World-first research reveals how your weight and genes can trigger a common heart condition that increases the risk of stroke.
The findings, published in a prestigious cardiology journal, provide valuable insights into how these two risk factors cause atrial fibrillation and could help to improve treatment options in the future.
Atrial fibrillation, or AF, is a type of arrhythmia that causes the heart to beat quickly and irregularly, reducing its ability to pump blood and increasing the risk of blood clots forming.
Director of Heart Rhythm Services at the Royal Melbourne Hospital (RMH) Professor Jon Kalman AO said being overweight or obese increased the risk of developing atrial fibrillation.
Until now, it hasn’t been clear how excess fat around the heart impairs the organ’s ability to function normally.
The hearts of 19 patients undergoing heart surgery at the RMH were analysed in a study led by Professor Kalman and Professor Lea Delbridge at the University of Melbourne’s Department of Physiology.
They focused on a pocket of fat beneath the outer lining of the heart: the epicardial adipose tissue. A small amount of fat in this region is normal, but too much can increase the risk of atrial fibrillation and make it harder for doctors to manage the condition.
In the study, the effects of larger pockets of fat on the heart’s electrical system were measured, using CT scans, echocardiograms and electrical testing, and by examining the microscopic structure of the tissue.
The findings, published in the prestigious Journal of the American College of Cardiology (JACC) found the increased fat slowed the electrical conduction in the heart, which affected its pumping rhythm.
“What transpires is that the fat starts to grow into the wall of the heart,” Professor Kalman said.
“It goes in-between the muscle bundles and releases substances that cause scarring, enabling fibrous tissue to deposit between the muscle bundles and these both disrupt the electrical conductivity of the heart.”
Prof Kalman said the findings not only improve our understanding of the way fat impacts on heart health, they also provide patients with additional impetus to lose weight.
“The flipside of this is that when you lose weight, the health of the heart can improve significantly- many of these changes seem to be reversible.”
In a second study, published in the Journal of the American College of Cardiology: Electrophysiology, Prof Kalman and Professor Diane Fatkin from the Victor Chang Cardiac Research Institute looked at how the most common genetic variation associated with atrial fibrillation impacts on the treatment outcomes of patients.
The study involved 106 patients who had a procedure commonly used to treat AF, known as ablation: this involves scarring some tissue in the heart, to disrupt the faulty electrical signals causing the irregular heartbeat.
“We found that the 40 per cent of patients who were carriers had significantly different electrical properties in their heart that predisposed them to atrial fibrillation,” Prof Kalman said.
Not only were their hearts ‘wired’ differently, they were also significantly less likely to be free of arrythmia two years or more after the procedure.
“Our research indicates that we may need to take a different approach to treating these patients in the future to increase the effectiveness of their treatment.”
A more targeted and intense approach to ablation, focused on the areas of the heart that are wired differently, may be required.
In the future, patients diagnosed with AF may also undergo genetic testing to determine whether they are carriers of the genetic variation, allowing clinicians to tailor their treatment approach. However, a larger study that randomised patients for different treatment regimens would be required first.