There are many myths that exist in medicine. Many of them stem from recommendations that once were thought to be true, but new evidence suggests otherwise. Here are 10 of the best examples in my specialty of cardiology:

1. Lowering blood sugar by taking medications for diabetes will reduce your risk of having a heart attack. Heart disease is the leading cause of death in people with diabetes. Yet, until recently, there was no evidence that medications that lower blood sugar, including insulin, also decrease cardiac risk. Recent studies using a new kind of medication called SGLT2-inhibitors (Jardiance and Invokana) show that adding this medication can lower risk of having a heart problem, especially congestive heart failure. These drugs are underused, primarily because they are still new and very expensive.

2. Having high blood pressure will cause a headache. Most people with high blood pressure do not have any symptoms at all, which it is why it is called the silent killer. Waiting for symptoms to arise may mean that the first symptom you have is a stroke.

3. Cardiac surgery will cure your heart problem. Bypass or stents are effective and a life-saving treatment for a heart attack but do not cure heart disease. Studies have shown that following an anti-inflammatory diet, losing weight, exercising, and taking medication can actually reverse coronary artery disease, and often be more effective then stenting or surgery.

4. Chest pain is the main warning signal of a heart attack. The classic symptom of a heart attack, which is crushing chest discomfort, occurs only about one-third of the time. Look for symptoms like sudden shortness of breath, pressure or tightness in the chest or arms, and know that unusual symptoms are more common in women than in men.

5. If you have a strong family history of heart attacks, you are doomed to have heart disease. Although people with bad family histories often have a genetic reason that their cholesterol is high, and may need statin medication, the benefits of a plant-based diet and exercise are highest in people with a family history of heart disease.

6. Fish oil will lower your cholesterol. The opposite is true. Most fish oil, also called omega-3 fatty acids, will actually raise your LDL (bad) cholesterol but lower triglycerides. A recent study showed that people with high triglycerides who are taking a statin may benefit from a kind of fish oil that is pure EPA, but evidence that fish oil helps the heart in other cases is scanty.

7. Sleep apnea occurs only in the overweight. This sleeping disorder, which is associated with an increased risk of atrial fibrillation, stroke, and high blood pressure, may be more common in heavy people but can occur in almost anyone. The only way to diagnose it is to have a sleep study, which can usually be done in your home.

8. Everyone should have a blood pressure less than 120/80. With new guidelines from the American Heart Association stating that lower is better, it is not surprising so many people are concerned when their blood pressure is higher than this “magical” number. It is meant as an ideal target to encourage people to lose weight, exercise, and cut back on salt, which can all lower blood pressure. If your top number (systolic) remains more than 140 mmHg and bottom (diastolic) near 90mmHg or higher, despite making these changes, it is time to see your doctor about starting a medication.

9. If your HDL (good) cholesterol is high, it will protect you. Although this was felt to be true for many years, studies have shown that medications to raise HDL showed an increase in cardiovascular risk, and HDL is no longer considered to be as cardioprotective as we once thought.

10. An aspirin a day keeps the doctor away. Taking a preventive daily low-dose aspirin is no longer felt to be necessary for everyone, and can do more harm than good. According to recent studies, if you have never had a heart attack, stroke, stent, or coronary bypass, and are over age 70, talk to your doctor because you probably should no longer be taking preventive aspirin. However, if you think that you might be having a heart attack or stroke, it is still crucial to take an aspirin right away, as it can then be lifesaving.

David Becker, M.D., is a frequent Inquirer contributor and a board-certified cardiologist with Chestnut Hill Temple Cardiology in Flourtown. He has been in practice for 25 years.