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, my name is Dr Warrick Bishop and I'd like to welcome you to my podcast and videocast station and of course welcome you to the Healthy Heart Network. Today I'm going to talk about blood pressure. Now I've spoken about blood pressure on a number of occasions and if I can emphasise it again, blood pressure is really, really important. Like it's really important. So always get it checked and follow up with your doctor and check where it is. Anyway, today the specific thing I would like to talk about blood pressure is what's more important? The top number or the bottom number on a blood pressure reading? Well, let's just quickly remember what the top number and the bottom number are. As the heart is pumping blood into the bloodstream, The valve connecting the heart to the aorta is wide open and the heart is squeezing full tilt and the highest pressure in the circulation is measured. That highest pressure in the circulation is called the systolic blood pressure. It's called the systolic blood pressure because the word we use for contraction of the heart is called systole. So we could call it the contraction of the heart blood pressure. But we tend to call it systolic blood pressure because that makes us sound quite aloof and knowledgeable because we're using jargon that you guys don't normally understand. Well, what's diastolic blood pressure? Well, diastolic blood pressure in actual fact is the blood pressure we get when the heart's not contracting. So let's think this through. Heart squeezes. Blood shoots out into the circulation. We measure the highest pressure during that time. That's the systolic blood pressure. Heart stops squeezing. Blood stops flowing out of the heart. Blood starts to come back into the heart, but the aortic valve closes. The system now relaxes, if you like. And the system relaxes and finds a blood pressure, which is related. to the recoil of the large blood vessels which have stretched and now coming back during the relaxing phase plus how tight the arteries are that the blood's being pushed into. So if there's plenty of recoil in the arteries during the relaxing phase of the heart contraction and the arteries are tight then the diastolic pressure will be fairly high. Does that make sense? If the Arteries do not recoil, then there's no energy to go back into the system. Let's say there's no energy. Let's imagine someone who's got stiff arteries and let's say they've got very open, major arteries, and let's say they've got very open small arteries that are being pumped into. So the diastolic pressure would be lots of runoff because all the little arteries are open, lots of runoff. and no recoil from the major arteries so that person would have a very low diastolic blood pressure. Okay that's a reminder of systolic and diastolic. Today I'd like to talk about what's more important systolic or diastolic and the reason I want to talk about that is that when I was training quite a few years ago We used to talk about the diastolic pressure being the most important one for us to measure to make decisions about blood pressure management in individuals. And we held that dogma, that feeling, for a long time, up until probably somewhere around the 90s. Somewhere around the 90s... we started to understand that it was probably pretty important to recognise that the systolic blood pressure was important and then more and more information accumulated supporting that fact. We've now moved very much to thinking that the systolic or the higher number, the blood pressure during contraction is more important. Well, just recently, a study published in the New England Journal of Medicine asked the question, is it systolic or is it diastolic that's more important? Can we check one and not the other or vice versa? Or do we have to check both? What a great question. So the researchers in this particular study found about 1.3 million people through the Kaiser Permanente Insurance Group in Northern California. They accessed about 36 million blood pressure readings on those 1.3 million people and they did this over a number of years. Now they had a number of cut-offs to try and understand where the risks were occurring. They looked at 140 systolic. and they looked at 90 diastolic and what they found was that when they compared the likelihood of a problem in an individual if their blood pressure was over 140 versus under 140 systolic and they matched these individuals for all the other potential variants age, sex, weight, diabetic status, smoking status et cetera, et cetera. What they found was that the chance of having a complication if your systolic pressure was above 140 was 1.18 times the risk of people with their blood pressure below 140. So that's about 18% higher isn't it? when they looked at the diastolic effect they looked at people with blood pressure diastolic over or above 90 they matched for all the variants and when they matched for all the variants but just took out the blood pressure they found that the people with diastolic blood pressures over 90 had a rate of event greater than those without blood pressure over 90 by a multiple of 1.06 which is between a 5 to 10% increase in risk. So this tells us that systolic blood pressure and diastolic blood pressure are both important. It tells us that your risk has increased relatively 20%. About 20%, close to 20%, if your systolic is greater than 140 mmHg, it tells us that your risk is increased if your diastolic is over 90 mmHg and it tells us that your relative risk is increased between 5 and 10% compared to patients whose blood pressure is normal. So what is this telling us? This is telling us that Both components of the blood pressure are important. It's telling us that the systolic is probably slightly more important in terms of predicting who may be at increased risk. It's telling us that both need to be looked at together. The same researchers looked at exactly the same data set but moved the numbers down to 130 over 80 and found exactly the same trend in results. They raised the possibility that diastolic pressures that were too low may have been associated with increased risk, but that's still hazy. We would consider that a J curve, i.e. you get benefit and benefit and benefit down to a certain point, and then if you keep blurring it, then mortality, morbidity increases, a J if you like. But that's not 100% certain because the people whose blood pressure was very, very low, diastolic in particular, It was very, very low. May well have had old stiff arteries and other factors may have been at play. What's the take-home message for you? Well, I've really carried on about blood pressure on a number of occasions on this podcast and I do it with my patients on a regular basis. The take-home message is this. Your blood pressure, whether it is systolic or diastolic, now we understand it's systolic a little more than diastolic but whether it's one or the other they both represent the wear and tear on your vasculature on your heart coronary arteries on your heart as a end organ it will potentially develop cardiac failure is elevated blood pressure is closely linked to atrial fibrillation and it is very closely linked to risk of stroke so Whatever your blood pressure is, if you can get any lower, get it any lower. That is going to be good. And when it comes to my patients in my rooms, they'll come in and say, oh, doc, my GP measured my blood pressure at 110 systolic and said I should probably come off my blood pressure tablets. And I will say, are you having symptoms? Are you getting lightheaded when you stand up? Can you not bend over and stand up without there being a problem? And if the patient says, no, I feel absolutely fine, then my strong advocacy is to say, look, the lower your blood pressure, as long as you're not having side effects or problems, then the better it will be in the long term for your vasculature. The SPRINT trial, which came out in the last year, clearly shows us that in high-risk patients really trying to drive down that blood pressure, without question, shows benefit for major adverse coronary event. But beyond that, the sooner we can get blood pressure down, the sooner we can start to reduce risk for an individual with stroke, heart attack, cardiac failure, and atrial fibrillation. It's got to be a good thing to keep down. Well, I hope I've shared with you some insights into blood pressure. The systolic measurement, probably a slightly better predictor than the diastolic measurement, but both really important if we're looking to mitigate risk for individuals. Please check with your local doctor, your pharmacist, your physio, whoever's checking your blood pressure. Please keep getting it checked. If it's not spot on, do something about it. Follow it through. It is a really big deal. I hope you've got something valuable from today's podcast. If you have any queries or questions, please drop us a note. If you have any suggestions for any future podcasts, let us know. As always, I wish you the very best and please don't dive in a heart attack. 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.
