Most of us think we know what a heart attack looks and feels like. Pain or discomfort in the chest…shortness of breath…a cold sweat…and perhaps even a sense of impending doom. But not so fast. Heart attack symptoms can vary widely from person to person—and may not be noticeable at all.

The reality: Of the 735,000 heart attacks that strike Americans every year, nearly half are silent—that is, there are no obvious symptoms. In fact, people who have had a silent heart attack don’t even know they’ve had one! These heart attacks don’t occur only in older adults—they are quite common in middle-aged adults, research shows.

Don’t be fooled: Many people assume that a silent heart attack is less harmful than a “real” heart attack, but that’s not true. In fact, some studies indicate that a person who has had a silent heart attack has a higher risk of dying from heart disease than a person who has had a recognized heart attack—perhaps because he/she doesn’t receive appropriate medical care.

ARE YOU AT RISK?

Some risk factors for a silent heart attack are obvious, such as high blood pressure, smoking and being overweight. But many other risks are hidden and largely unrecognized by doctors and patients alike.

If you have one or more of the risk factors below, make an appointment with an internist or a cardiologist and discuss getting an electrocardiogram (see below for details) to determine whether you have damage to the heart due to a silent heart attack you may have unknowingly suffered.

If your doctor discovers that you have had a silent heart attack, your treatment—such as medications, a heart-healthy diet and regular exercise—should be the same as that received by a person who has had a recognized heart attack. Your primary care physician can provide much of the care, but if you have had a heart attack, you should be seeing a cardiologist at least yearly. Important risks for silent heart attack…

• Low sensitivity to pain. Because pain is a major symptom of most heart attacks, it stands to reason that silent heart attacks are more likely in people who are less sensitive to pain—and recent research confirms this theory.

Recent finding: In a study of nearly 5,000 people, published in the Journal of the American Heart Association, researchers found that women with lower pain sensitivity were more likely to have had a silent heart attack than those who were more sensitive to pain. According to this study, people who can keep a hand in icy water for up to two minutes have a lower sensitivity to pain.

• Peripheral neuropathy. About 20 million Americans—many of them with type 2 diabetes—have peripheral neuropathy, nerve damage that causes symptoms such as numbness, tingling and burning pain, usually in the feet or hands. Having diabetes and peripheral neuropathy more than doubles the likelihood of having a silent heart attack—probably because sensitivity to sensation has been reduced.

Recent finding: A study of US adults in the National Health and Nutrition Examination Survey found that those with gout or high uric acid levels were at greater risk of suffering a silent heart attack and subsequently dying of heart disease that those whose uric acid was normal. Uric acid can be determined by a simple blood test and is often obtained by a chemistry panel obtained by primary care physicians during a periodic physical examination.

• Elevated blood sugar. A fasting blood sugar (glucose) test is typically ordered to detect elevated glucose levels and diabetes. You fast overnight for at least eight hours, and your blood is drawn in the morning and sent to a laboratory, where your glucose level is measured. If it’s 126 mg/dL or higher, you have diabetes. But if your glucose level is 100 mg/dL or higher, you’re 60% more likely to have had a silent heart attack than someone whose glucose level was normal (less than 100 mg/dL). Chronically high levels of glucose (even if they haven’t yet reached the point of diabetes) damage arteries, increasing risk for heart attack and stroke. Elevated glucose is common. The average adult in the US has a blood sugar level of 106 mg/dL.

• Sluggish kidneys. Two findings on routine laboratory tests that measure kidney function have been linked to a higher risk of having had a silent heart attack…

Albuminuria. This indicates that there are elevated levels of a protein in your urine that can signal kidney disease. Albuminuria is detected by a combination of two tests—a microalbuminuria test and a creatinine test.

Low glomerular filtration rate (GFR). This shows your kidneys are struggling to do their main job—filtering impurities out of your blood.

Scientific evidence: A study of nearly 19,000 people by researchers from the University of Alabama at Birmingham found that people with the highest levels of albuminuria (greater than 300 mg/g) were 2.5 times more likely to have had a silent heart attack than those with the lowest levels.

They also found that those with the lowest estimated GFR levels (less than 30) were three times more likely to have had a silent heart attack than those with the highest levels. (Normal GFR varies by age but ranges from 60 to 120.)

• Fatigue, swollen legs and/or breathing problems. All three can be symptoms of a weakened heart muscle—including one damaged by a heart attack. If you experience these symptoms but you haven’t had a detectable heart attack, you may have had a silent heart attack. Especially if one or more of these symptoms come on suddenly or unexpectedly, see a doctor promptly for an evaluation.

SMART STRATEGY

Detecting a silent heart attack is easy to do with an electrocardiogram (EKG or ECG). This five- to 10-minute test measures the electrical activity of your heart. If the EKG detects abnormal “Q-waves”—a lack of electrical activity in areas of the heart—your heart muscle has been damaged by a heart attack.  

If you’ve had a silent heart attack, you should promptly treat your heart disease. In my decades as a cardiologist, I’ve seen over and over again that treating cardiovascular disease with cholesterol-lowering medications, increasing daily exercise and improving diet dramatically decreases the risk for a second heart attack and premature death.

If you have had a silent heart attack, a second one is also more likely to be silent or have atypical symptoms, such as neck, jaw or back pain, nausea, dizziness and/or fatigue. Be on guard for unusual symptoms and a sense that you’re feeling “not quite right.” Also, be sure to see your physician for regular checkups.

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