Heart Failure: The Two Types of Heart Failure--Systolic and Diastolic
Guest: Dr. Michael Zile
Host: Dr. Pam Morris – Cardiology
Dr. Pam Morris: Hi, I am Dr. Pam Morris and you are listening to Heart Sounds. I am here today with Dr. Michael Zile. We have been talking about heart failure and, Dr. Zile, I would like to welcome you today.
Dr. Michael Zile: Thank you, Pam.
Dr. Pam Morris: Dr. Zile, we have been talking about heart failure. Are there different types of heart failure?
Dr. Michael Zile: Patients with heart failure can be generally divided into two groups, those with what is called systolic heart failure and those with what we call diastolic heart failure. Systolic heart failure is characterized by changes in the structure and the function of the left ventricle, which are different from the changes in the structure and the function of the left ventricle in diastolic heart failure. So, let me explain. In patients with systolic heart failure, the size of the ventricle increases dramatically, or dilates.
Dr. Pam Morris: May I ask you just a question here. The ventricle is the main pumping chamber of the heart?
Dr. Michael Zile: Right. The heart is divided into four chambers. It is like a four-room house. There are two rooms which are the receiving chambers, that receive blood back from the legs and arms and head, the right atrium, and another chamber which receives blood back from the lungs, the left atrium. Those receiving chambers store the blood for a short period of time and then put them into the two pumping chambers, the right ventricle which pumps blood to the lungs, so that it can get oxygenated, and the left ventricle which pumps blood to the brain and the arms and legs and liver, and so on, to provide nutrient flow to the vital organs.
So, when we talk about heart failure, predominantly we are talking about the main pumping chamber of the heart, or the left ventricle, which pumps blood to the brain and the muscles, and the vital organs. So, when we talk about two different kinds of heart failure, we are talking about abnormalities that affect the systolic properties of the left ventricle, systolic heart failure, and the kind of heart failure that predominantly affects the diastolic function of the left ventricle, diastolic heart failure.
So, in systolic heart failure, the left ventricle, the main pumping chamber of the heart, dilates. It gets markedly enlarged. And, while that helps a person compensate for an injury early on, later on, it causes decompensation. It becomes maladaptive. So, in systolic heart failure, the ventricle is very large and it pumps very poorly. So, the amount of blood that it ejects from the ventricle with each heart beat is markedly reduced. Physicians will use the term, the fraction of blood, which is ejected per beat, or the ejection fraction. So, people with systolic heart failure have a markedly enlarged left ventricle that pumps, or ejects, very poorly and has a low ejection fraction.
Dr. Pam Morris: What would a normal ejection fraction be?
Dr. Michael Zile: In normal patients, of all ages, a normal ejection fraction is when the heart ejects 50 percent or more of the blood within it with each heart beat. So, a normal ejection fraction would be one that exceeds 50 percent. When people develop systolic heart failure and their ejection fraction falls, it falls below 50 percent, and commonly falls to numbers which approach 25 to 30 percent.
Dr. Pam Morris: What would be some of the typical causes of systolic heart failure, or weakness of that pumping chamber?
Dr. Michael Zile: When people develop systolic heart failure, there has been an injury to the muscle of the heart. That injury can come because of a heart attack. With a heart attack, the blood supply to a particular portion of that muscle is completely interrupted. That muscle no longer gets blood and it basically dies. So, that muscle tissue dies. So, think of this as if you are trying to lift a box with two hands and one hand is taken away from you. Now, you have to lift the box with only one hand. That is what happens with a heart attack. A piece of the muscle dies, then the remaining muscle has to do the normal pumping job of the heart. Therefore, it cannot do it as well. So, the ejection fraction, or the amount of blood that is ejected per beat, is reduced.
So, a heart attack can do it. Poisons, like alcohol, can do it. So, if somebody uses alcohol, or abuses alcohol, the alcohol actually damages the muscle cells of the heart and those muscle cells die, so you end up with less muscle tissue to do the same amount of work. There are some other agents, which doctors give patients, which can injure the heart. These are agents which treat certain cancers. Commonly, high blood pressure can injure the heart. If someone has high blood pressure for a very long period of time and it is ineffectively treated, the presence of that high blood pressure can damage the muscle of the heart and weaken its ability to eject.
Dr. Pam Morris: Now, I know there are often times younger patients, such as women after pregnancy or younger teenagers, who may suffer a weakness of the pumping chamber of the heart, or systolic heart failure. What would be the types of causes of that?
