Assessing — and Lowering — Your Risk of Heart Disease
The past 25 years have seen a revolution in the management of heart disease. By far the most common form of heart disease is coronary artery disease, in which atherosclerosis damages the coronary arteries (the arteries that feed blood to your heart muscle). Coronary artery disease is responsible for nearly half of the deaths of older Americans. However, scientists are increasingly viewing atherosclerosis as a preventable illness. Correspondingly, I'm devoting more attention in my practice to looking for atherosclerosis and treating it before it causes major damage.
What is atherosclerosis?
Atherosclerosis means "hardening of the arteries". No one knows the exact cause of atherosclerosis, but somehow blood fats become deposited in the walls of larger arteries. Then the arterial wall becomes inflamed, thickened, and stiff. Usually this process requires decades to progress, but under certain circumstances, it can happen in months or a few years.
The early stages of atherosclerosis are mostly silent; you don't become ill until the disease has become advanced. Then two things can happen.
First, the mass of fatty deposits and scar tissue within the arterial wall can be so thick it narrows the inside of the vessel and impairs the flow of blood. The tissues downstream of this artery become ischemic (starved for oxygen) and start to malfunction. If this is your heart, you may develop angina, or chest pains due to inadequate blood supply. In your brain, you may have transient ischemic attacks, or temporary periods of weakness or numbness in one area of your body. Poor blood supply to a kidney can cause high blood pressure and kidney failure (your kidney doesn't clean the blood adequately). The same sort of arterial narrowing can affect your legs, your intestines, and other parts of your body.
The inflammation of atherosclerosis can also damage the blood vessel wall. A sudden blood clot may form that completely shuts off blood flow and kills the tissue supplied by the blood vessel. In your heart, this is a heart attack: a portion of the heart muscle dies from lack of blood. Or, equally likely, you can die suddenly and without warning. A blood clot blocking an artery in your brain causes a stroke. Other organs can also be damaged by lack of blood supply.
While the portions of arteries that have been severely narrowed by atherosclerosis are at risk for developing an occluding blood clot, in fact such a clot often occurs in areas that are only mildly narrowed. So just treating severely narrowed arteries does not remove the risk of atherosclerosis.
Atherosclerotic damage to the blood vessel can also cause it to enlarge like the bleb on a worn-out tire (called an "aneurysm"). This occurs most commonly in the aorta, the main artery arising from the heart that travels through the inside of the chest to the lower abdomen. Aortic aneurysms rarely cause symptoms until they rupture, but then the death rate from loss of blood is very high.
Current thinking on atherosclerosis is if you develop atherosclerosis in one area, it's present to some degree everywhere else in your body. It may affect multiple organs at once. So the new perspective is that atherosclerosis is a systemic illness: it affects all of you. Therefore it must be treated systemically: your whole body at once.
What causes atherosclerosis?
Atherosclerosis occurs when excessive cholesterol and other garbage is deposited in the inner walls of your arteries, which then become inflamed. Age is the most important factor determining your risk of atherosclerosis: over 50 for men and over 65 for women. But smoking greatly accelerates atherosclerosis, so it occurs at a much younger age. The same is true of diabetes, high blood pressure, and severe elevations of cholesterol. Other factors can damage your blood vessels too: obesity, extreme stress, a high-fat or junk-food diet, and lack of exercise.
How does atherosclerosis affect the heart?
Atherosclerotic heart disease (ASHD) has been the biggest killer of Americans for several generations. Also known as "coronary artery disease," it's responsible for the deaths of 900,000 Americans annually.
The current death rate is 30% lower than it was a generation ago, but our risk may soon climb upwards again. Why? Americans are becoming fatter and less physically active. We're developing more diabetes and high blood pressure.
Curiously, more women (500,000 annually) are dying per year than men (400,000). Though women rarely develop ASHD before age 65, they often have unusual symptoms like shortness of breath and fatigue, rather than chest pain. So it's often hard to tell when a woman is in the early stages of heart disease. By the time it's clear something is wrong, their illness is more advanced and harder to treat.
Usually, you find out you have coronary heart disease without warning: you drop dead, have a heart attack, or develop angina. Each is equally likely. My patients agree dropping dead or having a heart attack is bad for you. We'd all like to be able to prevent such a sudden catastrophe.
