有很多原因。首先,血压变异性有很多种类型,比如,24小时内的血压变异性。血压在白天和夜间都是有很大变异的。在夜间,血压普遍偏低但是除此之外在24小时内还有极短期持久峰或长时持久峰。
《国际循环》:那么24小时内的变异性呢?据我所知NICE指南正在制定动态血压检测标准。您会让患者在一天的时间里测量血压的变异性吗?
Dr Mancia: NICE指南并没有考虑到血压变异性,他们只关注白天血压的平均水平。这是另一个非常重要的问题。动态血压很重要吗?我们应该根据动态血压的结果还是临场血压来诊断高血压?我知道NICE指南的意思,但是我还是有所保留。我在动态血压方面做了很多年的工作但是我还是有保留地认为动态血压应该被视作常规检查。首先,NICE指南所做的只是考虑到了白天的血压。我不确定这是一个好事因为夜间血压具有预后价值并且非常重要。在一些情况下,夜间血压的预后价值要大于白天血压。同时,我没有发现指南建议的在晚上10点之前停止血压记录的好处,不管怎样患者都要在第二天归还设备,那为什么不收集夜里的血压信息呢?另一个问题是指南认为在1小时内只测量一个血压值就够了,所以总的血压值是14次。但是指南并没有指出这种建议的依据是如何从研究中搜集得到的;以前测得的数据更多,会达到70到90次。我认为从与之前不同的方式收集证据并假设测量更少血压值是没问题的这种做法值得质疑。实际上很多年前我们就表明如果测量的血压值太少就不能得到很好的24小时平均值。除此之外,如果像NICE指南建议的那样,患者就诊时测得的血压很高而白天血压则正常(他们设定为小于135/85mmHg),这意味着患者是白大衣性高血压,并认为患者血压正常。这种定义的依据何在?他们选择了排除那些介于真正高血压个体和完全血压正常个体之间的中度风险的患者。还没有试验对白大衣高血压患者进行研究,但是由于这种现象非常普遍,达到30-40%的高血压患者可能为白大衣高血压,因此可推测试验中的这些患者显示出治疗的益处。那时(甚至是现在),动态血压的使用并不是很普遍。这些患者可能还有很大程度的靶器官损害特别是左心室肥厚。我们已知这类患者群的心血管风险更高。十年里,这类患者发生糖尿病,确诊高血压(真正的高血压)以及LVH的几率更大,并且他们还会有很多代谢性危险因素。我认为有证据表明这些患者应该被细致诊治。
International Circulation: What about variability within 24-hours? I know that the NICE Guidelines are moving to make ambulatory blood pressure monitoring standard. Would you want your patients to measure their variability during the course of a day?
Dr Mancia: What the NICE Guidelines don’t do is consider variability; they consider only the mean daytime levels. This is another very important part. Is ambulatory blood pressure important? Should we make the diagnosis of hypertension by ambulatory blood pressure and not by clinic blood pressure? I know what the NICE Guidelines have said and we have some reservations. I have been working with ambulatory blood pressure for many years but I have some reservations that this should be regarded as routine. First of all, what the NICE Guidelines do is only consider daytime blood pressure. I am not sure that this is a good thing because night-time blood pressure is of prognostic value and quite important. In some conditions, the prognostic value of night-time blood pressure is greater than the daytime. Also, I do not see the advantage of stopping recording at 10pm as the Guidelines suggest, as the patient has to take the instrument back the next morning anyway so why not collect information overnight. The other thing is they say it is enough to collect one value per hour, so a total of fourteen values. But that is not how the evidence has been collected in the studies; the number of values has been much greater, up to seventy or ninety values. I think it is rather questionable to take evidence collected in a different fashion and assume that it would be OK to have a much smaller number of values. We have in fact shown many years ago that if readings are too few you cannot get a good 24-hour mean. Apart from that, if, as the NICE Guidelines say, you have a patient with a high clinic blood pressure and a “normal” daytime pressure (which they place <135/85mmHg), this means that patients with white coat hypertension are regarded as normotensive. Where is the evidence for this? They have chosen not to have a stage of intermediate risk between being truly hypertensive individuals and truly normotensive individuals. There are no trials on people with white coat hypertension, but since this is a very common phenomenon with up to 30-40% of hypertensive patients possibly being white coat hypertensives, then presumably these people were included in trials demonstrating the beneficial effects of treatment. At that time (and even now), ambulatory blood pressure was not commonly used. These patients also have a much greater incidence of organ damage and particularly left ventricular hypertrophy. We have seen that for this population cardiovascular risk is greater. Over ten years, they stand a much greater chance of developing diabetes, established hypertension (true hypertension) and LVH and they have a lot of metabolic risk factors. I think there is good evidence that these patients should be looked at carefully.