You already know the best ways to prevent a heart attack—give up cigarettes if you smoke…get regular exercise…lose weight if you’re overweight…and prevent (or control) high blood pressure (hypertension), elevated cholesterol and diabetes.

Yet millions of Americans continue to jeopardize their cardiovascular health by not fully understanding how to address these key risk factors.

Example: One common misconception is that you must do hard aerobic exercise to protect the heart. While it’s true that people who increase the intensity and duration of their exercise may have greater reductions in cardiovascular disease, that doesn’t mean you have to run on a treadmill or work up a sweat on a stair-climber to help your heart. A daily brisk walk (ideally, 30 minutes or more) will provide significant improvements in blood vessel function and heart-muscle efficiency.

Other misconceptions…

Misconception #1: Reducing dietary fat is the best way to control cholesterol. In the 1960s, the average American consumed about 45% of calories from fats and oils. After decades of warnings that a high-fat diet increased cholesterol, that percentage has dropped to about 33%.

That sounds like good news, but it’s not. Research clearly shows that the best diet for improving cholesterol is not a low-fat diet.

Reason: People who cut back on fat tend to reduce all fats in the diet, including healthful monounsaturated fats such as olive and canola oils. These fats improve the ratio of LDL “bad” cholesterol and HDL “good” cholesterol—a critical factor in reducing heart disease.

What to do: Cut back on saturated fat (ideally, less than 7% of total calories)—this fat does increase cholesterol.

But make sure that your diet includes healthful monounsaturated and polyunsaturated fats. In addition to olive and canola oils, foods that are high in monounsaturated fats include avocados, almonds, pecans, and pumpkin and sesame seeds. We get most of our polyunsaturated fats from sunflower, corn, soybean and other oils. Foods containing polyunsaturated fats include walnuts, fish and flaxseed.

Important: Of course you should avoid trans fats—engineered fats that are commonly used in commercially made cookies, crackers and other baked goods, as well as in deep-fried fast food. It’s been estimated that for every 2% of calories that are consumed daily in the form of trans fats, the risk for heart disease rises by as much as 23%!

Misconception #2: Blood pressure medication should be stopped if it causes side effects. Everyone knows that hypertension is a very strong risk factor for heart disease and a subsequent heart attack. Yet studies show that many patients who have been diagnosed with hypertension don’t achieve adequate control.

Blood pressure drugs are usually effective—but only if taken as directed. The problem is that these medications often cause uncomfortable side effects, including fatigue, dizziness or even fainting.

As a result, many patients—consciously or not—find excuses to skip doses or stop the medications altogether. It’s been estimated that only about 60% of patients follow all of the instructions for taking these medications.

But reducing or stopping blood pressure medications abruptly can cause a rebound, in which blood pressure suddenly spikes to dangerous levels.

What to do: Don’t suddenly stop medications because of side effects. And do your best not to forget doses or neglect to fill a prescription on time. Even if you do experience side effects when you first start a blood pressure medication, try to be patient and speak to your doctor, if necessary. Side effects typically go away on their own within a few weeks as your body adjusts to the lower blood pressure. Important: If a side effect is severe (fainting, for example), seek immediate medical attention.

With good control, people with high blood pressure can dramatically reduce their risk for heart attack and stroke. Studies have shown, for instance, that people who lower their systolic (top number) pressure by just five points can reduce heart attacks by 15% to 20% and strokes by 25% to 30%.

Misconception #3: There’s nothing you can do about your family history. We all know that heart disease “runs in the family.” If a close sibling or either of your parents developed heart disease before age 55, your risk of developing it is approximately one and a half to two times as high as someone without the family link. And if you have a first-degree relative (a parent or sibling) who developed atrial fibrillation (an irregular and often rapid heartbeat) at any age, your chance of developing heart disease is increased two to three times.

What to do: Even though family history is considered a nonmodifiable risk factor, you still can take precautions that will reduce your risk. If you have a family history of atrial fibrillation, for example, ask your doctor if you should have a yearly EKG. It can be included as part of an annual exam.

You should also be particularly vigilant about managing other risk factors for heart disease. Multiple risk factors—say, family history plus high cholesterol or hypertension—increase your risk far more than any one factor alone.

Misconception #4: Stress isn’t a danger once you’ve calmed down. It’s widely known that acute emotional stress caused by a near accident or some other frightening event causes a momentary spike in blood pressure and heart rate that can have harmful consequences. Anger, one of the most common stressful emotions, has been found to precede 2% of all heart attacks.

However, ongoing stress (due to financial or health worries, for example), which triggers chronically high levels of the stress hormone cortisol, is an often under-recognized threat to one’s heart and blood vessels.

What’s more, even though obesity is a factor in about 90% of patients with diabetes, some research suggests that chronic stress also may increase risk for diabetes—a known risk factor for heart attack and stroke.

What to do: Do whatever it takes to avoid chronic stress. Exercise, including yoga, is among the best ways to reduce stress while also protecting the heart. But find whatever works for you to defuse stress—for example, listening to music and reading are also helpful.