Key result
In an in vitro pulse duplicator model, the Triflo trileaflet mechanical heart valve preserved early helical flow and angular momentum, whereas the bileaflet valve acted as a flow straightener.
Why the study?
Recent studies suggest early helical flow occurs in the valve plane, but the existence of premature ventricular outflow swirl and how different mechanical valve designs impact its preservation remain unknown.
Does the Triflo trileaflet mechanical heart valve preserve early helical flow better than a bileaflet valve in an in vitro pulse duplicator model?
Does the Triflo trileaflet mechanical heart valve preserve early helical flow better than a bileaflet valve in an in vitro pulse duplicator model?
The Triflo trileaflet mechanical heart valve preserves physiological early helical flow better than a classical bileaflet valve in an in vitro model, suggesting potential hemodynamic benefits.
Early LVOT swirl observation is preliminary; leaves open physiological role and requires prospective validation before any clinical relevance.
Background - Physiological helical flow in the ascending aorta has been well documented in the last two decades, accompanied by discussions on possible physiological benefits of such axial swirl. Recent 4D-MRI studies on healthy volunteers have shown indication of early generation of helical flow, early in the systole and already close to the valve plane. Objectives - Firstly, the aim of the study is to investigate the hypothesis of premature swirl existence in the ventricular outflow tract leading to already helical flow in the valve plane, and second to investigate the possible impact of two different mechanical valves design on the preservation of this early helical flow and its subsequent hemodynamic consequences. Methods - We use a pulse duplicator with an aortic arch and High Speed Particle Image Velocimetry to document the flow evolution in the systolic cycle. The pulse-duplicator is modified with a swirl-generating insert to generate early helical flow in the valve plane. Special focus is laid on the interaction of such helical flow with different designs of mechanical prosthetic heart valves, comparing a classical bileaflet mechanical heart valve, the St Jude Medical Regent valve (SJM Regent BMHV) with the Triflo trileaflet mechanical heart valve T2B version (Triflo TMHV). Results – When the swirl-generator is inserted, a vortex is generated in the core flow demonstrating early helical flow in the valve plane, similar as observed in the recent 4-D-MRI study taken for comparison. For the Triflo trileaflet valve, the early helical flow is not obstructed in the central orifice, similar as in the case of the natural valve. Conservation of angular momentum leads to radial expansion of the core flow and flattening of the axial flow profile downstream in the arch. Furthermore, the early helical flow helps to overcome separation at the outer and inner curvature. In contrast, the two parallel leaflets for the bileaflet valve impose a flow straightener effect, annihilating the angular momentum with negative impact on kinetic energy of the flow. Conclusion - The results imply better hemodynamics for the Triflo trileaflet valve based on hydrodynamic arguments under the discussed hypothesis. In addition, it makes the Triflo valve a better candidate for replacements in patients with pathological generation of nonaxial velocity in ventricle outflow tract.
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Bruecker et al. (2020) studied Mechanical heart valve replacement. Triflo trileaflet mechanical heart valve vs. St Jude Medical Regent bileaflet mechanical heart valve was evaluated on Flow evolution and preservation of early helical flow. In an in vitro pulse duplicator model, the Triflo trileaflet mechanical heart valve preserved early helical flow and angular momentum, whereas the bileaflet valve acted as a flow straightener.
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