Up to 5% of the general population has some form of heart arrhythmia, the most common being atrial fibrillation ( “Afib”), with doctors saying people with type 2 diabetes are 34% more likely to develop the condition than those without diabetes.
They have called for more work to determine why this is so, and which drugs can effectively target both conditions simultaneously, reports TIME.
“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 Centre.
“Between 60 and 100 beats per minute is normal. 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.”
The US Centres for Disease Control and Prevention (CDC) says about one in every seven strokes is caused by Afib.
This and other life-threatening complications have led researchers to scrutinise the most common risk factors for Afib and other arrhythmias.
“There’s a long list of things that can promote or trigger Afib, one of the big ones being diabetes,” says Piccini.
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 to uncover potential risk factors for heart disease. Thanks in large part to the Framingham Heart Study, researchers recognised that smoking, high blood pressure, too little physical activity, and many other variables could raise the 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, apart from 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.
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), 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 says.
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 without 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 localised 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.
Prevention and treatment
There is good evidence that people who have well-controlled diabetes have less likelihood of developing Afib or other types of arrhythmias than people with poorly controlled diabetes.
“We’ve learned that the higher the glycaemic load, the higher the chance of developing Afib,” Piccini says. Managing glycaemic load (keeping blood sugar at a healthy level) is the main purpose of taking medication for diabetes.
Some newer types of diabetes drugs may also help lower a person’s odds of developing an arrhythmia.
“There’s some evidence that SGLT2 inhibitors, for instance, may reduce the risk of atrial arrhythmias,” Green says. There are also some aimed specifically at heart complication risks in diabetics.
For example, a drug called finerenone may lower the likelihood that someone with diabetes will develop heart complications, including an arrhythmia.
While some of this work is promising, Green says more follow-up is needed. “Much of what’s been published already are analyses of observational data… looking at outcomes among people receiving the drugs and seeing how they do.
“That’s helpful, but we need randomised controlled trials to see if these drugs really do reduce risks.”
Piccini agrees. “There really haven’t been any studies expressly asking, does treatment with one of these lead to better outcomes?” he says. These sorts of studies are in the works, he adds, but we don’t have answers yet.
For a person diagnosed with both diabetes and a heart arrhythmia, the situation is much the same. Some drugs have shown promise in treating both conditions, but again, more work is needed.
Says Piccini: “If someone has Afib and diabetes, should we be using some medications in preference to others? This is an area where we need more information.”
Setting aside treatments that target both conditions, there are many effective ways to handle an arrhythmia, regardless of whether a person is diabetic.
One technique called electrical cardioversion uses low-energy electrical pulses to help reset and normalise the heart’s rhythm. The introduction of a pacemaker or other less-invasive procedures can also resolve or reduce the risks of an arrhythmia.
The good news is that there are many promising medications in the research pipeline.
In the meantime, there’s evidence that controlling diabetes using a mixture of existing medications and healthy lifestyle practices can prevent heart complications, including arrhythmias.
TIME article – The Connection Between Diabetes and Heart Arrhythmias (Open access)
Framingham Heart Study (Open access)
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Rethinking AF treatment to prevent life-threatening conditions – Canadian studies
AHA names 2021’s top heart disease and stroke research advances
Weight loss improves prognosis for obese Afibs