Guo G X, Romero C M, Kingsbury C, Quijano R C
Baxter Healthcare, Inc., Edwards CVS Division, Irvine, CA 92714.
Biomed Sci Instrum. 1993;29:457-64.
The effective orifice area (EOA) of a mechanical heart valve is an index of how well the valve design utilizes its primary orifice area (POA). In vitro measurements of EOA of aortic valves were maintained by means of pressure drop and root mean square flow rate measurements in a pulse duplicator during systole. Edwards-Duromedics, St. Jude Medical, and Carbomedics aortic valves of sizes 19 19 mm, 21 mm, 25 mm, and 27 mm were analyzed over a cardiac output range of 3 to 7 liters/min. The resultant ratios of EOA/POA were in the range of 0.6-0.8. A simplified equation suggested by the FDA was used in this study to calculate EOAs. To agree with original assumptions of the simplification, the entrance flow area (EFA) where upstream pressure is measured, must be large as compared to that of the test valves. If not, the formula can yield questionable results such as implying that the EOA can be larger than the POA (Walker P et al, 1992) [1]. This paper discusses the limitations in using such an equation. In conclusion, we suggest utilizing the parameter square root of 1-(POA/EFA)2 to evaluate the validity of the data processing, before using the equation. The parameter should be close to one, and in this study it was 0.997.
机械心脏瓣膜的有效开口面积（EOA）是衡量瓣膜设计对其主要开口面积（POA）利用程度的一个指标。在体外，通过在脉动复制器中于收缩期测量压力降和均方根流速来维持主动脉瓣EOA的测量。对尺寸为19毫米、21毫米、25毫米和27毫米的爱德华兹-杜罗米迪克斯、圣犹达医疗和卡博梅迪克斯主动脉瓣在3至7升/分钟的心输出量范围内进行了分析。所得的EOA/POA比值在0.6 - 0.8范围内。本研究使用了美国食品药品监督管理局（FDA）建议的一个简化方程来计算EOA。为符合简化的原始假设，测量上游压力处的入口流动面积（EFA）必须比测试瓣膜的入口流动面积大得多。否则，该公式可能会得出有问题的结果，比如意味着EOA可能大于POA（沃克P等人，1992年）[1]。本文讨论了使用这样一个方程的局限性。总之，我们建议在使用该方程之前，利用参数1 - (POA/EFA)²的平方根来评估数据处理的有效性。该参数应接近1，在本研究中它为0.997。
