Abstract
PurposeTranscatheter aortic valve implantation (TAVI) has been associated with large incidence of ischemic events, whose sources are still unclear. In fact, sub-acute complications cannot be directly related to the severity of the calcification in the host tissues, nor with catheter manipulation during the implant. A potential cause could be local flow perturbations introduced by the implantation approach, resulting in thrombo-embolic consequences. In particular, contrary to the surgical approach, TAVI preserves the presence of the native leaflets, which are expanded in the paravalvular space inside the Valsalva sinuses. The purpose of this study is to verify if this configuration can determine hemodynamic variations which may promote blood cell aggregation and thrombus formation. MethodsThe study was performed in vitro, on idealized models of the patient anatomy before and after TAVI, reproducing a range of physiological operating conditions on a pulse duplicator. The fluid dynamics in the Valsalva sinuses was analyzed and characterized using phase resolved Particle Image Velocimetry. ResultsComparison of the flow downstream the valve clearly indicated major alterations in the fluid mechanics after TAVI, characterized by unphysiological conditions associated with extended stagnation zones at the base of the sinuses. ConclusionThe prolonged stasis observed in the Valsalva sinuses for the configuration modelling the presence of transcatheter aortic valves provides a fluid dynamic environment favourable for red blood cell aggregation and thrombus formation, which may justify some of the recently reported thromboembolic and ischemic events. This suggests the adoption of anticoagulation therapies following TAVI, and some caution in the patients׳ selection.
Highlights
Transcatheter aortic valve implantation (TAVI) as compared with medical management and, in comparison with surgery, a significantly shorter length of stay and earlier improvement in functional status (Reynolds et al, 2012; Smith et al, 2011)
This paper presents a study aimed at verifying the hemodynamic variations produced by the presence of the native aortic valve in the paravalvular space, and its potential contribution to thrombosis and subacute Cerebrovascular Events (CEVs)
This study shows that the presence of transcatheter aortic valves produces unphysiological flows in the aortic root that result into stagnation at the base of the Valsalva sinuses, supporting the hypothesis that the presence of the native aortic valve in the paravalvular space might promote blood stasis, which is a main contributing factor towards thrombosis and thromboembolic events (Ducci et al, 2013; Rodés-Cabau et al, 2013)
Summary
TAVI as compared with medical management and, in comparison with surgery, a significantly shorter length of stay and earlier improvement in functional status (Reynolds et al, 2012; Smith et al, 2011). TAVI is associated with new complications which include recurrence of mild to moderate paravalvular leakage, resulting in a less favourable late survival (Makkar et al, 2012); higher risk of injuries to the atrioventricular conduction system producing partial or complete heart blockage (Eltchaninoff et al, 2011; Moat et al, 2011); and high incidence of procedural and subacute ischemic events and subclinical leaflets thrombosis (Astarci et al, 2011; Kahlert et al, 2010; Makkar et al, 2015; Rodés-Cabau et al, 2010; Samim et al, 2015).
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