Heart Disease Explained
Heart Disease Explained
Rose Marie Robertson, MD, FAHA, FACC, FESC (Chief Science Officer and Past President of the Board of American Heart Association) gives expert video advice on: What are the risk factors for a stroke?; What are the environmental risk factors for heart disease?; Does exercise help prevent heart disease? and more...
What are the risk factors for coronary heart disease?
Coronary heart disease or coronary artery disease is associated with a number of risk factors, some of which we can do something about and some of which we can't. Things we can't do much about are age. There's much more coronary heart disease (or coronary artery disease) in older people than in younger people, although coronary disease actually begins in the teens and twenties but is often seen only later in life. We can't do much about changing our gender. Men do develop coronary disease at an earlier age than women, so that's an inevitable risk factor. We can't do anything about our family history. You can't choose your ancestors. However, there are many risk factors that we can do something about. Right at the top of the list is smoking. So to prevent coronary artery disease (or coronary heart disease) and of course many other diseases, it's clear that people shouldn't smoke and should stop if they smoke now. High cholesterol levels are associated with and cause coronary artery disease or atherosclerosis. High blood pressure is also associated with atherosclerosis. Those are two very treatable risk factors. In addition, and people don't often think about these, having poor nutrition and being overweight or obese, and being physically inactive, are also major modifiable risk factors for coronary artery disease or coronary heart disease, and those are things we can do something about. Diabetes is one of the most powerful risk factors for coronary disease and, while you can't change that if you develop it early (if you have Type 1 diabetes), you can certainly try to treat it as effectively as you possibly can. You can also try to prevent yourself from getting Type 2 diabetes by staying lean and active, because Type 2 diabetes associated with insulin resistance is very commonly present in people who have become obese.
What are the risk factors for non-coronary heart disease?
There are many processes that can lead to heart disease not associated with coronary disease or atherosclerosis, just as the same processes can cause disease in other organs. For example, trauma is such a cause. If we're in an auto accident, and we run our chest up against the steering wheel, the trauma of that; the actual physical force against the hardened blood vessels as they sort of swing forward and hit our chest wall, can actually damage the heart. It can particularly damage the great vessels. People recognise, for example, that Princess Diana died because blood vessels were torn in her chest when she was in an auto accident. This is a very common cause of death in people who die at the scene in an auto accident. Likewise, the process of infection can affect the heart. For example, intravenous drug users will often get an infection of the bloodstream. That infection can actually affect the valves of the heart, and can destroy the tissue of those valves, so that the valves leak, and that's a kind of heart disease. One can have inflammatory processes; inflammatory diseases that affect the heart. For example, lupus, systemic lupus erythematosus, is an inflammatory process and it can affect heart valves so that they leak. So, there are a whole series of processes that can affect the heart; infection with viruses, infection with bacteria, and trauma that can cause problems for the heart muscle. In that case we call that a cardiomyopathy, where the heart muscle doesn't pump and function so well. If we have inflammation of the pericardium, the sac around the heart, we have pericarditis, a painful process that fits into the category of these cardiovascular and heart diseases that are not caused by coronary artery disease and not necessarily related to it. Some processes are actually associated with other diseases or other risk factors. Hypertension, for example, which causes the heart to have to work harder, to pump against that higher pressure, will actually lead to the heart muscle getting thicker; just as when we exercise a muscle by lifting weights, we can exercise the heart and have it get thicker. That's not necessarily so good for the heart; if the heart muscle becomes thick, it becomes hard to fill the heart with blood so that it can pump it out, and that can cause a kind of heart failure. Diabetes, likewise, can affect the tissues of the heart so that the heart is stiffer than it normally would be, also leading to a kind of heart failure called diastolic dysfunction or diastolic heart failure.
What are the risk factors for a stroke?
The risk factors for stroke are very similar to the risk factors for coronary artery disease or atherosclerosis, because atherosclerosis or hardening of the arteries is the basis both for heart disease, coronary disease, and of the great majority of strokes, what we call ischemic strokes caused by clots to the brain. Smoking, high cholesterol, high blood pressure, being over weight, being physically inactive, and having diabetes are all risk factors for stroke. High blood pressure has a particular effect for stroke because it increases the risk, not only of atherosclerosis, but also of hemorrhagic stroke, the strokes that are caused by bleeding into the brain by having a small leak in the blood vessel in the brain. In addition, you can have a stroke for several other reasons. People who have sickle cell disease are prone to having strokes and there is a kind of heart rhythm problem called atrial fibrillation - really quite a common rhythm problem - that also makes people more likely to have strokes. If you have heart valve disease or have had a large heart attack, you also have the propensity to have a clot form that can be sent to the brain and cause a stroke. There are more causes for strokes than for heart disease but many of them are similar, so many strokes can be prevented.
What are the environmental risk factors for heart disease?
