Minimum stent area, stent expansion and ultrasonic flow ratio post pci: insights from multivessel talent trial

Background Ultrasonic flow ratio (UFR) is a novel method for fast computation of fractional flow reserve (FFR) from intravascular ultrasound. Recently studies have shown the feasibility of morphofunctional computational methods to reliably estimate coronary physiology from intravascular ultrasound images. Purpose To assess minimum stent area and stent expansion and its relation to ultrasonic flow ratio post percutaneous coronary intervention. Methods The study population consisted of 150 consecutive patients (280 vessels) who underwent intravascular ultrasound for optimization of PCI for three vessel disease as mandated in the ongoing MULTIVESSEL TALENT trial (NCT04390672). The UFR analysis was performed at the CORRIB Core Lab by an analyst who was blinded to the clinical data using a prototype software package (IvusPlus prototype, Pulse Medical Imaging Technology, Shanghai, China). The stent expansion and minimum stent area was automatically detected by the software. Results The median and mean UFR of 280 vessels post-PCI was 0.94 (0.91-0.97).and 0.93±0.04, respectively. Twenty three percent (n=115) of the 280 vessels had a UFR less than 0.91.The average minimum stent area (MSA) among the population was 5.82 ± 1.95 mm2. The mean stent expansion among the population was 97% ± 22%. We compared the site reported MSA with the software derived MSA which showed strong correlation (r=0.859; P<0.001). There was no correlation between MSA and UFR (r= -0.13, P=0.81). The stent expansion among patients who had UFR <0.91 when compared to ≥0.91 was significantly lower (82% vs 98%, P<0.001). The delta UFR within the stent was significantly higher in patients who had a UFR<0.94 vs ≥0.94 (0.06 vs 0.02; P<0.01). Delta UFR within the stent was higher when the stent expansion was <80% and <90% when compared to >80% and >90% (0.07 vs 0.03; P<0.01) and (0.06 vs 0.02; P<0.01) respectively. Conclusion Combination of IVUS and FFR enables the operator to conform to highest standards in PCI. This study demonstrates that UFR is not related to the minimum stent area, and patients who have UFR <0.94 have sub-optimal stent expansion.MSA and UFRUFR and Stent expansion