Dr. Michael Zile: There are actually three categories. One is a virus infection. There are certain viruses which can actually attack the muscle of the heart, damage that heart and cause those heart muscle cells to die and you end up with less heart muscle tissue. The second is a phenomenon which occurs after pregnancy that we call postpartum, or after pregnancy, cardiomyopathy. Cardiomyopathy is a term that you hear doctors use. Let me explain what cardiomyopathy means: Cardio, the heart, myo, the muscle, pathy, pathology. So, when you hear a doctor use the term cardiomyopathy, they mean heart muscle disease. So, after pregnancy, women can develop a cardiomyopathy. We do not really understand why that happens. We know it is associated with pregnancy. We do not know why it is associated with pregnancy. The third category is what physicians call, idiopathic. Idiopathic basically means, we do not really know what caused it. One can think of idio, being an idiot, physicians are idiots. They are not idiots. They just do not understand exactly what the cause is yet. Lots of people are working on trying to understand that. We are working on that here at the Medical University. But, that is a category of disease that we just do not really understand what causes it, but we know that it is present.
Dr. Pam Morris: Now, you mentioned a second type of heart failure, diastolic heart failure. Could you explain that?
Dr. Michael Zile: Diastolic heart failure is characterized by different changes in the structure and function of the heart. In systolic heart failure, the heart muscle is weak and cannot contract. That is not present in diastolic heart failure. In diastolic heart failure, the function of the muscle in terms of contraction, or systole, is actually normal. What is wrong with the heart in diastolic heart failure has to do with the function of the heart in diastole, when it is supposed to relax and fill, and fill at low pressures. Patients with diastolic heart failure have a thickened heart muscle which relaxes more slowly, fills incompletely, and is stiffer than normal.
Think of a thin-walled balloon. If you were going to try to blow up a thin-walled balloon, how much force would you have to use to fill that balloon with air? Not much force, it fills pretty easily. What if the balloon were very thick and stiff? You would have to blow like crazy to fill that balloon with air. That is exactly what happens in the heart. When the heart gets thick and stiff, it takes a lot of force to fill that heart, so the heart fills at higher pressures. What that means is, if you are looking at this from the point of view of the lungs, the vessels that go to the lungs have an increase in pressure. That pressure causes fluid to leak out of the blood vessel and into the lung tissue. When that lung tissue gets filled with fluid, it is hard to breath, and it is hard to bring new oxygen into the lungs. If you look at it from the point of view of the tissue in your legs, if the pressures inside the veins in your legs go up, fluid leaks out of the veins and into the tissues and you get swelling there. So, in diastolic heart failure, the pressures during diastole go up and force fluid out of the vessels and into the lungs and cause shortness of breath, and forces fluid out of the veins and into the tissues, into the skin, and cause swelling.
Dr. Pam Morris: Why would it be important to distinguish between the two different types of heart failure?
Dr. Michael Zile: It has only been over the last 20 years that physicians and scientists have begun to recognize the fact that heart failure can occur with a normally squeezing heart. It was only been in the last 20 years that physicians recognized that you can have heart failure with a normal ejection fraction. What we have come to understand over the last 20 years is, 50 percent of the patients that we see in our office, or in the hospital, in fact, have a normal ejection fraction. That is, they have diastolic heart failure. Now, think about that. Half of all the patients with heart failure have diastolic heart failure. So, the incidence, or prevalence, or frequency of this disease is markedly elevated. The second factor is the effect on survival. The presence of diastolic heart failure is almost as equally devastating as it is for systolic heart failure. Third, patients with diastolic heart failure have a similar amount of suffering, significant amount of healthcare burden, as people with systolic heart failure. That is, they get symptoms just as frequently. They have just as much of an impairment of their ability to exercise. They get admitted to the hospital with equal frequency.
The last reason this is important is that diastolic heart failure appears to occur more often in women than in men, more often as we get older than in younger patients, more often in people with hypertension, that is high blood pressure, or diabetes, high sugar, or people who are obese and have what is called a metabolic syndrome. So, it happens in populations which are slightly different than patients with systolic heart failure.
Dr. Pam Morris: Well, Dr. Zile, thank you for that fascinating discussion. We will come back again and talk more about treatment for the different forms of heart failure.
Dr. Michael Zile: Thank you, Pam. It has been a pleasure to be here.
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