DOES THE GEOMETRY OF THE ASCENDING AORTIC PROSTHESIS AFFECT TRANSVALVULAR HEMODYNAMICS? EXPERIMENTAL STUDY AND ONE CLINIC'S EXPERIENCE

Highlights

• Preservation of native aortic root geometry improves transvalvular hemodynamics (optimal opening and closing of the flaps, minimal transvalvular gradient and minimal energy loss) in comparison with classical prosthetics with cylindrical valve-containing conduit, as demonstrated in the experiment.
• When comparing postoperative parameters using root-conserving and root-bearing prosthetic techniques in comparable groups, confirmation of the experimental data was found.
• Preservation of native aortic root geometry in Bentall-type surgeries offers advantages in the form of better left ventricular remodeling (reduced myocardial mass and end-diastolic volume).

Abstract

Background. Currently, various modifications of this operation have been proposed, and valve-containing conduits of different designs are produced – with linear aortic prosthesis and with sinus prosthesis (so-called Valsalva-graft), with mechanical prosthesis and with biological prosthesis. The search for an optimal valve-containing conduit, implantation of which would be associated with greater freedom from prosthesis-dependent complications, is ongoing. Preservation of natural transprosthetic hemodynamics is one of the priority objectives of conduit design. Therefore, this study investigates the role of aortic prosthesis geometry in hemodynamics.

Aim. To evaluate whether the geometry of an ascending aortic valve-containing prosthesis affects transvalvular hemodynamics by comparing a linear valve-containing conduit with a native aortic root.

Methods. We recreated transvalvular hemodynamics in WETLAB and compared transvalvular hemodynamic parameters in two surgeries-flap + native root surgery and flap + linear prosthesis surgery-in a pulse duplicator (ViVitro Labs Inc., Canada). Ten conduits (23 mm in size) were prepared, and hemodynamics measurements were continued for 10 cycles of opening-closing.

Experimental data were also compared with postoperative results for similar operations with and without aortic root preservation.

Results. In the first stage, it was found that, all other things being equal, the geometry of the native porcine aortic root provided better aortic leaflet function than the linear prosthesis. In the aortic root-preserved operation, the valve opening area was larger and the closing velocity was lower, resulting in less resistance to opening and less energy loss at closure. At the second stage, we studied the clinical results of operations in which the aortic root was preserved and in which it was replaced by a linear prosthesis (the compared groups were comparable in terms of the size of the fibrous ring and left ventricular dimensions; only hemodynamic parameters were evaluated, since otherwise these operations could not be compared). Results comparable to the experimental ones were obtained. It turned out that these differences had clinical significance – the reverse remodeling of the left ventricle was faster when the aortic root geometry was preserved.

Conclusion. When creating valve-containing prostheses to replace aortic root structures, native geometry should be mimicked to achieve the most natural transvalvular hemodynamics.

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