Transcatheter aortic valve replacement alters ascending aortic blood flow and wall shear stress patterns: A 4D flow MRI comparison with age-matched, elderly controls

Abstract

Background With the implementation of transcatheter aortic valve replacement (TAVR) in lower-risk patients, evaluation of blood flow characteristics and the effect of TAVR on aortic dilatation becomes of considerable interest. We employed 4D flow MRI in the ascending aorta of patients after TAVR to assess wall shear stress (WSS) and compare blood flow patterns with surgical aortic valve replacement (SAVR) and age-and gender-matched controls. Methods Fourteen post-TAVR patients and ten age-and gender-matched controls underwent kt-PCA accelerated 4D flow MRI of the thoracic aorta at 3.0 Tesla. Velocity and wall shear stress was compared between the two groups. In addition, aortic flow eccentricity and displacement was assessed and compared between TAVR patients, controls and 14 SAVR patients recruited as part of an earlier study. Results Compared to controls, abnormally elevated WSS was present in 30±10% of the ascending aortic wall in TAVR patients. Increased WSS was present along the posterior mid-ascending aorta and the anterior distal-ascending aorta in all TAVR patients. TAVR results in eccentric and displaced flow in the mid-and distal-ascending aorta, whereas blood flow displacement in SAVR patients occurs only in the distal-ascending aorta. Conclusion This study shows that TAVR results in increased blood flow velocity and WSS in the ascending aorta compared to age-and gender-matched elderly controls. This finding warrants longitudinal assessment of aortic dilatation after TAVR in the era of potential TAVR in lower-risk patients. Additionally, TAVR results in altered blood flow eccentricity and displacement in the mid-and distal-ascending aorta, whereas SAVR only results in altered blood flow eccentricity and displacement in the distalascending aorta. Key Points • TAVR results in increased blood flow velocity and WSS in the ascending aorta.• Longitudinal assessment of aortic dilatation after TAVR is warranted in the era of potential TAVR in lower-risk patients.• Both TAVR and SAVR result in altered blood flow patterns in the ascending aorta when compared to age-matched controls.

Hemodynamic Profiles Before and After Surgery in Bicuspid Aortic Valve Disease—A Systematic Review of the Literature

“…All ARR studies reported data on the flow pattern or helicity in the aortic arch, with four also reporting WSS, and four reporting PV values. Three studies of isolated AVR identified by the initial search criteria did not provide characteristics of the native valve type of included patients ( 60 – 62 ). These were therefore not included in the summary table, however their results were deemed to be important in understanding post-operative hemodynamic changes, and have been reviewed below.…”

“…To date few studies have examined the hemodynamic effects after TAVI, and none have included BAV patients. One report found TAVI results in increased flow eccentricity and flow displacement in the AAo compared to surgical AVR and controls ( 62 ). Others have shown reduced helical flow with TAVI (Edwards Sapien XT) compared to bioprosthetic AVR, but still abnormal compared to healthy controls ( 60 ).…”

Fully quantitative mapping of abnormal aortic velocity and wall shear stress direction in patients with bicuspid aortic valves and repaired coarctation using 4D flow cardiovascular magnetic resonance

“…All datasets [ 5 ] as well as a subgroup of patients with repaired coarctation and healthy subjects [ 29 ] were previously used for the evaluation of abnormal magnitude of hemodynamics. Furthermore, a subgroup of the healthy subjects was used to evaluate abnormal hemodynamics in patients with transcatheter aortic valve repair and implantation of a bileaflet mechanical valve [ 30 , 31 ]. All participants provided written informed consent.…”

Is wall shear stress ready to become a prime-time clinical tool?—measurement of post-surgical patterns in patients undergoing aortic valve and thoracic aortic replacement using 4-dimensional flow magnetic resonance imaging

“…The work by Bolleche and others demonstrates that WSS is now a reliable technique, capable of being deployed in a routine clinical setting (1,10,11). What is now needed are large, prospective longitudinal studies that link these observations to clinically relevant outcomes.…”