Arnold Schwarzenegger pacemaker - why elite endurance athletes can suffer heart problems

Arnold Schwarzenegger has recovered well from his pacemaker fitting but this event, in such a high-profile ultra-fit man, has highlighted recent medical studies that show that athletes can be more prone to abnormal heart rhythms later in life.

In must be emphasised that regular exercise is one of the best ways to protect the heart from heart attacks and heart failure. It directly strengthens the heart muscle and helps lower blood pressure and cholesterols reducing the risk of hardened coronary arteries.

However, despite these well-recognised benefits, sustained endurance exercise in athletes, footballers and other sportspeople can lead to an increased risk of abnormal heart rhythms - known as cardiac arrhythmias, including heart block. Normally, this doesn’t cause any problems for young athletes, and many do not experience any symptoms. But heart block in later life can progress to a more serious form, called second-degree heart block, which can cause dizziness, fainting, even stroke and increase likelihood of needing an electronic pacemaker later on.

Overall lifestyle factors such as smoking, alcohol, high cholesterol, high blood pressure, diabetes, poor diet and obesity remains the biggest risk factors for needing a pacemaker.

Arnold also had previous heart surgeries to repair a genetically damaged aortic and pulmonary values which may have led to some scarring damage to the electrical pathways. Being tall and of European descent are also slight risk factors for electrical heart issues.

Heart block can be associated with the development of another abnormal heart rhythm called atrial fibrillation. This is a more serious issue that can cause an irregular fast heart rate which is been linked to an increased risk of heart failure and stroke.

We know that the heart rate is regulated by an area in the heart called the AV node. This is made up of specialised heart cells which contain a set of unique ion channels that allow it to spontaneously generate and send electrical signals from the top of the heart to the bottom of the heart. Normally, the AV node receives input from the automatic nervous system, which regulates involuntary functions and triggers a faster heart rate when needed such as during exercise or digestion.

Cardiologists still don't fully understand why some endurance athletes get damage to their AV node and why they experience heart rhythm disturbances although a team of international team of scientists from Manchester, Montpellier and Copenhagen have shed more light on the underlying causes.

The head of the research Dr Alicia D’Souza explains: "It’s well known that athletes are predisposed to heart block which may be ‘a canary in a coalmine’ for necessitating the implantation of a pacemaker in some individuals."

The scientific team found that heart block was associated with defects in key ion channels responsible for sending electrical signals in the AV node, an area between the two heart chambers. In particular, that intense prolonged exercise could be traced to an increase in small molecules known as microRNAs which interfere with ion channels in the AV node.

These molecules directly bind to genes and inhibit their activity – so in this case, they prevented the ion channels from being able to work properly. This team, as well as others from around the world, are now researching practical ways to suppress this excess microRNA in the AV node, potentially avoiding the need for a pacemaker.

Although this issue is more relevant for elite athletes such as Arnold Schwarzenegger, more regular people or weekend warriors are participating in endurance and ultra-endurance events, so this may be relevant for many fit people going forward.

Obviously, I do not want to discourage anyone from profiting from the enormous, multiple benefits of exercise, particularly regular walking and cycling. Exercise remains one of the most crucial modifiable lifestyle strategies to improve heart health, avoid chronic degenerative disease such as dementia, diabetes, arthritis, osteoporosis and even cancer.

However, if you are over 60 years of age and have performed or continue to perform intense endurance exercise it would not be unreasonable have a health check which includes an electrocardiograms (ECG), a simple test that checks the heart’s rhythm and electrical activity, as early changes may be spotted. Moreover, if you have experience palpitations, especially those associated with dizziness, an appointment with your doctor may just save your life.