Podcast Summary

Welcome to Dr. Warrick's podcast channel. Warrick is a practicing cardiologist and author with a passion for improving care by helping patients understand their heart health through education. Warrick believes 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, today I'd like to talk about blood pressure and the significance blood pressure has on our vascular system and our risk of heart attack and stroke. It turns out that in the United States and in most first world countries that hypertension is the single most significant modifiable risk factor for atherosclerotic. cardiovascular disease meaning it is the biggest contributor to stroke and heart attack. That means it's a very very serious issue to deal with on a population basis. High blood pressure is defined as a systolic blood pressure over 130 millimeters of mercury and a diastolic blood pressure over 80 millimeters of mercury and we know that for every incremental increase in that systolic or diastolic blood pressure, we see an incremental increase in the risk of stroke, heart attack and cardiovascular and cerebrovascular consequences. So if we were to increase the systolic blood pressure by 20 millimeters of mercury or the diastolic blood pressure by 10 millimeters of mercury, we would see a doubling of risk for that individual. Well, what is the systolic and what is the diastolic blood pressure? Well systolic blood pressure simply relates to the highest blood pressure in the vascular tree and coincides with the contraction of the heart when the main valve the aorta is open and blood is coming out from the heart into the vascular tree or the aorta systole is the word we use for contraction of the heart so systolic blood pressure means the blood pressure associated with the contraction of the heart the highest pressure within the system when the heart's finished contracting it relaxes and as it relaxes and the pressure drops that valve the aortic valve closes when the aortic valve closes then the blood pressure within the system is called the diastolic blood pressure now if you think about it the word we use for the heart relaxing is diastole so diastolic blood pressure is the blood pressure while the hearts relaxing and in fact because the aortic valve is closed the inside of the heart and the vasculature are actually not connected. When the heart squeezes the pressure that we measure is really a direct relationship to how hard the heart is squeezing but also how much the blood vessels it squeezes into relax. So just imagine this. If we're trying to measure systolic blood pressure and the heart squeezes very vigorously but the aorta relaxes and absorbs a lot of that energy the pressure may not be very high. If the heart squeezes with the same vigor but the arteries are not able to relax or are not very compliant and stiffer then all the pressure from the heart contracting is transmitted into the vascular system and the pressures within the system go up higher. When the heart's finished contracting it is the recoil of the large blood vessels the aorta and the like recoiling that determine the diastolic blood pressure. Think again of the heart squeezing hard, the aorta dilating, or having enough compliance to stretch and then when the heart stops contracting it springs back as it springs back that spring back yields energy which maintains the diastolic blood pressure. If the aorta doesn't move if it's stiff and rigid then there's little spring back and that means when the heart stops contracting. and the aortic valve closes that there's not a lot of recoil that there's not a lot of energy to maintain the diastolic blood pressure and it's relatively low this is best demonstrated in the hypertension of the elderly which is of course common and we see as people's arteries get stiffer their aorta gets stiffer their systolic blood pressure goes up because none of the energy is absorbed effectively by the aortic wall and their diastolic pressures become low so there's a big gap between the systolic pressures and the diastolic pressures and that big gap is because there's little recoil in the artery that doesn't bring energy back into that diastolic phase. Well how do we measure blood pressure? Well for years we've measured it with a cuff around the arm in the office but of course that's subject to a lot of variability and about 20 to 25% of people that blood pressure pops up regardless of whether they feel nervous or not and that's called white coat hypertension and really can throw off our measurements. To get around that we often ask people to measure their blood pressure at home and do it on a number of occasions and of course if you're a white coat person then doing your blood pressures at home without any perceived stress by being in a foreign location should be mitigated and so you should get clearer results. One of my favourite ways to check blood pressure, and I believe it's the best we've got as a clinical gold standard at the moment is to use what we call a 24-hour blood pressure monitor. And that's where we literally put on a blood pressure cuff that can stay there for 24 hours measuring the blood pressure. every 30 minutes during daylight hours and every hour overnight giving us a beautiful profile of exactly what's going on with an individual's blood pressure and allowing us to see the averages we're dealing with not just the highs and lows which can be misleading. Of course we can measure the blood pressure if we put a catheter or a tube into the artery and directly measure that but that's pretty uncommon and we tend to only do that in the laboratory when we're doing invasive procedures so that's really not a useful tool in a clinical outpatient setting. But that information does give us good information and informs us about the accuracy and reliability of our other modalities for measuring blood pressure. Lastly there's lots of new technology coming out which is looking to sample the artery. the artery wall and the pulse pressures in different ways and I think the next years will show us and demonstrate to us very interesting opportunities for looking at blood