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Woman doing stretching exercises.

Experiencing irregular heartbeats during exercise may increase the risk of developing heart conditions and death, according to a new study led by researchers at Oxford Population Health and the Big Data Institute. The study is published in Circulation.

Exercise tests are commonly used to help doctors diagnose problems with the heart that may not be obvious at rest. The results help doctors to understand how likely a person is to develop heart conditions later on and take action to reduce this risk.

Premature ventricular contractions (PVCs), where the heart’s normal rhythm is disrupted by an early, out-of-place electrical signal in the lower chambers (ventricles) causing the heart to contract prematurely, are commonly found during exercise tests. The risks associated with these ‘extra’ beats for people with heart disease are already well known. However, there was less evidence available on the impact of these PVCs in people who do not have symptoms of heart disease.

In this study, the researchers counted the number of PVCs recorded in electrocardiograms (ECGs) recorded during a bicycle exercise test carried out on 48,315 participants in the UK Biobank study. The participants exercised at a moderate level for six minutes followed by one minute of recovery.

A subset of 4,607 participants also had blood test measures that are commonly used to diagnose heart failure taken at the same time as the exercise test. 6,290 participants underwent a magnetic resonance imaging (MRI) scan around six years after the exercise test to see whether or not they had any heart disease that was not advanced enough to cause symptoms.

The average age of the participants in this study was 56.8 years and 51.1% of the participants were women. The researchers looked at the health records of the participants after they had completed the exercise test for an average of 12.6 years to see whether or not they had developed any heart conditions or had died from heart-related causes in this time.

Key findings:

  • Increased PVC counts were associated with a higher risk of developing major heart conditions: A low PVC count (1-5) during exercise and recovery increased risk by 20 to 30% but a high PVC count (more than 20 during exercise, more than five during recovery) increased risk by 60 to 80%.
  • High PVC counts were also found to be associated with a higher risk of death from any cause by 50 to 60%;
  • Complex PVC rhythms were associated with a higher risk of heart conditions and death when compared to more typical PVC rhythms;
  • Results from the MRI scans showed that the participants with the highest number of PVCs during exercise (more than 20) had a lower volume of blood pumped with each heartbeat (a key indicator for heart failure), when compared with participants who did not have any PVCs;
  • The blood tests also showed that participants with more than 20 PVCs during exercise were also more likely to have indicators for heart failure present in their blood samples.

Dr Stefan van Duijvenboden, researcher in Health Data Science at Oxford Population Health and the Big Data Institute, said ‘The number of people without obvious symptoms of heart disease using easily accessible technology such as smartwatches that can track heart activity such as PVCs during everyday life is increasing. So, we anticipate that more people will contact their doctor for advice on health risks associated with PVCs.

‘The results of this study may be able to support doctors and clinicians in assessing and managing the risk of heart disease in middle-aged and older populations. Future studies should aim to understand how PVCs may influence the risk of disease in younger people.’