<International Circulation>：So for my last question: when it comes to silent atrial fibrillation (AF) for ischemic stroke could you please discuss the relationship between silent AF and stroke?
Rabinstein：There is not so much research on this but why this is important is because after doing all sorts of studies you cannot find the cause for stroke in a quarter to a third of all patients. Unlike a heart attack where pretty much all of them occur because of an accident. In the cases of the stroke you can have it from a variety of diseases. If you examine everything， you examine the circulation in the neck， you examine the circulation in intracranially， you check the heart and don’t find a cause then you go from the known causes of stroke to the unknown causes and you treat those. What do you do in such cases? This is a cryptogenic stroke， a stroke with no known cause， and you treat them generically. Nowadays this is based on limited studies. In terms of anti-thrombotic therapy those patients are going to be on antiplatelet tracts. Yet， many of these cryptogenic strokes have embolic appearance on brain imaging， meaning that it seems as though it was an embolism that traveled from a proximal region so we examine the region. Then we assume it may be coming from the heart but we don’t identify a cardiac abnormality that could be the source of the embolism and you don’t see major aortic plaque at the level of the arch to explain it so you are left with this uncomfortable problem that you think it is from an proximal embolus but you can’t prove it. In such a situation the standard of care is to treat them with antiplatelet therapy as opposed to anticoagulation which is what you would do if you could confirm that the clot came from the heart. So that is the background as to why looking for atrial fibrillation is becomes an issue. The patient can be asymptomatic or can be very briefly episodic. The way we have been searching in practice is that we keep the patient closely monitored in the hospital for 24-48 hours and then after they leave the hospital you do a Holter monitor for 24-48 hours and then that’s it. The advent of these new techniques that can allow you to monitor patients for a long time has changed the field. Now we know that a substantial minority of patients representing strokes you can have brief episodes of atrial fibrillation. The problem is that for patients for comparable age， gender and vascular factors you can also find episodes of paroxysmal AF in other patients. Myself and my colleagues did a study comparing patients with cryptogenic stroke versus patients with an established other， well-known cause for the stroke. What we found is that the difference in the occurrence or detection of paroxysmal atrial fibrillation is that it is not significantly different with the patients with cryptogenic stroke versus the patients with a known cause. And so， what do you do with these cases of cryptogenic stroke: do you anticoagulate them or not; if you are finding maybe what you would be finding in patients that have these same spectrum of risk-factors? And therefore these episodes that you are finding may or may not be the cause of the stroke. And that is where we are in that we need to further categorize what these brief episodes of inter-coagulation mean when you find them on patients of cryptogenic stroke with prolonged monitoring. It also needs to be determined when finding these episodes， whether they are short or infrequent， if this merits the use of anticoagulation.

　　<International Circulation>：我的最后一个问题是关于无症状房颤和缺血性卒中。您能介绍无症状房颤和卒中的关系吗？
Rabinstein：关于这个问题没有很多研究。但是这个问题很重要，因为即使经过各种各样的检查，仍然有约1/4～1/3的患者无法查明卒中原因。和心脏病发作不同，很多卒中的发生都是因为意外。卒中可由多种不同疾病导致。如果进行全面检查，检查颈部血管、颅内血管、心脏，并且仍然找不到原因，那么就需要寻找卒中的未知原因并进行治疗。对于这部分患者应当怎么做？对于不明原因卒中只能进行一般治疗。目前这些都基于有限的研究。这些患者会使用抗血小板药物进行抗栓治疗。但是很多不明原因卒中大脑影像学检查都能够发现栓子，意味着栓子来自近端，我们会对这一部分进行检查。我们假定栓子可能来自心脏，但是我们并没有确定可能成为栓子来源的心脏异常，也没有发现明显的大动脉的斑块。这就是难以解决的问题：尽管认为是来自近端的栓子，但是无法证实。在这种情况下，由于无法确定血栓来自心脏，因此标准治疗是抗血小板治疗而非抗凝治疗。这就是房颤问题的背景。患者可能没有症状或者只是短暂的阵发性症状。我们在临床实践中的检查方法是在医院中密切监测患者24～48小时，然后患者离院，再进行24～48小时的Holter监测。新技术能够允许对患者进行长时间的监测，改变了这一领域。现在我们知道，只有很少的卒中患者能够观察到短暂的房颤发作。问题是对于年龄和血管情况相似、性别相同的其他患者同样能够发现阵发性房颤发作。我和我的同事做了一个研究对比不明原因卒中和确定其他原因卒中的患者。我们发现这两部分患者在阵发性房颤的发作或检测方面并没有显著区别。如果在有类似危险因素的患者中也可以发现房颤，那么对于不明原因卒中患者是否需要抗凝治疗？你所发现的房颤发作可能是，也可能不是卒中的原因。因此我们需要对这部分患者进一步分类。在对不明原因卒中患者延长的监测中发现房颤发作时，发作长度和频率都决定了是否需要采取抗凝治疗。

<International Circulation>： Excellent. Well， that’s it for my questions…