When we think about environmental risk factors for heart disease, we often think about things like pollutants in the air. There are environmental pollutants that can increase your risk of heart disease. In particular, the one that we see most often is the one with which we're most familiar and that's tobacco smoke. But other particulates in the air can also raise the risk of heart disease. Clearly the one we need to work most to avoid because it has the most enormous impact on our society, is tobacco smoke, both for the individual smoker, and for people who are otherwise forced to breathe what clearly is a risk to them, second-hand smoke. There are two other environmental factors that I think are worth thinking about. One is that we, in terms of obesity, live in an environment where food is always available, and not only food has calories, but beverages as well. So it's important to think about that environment and to work our way through it as we go about our day planning, thinking about ways to avoid taking in excess calories and calories we don't need and that we're not going to burn, that will put us at risk by making us obese. In addition, we need to find ways to build exercise routines into our environment and convert what is otherwise an unhealthy environment into one that fosters a healthy lifestyle for us.
How are obesity and heart disease related?
The exact way in which obesity increases the risk of coronary disease is uncertain. We know a number of things: we know that obesity is very frequently seen in a constellation of factors that we now talk about as making up the metabolic syndrome. People can have three, four, or five of these different factors. If you see them clustering together in someone, we know that they are increased risk. For example, people who have an increased waist circumference. They are not only obese but their weight is carried in the middle: they have abdominal obesity, belly fat. People who have high blood pressure, it doesn't even have to be too much, a little high blood pressure, a little hypertension. People who have increased fasting glucose, that is they are insulin resistant. They have Type II Diabetes or they have Pre-Diabetes: they're in early stages of it. People can have increased triglycerides: that is another kind of lipid or fat that circulates in the blood. Particularly with women, that seems to be associated with a higher risk of coronary disease. Those things are all increased, and decreased is the good cholesterol, the HDL cholesterol. We've mentioned five factors, and any three of those together come together to give us the diagnosis of the Metabolic Syndrome. That tells us that those patients are increased risk, and we need to treat all their risk factors, not just their obesity, to try to reduce their risk of coronary disease.
Why does "belly fat" specifically affect heart disease?
We know that obesity is associated with an increased risk of coronary artery disease. But it's a particular kind of obesity. It's the kind where you carry the fat and carry the weight in and around the abdomen. The reason for that is that that kind of abdominal obesity is associated with fat around the organs. It's unlike the fat that people have--we call pear-shaped--who have the fat around the buttocks and hips. That's not quite as much of a risk factor. But abdominal obesity means that if you took the heart and you looked at the heart, what you'd find is that it was actually, the coronary arteries are actually outlined in fat, so that over each blood vessel you'd see a big chunk of fat lying around the heart. And there appears to be something about having the fat there as, as opposed to having it distribted under the skin around the rest of the body that really raises your risk. We don't know quite why that is, but we know it's there. You can see that because if the fat increases in the abdomen, the belly's going to expand. If the fat increases in the chest, it can't expand because we have ribs that keep it fixed. So abdominal obesity is the important, is the important kind to look for. And we think it's important for people to keep their waist circumference under 40 inches for men and under 35 inches for women to not be in that category of higher risk.
How are stress and depression related to heart health?
Controlling stress is something that certainly makes ones life more pleasant in may ways. Patients often ask if stress is a problem in terms of their heart health, if being under stress adversely affects them, and the short answer to that is that we really don't know the specific ways that stress might affect the heart. We can speculate easily about stress hormones, the effects they may have on the blood clotting and blood vessels, and there's certainly are examples of people who in acutely stressful circumstance - psychologically stressful circumstance - have had a sudden cardiac arrest, developed heart arrhythmias. There are anecdotal suggestions that stress and heart attacks may be related, but for most people the issue is what kind of long term effect does stress have and what can they do about it. There's no question that if one is stressed, overwhelmed and unable to really deal with the other aspects of your life that would normally make you healthier, then stress could certainly have an indirect affect. A related area is the issue of depression, and there's no question that depression should be found and treated, simply from the point of view of quality of life. Depression can make people less able to comply with the appropriate kinds of risk factor reduction and activities that they need to do. Depression also can have an effect on the heart, albeit in a indirect way.
Why is diabetes a risk factor for heart disease?
Diabetes, both type 1 and type 2 is an important risk factor for heart disease, particularly for coronary heart disease. In fact, most people with diabetes actually die of the heart disease rather than of the diabetes itself, or of the complications. Diabetes can have multiple effects on the blood vessels, on the heart muscle itself and its function, and on the stiffness of the heart muscle so that heart failure can be a problem with diabetes. But the thing that we worry most about is the factors that relate to increasing risk for heart attacks and strokes; increasing atherosclerosis.
Does exercise help prevent heart disease?
There have been many studies over the years that have associated a healthy amount of exercise with a lower risk of heart disease. From the Harvard Physicians' study, to Mr. Fit, many studies have looked at people who engage in physical activity and compared them to who don't. There's no question that being physically active is good for us in many ways, and one of the ways is helping reduce our risk of heart disease. Being vigorously active is particularly beneficial, and in the Harvard Physicians' study, it was vigorous physical activity that gave you the greatest benefit. That allowed you to say, "For every hour I exercise, I'll actually gain two hours of longevity - I'll live two hours longer". Even lower levels of exercise are of benefit to us. We think that people should all exercise at least thirty minutes on most, if not all, days of the week. Unfortunately, very few people in this country actually get leisure time physical activity. The better-educated get more. We have a misdistribution of exercise by ethnic groups. Leisure time physical activity is a great lack in terms of peoples' lifestyle, and one that - while it's not always easy to build in, in terms of schedule - can be built in and has a big benefit in terms of preventing heart disease.