Welcome, my name's Dr. Warrick Bishop. I'm a cardiologist, I'm an author and a keynote speaker. I'm CEO of the Healthy Heart Network. I'm all about trying to help people live as well as possible for as long as possible. Heart disease is huge in Australia. Every 20 minutes someone suffers a heart attack. Most of these could probably have been avoided if only we knew what to do. This podcast is all about helping you understand blood pressure, weight, cholesterol for better health. If you enjoy this podcast, I would be honored for a five-star review. You can share it with your family and friends. It may well save someone you love. Hi, my name's Dr. Warrick Bishop and I'd like to welcome you to my podcast and videocast station. Thank you so much for tuning in. Now, today, what I'd like to do, and over the next couple of podcasts, is share with you some of the super exciting stuff and some of the learnings I took from recent Cardiac Society of Australia and New Zealand meeting that was in Adelaide in August of 2023. So, let me share with you some bits and pieces around that, which I think are absolutely fascinating. you equally, as me, find them enjoyable and informative. So, one of the first topics I'd like to talk about is myocardial bridges. Well, there's every chance you've never heard of that, and I wouldn't blame you if you hadn't. It's a bit of a, well, it's a bit of a cardiological term, and what it means is that when we think about the arteries that supply the heart, In general terms, those arteries run over the surface of the heart. So if you think about it, when the left ventricle squeezes, blood goes out the aorta. As soon as that blood enters the aorta, it's outside of the left ventricle or the main pumping chamber and within millimetres to a centimetre. of the blood leaving the ventricle, the aorta gives off two main branches. One is called the left main. The other is called the right coronary artery. And those arteries, which are now outside the left ventricle, reflect back onto the heart and cover the surface of the heart with penetrating branches into the... muscle of the left ventricle and the right ventricle and of course supply the atria as well. Well I guess that makes sense doesn't it? So the artery is running on the surface of the ventricle. Let's concentrate on the left ventricle mainly because that's pretty well the easiest to visualize and generally the one that will give us problems if problems are likely to occur. Well, I've indicated that we normally expect the coronary arteries to run over the surface of the heart. Occasionally, and it turns out that it can be in up to 20% of the population, the arteries running over the surface of the heart actually run through the muscle that they're meant to be supplying. Now, historically we've been aware of this, and when you think about it, We've generally reasoned it away by saying it's unlikely to be a problem because when we think about flow within the muscle of the left ventricle, we recognize that that flow can only occur during the relaxation phase of the pumping or cardiac cycle. Now let's think that through for a moment. If we think about the left ventricle contracting, then the pressure generated in the left ventricle is going to be very similar, and if anything, perhaps slightly less than the pressures generated in the muscle driving that blood out of the heart. That means that the blood vessels which I just described that run over the surface of the heart are unlikely to have high enough pressure to overcome the pressure that's coming out of the aorta, to allow blood to flow during systole. And it's only when the left ventricle relaxes that that blood can then flow easily into the muscle and supply the muscle with oxygen and nutrients. I hope that makes sense. So obviously when the muscle's squeezing during... that contraction phase, we call that systole, the pressures in the ventricle are going to be as high or higher than the pressures that are in the proximal part of the aorta and therefore greater than the pressures within the arteries that should be supplying the ventricle and therefore no blood flowing. Alright, so in these circumstances where there may be the Coronary artery running through the muscle. The feeling has always been that the muscle squeezes it and no flow occurs. And that doesn't matter because flow wasn't going to occur anyway. Well, with that as a backdrop, I went to a fascinating presentation given by a Dr. Jennifer Tremel from Stanford in the USA. And she was fantastic. What she talked about was the rare circumstance in which these arteries that run within the muscle, and we call that myocardial bridging because there's a bridge of muscle across the top of the artery, in rare circumstances where that particular condition can give rise to symptoms not dissimilar to angina, i.e. the enclosure. of the artery by that muscle band or bridge is so significant that in certain people they generate the equivalent of an anginal syndrome meaning that the artery is limiting blood flow to that individual's heart in the region, the region subtended by that artery. during not just systole, but also parts of diastole. And that's related to that being a more extensive or a deeper bridge. So, very complicated. It is one of the causes of a condition called minoca. And that term minoca stands for myocardial, relating to the heart muscle. Ischemia, I, so min. M-I, in the setting of non, N-O, obstructive, C, coronary, A, arteries, minoca. And we see minoca pop up as an anginal syndrome. And it can occur in people as young as 10 and as old as 70. So how complicated is that? Minoca. is a situation or a diagnosis we will often give to people when we've looked for standard plaque build-up, standard coronary artery disease giving rise to their symptoms of angina, i.e. they increase their workload and they get chest pain or sureness of breath. But Minoka is the diagnosis we make. myocardial ischemia with non-obstructive coronary arteries when we've explored all those options we can't see any narrowing in the arteries but the patient's behaving as if there are narrowings in the arteries well myocardial bridging in a proportion of these people can actually be the cause of this person's symptoms very very difficult to assess because it's a complicated finding nearly 20% of the standard population will have these bridges. It's a real rigmarole to try and be as clear as possible if this particular individual with their myocardial bridge and their symptoms that sound like a Menoka syndrome or an ischemic or an angina syndrome are actually all linked. So Dr. Tremel spoke about her lab, her center, her hospital, and what they do. They do look at CT coronary angiography because that shows us lovely pictures of the arteries diving through the muscles. They talked about stress testing, which often doesn't give a clear diagnosis. It's invasive angiography of its own. doesn't really help but she did say that if we are able to pass a wire down the arteries using intravascular ultrasound which is an extremely extremely sensitive way of looking at the arteries and looking at the composition of the walls of the arteries that if we demonstrated a greater than 10 percent compression of an artery in a myocardial bridge that there was a very good chance that that particular artery could be Now that's a surgical procedure. They snip the surrounding muscle away and free up the artery. Now really importantly, she made the point that putting a stent in is unlikely to fix the problem. And this person does not need coronary artery bypass grafting. So there is a procedure where they actually de-roof myocardial. bridges having said all that standard medications for angina the sort of things like beta blockers and calcium channel blockers and nitrates the things that go under the tongue and give you a headache can all be helpful as well so that's myocardial bridging to be honest my opinion had been up until this lecture that they occurred commonly and for the reasons about the physiology that i described at the beginning that is that blood flow only occurs during the diastolic or relaxation phase of the cardiac cycle, I always thought that they were unlikely to be of any clinical significance at all. So this particular presentation, beautifully done, it blew my mind and I'm super excited to have shared it with you. As always, if you have any queries or questions, drop us a note at info at drWarrickbishop.online. Similarly, if you've got any suggestions for future podcasts, we're always interested to hear as well. As always, I am really delighted and grateful that you've taken the time to listen. I do appreciate that. And if you have subscribed, thank you very much. I have been dropping in and out of the top 100 medical podcasts in Australia, and your subscription means a lot to me. For now, I'd like to wish you the very best. I hope you live as well as possible for as long as possible. Take care and bye for now. www.virtualheartcheck.com.au You'll find out about your risk and what can be done beyond that to be even more precise.
