Czer L S, Gray R J, Bateman T M, DeRobertis M A, Resser K, Chaux A, Matloff J M
J Am Coll Cardiol. 1986 Feb;7(2):284-94. doi: 10.1016/s0735-1097(86)80493-4.
Porcine bioprostheses are physiologically stenotic valves. Degenerative calcification leading to pathologic stenosis is an increasingly recognized serious late complication of mitral valve replacement with a porcine bioprosthesis. Hemodynamic differentiation of pathologic from physiologic stenosis is important for identification of porcine bioprosthetic valve dysfunction. In 42 patients with a normal Hancock porcine bioprosthesis (standard model, sizes 27 to 33 mm), mean diastolic flow (65 to 461 ml/s), mean gradient (2.0 to 13.4 mm Hg) and effective orifice area (1.1 to 4.4 cm2) were determined at rest, during epicardial pacing (90, 110 and 130/min) and with isoproterenol infusion. A statistically significant increase in mean gradient occurred with increases in flow and decreases in valve size (p less than 0.05). Effective orifice area increased significantly as flow rate increased and as valve size increased (p less than 0.05). These measurements were compared with those in 16 patients with pathologically confirmed porcine bioprosthetic valve stenosis: 8 patients with reoperation (1.1% per patient-year) 3 to 8.5 years after mitral valve replacement and 8 previously reported abnormal cases. Stenotic failure rate was inversely related to valve size (2.1, 1.4, 0.5 and 0% per patient-year for sizes 27 to 33 mm). Stenotic and normal bioprostheses were not accurately differentiated on the basis of a single value for gradient or effective orifice area. A mathematical model that related flow to the square root of the mean gradient allowed complete separation of stenotic from normal prosthetic valve function, after valve size was accounted for and normal confidence limits were established (r = 0.74 to 0.94, sizes 27 to 33, p less than 0.0001). The effective orifice area-flow relation did not provide accurate differentiation of abnormal from normal function. Thus, normal mitral bioprostheses have significant transvalvular gradients whose magnitude depends on flow. Risk of stenotic failure is increased in the smaller valves, which have a larger gradient at implantation. Differentiation of pathologic from physiologic stenosis cannot be made on the basis of a single value for gradient or effective orifice area. Accurate hemodynamic differentiation is achieved by relating mean gradient to mean diastolic flow rate and valve size.
猪生物瓣膜是生理性狭窄瓣膜。导致病理性狭窄的退行性钙化是二尖瓣置换猪生物瓣膜后一种日益被认识到的严重晚期并发症。病理性狭窄与生理性狭窄的血流动力学鉴别对于识别猪生物瓣膜功能障碍很重要。在42例使用正常汉考克猪生物瓣膜（标准型号，尺寸为27至33毫米）的患者中，测定了静息状态、心外膜起搏（90、110和130次/分钟）以及输注异丙肾上腺素时的平均舒张期血流（65至461毫升/秒）、平均压差（2.0至13.4毫米汞柱）和有效瓣口面积（1.1至4.4平方厘米）。随着流量增加和瓣膜尺寸减小，平均压差出现统计学上的显著增加（p<0.05）。有效瓣口面积随着流速增加和瓣膜尺寸增加而显著增加（p<0.05）。将这些测量结果与16例经病理证实的猪生物瓣膜狭窄患者的测量结果进行比较：8例二尖瓣置换术后3至8.5年再次手术的患者（每年每例患者1.1%）以及8例先前报告的异常病例。狭窄失败率与瓣膜尺寸呈负相关（27至33毫米尺寸的患者每年分别为2.1%、1.4%、0.5%和0%）。根据压差或有效瓣口面积的单一值不能准确区分狭窄和正常的生物瓣膜。在考虑瓣膜尺寸并建立正常置信区间后，一个将流量与平均压差平方根相关的数学模型能够完全区分狭窄和正常人工瓣膜功能（r=0.74至0.94，尺寸为27至33，p<0.0001）。有效瓣口面积-流量关系不能准确区分异常和正常功能。因此，正常二尖瓣生物瓣膜具有显著的跨瓣压差，其大小取决于流量。较小的瓣膜狭窄失败风险增加，这些瓣膜在植入时具有较大的压差。不能根据压差或有效瓣口面积的单一值来区分病理性狭窄和生理性狭窄。通过将平均压差与平均舒张期流速和瓣膜尺寸相关联可实现准确的血流动力学鉴别。
