Combined Coronary CT-Angiography and TAVI Planning: Utility of CT-FFR in Patients with Morphologically Ruled-Out Obstructive Coronary Artery Disease

Figure 1. Flowchart of the study population according to diagnostics received. CAD−—no obstructive CAD on cCTA; CAD+—obstructive CAD (stenosis ≥50%) on cCTA; cCTA—coronary CT-angiography; CT-FFR—CT-derived fractional flow reserve; cCTA—coronary CT-angiography; ICA—invasive coronary angiography; QCA—quantitative coronary analysis.

Figure 2. Dot-plot of cCTA image quality parameters and categorization according to ML-based CT-FFR of patients without morphological signs of obstructive CAD on cCTA. Recategorization of patients as false positive was independent of image quality, regardless of the concrete measure and accrued with comparable frequency in exams with diagnostic, good and exceptional image quality. The standard of reference was ICA with QCA. Thresholds were ≥50% diameter for cCTA and QCA and ≤0.80 for CT-FFR. Note—the two patients and vessels falsely categorized as negative with cCTA were excluded from this plot. cCTA—coronary CT-angiography; FN—false negative; FP—false positive; HU—Hounsfield units; ICA—invasive coronary angiography; ML—machine learning; QCA—quantitative coronary analysis.

Figure 3. Dot-plot of patients’ and vessels’ CAC and categorization according to ML-based CT-FFR of cCTA studies without morphological signs of obstructive CAD on cCTA. Recategorization of patients and vessels was independent of CAC, occurring with roughly equal frequency with various extents of CAC. The standard of reference was ICA with QCA. Thresholds were ≥50% diameter for cCTA and QCA and ≤0.80 for CT-FFR. Note—the two patients and vessels falsely categorized as negative with cCTA were excluded from this plot. CAC was not available for all patients. CAC—coronary artery calcium score; cCTA—coronary CT-angiography; CX—circumflex artery, FN—false negative; FP—false positive; ICA—invasive coronary angiography; LAD—left anterior descending artery; ML—machine learning; RCA—right coronary artery; QCA—quantitative coronary analysis.

Figure 4. CT-FFR rendering values indicating hemodynamic significance with no apparent luminal narrowing on cCTA nor ICA: Mildly calcified left coronary artery (total CAC = 72 AU) with trifurcation into left anterior descending (LAD), left circumflex (LCX) and intermediate artery. CT-FFR values drop below 0.80 between the middle and distal segment (segment 6/7) (asterisk) (a). There is no discernable luminal obstruction on cCTA depicted as curved multiplanar reformation (b) nor on the corresponding projection of ICA (c). CAC—coronary artery calcium score; cCTA—coronary CT-angiography; CT-FFR—CT-derived fractional flow reserve; ICA—invasive coronary angiography.

Figure 5. CT-FFR confirming negative cCTA: Heavily calcified left coronary artery (total CAC = 1834 AU) with trifurcation into left anterior descending (LAD), left circumflex (LCX) and intermediate artery without luminal obstruction depicted on cCTA as curved multiplanar reformation (a) and volume-rendered technique (b). The corresponding projection of invasive coronary angiography shows no stenosis (c). CT-FFR shows normal values well above 0.80 up to the distal vessels with a physiological drop-off of values only in the most distal runoffs (d). CAC—coronary artery calcium score; cCTA—coronary CT-angiography; CT-FFR—CT-derived fractional flow reserve. Adapted with permission from Gohmann et al. [8].