, be used to assess the coronary arteries themselves for the presence or absence of disease. However, the presence of marked calcification in many patients with aortic stenosis as well as appropriate caution in the use of beta-blockers to slow heart rate may lead to reduced sensitivity and specificity of CCTA. Peper et al asked whether the addition of CT-derived fractional flow reserve (CT-FFR), a technique that can be retrospectively applied to the standard TAVR protocol CCTA, could significantly improve the diagnostic accuracy of CCTA in pre-TAVR patients.
In this single-center, retrospective study, researchers assessed 818 consecutive patients referred for TAVR. They excluded 328 patients with a history of coronary revascularization. Of the remaining 490 patients, 99 produced CCTAs that were incompatible with CT-FFR; there were no imaging data available for 10 others. The authors excluded an additional 36 patients after they judged their CCTAs to be of low quality. Ultimately, 338 patients were included in the analysis. All patients underwent full analysis of the CCTA and CT-FFR, and all patients underwent invasive coronary angiography per protocol. In this analysis, coronary stenosis of more than 50% was deemed to represent significant CAD.
Compared with invasive angiography in this pre-TAVR population, CCTA carried a sensitivity of 69.7% and a specificity of 84%. Adding CT-FFR increased these values to 85.5% and 94.7%, respectively. The main advantage of CCTA in this population was to allow patients to forego invasive cardiac catheterization. For this reason, the negative predictive value (NPV) is particularly important information. CCTA on its own showed a NPV of 97.1%, which increased to 98.7% after applying CT-FFR. Using these techniques, the authors reported using CCTA would have allowed 43.6% of patients to avoid invasive coronary angiography, while 57.1% of patients could have done so after application of CT-FFR. They concluded CT-FFR improved the diagnostic accuracy of cardiac CT in the diagnosis of CAD in a pre-TAVR population. This finding would translate to a greater fraction of patients who could safely forego invasive angiography.
COMMENTARY
The focus of the Peper et al paper was the evaluation of CT-FFR as a diagnostic tool in the work-up of pre-TAVR patients. However, the more important story here was the focus on using CCTA to screen for significant CAD. As TAVR has moved to a lower-risk population, the added lifetime risk of coronary events in these younger patients adds even more importance to pre-TAVR assessment of coronary disease, since this may affect the choice of valve or even the choice of TAVR itself as a therapy.
Most patients still undergo invasive coronary angiography in preparation for TAVR. However, many also undergo gated CCTA to evaluate the valve itself and to plan for vascular access. The same CCTA, with essentially no added procedures, may be examined for coronary disease. In this study, among patients without a history of coronary revascularization, simple CCTA excluded the presence of significant CAD and prevented cardiac catheterization in nearly 44% of patients. The addition of CT-FFR raised this proportion to 57%. While this represented only 27% of the overall population (once patients with prior CABG or percutaneous coronary intervention were excluded), this means more than one-quarter of patients could be spared an additional invasive procedure on the way to TAVR. Using CCTA as a gatekeeper before reflexively obtaining invasive cardiac catheterization seems a rational step for most TAVR centers.
CT-FFR is not available in all centers today and remains a relatively costly addition to basic CCTA. Still, it may be worthwhile for clinicians to add this technique in patients for whom significant CAD is not effectively ruled out by CCTA. More work will be needed to determine whether these techniques may be applied to patients with a history of revascularization.
Among those undergoing evaluation for transcatheter aortic valve replacement, coronary CT angiography and CT-derived fractional flow reserve demonstrated good diagnostic performance, potentially preventing invasive coronary angiography for many patients.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content