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, my name is Dr. Warrick Bishop and I'd like to welcome you to my podcast station, videocast station and to the Healthy Heart Network. Today I'd like to talk about ejection fraction and understanding the percentages. Well, ejection fraction is the term we use for how well the heart is working. And mainly we are talking about the left ventricle, which is the main pumping chamber of the heart. If I can get you to try and imagine the shape of the left ventricle, imagine a bullet. Well, the left ventricle is the shape of the end of a bullet. But it's hollowed out. So the blood can pour into it. That chamber is all muscular. So as blood flows into it, it fills up. The time that blood is flowing in, we call diastole. It's the resting phase of the heart cycle. When the heart contracts and squeezes, we call that systole. So diastole and systole. You may have heard those words when we talk about blood pressure. We talk about systolic blood pressure, i.e. the highest pressure when the heart's pumping. And we also talk about diastolic blood pressure. the pressure that's present in the circulation when the heart's resting. Ejection fraction is talking about the amount of blood ejected from the left ventricle with each beat. So let's think about that chamber. What I'd like you to understand is that the chamber doesn't close completely. So with a normal heartbeat, We don't see every drop of blood expelled from the chamber. If we saw every drop of blood expelled from the chamber, then we would be thinking that we're dealing with an ejection fraction of 100%, i.e. all the blood that goes into the left ventricle during diastole is expelled with systole. Well, that's just not the case. The heart muscle doesn't contract down to... zero to nothing what it does is it squeezes a proportion it turns out that the proportion that the heart squeezes on most beats is approximately 60 percent so nominally if the heart held 100 mils each contraction would expel approximately 60 mils very simple an ejection fraction of 60 percent The normal range is somewhere around 55% to 65%. And when you exert yourself, when you do exercise of some descript and make the heart work harder, then what we see is a process of recruitment, which may see that ejection fraction come up a bit. But we just don't see all the blood expelled in one compression of the left ventricle. So when we're talking about cardiac failure, we're really measuring more often than not the ejection fraction, which we most commonly measure using an ultrasound or echocardiogram of the heart. So if we were to talk with someone who had reduced function of their heart and we were to say that their ejection fraction is 40%, sometimes the patient hears... 40% and thinks normal is 100%. And I would like to dispel that confusion. If we're talking about a patient having an ejection fraction of 40%, we're comparing it to an ejection fraction of 60%, which is normal. So if we're talking from going 60% to 40%, we're actually talking about a 33% reduction in function. Now that's not ideal of course, but if you interpret 40% as 40% of 100%, then in fact that's a 60% reduction in function. And that's not what we're saying. So ejection fraction is all about how much the blood expels as a percentage of the full chamber at the end of diastole. The heart doesn't expel all the blood in one go. it can't it just doesn't close down fully so we never see an ejection fraction of 100% normal ejection fraction is in the order of 60% and if we're dealing with someone who has a problem with their heart and we for example measure their ejection fraction of 40% we're normally talking about 40% ejection not 40% of normal Really important to get those distinctions right, otherwise some people will quite reasonably hear 40% and be thinking that that's in the context of 100% being normal and really take on board that they're, or misconstrue, that they're much worse than they actually are. So that's how we consider ejection fraction. I hope that makes a little bit of sense. I invite any queries or questions, please send them along. And if you have any suggestions for further podcasts, we're more than happy to hear them. So for now, I'd like to wish you the very best. Bye for now and take care. 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.