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Page 4 of 11 Raval et al. Vessel Plus 2024;8:5 https://dx.doi.org/10.20517/2574-1209.2023.99

only 21.5% needed PCI, which was performed before, concomitantly, or after TAVI. Thirty-day and 1-year
major cardiovascular and cerebrovascular events post-TAVI were similar in patients who only received
coronary CTA compared to both CTA and ICA.

In a meta-analysis of 7 studies totaling 1,275 patients treated with TAVI, an attempt was made to evaluate
the performance of coronary CTA for accurate detection of CAD . Sensitivity was noted to be 95%, with a
[18]
negative predictive value (NPV) of 94%. Specificity was poor at 65%. However, given the high NPV, the
routine use of coronary CTA could reduce the need for pre-TAVI ICA by 37%.

Another retrospective study in 1,060 patients validated these results by showing that pre-TAVI coronary
CTA excludes > 50% stenosis with a sensitivity of 96.4% and a NPV of 98% . For > 70% stenosis, it offers a
[19]
sensitivity of 96.7% and NPV of 99%. It was suggested that coronary CTA would reduce the need for ICA by
52%-70%, depending on the severity of stenosis used to define CAD.

The addition of fractional flow reserve to CT with FFR-CT provides the additional advantage of obtaining
physiologic in addition to anatomic assessment of CAD. FFR-CT uses the coronary CTA to perform
segmentation of the coronary arteries, providing the coronary flow dynamics, and allowing physiological
[20]
information about the stenotic lesion . A prospective study assessing CT-FFR to invasive FFR in 42
patients with severe aortic stenosis found sensitivity, specificity, positive predictive, and negative predictive
values for physiologically significant CAD to be 76.5%, 77.3%, 72.2%, and 81.0%, respectively, with a 76.9%
diagnostic accuracy . These results are similar to patients who have CT-FFR without aortic stenosis. In
[21]
another study in 296 patients with stable angina and with intermediate to high pre-test likelihood of CAD,
Peper et al. reported a similar sensitivity of 81.2%, specificity of 83.3%, positive predictive value of 84.1%,
and negative predictive value of 80.2%, with an overall diagnostic accuracy of 82.2% . Thus, it is possible
[22]
for FFR-CT to become a first-line test for CAD evaluation in aortic stenosis patients, at least in young
patients with a lower pre-test likelihood of CAD.

However, there are major limitations to coronary CTA imaging. In patients with prior PCI and significant
CAD, coronary CTA is less likely to provide adequate imaging due to stent artifact or severe coronary artery
calcifications . In these patients, ICA still remains the first line and gold standard test for CAD evaluation.
[23]
Catheterization and ICA offer additional benefits that cannot be obtained with coronary CTA.
[24]
Hemodynamic assessment of the severity of AS can be determined invasively prior to TAVI . When the
severity of CAD is intermediate, ICA offers options to obtain a functional physiological assessment of the
lesion and decide whether PCI is indicated and potentially beneficial. Pre-procedure ICA may also better
help identify whether SAVR + CABG may be more beneficial than TAVI + PCI. However, for patients who
are not surgical candidates for AVR, or who are elderly with a low probability of CAD or need for PCI, it is
reasonable to avoid CAD assessment pre-TAVI and proceed directly to TAVI.

Fractional flow reserve (FFR) and instantaneous wave-free ratio (iFR) with ICA provide invasive
physiologic assessment of CAD. A retrospective study by Stanojevic et al. assessed the safety of IV
adenosine during FFR evaluation of intermediate CAD in patients who had severe AS . The study
[25]
demonstrated good tolerance of adenosine without any significant adverse events.

[26]
However, the interpretation of FFR and iFR in the setting of severe AS remains debatable . Patients with
severe AS have left ventricular hypertrophy, which has the potential to alter coronary blood flow and thus
affect FFR results. A prospective study of 28 patients by Ahmad et al. demonstrated that systolic and