The Number One TestThat Predicts You Might Die Suddenly From A Heart Attack

The surprising number one test to identify your risks of a heart attack is not what you think.

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Other than cancer and Alzheimer’s disease, people fear heart disease and stroke. It is, therefore, no surprise that millions of dollars are spent by insurance companies and individuals trying to identify their risk of death and disability from heat-related illnesses. There are many tests available. However, I believe one tops the list.

But before we get to the answer, I need to post a disclaimer: The following does not constitute medical advice or recommend what is best for your body and health. You should always consult your physician for these specific concerns and recommendations.

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Electrocardiogram (EKG or ECG)

This quick and easy test is the oldest for examining your heart’s health. It records the electrical signals from the heart, is inexpensive, safe, and provides valuable information. However, its ability to predict a heart is woefully poor. EKGs can only identify old heart attacks in 48% of cases, which is about as useful as flipping a coin.

With symptoms like chest pain, sweating, and shortness of breath, an abnormal EKG is more accurate at predicting a near heart attack. However, many people with fears of dying suddenly or having a heart attack with little or no warning often have normal EKGs.

In summary, EKGs, by themselves, are not useful in a predictive sense. 

Stress tests

If you have no symptoms of heart problems, the routine stress test is often advised to look for signs of underlying coronary artery disease (CAD) or blockages that lead to a heart attack. However, the predictive accuracy of this test is poor too. 

In a recent study, about one-third of these asymptomatic patients with a normal stress test will ultimately be found to have severe underlying CAD. In other words, their disease was missed by the stress test.

About one-quarter of these asymptomatic patients with an abnormal stress test will later be shown to have little or no CAD.

Thus, while better than a resting EKG at identifying underlying heart blockages, a plain stress test is not all that accurate. Many asymptomatic patients have false-negative results where severe disease is missed, and others, called false-positive results, where the tests say there are severe blockages, yet none are found upon further study. 

Stress tests are inexpensive and relatively safe. Your chances of dying from an office stress test are 1 out of 10,000.

Nuclear Medicine and Stress Echo Tests

Due to the lack of great accuracy, other forms of stress tests have been designed. One is called a perfusion stress test. A patient walks on a treadmill or is given an intravenous drug infusion that mimics the effect of exercise on the heart, and near the end of the test, a radioactive substance is injected and follows blood flow to the heart. A scan at rest and after exercise is compared to see if blockages limit blood flow. 

With a stress echocardiogram, no radioactive substances are used. A resting ultrasound study of the heart muscle (echocardiogram or echo for short) is done at rest and after exercise. The heart muscle’s response to exercise is compared. 

How Accurate Are These Studies?

This article is somewhat old (2012); however, it is still relevant. It grouped many studies (called meta-analysis) to look at the numbers.

Looking at the arteries indirectly with a radioactive substance before and after a conventional treadmill stress test identified significant blockages in 88% of patients. However, there was a 30% false positive rate, meaning blockages were concluded from the test when, upon further testing, there was none. 

“Chemical” stress tests had about the same figures. Thus, these tests are still better than ordinary stress tests, yet they are far from perfect. And then there are the drawbacks to these tests:

• Expensive

• It requires two or more hours of patient time.

• Small, although generally considered safe, dose of a radioactive substance. 

• Reversible but unpleasant side effects if an intravenous chemical stress test is done. 

Coronary Calcium Score Test

The coronary calcium score test (CCST) does not require chemicals, radioactive substances, or exercise. It uses computerized tomography (CT) technology to determine where and how much calcium is in a person’s coronary arteries. The only safety issue is the dose of radiation (1 millisievert), which is about the equivalent of 10 chest X-rays.

When CAD occurs in the arteries over the heart, they thicken, and calcium is deposited inside the walls. Thus, calcium is a marker for the presence of blockages, but in and of itself not dangerous. The more calcium found, the higher the individual’s risk of future heart attacks.

The only downsides to the test are the radiation and the fact that many insurance companies do not pay for it. However, I have seen many tests offered for $100 or less. 

The accuracy of the test is “thought to be” high. However, to understand this, we must dip our feet into the dreaded world of statistics. The accuracy of the test depends entirely upon the type of people who are undergoing the test. This is the concept of “pre-test probability.”

I like simplicity, and therefore, I will use an analogy. Suppose you want to know what percentage of the population can’t walk. You could randomly count 1,000 people and get that number. According to the CDC, that number is 12%. However, suppose you count the number of people who can’t walk by visiting a disability section of a stadium. The number would be much higher.

The same is true of the calcium index score. The score will increase with age because older people have more hardening of the arteries. If you are 75 years old with no symptoms, risk factors, or history of heart problems, a higher calcium score is less accurate than if it was done when you were 25 or 45.

Therefore, middle-aged people benefit the most from the information this test yields. Because the accuracy is age and pre-test risk-dependent, I don’t believe or trust the accuracy numbers by themselves. 

If the test is combined with other factors, like cholesterol, blood pressure, and diabetes, it is very accurate. However, I promised you one test. And here is the winner:

Coronary CT Angiogram

The coronary CT angiogram (CCTA) is the best test for looking at the presence or absence of blocked heart arteries and, if present, where and how severe they are.

This test combines CT scanning with an injection of a dye in a vein to outline in great detail if you are at risk of a heart attack from blocked arteries. CCTA can identify significant blockages in 95% of patients, with a respectable 83% false positive accuracy. These numbers are comparable to that of conventional cardiac catheterization, long considered the gold standard for blocked arteries or risks of future serious heart events, including sudden death.

Downsides

• Expensive

• Requires more radiation (approximately three times more than a calcium index score CT)

• Requires intravenous contrast containing iodine, which could result in serious allergic reactions.

Caveats

The ‘gold standard” for coronary artery blockages is cardiac catheterization. However, even this test is not 100% accurate. And it requires poking a hole in a groin or wrist artery. Significant blockages (equal to or greater than 75% luminal diameter reduction) can easily be found. But if the blockage is hard, it is more likely to cause angina or heart pains rather than a heart attack or sudden death. The blockages that cause those are generally only 40–70%.

The CCTA can identify both the severely narrowed ones that cause angina and the moderate ones that can lead to a heart attack or sudden death.

The blockage quality, not only the narrowing percentage, is important. The “softer” blockages are more unstable and attract inflammatory cells and chemicals, often resulting in a blood clot inside the artery. The moderate (40–70%) lumenal diameter reduction blockages are the ones more likely to become unstable. Should a clot form, it can lead to very bad things, like a heart attack or sudden death. 

If you want to know your heart disease risk, combining multiple tests is best. This would be a consideration of risk factors like smoking, high blood pressure, high cholesterol, and diabetes. Add to that a special blood fat test, Lp(a), and one of the above imaging studies, and your accuracy in predicting a future heart attack improves greatly. 

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I hope this discussion has answered your questions and concerns about certain heart tests. The field continues to evolve. Although I identified the best test that doesn't require poking a hole in an artery and therefore is less “invasive,” no single test can give you the best answer.