International Circulation: In what ways are they more difficult?
　　Dr. Dean: Well， they are bulky. When you put a filter on the end of a wire， you change the characteristics of that wire. So， while modern wire technology can twist and turn around impressive tortuosity， embolic protection devices are limited in their maneuverability.
　　《国际循环》：难度体现在哪些方面呢？
　　Dean教授：当把滤网放在导丝末端时，会改变导丝的特性。因此，当今的导丝技术允许其扭曲和通过很曲折的部位，但血栓保护装置的可操作性有限。
　　International Circulation: Is chronic oral anticoagulant therapy necessary in patients after PCI with a SVG?
　　Dr. Dean: I think it is. Last week， we had a discussion around a case at the University of Washington about the problem with vein grafts. Older vein grafts of 15 and 20 years have extensive degeneration， which is the natural history of the graft. Doing anything with them or to salvage them at that point is difficult. Medical therapy is not going to achieve desirable results because the vein graft is at the end of its life. It is almost like trying to take anything else at the end of its life and trying to resurrect it. That is difficult to do. However， medical therapy is certainly important from the standpoint of maintaining graft patency. Therapy would not include anti-platelet therapy， but rather treatment with anti-hyperlipidemics for cholesterol. This has been shown to improve graft patency. Once you get to the end of vein’s life， we lack good tools， whether medical， mechanical， or surgical. The SVGs are  different . For example， with the filters， we can make the SVG look healthy during the procedure， but what happens six months to a year later has more to do with the natural history of the disease process.
　　《国际循环》：SVG行PCI后是否有必要给患者长期服用口服抗凝药？
　　Dean教授：我认为需要。上周我们在华盛顿大学讨论了一个病例，是关于SVG的问题。时间为15年和20年的SVG广泛变性，这是SVG的自然变化。此时采取任何措施挽救SVG都是有难度的。药物治疗不会获得理想的效果，因为SVG的寿命已快，这几乎与挽救生命晚期的其他事物并使之重生一样很难实现。但是，当然从维持SVG通畅的角度来看，药物治疗有重要意义。药物治疗可不包括抗血小板治疗，而需包括调脂治疗。调脂药物被证实可改善SVG的通畅度。一旦SVG到了寿命的晚期，我们就缺乏良好的工具，无论是药物、器械还是外科技术。SVG的情况各有不同。例如，采用滤网可使SVG在操作过程中看起来更好，但6个月至1年后，所发生的事情更多地与疾病进展的自然病程有关。