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New JAMA Study Shows That Testing Gut Bacteria Can Predict Risk of Heart Attack

Jan 31, 2017 02:14 AM

Feb 7, 2017 09:43 PM

It feels like someone reached into your chest and squeezed. Your head throbs in unison with your heartbeat. Clammy dread coats your body in sweat. Whether you call 911 or someone does it for you, the ER is your next stop.

Stable but still scared on the gurney, you are heading for a lot of tests. The results of one blood test come back fairly quickly. It surprises you when your doc says this one actually measures a molecule made by bacteria in your gut. The good news is, your gut seems to think you are going to be okay.

Fact, fiction, or somewhere in-between? New research published in the European Heart Journal suggests that levels of trimethylamine N-oxide (TMAO), a molecule produced by bacteria in the gut, could be indicative of coronary issues to come.

The study found correlation between high levels of TMAO in the blood and increased risk of a future cardiovascular incident. The simple, fast blood test gives a credible prediction over the short and long term, and it only costs a hospital about $55 per test. Sound like fiction? Apparently it is not.

Jon Sullivan/Wikimedia Commons

Your gut is home to the largest concentration of bacteria in your body, roughly 100 trillion, representing about three pounds of weight. At work 24/7, these bacteria, your gut microbiome, play a big part in digestion, immune function, metabolism, and more.

When you were born, your body was already seeded with beneficial bacterial from your mother. Over time, your microbiome, or microbiota, took on an identity as unique as your fingerprints. No two people have the same microbiome, and there is no standard of what kind of microbiome is best. Your microbiome reflects your genetics, environment, diet, hygiene, and many other habits—it reflects you.

As they say, you are what you eat, and the microbiome takes that to heart. A sedentary lifestyle with a diet high in refined sugar and processed food nurtures a different type of microbiome than one within an active person who eats vegetables, fruit, grains, and lean proteins.

Whatever you eat, gut microbiota see some of that action. After metabolizing food, gut bacteria synthesize and produce several products. In the case of foods like steak, dairy, and eggs, gut bacteria produce elevated levels of the molecule TMAO.

A Study That Looked at the Gut to Gain Knowledge About the Heart

In the study, researchers followed two groups, one at the Cleveland Clinic in the US, and the other at university hospitals in Bern, Lausanne, Zurich, and Geneva, Switzerland. The US group included 530 patients, while the Swiss study included 1,683 participants. Both studies included patients over 18 years of age who were admitted to the hospital for chest pains. The Swiss study included patients who underwent coronary angiography within five days of admission.

Coronary angiography is a common procedure involving the use of contrast dye and x-ray to view potential blockages in coronary arteries that could lead to heart attack or stroke.

For anyone, chest pain is always a reason to be medically evaluated. Yet chest pain can have causes that do not involve the cardiac muscle. Some of the symptoms of heart attack can be mimicked by stress, anxiety, or costochondritis, commonly known as "chest wall pain," which can be stabbing, throbbing, and/or unexpected pain.

More than seven million people each year visit emergency departments due to chest pain. According to research published in JAMA Internal Medicine, most of those evaluated are eventually given a noncardiac-associated diagnosis. Admitting these patients, who have a low risk of adverse events, represents about $11 billion in healthcare costs each year. A diagnostic tool with predictive capabilities could help physicians make informed admission decisions, and help reduce patient fears.

By following these cohorts of patients for several years, study findings were straightforward:

Patients with elevated TMAO levels were more likely to suffer a cardiac event within 30 days, six months, and seven years after initial admission.
Individuals with TMAO levels in the top 25% were approximately six times more likely to suffer heart attack, stroke, require surgery, or die between 30 days and six months later. At seven years, the risk of death from elevated TMAO was still twice that of patients with lower levels.
Troponin T is a protein released into the blood when the heart muscle is damaged. Blood tests measuring troponin T are often used to assess a cardiac event. Patients in this study who measured with low or negative amounts of troponin T on admission, but showed levels of TMAO in the top 25th percentile, were six times more likely to suffer cardiovascular trouble.

This study does not connect the dots to advise that steak, dairy, and eggs specifically increase your risk of cardiovascular event. But it does give doctors a reason to recommend a healthier diet to those who have elevated TMAO and are therefore at a higher risk of a coronary event.

"TMAO offers a better understanding of the clinical impact that our daily diet has on the cardiovascular system, specifically in patients presenting with acute coronary syndrome," co-author Slayman Obeid, a junior consultant at the University Heart Centre, Zurich, said in a press release. "This opens the way for new preventive measures, such as encouraging patients to switch from a diet rich in red meat, dairy products and eggs to a Mediterranean diet rich in green leafy vegetables and fibre."

American College of Cardiology

Available through the Cleveland HeartLab, the new blood test may prove a powerful partner when assessing patients suffering or concerned about cardiac symptoms. Study authors note in the paper that:

It is therefore tempting to speculate that the ability to generate rapid and accurate TMAO results through point-of-care testing could significantly improve rapid triaging and risk stratification amongst subjects presenting with the complaint of chest pain and suspected acute coronary syndromes.

Further work is needed to better define the role of TMAO in cardiovascular health and cardiac events. Many healthy foods, like fish, result in temporarily high levels of TMAO in the blood. The Mediterranean diet advanced by study authors includes daily portions of seafood and fish. TMAO can also spike due to lecithin, a compound that contains a cell-signaling molecule called choline. Lecithin is used as a processed food additive, but is also naturally found in eggs—which have been cleared after years of worry about the cardiovascular implications of cholesterol levels.

Hopefully, you will never find yourself in an emergency room with chest pains. If you experience any warning signs of a heart attack, call 911, do not wait. During a heart attack or stroke, minutes make a difference to lasting heart muscle or vascular damage. Trust your gut—and get help.