Excluding significant coronary artery disease in patients planned for TAVR using CT: Diagnostic accuracy of newest generation dual source photon counting scanner compared to coronary angiography
Authors: Zuhair Kassem T , Achenbach S , Marwan M 
Published: October 2024

Abstract

Introduction
Patients with significant aortic stenosis routinely undergo CT for evaluation of the aortic root prior to interventional aortic valve replacement (TAVR). Assessment of CAD is usually performed by invasive coronary angiography. We assessed the diagnostic accuracy of the latest generation dual source photon counting scanner for exclusion of relevant CAD in a contemporary TAVR cohort.

Methods
Patients referred for cardiac CT prior to transcatheter aortic valve implantation were screened for inclusion this analysis. All cardiac CT exams were performed by dual source photon counting scanner (NAEOTOM alpha, Siemens healthineers, Germany). CT acquisitions were performed using retrospectively triggered spiral acquisition (30-70% of the cardiac cycle) without ultra-high resolution. For each patient, several reconstructions were rendered (thin slice reconstruction with 0.4 mm slice thickness: best diastolic phase, best systolic phase, 200-350 ms folllowing R-wave in 50 ms intervals as well as 0.6 mm slice thickness multiphase reconstruction 0-90% of the cardiac cycle in 10 % increments). Assessment of significant CAD was performed in CT and invasive angiography on a per-vessel analysis and a per-patient analysis using 2 thresholds: ≥ 50% stenosis and ≥ 70% stenosis. Assessment of stenoses in CT was performed using multiplanar reconstructions (MPR) and curved MPR and only in vessels &gt; 1.5mm diameter. Assessment of stenosis in invasive angiography was performed using the projection with the most relevant lumen reduction. Image quality in CT was assessed on a likert scale from 1 to 4 (1=excellent, 2=minor artifacts, 3=major artifacts still assessable, 4=non-assessable).

Results
In this analysis 31 consecutive patients were included (mean age 79.5y, 64.5% males, 35.5% females). Mean heart rate was 66.5 bpm and 19% were in atrial fibrillation during CT acquisition. Mean image quality was 1.4. 13 Patients had no relevant CAD (stenosis ≥50%) in invasive angiography and in 18 patients at least 1 vessel was deemed to have ≥ 50% stenosis in invasive angiography. On a per vessel analysis, sensitivity, specificity and accuracy of cardiac CT to exclude stenoses using 50% and 70% thresholds were 98%, 93% and 94% vs. 97%, 93% and 94%, respectively. Negative likelihood ratio was 0.02 vs. 0.03 respectively. On a per-patient level, sensitivity and specificity were 100%. Out of 31 patients, only 2 vessels in 2 patients were deemed non-assessable. 3 patients with previous PCI as well as 3 patients with previous CABG were included in this analysis. Only 1 false negative vessel was reported in a very distal LAD segment.

Conclusion
Using newest generation dual source CT with photon counting, CT allowed highly reliable diagnostic workup regarding the presence of CAD in this TAVR cohort. The use of CT to assess CAD in TAVR patients seems clinically feasible especially in patients without previous percutaneous revascularisation.