Here's the good news: techniques developed in the last 10-20 years can detect the increased risk of heart disease in many people. Targeted treatment can then lower the risk of a cardiac event by 40-80%.
Preventing destructive cardiac remodeling
Sometimes people with heart disease develop one complication after another, moving from disaster to disaster. We've learned that much of the problem occurs long before patients develop symptoms: the heart is damaged by elevated blood pressure, high blood sugar, stress, and cholesterol in ways that make it much more likely to be harmed by any subsequent events. For example, one of the earliest changes is that heart muscle walls become stiff and don't relax enough to let the blood flow freely into the heart between contractions. As stiffness progresses, the heart enlarges and doesn't empty well when it does contract. As a result, the heart does an increasingly poor job of its essential function: pumping the blood. People start to feel tired for no obvious reason and restrict their activity. But excessive rest is bad for the heart, and so a series of vicious cycles ensues.
Preventing this cascade of bad news requires detecting problems and intervening before they become obvious. Early destructive remodeling responds to effective treatment, but the longer you wait, the more likely harmful cardiac remodeling has become permanent.
The key to lowering your risk of heart disease is to determine how much risk you have now -- none, low, intermediate, high, or severe -- before you develop symptoms. Then we match treatment to the degree of risk. No risk means no treatment. If your risk is low, lifestyle modification (exercise, diet, etc.) may be the only approach you need. Higher levels of risk require progressively more intensive treatment.
Most people who develop heart disease have factors that predict they are likely to have a problem. Here are the basic risk factors.Most important:
- Previous heart attack or other clear-cut heart disease
- Uncontrolled high blood pressure
- Impaired kidney function (measured with a blood test)
- Family history of early heart disease
- Abnormal cholesterol or other blood fat levels
- Obesity (particularly around your middle)
- Atherosclerosis (hardened, narrowed arteries) elsewhere in your body
- Lack of exercise
- Elevated blood sugar not high enough for a diagnosis of diabetes
- Metabolic syndrome (includes several of the other factors but is also important by itself)
Some people who have a heart attack never had any risk factors, but usually several have been present for some time. Thankfully, of all the risk factors just listed, there are only a few you can't improve.
Estimating Risk Severity
The best quick estimate of the likelihood of a cardiac event (heart attack, sudden death, or chest pain) comes from the Framingham Heart Study. Federal researchers have studied inhabitants of Framinghamm Massachusetts for over 50 years. Using that information, we can determine your Framingham Risk Score. What you get is a percentage: your risk of having a cardiac event in the next ten years. Low risk is less than 10%; intermediate risk is 10 to 20%, and high risk is greater than 20%.
You can determine your Risk Score right now if you wish: here's a calculator from the American Heart Association and another from the Cleveland Clinic. You need to know your age, gender, blood pressure, smoking status, total and HDL cholesterol levels, and whether you have diabetes. Both of these sites let you play with the numbers to see the effect on your risk.
Cholesterol and triglyceride (blood fat) levels greatly influence your heart disease risk. This is a big topic, which I discuss separately.
Refining Your Risk Estimate
For people of at least intermediate risk (three or more risk factors, or a Framingham Risk Score of 10% or more), it's important to get a more precise estimate of your likelihood of having coronary heart disease, so we can determine how intensively to treat you.
1. Performing a history and physical exam and running an electrocardiogram are critical to starting the process of determining risk. It's possible we'll learn you've progressed further down the path of heart disease than anyone knew.
2. Coronary artery calcium screening uses a special CT scan to show how much your arteries have scarred from atherosclerosis. This $400 computerized X-ray isn't covered by every insurance plan but gives excellent results. It has one failing: it measures the degree of inflammation on the outside of your arteries, not the narrowing within them. It doesn't work well in diabetics. Still, it's a good indicator of overall arterial disease.
Some cardiologists pooh-pooh coronary artery calcium screening as a waste of time. They say calcium deposits on the outside of your arteries do no harm. What you want to see is the insides of the arteries, looking for critical narrowing. (Indeed, 10% of people with heart attacks have zero coronary artery calcium.) To a degree they're right, but this approach beggars the larger question of risk. By the time you've developed critical narrowing, atherosclerosis is far advanced. Coronary artery calcium is an early measure of how much overall atherosclerosis there is. By providing a means to detect disease before the clinical event, we can often detect and mitigate risk before the crisis.
