Ex vivo evaluation of the Ozaki procedure in comparison with the native aortic valve and prosthetic valves

Abstract

Objectives: We investigated the hydrodynamic performance and cusp kinematics of the Ozaki neocuspidized aortic valve in comparison with the native aortic and prosthetic valves in an ex vivo study.

Methods: Native aortic valves of swine hearts were replaced by aortic valve substitutes, and their hydrodynamic performance (effective orifice area and mean pressure gradient) was evaluated in a mock circulation under defined conditions. The following aortic valve substitutes were investigated: native aortic valve, Ozaki valve, Perimount Magna Ease, Trifecta and St. Jude Medical Masters. All prosthetic valves had a labelled size of 21 mm.

Results: The Ozaki valve and native aortic valve showed a similar and significantly larger orifice area than all investigated prosthetic valves particularly at high flow rates. There was no significant difference between the Ozaki valve and the native aortic valve. The native aortic valve and Ozaki valve showed a similar increase in orifice area with increasing flow through the valve while prosthetic valves showed a markedly weaker increase. Similarly, the native and Ozaki valve showed a similar increase in mPG with forward flow which was weaker than prosthetic valves. Cusp kinematics were similar between the native and Ozaki valve, whilst prosthetic valves were clearly distinguishable from them.

Conclusions: The Ozaki procedure showed excellent hydrodynamic performance compared to prosthetic valves and showed similar cusp motion characteristics to the native aortic valve. Our results suggest that the Ozaki neocuspidized valve behaves physiologically in many aspects, which may contribute to beneficial clinical outcomes.

Keywords: Aortic valve replacement; Ex vivo; Hydrodynamic performance; Ozaki procedure; Valve motion.

Figure 1:

Study design and methods. (A) Flow chart of the investigated experimental groups. A fresh native porcine aortic root was dissected and connected to a Dacron prosthesis at the left ventricular outflow tract and the coronary arteries were ligated. Surgical aortic valve replacement was performed using 4 substitutes: the Ozaki valve, Perimount Magna Ease (PME) 21 mm, Trifecta (TRI) 21 mm and Masters mechanical heart valve (SJM) 21 mm. (B) Schematic depiction (left) and photographs (right) of the custom built mock circulation loop including the pulse duplicator (modified with permission from Scharfschwerdt et al. [10]). (1) Atrial reservoir, (2) disc valve, (3) cam plate, (4) piston pump, (5) adjustable input compliance, (6) fluid reservoir with an interchangeable aortic valve compartment, (7) visualization chamber, (8) adjustable aortic compliance, (9) non-linear resistance element, (10) height variable fluid column, (11) pressure sensor, (12) ultrasonic flow probe and (13) high-speed camera. (C) Exemplary illustration of GOA tracing.

Figure 2:

(A) Effective orifice area of the investigated aortic valves as a function of forward flow. Lines show quadratic regression lines. (B) Mean pressure gradient over the investigated aortic valves as a function of forward flow. Lines show quadratic regression lines.

Figure 3:

GOA-flow-time plots of (A) native aortic valve, (B) Ozaki valve, (C) Perimount Magna Ease, (D) Trifecta and (E) St. Jude Medical Masters HP.

Figure 4:

Overlay of GOA-flow-time plots of all investigated valves. (A) The maximum GOA was normalized to 100% for all valves. (B) Detailed view of GOA-flow-time plots at the very beginning of valve opening.