<International Circulation>:The level of the diastolic blood pressure is important for the patient with coronary disease. When you see an elderly patient in the clinic with a high level of systolic blood pressure but a low level of diastolic pressure， what do you think is the best strategy for their hypertension treatment?
　　Dr Rosendorff: That’s a very difficult and controversial question. The reason it is controversial is because we know that the myocardium is particularly susceptible to low diastolic pressures. The reason for that is that the myocardium is perfused almost exclusively during diastole and therefore the diastolic pressure is the coronary filling pressure， the pressure that perfuses blood through the myocardium. The blood flow through the myocardium is also unique in that oxygen is almost 100% extracted from the blood so the myocardium cannot compensate and increase its oxygen supply by extracting more oxygen from the blood. The only way it can do that is by increasing blood flow. Normally flow is regulated such that it is relatively constant down to a fairly low diastolic blood pressure. But of course if one goes even further than that， then myocardial blood flow will start to decrease and the patient is then in danger for developing myocardial ischemia and even a heart attack. The problem is that we don’t really know the exact value of this lower limit of coronary autoregulation. If we knew that then we would know exactly that that pressure is the lowest diastolic pressure that we should allow in our patients. We must rely on indirect evidence and the indirect evidence is very conflicting but to summarize a large amount of that evidence， I can say that lower is better for stroke; there is no question about that. The evidence for lower blood pressures (i.e. systolic pressures less than 130mmHg or 120mmHg and diastolic pressures less than 80mmHg) appears to be reasonably safe but certainly the outcomes are not improved at those lower diastolic levels. So what do we do with patients who have isolated systolic hypertension with a very high systolic pressure and a normal and even low diastolic pressure? To begin with， one must be very careful. One would use conventional antihypertensive drugs in patients with coronary artery disease which would lower the blood pressure slowly. If the patient had any symptoms of angina or myocardial ischemia， one would slow down the rate of titration of the drug or even reduce the dose of the drug. So caution is advised in patients who have coronary artery disease or in patients who are elderly or in patients who have diabetes. I must mention the ACCORD study in which this very question was addressed in patients with diabetes who can all be assumed to have coronary artery disease. The idea of the ACCORD study was to test the hypothesis that lowering blood pressure to below 120/80mmHg was better in terms of outcomes than lowering blood pressure to a more conventional 140/90mmHg or below. The outcome in ACCORD was that stroke outcomes were better at the lower blood pressure but there was no benefit of lowering blood pressure to the lower levels as far as myocardial infarction was concerned. I take a more optimistic view of ACCORD and say that at those low levels of blood pressure， there was no harm done to the myocardium which gives me a lot of confidence in saying that blood pressures below at least 130/80mmHg are reasonably ok in patients who have isolated systolic hypertension with coronary artery disease or in the elderly as long as the blood pressure is lowered slowly and attention is paid to any adverse events.

　　《国际循环》：舒张压水平对于冠心病患者是重要的。当我们接诊了一位收缩压高而舒张压低的老年患者时，您认为控制血压的最佳策略是什么？
　　Rosendorff博士：这是一个很难回答的、有争议的问题。有争议是因为我们知道心肌对低舒张压尤其敏感。原因在于心肌几乎是只在舒张期完成灌注的，因此舒张压就是冠状动脉充盈压，即血压灌注心肌的压力。灌注心肌的血液的另一个独特之处就是几乎100%的氧来自于血液，因此心肌不能够代偿，不能通过从血液中摄取更多的氧来增加氧供应。唯一的办法是增加血流。通常，心肌的血流被调节到相对稳定的状态，适合非常低的舒张压水平。但是，如果舒张压进一步下降的话，心肌血流就会减少，患者就有发生心肌缺血甚至心脏病的风险。问题是我们并没有明确冠脉自我调节下限低的意义。如果我们知道的话，我们就会知道患者所能容许的最低舒张压是多少。我们必须得依赖间接的证据，而间接的证据又是互相矛盾的，不过综合大量证据，我可以说血压低有利于预防卒中，这是毫无疑问的。有关血压更低（即SBP <130 mm Hg或120 mm Hg和舒张压<80 mm Hg）的证据显示，这是相当安全的，但是舒张压更低当然没有改善转归。所以遇到单纯收缩期高血压患者，也就是患者的收缩压高而舒张压正常甚至降低，我们该怎么办？首先，我们要相当小心。可以应用在冠心病患者常规应用的、缓慢降低血压的药物，可以减缓药物加量的速度，甚至减少药物剂量。对于冠心病患者、老年患者或糖尿病患者，建议大家谨慎治疗。我必需要提的是ACCORD研究，该研究观察了合并冠心病的糖尿病患者的血压问题。ACCORD研究的目的是验证下述假说，即把血压降至120/80 mm Hg以下比降至传统的140/90 mm Hg以下转归更好。ACCORD研究的结果显示血压更低时，卒中更少，但是血压更低并没有减少心梗发生。我对ACCORD研究的结果持更乐观的看法，我认为ACCORD试验将血压降得低一些并没有对心肌造成损害，这给了我相当大的信心，对于合并单纯收缩期高血压的冠心病患者或老年患者，血压在130/80 mm Hg至少是合理的，只要血压是缓慢下降的同时注意任何不良事件的话。