**EP08: Let's Talk About Blood Pressure**
**Dr. Warwick:** Welcome to Dr. Warwick's podcast channel. I am a practicing cardiologist and author with a passion for improving care by helping patients understand their heart health through education. I believe educated patients get the best health care. Discover and understand the latest approaches and technology in heart care and how this might apply to you or someone you love.
Hi, my name's Dr. Warwick, and I'd like to welcome you to my consulting room. Today, I'd like to talk a little bit about blood pressure. Blood pressure is pretty common. So, what is it? Well, blood pressure is what we measure to give us an appreciation of the pressure of the blood flowing through the main arteries. You've probably heard of the upper blood pressure measurement and the lower blood pressure measurement, and these are called systolic for the upper one and diastolic for the lower one. Systolic is normally the higher one; you'll remember that if you see it, and diastolic is the lower one.
Systolic blood pressure is the one that reflects the blood pressure through the arterial circulation at the time of the full force of the contraction of the heart. So, the heart is expelling blood, the aortic valve into the aorta is open, the blood is flowing through, and we're seeing the highest pressure in the system. This is called the systolic blood pressure. Things that would affect the systolic blood pressure are how stiff the aorta is and how stiff some of the other pipes are.
Think of an irrigation system. If you were trying to push water into an irrigation system, if the pipes gave and had some elasticity, then the pressure within those pipes would be less because some of the energy would be absorbed by the expansion of the pipes. This is why, as people get older and their arteries get stiffer, their systolic blood pressure gets higher and higher. The heart compresses and squirts blood into a stiff tube, which really doesn't give at all. Well, it gives less than when that person was much younger, so the systolic pressure goes up.
The diastolic pressure is then the pressure that we see when the aortic valve of the heart is closed. It's the pressure that the circulation rests at, the arterial circulation rests at, before the next beat. This is really defined by the recoil within the major arteries. So, if there is a recoil, an elastic recoil within the arteries, then that will maintain the diastolic pressure. But it's also related to the resistance within the circulation. If the small blood vessels that the blood is flowing into are tight, then there's a resistance within the system, and that'll keep the blood pressure up. If those small blood vessels are relaxed and open, then the blood will flow freely into the vascular space, and that will lower the blood pressure.
So, systolic is the highest blood pressure; it's the one on top, and it's related to the contraction of the heart. Diastolic is related to the pressure within the system when the heart's relaxing and refilling, ready for the next compression.
Well, why do we bother about blood pressure? We talk about it a lot, and there are campaigns raising awareness about it. What's the big deal? Why do we worry about it? Well, we know that blood pressure is very important in the stress forces that it applies to blood vessels. It can apply stress force to the blood vessels of the neck and of the heart, but it can also put blood vessels under strain within the brain. Elevated blood pressure is a very significant driver of stroke, heart attack, and stroke that is from clot forming in the carotid artery, which is damaged from high blood pressure, or from rupture of an artery because it's under too much blood pressure load.
So, in terms of stroke and heart attack, we really want to keep that blood pressure down. We also know that elevated blood pressure is closely linked to the development of atrial fibrillation, and this is a condition that is very common. The better we can lower blood pressure, the better we can reduce the development of atrial fibrillation, which of its own slows people down and has an impact on people's lives. Lastly, and really importantly, one of the big things that blood pressure drives is cardiac failure. Cardiac failure is a sinister, slow-to-develop condition in many cases, particularly associated with blood pressure, because the blood pressure-related heart thickens up to deal with that increased pressure. It thickens up and becomes stiffer and just doesn't work as well. That heart gets older and stiffer faster than it should, and that cardiac failure is a really big issue as people age. So, the importance of looking after blood pressure in that situation cannot be underscored enough.
Well, I've told you what it is. I've told you why we worry about it. How do we check it? Well, we can check blood pressure in the clinic. Your GP would often put on a cuff and listen to the artery at the elbow, checking for systolic and diastolic pressure. This is a really good way to do it, and it's what we've done for many, many years.
One of the limitations, though, of clinic blood pressure measurements is that we know blood pressure varies considerably, and some people, up to 20%, sometimes even more in some studies, can respond with an elevated blood pressure just because a doctor is taking it. So, sometimes it's best to get the nurse to take it because the nurse doesn't put the patient's blood pressure up quite as much as the doctor. The trouble with that volatility of blood pressure is it sometimes makes it very hard to know where you are. If the blood pressure is high, is that a true reading? Or is it a spike because of that moment where the patient is perhaps a little bit anxious about having their blood pressure checked?
One way to get around that is to undertake home blood pressure measurements. This is becoming more and more common, and the availability of more reliable machines that can be taken home makes this a valuable alternative. Home blood pressure measurements, which are really low and settled compared to, say, a clinic measurement which is up and down, can give the doctor some information and insight into understanding that this particular person could have some white coat hypertension, and when they take their own blood pressures, they are not so troubled.
The next step past home blood pressure measurements is 24-hour blood pressure monitors. These are simply a cuff put on the arm, hooked up to a little machine like an old-fashioned Sony Walkman. This device goes off generally twice an hour for the 14 hours of daylight and then once an hour for the eight hours of sleep. This gives a beautiful profile of exactly what happens over a 24-hour period for the patient. My own preference is to use that sort of testing to get the clearest information before making decisions on therapy introduction or therapy changes for the patient. Once I'm happy with the 24-hour blood pressure monitor, I'm more than happy to come back and use home monitoring to support ongoing surveillance.
So, there are a number of ways we can look at blood pressure, and my own feeling is the best way to use those is a combination that works best for the individual patient. What I'd like to leave you with, though, is an idea about where blood pressure fits. The way I often explain this to patients is that there are things that are important and there are things that are not important. There are things that are urgent and there are things that are not urgent. We can imagine four boxes or a two-by-two matrix.
If we look at important and urgent, then a very good example of that is someone having a heart attack. It is both important and urgent—no delay. Something that's urgent and not important is the phone going, and you're answering it because the phone demands that you answer it, and it's a telemarketing call. So, urgency, but not important. If we look at not urgent and not important, well, maybe cataloguing your Christmas cards from 25 years ago into alphabetical order could be considered not urgent and not important.
But what I want you to get is in this matrix down here, where we've got not urgent and important, that's where blood pressure sits. My message to patients is that sometimes we don't fix the blood pressure immediately with one magic wand swing. Sometimes, in fact, most of the time, we need to take a long-term approach to getting that blood pressure sorted as best as possible for that individual because the consequences in the long term are so significant. So, blood pressure is important, but not urgent.
I do have to say that occasionally very elevated blood pressure is a medical emergency, but I'm talking about general clinic management. So, please get your blood pressure checked, work with your GP to make sure it's kept under control. Understand that we're really trying to reduce major conditions like stroke, heart attack, atrial fibrillation, and cardiac failure. This is why we bother measuring, and this is why we try and encourage people to take something even though they might not feel unwell.
It is a challenge to be asked to take a tablet when, on a day-to-day basis, you feel pretty good. But the reasons are really clear, and the consequences are significant. If we can control blood pressure better for you, you will get a better outcome from that.
I hope this has made a little bit of sense. I hope you've enjoyed it. Thank you for joining me today, and I wish you good health.
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