The human heart beats roughly 3 billion times during the course of an average lifetime. Every single time it beats, blood is drawn into its two upper chambers, held there briefly by a network of valves, and then pumped out forcefully through its two lower chambers. This drawing-and-pumping action ensures that about six liters of freshly oxygenated blood leaves the heart and enters the bloodstream every minute—a volume that can rise to more than 35 liters per minute when someone is exercising. But none of that can happen unless the heart’s complicated machinery—its assorted valves and muscles and electrical circuitry—is working in harmony. When that harmony breaks down, the heart can pump too fast or too slow, or it can lose coordination among its various chambers. This breakdown is known as an arrhythmia, and it can lead to complications ranging from fatigue or shortness of breath to a heart attack or stroke. “When we say arrhythmia, we literally mean the heart is out of rhythm,” says Dr. Jonathan Piccini, a cardiologist and arrhythmia specialist at Duke University Medical Center. He compares the heart’s operation to a symphony orchestra. “If someone was playing off the wrong sheet of music or if their instrument were out of tune, that would not be subtle. It would be profoundly disruptive,” he says. “The same is true of a heart arrhythmia.” Heart arrhythmias are common; up to 5% of the general population has some form of the condition. The most common form, by far, is atrial fibrillation, or “Afib.” This is a type of arrhythmia that arises in the upper chambers of the heart. “Between 60 and 100 beats per minute is normal,” Piccini says. “In Afib, the top regions of the heart are in total chaos and could be beating on the order of 400 to 600 beats per minute.” According to figures from the U.S. Centers for Disease Control and Prevention (CDC), about one out of every seven strokes is caused by Afib. This and other life-threatening complications have led researchers to scrutinize the most common risk factors for Afib and other arrhythmias. “There’s a super long list of things that can promote or trigger or cause Afib, and one of the big ones is diabetes,” says Piccini, whose work in the Journal of the American College of Cardiology has examined the relationship between the two conditions. By some estimates, people who have Type 2 diabetes are 34% more likely to develop Afib than people without diabetes. Here, Piccini and other experts explain how diabetes and heart arrhythmias may be connected. They also discuss how both conditions are treated—either alone or in tandem—and how people with diabetes can protect themselves from serious heart complications. The diabetes-arrhythmia connection The Framingham Heart Study is one of the most famous and fruitful research efforts ever undertaken. It began in 1948 with 5,000-plus study participants—all from the town of Framingham in Massachusetts—and continues to this day. The purpose of the study is to track participants’ health and lifestyles over time in order to uncover potential risk factors for heart disease. Thanks in large part to the Framingham Heart Study, researchers recognized that smoking, high blood pressure, too little physical activity, and many other variables could raise a person’s risk for heart disease. Almost 30 years ago, data from the Framingham Heart Study helped reveal that people with diabetes are at increased risk for Afib. However, the connection between the two conditions has only recently garnered serious research attention. “This is an area of tremendous interest primarily because we have discovered newer classes of medications that, in addition to lowering glucose, can also reduce the risk of heart complications,” says Dr. Jennifer Green, a diabetes and metabolism specialist at Duke who, along with Piccini, has conducted research on diabetes and Afib. A lot more work is needed to determine exactly why people with diabetes are at increased risk for Afib. “But there does seem to be a cause-and-effect relationship between the two,” she says. One hypothesis is that elevated levels of blood sugar (or glucose), which is a hallmark of diabetes, causes damage to the heart that may result in arrhythmias. “There are things we call advanced glycation end products”—harmful compounds that arise when blood sugar combines with blood proteins or fats—“that we know can be responsible for organ damage,” she explains. Another hypothesis is that diabetes contributes to the development of high blood pressure (hypertension), which may cause damage to the heart in ways that result in an arrhythmia. “Diabetes affects the blood vessels in ways that make them stiffer and that makes blood pressure rise,” says Dr. Mattias Brunström, a hypertension specialist and physician researcher at Umeå University in Sweden. Roughly two-thirds of adults with diabetes also have hypertension, and people with hypertension are almost twice as likely to develop Afib as people who do not have hypertension. Yet another possibility is that diabetes-related inflammation may contribute to the development of an arrhythmia. “In people with diabetes, there are both systemic and localized increases in inflammation that, if severe enough and prolonged enough, could increase the risk of arrhythmia,” Green says. All of these hypotheses could turn out to be accurate. “It’s probably not just one mechanism or one explanation, but several,” she says. Read More: High Blood Pressure and Diabetes Are Linked. Here’s How to Reduce Your Risk for Both Prevention and treatment There is good evidence that people who have well-controlled diabetes are much less likely to develop Afib or other types of arrhythmias than people who have poorly controlled diabetes. “We’ve learned that the higher the glycemic load, the higher the likelihood a person will develop Afib,” Piccini says. Managing glycemic load (keeping blood sugar at a healthy level) is the main purpose of taking medication for diabetes. It’s possible that people who are undergoing treatment for diabetes don’t need to do anything different to lower their risk for an arrhythmia. “For anyone with diabetes, the goal is good glycemic control,” he
