Patients need enough exercise to reduce the risk of incident atrial fibrillation (AF) or improve symptoms in those who already have the condition – without overdoing it.

Speaking at the CSANZ annual scientific sessions, interventional cardiologist Dr Anthony Lau said treating weight and managing risk factors significantly improves and even reverses AF symptoms and the need for further invasive treatment and heavy reliance on drug therapy.

But he warned that some patients who get too enthusiastic about the benefits of exercise and who start training excessively could see their AF reappear.

Dr Lau, from Sydney’s Prince of Wales Hospital, said atrial fibrosis and inflammation were the key abnormalities leading to AF in both obese patients and also in those undergoing high intensity exercise.

And while an increased risk of AF is well documented in elite athletes, he said the gap between enough exercise and too much may not be as great as researchers once thought.

“There are a handful of people in our clinic who have gone on to do excessive exercise after having undergone our weight loss intervention and, despite the return of their body weight to normal, suddenly we see recurrent AF. When we took a more careful history these patients admitted to really being into an endurance style of exercise and we have had to ask them to pare back on the activity.”

According to Dr Lau, people engaging in high intensity physical activity such as cross country skiing, marathon running and professional cycling have a five to eight fold increased risk of AF compared to those with a normal or healthy physical activity level.

“With normal healthy AHA guideline activity you can decrease your risk of AF but when you start to increase your activity to at least moderate intensity like in the physician’s health study, where people were jogging five to seven days a week, your risk of AF starts to increase. When you go to the high intensity range, like professional cyclists, your risk gets even higher – you see progressive enlargement of both ventricles and both atria but notably it’s the significant enlargement in the right ventricle that you see in those undergoing extreme exercise,” he said.

“Moderate exercise is what we should encourage our patients to undertake to reduce their risk of AF. If we follow the AHA physical activity guidance the amount of dedicated exercise is minimum – fast walking for 150 minutes. But if we look at people who already have AF then those guidelines won’t apply as it all depends on where they start off, how sedentary they were in the first place, and then you have to tailor what they can do based on their physical limitations.”

“Every heart is different in terms of how you can sustain a certain amount of exercise before you decompensate and have more side effects from it.”