The latest research suggests that prolonged, strenuous exercise such as running ultramarathons can cause right heart deformation.
Research on how endurance exercise affects the heart has been built up over the last three decades, said Dr David Oxborough, Reader in Cardiovascular Physiology at Liverpool John Moores University.
The advances in echo during that time have provided a greater understanding, Dr Oxborough said.
Seminal finding
Back in the 1960s, a study of circulatory response during prolonged severe exercise found that as heart rate increased, stroke volume decreased1. “Where you'd expect stroke volume to be maintained or increased, there's actually a fall, and, in order to maintain cardiac output, the heart rate still increases. So, there's something going wrong here with the heart in terms of not being able to maintain a stroke volume during prolonged stimulus,” he said.
As echo technology has advanced, so has our understanding of what causes this gradual reduction, he added.
“Conventional echocardiography demonstrates changes, both pre- and post-, and during prolonged, strenuous exercise. However, these tools are limited by preload and by afterload, and we know that the heart is more complex than that.”
The introduction of speckle tracking echocardiography, around 2008, allowed a more comprehensive view of the left ventricle (LV) and functional assessment of cardiac mechanics. “The advent of this technology really moved this area of research,” Dr Oxborough.
Right heart shift
After noticing an increase in right heart size and an inter-septal flattening immediately post-endurance exercise in one dataset, Dr Oxborough’s team started to look to the right heart for answers and published their results in 2011.2
He said: “It was only 15 participants, but it was significant across parameters of RV and diastolic area. RV fractional area change was reduced post-race, RV outflow and inflow indices were also bigger. There was structural change. The ventricles got bigger and would become more dysfunctional.”
These results, which have been reproduced in various other studies globally, were more apparent in the faster runners and those with the least experience, the study showed.
Since then, studies have demonstrated that the change is regional, affecting the hinge points of the RV or the spectrum, and the RV free wall, whereas the lateral and posterior wall seem to be preserved.
Using a technique that assesses the area of the chamber alongside deformation, Dr Oxborough’s team showed that post-prolonged strenuous exercise, there is a rightwards shift in the RV. This is accompanied by a leftward shift and slight reduction in the size of the LV. “You’re getting this displacement of the septum into the LV and this appears to be a definite driver from the right side causing a serial and parallel impact on the left,” he said.
Right heart stress
Dr Oxborough suggested that a relative increase in pulmonary vascular resistance was driving this stress on the RV, as pulmonary circulation doesn't adapt or dilate in the same way as a systemic circulation during exercise. Studies have also shown the LV wall is under a disproportionate amount of stress, even during normal exercise. “The hypothesis now is that running 100 miles with this prolonged stimulus causes an increased elevation in RV wall stress which has an impact on the RV which in turn has an impact on the LV,” he said.
The bottom line, he said, is that there are changes, and that these appear to be driven by the right side. “It may act as a stimulus for adaption, but it may act as a stimulus for maladaptation.”
More research is needed before we can understand the long-term impact, he concluded.
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References
- Saltin, B. and Stenberg, J., 1964. Circulatory response to prolonged severe exercise. Journal of applied physiology, 19(5), pp.833-838
- Oxborough, D., Shave, R., Warburton, D., Williams, K., Oxborough, A., Charlesworth, S., Foulds, H., Hoffman, M.D., Birch, K. and George, K., 2011. Dilatation and dysfunction of the right ventricle immediately after ultraendurance exercise: exploratory insights from conventional two-dimensional and speckle tracking echocardiography. Circulation: Cardiovascular Imaging, 4(3), pp.253-263