Visualization of the coronary arteries by photon counting CT in data sets acquired for TAVI planning: Analysis of image quality for assessing coronary artery disease

Silvia Smolka (Erlangen)1, M. Moshage (Erlangen)1, M. Marwan (Erlangen)1, S. Achenbach (Erlangen)1

1Universitätsklinikum Erlangen Medizinische Klinik 2 Erlangen, Deutschland


The diagnostic accuracy of coronary CT angiography substantially depends on image quality. In data sets acquired for the preparation of transcatheter aortic valve implantation, arrhythmia, lack of heart rate control and the inability to administer nitrates for coronary dilatation, along with often substantial coronary calcification, impact image quality and may limit the ability to rule out coronary stenoses. With the improved resolution of photon counting CT, some of these limitations might be overcome. We therefore investigated whether pre-procedural photon counting cardiac CT for TAVI yields diagnostic image quality for coronary assessment and may help avoid subsequent invasive coronary angiography in a patient group well known for frailty. 

We analyzed 79 consecutive patients who underwent pre-procedural cardiac CT for TAVI at our institution from September to October 2023, using a photon counting CT scanner (Siemens Naeotom Alpha). Imaging protocols aimed at optimal visualization of the aortic annulus by using retrospective image acquisition, no specific adjustments were made for optimizing for coronary visualization (e. g. no administration of nitrates or beta blockers). Heart rate, heart rhythm (sinus rhythm vs. arrhythmia including AF/PVC) and scan parameters (keV; mAS, CTDI) were recorded. Coronary arteries were classified as „fully diagnostic“ vs. „non-diagnostic“, depending on the ability to detect or rule out coronary artery stenoses in segments ≥ 2.0 mm diameter. 

Of the 79 patients, 61% were male with a mean age of 80 +/- 7 years. Mean heart rate was 70 ± 13 bpm with sinus rhythm at the time of the scan in 68% of patients. Scan parameters included 138 +/- 6.6 keV tube voltage and 396.2 +/- 180.2 mAS tube current, resulting in an average radiation dose (CTDI) of 40 +/- 17.9 mGy. Fully diagnostic image quality to rule in or rule out coronary artery stenoses was found in 45 cases (57%).  Fully diagnostic image quality was significantly more frequent in patients with sinus rhythm (70% vs. 23%, p < 0.001) and in patients with lower heart rates: heart rate below 70 bpm (70% vs 40%, p = 0.007). In patients with sinus rhythm and a heart rate < 65 bpm (n = 28), fully diagnostic image quality was found in 82%. In multivariable regression analysis, presence of sinus rhythm was the only independent predictor of fully diagnostic image quality (p < 0.001). 
In pre-procedural photon counting CT scans acquired for TAVI, fully diagnostic image quality to rule out coronary artery stenoses could be achieved in the majority of patients with sinus rhythm. This may allow to avoid invasive angiography in selected patients scheduled for TAVI which is of clinical relevance in this patient group known for frailty. 
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