Gabbay S, Kadam P, Factor S, Cheung T K
Department of Cardiothoracic Surgery, UMDNJ-New Jersey Medical School, Newark 07103.
J Thorac Cardiovasc Surg. 1988 Feb;95(2):208-15.
Although heart valve bioprostheses provide a normal quality of life, their durability is still of great concern. Their durability failure is defined as "degeneration," which is considered to be a consequence of metabolic factors. In this study, we demonstrate that mechanical and design factors can also be responsible for bioprosthesis failure. Large numbers of porcine and pericardial bioprostheses were tested in a fatigue-testing system in which the test conditions were proved to be reproducible and accurate by a laser Doppler anemometer. The results have allowed us to define causes of failure, previously insufficiently stressed, in each type of valve tested. There is a clear difference in factors influencing tissue disruption between porcine and pericardial valves. We have compared these in vitro results with in vivo clinical findings. The main inferences are as follows: (1) Bioprostheses rupture and fail in the same fashion in both in vitro and in vivo studies. (2) Mechanical and design factors are involved in tissue failure. (3) The in vitro/in vivo durability ratio is not 1:1. This ratio depends on the test conditions. (4) Pericardial valves fail because of damage during closure, whereas porcine valves are damaged during both opening and closing (mostly opening) because of design features. (5) Once one cusp fails and prolapses, the other cusps will fail in an accelerated fashion. (6) In vitro durability of 100 X 10(6) cycles can be considered excellent and is an achievable goal. (7) Variability is the key impediment to predicting the durability of bioprostheses. Valves can fail within 2 to 3 million cycles or can last more than 100 million cycles. Similarly, bioprostheses may require explantation within a few months or can last 10 to 13 years in patients. (8) Fatigue testing is an excellent and valuable tool to elucidate the mechanical factors responsible for this variability.
尽管心脏瓣膜生物假体能提供正常的生活质量，但其耐久性仍是备受关注的问题。其耐久性失效被定义为“退化”，这被认为是代谢因素的结果。在本研究中，我们证明机械和设计因素也可能导致生物假体失效。大量猪心包生物假体在疲劳测试系统中进行测试，通过激光多普勒风速仪证明测试条件具有可重复性和准确性。结果使我们能够确定每种测试瓣膜中先前未得到充分强调的失效原因。猪心包瓣膜在影响组织破坏的因素方面存在明显差异。我们将这些体外结果与体内临床发现进行了比较。主要推断如下：（1）生物假体在体外和体内研究中以相同方式破裂和失效。（2）机械和设计因素与组织失效有关。（3）体外/体内耐久性比率并非1:1。该比率取决于测试条件。（4）心包瓣膜因关闭时受损而失效，而猪瓣膜由于设计特点在打开和关闭（主要是打开）过程中均会受损。（5）一旦一个瓣叶失效并脱垂，其他瓣叶将加速失效。（6）100×10⁶次循环的体外耐久性可被视为优异，且是一个可实现的目标。（7）变异性是预测生物假体耐久性的关键障碍。瓣膜可能在200万至300万次循环内失效，也可能持续超过1亿次循环。同样，生物假体在患者体内可能需要在几个月内进行植入，也可能持续10至13年。（8）疲劳测试是阐明导致这种变异性的机械因素的优秀且有价值的工具。
