Purpose

The goal of this study was to demonstrate the range in effective orifice area (EOA) values that may be possible given the ISO 5840 definition of EOA and the practical limits in the accurate measurement of pressure differential across large diameter valves.

Methods

A 31 mm mechanical valve was tested on a commercially available pulse duplicator configured for mitral valve testing and tuned to nominal conditions. The experimental data was used as a basis for performing Monte Carlo analyses with published specifications for commonly used pressure sensors as well as measurement equipment accuracy requirements described in ISO 5840. The sources of error were modeled as normally distributed random variables and the simulation was iterated 1,000,000 times.

Results

Experimentally-derived EOAs ranged from 2.7 to 5.0 cm², while the Monte Carlo simulation provided results ranging from approximately 0.4 to 6.7 cm². Many of these results are clearly non-physical with EOAs larger than the valve’s geometric orifice area and exceedingly short positive pressure differential periods, yet they align with other published results for the same valve model.

Conclusions

The volatility of the standard EOA formulation at low mean gradients combined with the difficulty in accurately measuring such small differentials with industry-standard fluid pressure transducers results in a performance metric which is very sensitive to test execution, particularly for low-gradient prostheses.

中文翻译：

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无效孔口面积：低梯度心脏瓣膜假体准确 EOA 评估的实际局限性

目的

本研究的目的是证明根据 ISO 5840 对 EOA 的定义以及精确测量大直径阀门压差的实际限制，有效孔口面积 (EOA) 值的范围是可能的。

方法

一个 31 mm 的机械瓣膜在用于二尖瓣测试的商用脉冲复制器上进行测试，并调整到标称条件。实验数据被用作执行蒙特卡洛分析的基础，该分析针对常用压力传感器的已发布规格以及 ISO 5840 中描述的测量设备精度要求。误差源被建模为正态分布随机变量，模拟迭代 1,000,000次。

结果

实验得出的 EOA 范围为 2.7 至 5.0 cm ²，而蒙特卡罗模拟提供的结果范围约为 0.4 至 6.7 cm ²。其中许多结果显然是非物理的，EOA 大于阀门的几何孔口面积和极短的正压差周期，但它们与同一阀门模型的其他已发表结果一致。

结论

标准 EOA 配方在低平均梯度下的波动性以及使用行业标准流体压力传感器准确测量如此小的差异的困难导致性能指标对测试执行非常敏感，特别是对于低梯度假体。