Stent underexpansion is associated with high wall shear stress: a biomechanical analysis of the shear stent study.

Coronary stent underexpansion is associated with restenosis and stent thrombosis. In clinical studies of atherosclerosis, high wall shear stress (WSS) has been associated with activation of prothrombotic pathways, upregulation of matrix metalloproteinases, and future myocardial infarction. We hypothesized that stent underexpansion is predictive of high WSS. WSS distribution was investigated in patients enrolled in the prospective randomized controlled study of angulated coronary arteries randomized to undergo percutaneous coronary intervention with R-ZES or X-EES. WSS was calculated from 3D reconstructions of arteries from intravascular ultrasound (IVUS) and angiography using computational fluid dynamics. A logistic regression model investigated the relationship between WSS and underexpansion and the relationship between underexpansion and stent platform. Mean age was 63±11, 78% were male, 35% had diabetes, mean pre-stent angulation was 36.7°±14.7°. Underexpansion was assessed in 83 patients (6,181 IVUS frames). Frames with stent underexpansion were significantly more likely to exhibit high WSS (> 2.5 Pa) compared to those without underexpansion with an OR of 2.197 (95% CI = [1.233-3.913], p = 0.008). There was no significant association between underexpansion and low WSS (< 1.0 Pa) and no significant differences in underexpansion between R-ZES and X-EES. In the Shear Stent randomized controlled study, underexpanded IVUS frames were more than twice as likely to be associated with high WSS than frames without underexpansion.

Characterization of aortic root geometry in transcatheter aortic valve replacement patients.

PURPOSE: The study aimed to characterize the geometry of the aortic root pre- and post-transcatheter aortic valve replacement (TAVR) and investigate differences in pre- and post-TAVR anatomy. BACKGROUND: A greater understanding of how aortic root geometry changes after TAVR is needed to facilitate further investigation into the hemodynamic profiles of the post-TAVR aortic root. METHODS: Anatomical measurements were conducted on de-identified, retrospective post-TAVR 4DCT scans of 109 patients with aortic stenosis obtained from the RESOLVE study. The diameter of the aortic root was measured at the level of the annulus, left ventricular outflow tract (LVOT), sinus of Valsalva, sinotubular junction (STJ) and ascending aorta. The heights of the STJ and coronary arteries were also measured. RESULTS: All aortic root dimensions were normally distributed across the cohort and changed significantly between pre- and post-TAVR conditions (P < 0.01). Post-TAVR dimensions changed significantly from peak systole to end diastole (P < 0.01). Regression models were obtained for all aortic root dimensions in terms of annulus diameter with excellent coefficient of determination (R2 > 0.95, P < 0.001). CONCLUSIONS: There are significant differences between pre- and post-TAVR as well as peak systolic and end diastolic aortic root anatomy. Appropriate anatomical dimensions should be selected for benchtop testing as the geometry varies greatly throughout the cardiac cycle.