pressure and detecting blood pressure more effectively probably at home and probably in association with smartphones and apps bringing more and more information to that area and allowing us to really hone in on the issues at hand. Well why is blood pressure such a problem? The way I try and explain this to patients is I ask them to try and imagine if they were farmers and they had their irrigation system set up to water the crops. Well if you think about it if your irrigation system pressures can run a bit lower then there's less wear and tear on your pipes. The pipes in the body that we're most interested in are. the pipes or the arteries going to the heart or the pipes or the arteries going to the brain. So less wear and tear on the pipes, less risk of heart attack, less risk of stroke. But if you lower the pressure in the system you're also reducing the pressure on the pump and the pump can have a timing issue because it's been put under pressure and in our own body the pump responds by potentially going into atrial fibrillation. chaotic and irregular rhythm strongly linked to increased blood pressure over time. The other thing that we see is that the pump could come under load and just not work properly. In our hearts, in humans, that pump response is development of cardiac failure. The heart becomes stiff and just doesn't relax properly because it's been working too hard over time. heart attack, atrial fibrillation and cardiac failure looking after the pipes and the pump and lastly of course blood pressure can impact your filtration system. Well you don't want to blow your filtration system in your irrigation system and nor do you want to blow your filtration system in your own body and in your own body. It's your kidneys and we know that if we keep the blood pressure down we can look after kidneys in the long term. So really the big five that blood pressure can impact heart attack, stroke, atrial fibrillation, cardiac failure and renal failure. It is so important to look after blood pressure and keep it under control. Well if someone does have blood pressure what can we do about it? Well, first of all, we need good, accurate measurements, and I've talked about that already. But once we've established that there is elevated blood pressure, lifestyle measures are a very important starting point. If that patient is overweight, we know that about one millimeter of blood pressure reduction is associated with one kilogram of weight loss. So losing 5 to 10 kilograms is about as effective as giving someone a tablet. Pretty good deal. We also know that exercise can lower blood pressure and if we can get people exercising regularly two through four times a week with some wriggle we know that that can lower blood pressure approximately five millimeters of mercury as well. So again about as effective as a single medication. It's really important to then keep a close eye and make sure that we've got those blood pressures where we want it and we can use medications there's multiple medications available and there's even techniques which allow us to denovate which means destroy the nerves around the renal arteries and this has been shown. to reduce blood pressure in very specific circumstances. So we've got a number of medications and interventions for blood pressure but what is the perfect blood pressure and I get asked this all the time. Well my answer is this, if we think about blood pressure as a continuum from low to high then we would accept that everyone's a little bit different. My children when they were 10 years of age would have had very low blood pressures compared to my parents who were elderly who'd have quite high blood pressures. So how do we know for an individual what's perfect? Well for the patients I deal with particularly who are at high risk, maybe high risk of heart attack, maybe have had a heart attack, maybe cardiac failure or development of atrial fibrillation and I want to be most precise in getting their blood pressure to the right level. The way I do that is I recognise this continuum of blood pressure and I look to find the point which is the lowest point we can get their blood pressure to without them developing regular symptoms. from their blood pressure. So the symptoms from low blood pressure would be something like lightheaded when you stand up, lightheaded when you bend over and get up, getting out of bed and being a bit lightheaded and loss of energy associated with that. So imagine that continuum, imagine the point such that below that point patients are suffering side effects of low blood pressure. So when they get up, stand up quickly, they're lightheaded. We don't want people in that position all the time. But if we can get really close to that switching point so that the individual is so close that maybe once or twice a week they have a little bit of lightheadedness when they stand up quickly and they know it's because of their tablets and they know that that means that they're very close to that point. below which they're going to have symptoms then we've got them as low as possible with negligible side effects and getting the real benefit or upside of keeping their blood pressure down. If they're above that point and they're not getting any symptoms at all we can't be as sure that we've got them as low as possible. We do have to rely more on our measurements but I've got many patients who will report that they get a little bit of lightheadedness once or twice a week. They understand it's related to their medication and they understand it's telling us that they're very very close to this perfect blood pressure level. So that's blood pressure. It's a really big deal. Certainly important not to get your blood pressure up worrying about it, but certainly really important to sort it out. I hope that all makes a bit of sense. Take care. I wish you the very best. Bye for now and please don't die from a heart attack. Goodbye. You have been listening to another podcast from Dr. Warrick. Visit his website at drWarrickbishop.com for the latest news on heart disease. If you love this podcast, feel free to leave us a review.