3. Exercise testing is superb means of estimating current risk. By monitoring you carefully while you walk on a treadmill, we can tell if your heart is up to the task. When more detailed information is needed, imaging how well blood flows in the exercising heart provides valuable additional diagnostic information. (SPECT nuclear imaging during a treadmill, using the newest high-resolution technology, can pick up early impairments of blood flow before clinical events.)
4. An echocardiogram uses sound waves to image the heart while it's beating, much as obstetricians use ultrasound to see a developing fetus. Newer echocardiogram machines can detect early destructive remodeling, before permanent damage has been done to the heart.
5. If we're extremely concerned about your heart, the definitive test is coronary angiography: using x-rays to look directly at the insides of the coronary arteries. This procedure detects critical narrowing that requires immediate treatment, but it's not nearly so good at detecting early risk.
How Do You Lower the Risk of Heart Disease?
Several individual treatments each lower the risk of having a cardiac event by 10-60%. None by itself is a slam-dunk, but when you add them together, their benefit is impressive. In this section I'll discuss groups of medications rather than individual drugs, because we have multiple choices among members of each class of drugs.
As you'll see in the next section, the higher your risk, the more treatment you'll need to remain healthy:
1. The single most effective treatment is taking a statin type cholesterol-lowering drug. Trade (generic) names include Mevacor (lovastatin), Pravachol (pravastatin), Zocor (simvastatin), Lescol (fluvastatin), Lipitor (atorvastatin), and Crestor (rosuvastatin). As noted in the discussion of lowering your cholesterol, these medications cut your heart disease risk by 30-50%. They work better than any other cholesterol-lowering drug, but occasionally they cause annoying side effects.
2. If your blood pressure is high or your risk is at least intermediate, you should be on an "ACE inhibitor" or "ARB" (angiotensin receptor blocker). Lowering high blood pressure cuts risk by up to 60%. Even if you have a normal blood pressure, for those with more than mild risk, an ACE inhibitor or ARB cuts risk by 15-20%. There are few potential problems with these medications, and patients usually tolerate them quite well. They are quite effective at reversing cardiac remodeling.
3. Two other types of blood pressure medications can also prevent dangerous heart remodeling and lower risk: calcium channel blockers and beta-blockers. Generally you'd take one or the other. Some people now are recommending beta-blockers for those with documented heart disease and calcium channel blockers if no cardiac events have occurred.
4. Taking a low-dose aspirin every day is probably the best-known way to lower heart disease risk: you achieve a risk reduction of about 15-20%. The problem with aspirin is while it lowers the risk of a cardiac event, it increases the risk of hemorrhaging into the brain. Brain hemorrhage is quite rare, but if it occurs, the results are quite unpleasant. Bottom line: taking a daily aspirin is a bad idea if your heart risk is low, but it's of proven benefit for those with at least intermediate risk.
5. Lifestyle changes are critical to lowering your heart disease risk. Stopping smoking is the single most important thing you can do for your health. Though it's often difficult to lose weight, changing your diet (more fresh vegetables and fruit, less animal fat, less junk food) produces enormous health benefits. Modest exercise reduces your heart disease risk by 50%, improves function, and dramatically lowers the risk of virtually every illness.
Treating According to Risk
Once we've determined your level of risk (none, low, intermediate, high, severe), we then tailor treatment to the risk:
- None: Go walk in the sunshine. You don't need any treatment per se, but for heaven's sake, if you smoke, stop.
- Low: Improve your lifestyle -- smoking, diet and exercise.
- Intermediate (two or three risk factors): In addition to the lifestyle changes just mentioned, be sure your blood pressure is well controlled, and use a statin drug to lower LDL cholesterol to less than 130. An ACE inhibitor or ARB is a good idea for most. Many people should also be on daily aspirin.
- High (multiple risk factors): You need lifestyle changes, a well-controlled blood pressure, and an LDL cholesterol less than 100. In addition, most patients should take a daily 81-mg aspirin, an ACE inhibitor or ARB, and a beta-blocker or calcium channel blocker.
- Very high (diabetes, smoker, kidney disease, previous heart attack): Same as "high," with an LDL cholesterol target of less than 70.
Last updated Fri, Jun 19, 2015
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