Charlotte Stephens, Research Correspondent, ME Association.
Linda van Campen and Frans Visser from the Netherlands have just published a study that examined stroke volume and cardiac output in ME/CFS. It confirmed earlier findings from a smaller study that changes occurred in these two key cardiac measures despite normal tilt-table results (Timmers et al., 2002).
Both studies found reduced cardiac output and stroke volumes during a tilt table test in ME/CFS patients compared to healthy controls. However, these patients had normal tilt table results, meaning their heart rate and blood pressure did not change significantly enough to be diagnosed with orthostatic intolerance.
The authors of the earlier study suggested that these findings were due to deconditioning, but in this new, larger study, Van Campen and Visser showed they were not as they found no difference in results between different disease severities.
If it were a case of deconditioning, the cardiac measurements would be worse in the more severely affected compared to the mild, as they have poorer physical functioning.
What made this study better than the previous one?
- Much larger patient cohort. The previous study tested 26 ME/CFS patients, whereas this current study involved 150 ME/CFS patients.
- Improved method of measuring cardiac parameters. The reliability of the previous study’s method (pulse contour analysis) is questionable, whereas the current study used a validated technique (suprasternal aortic Doppler echography) (van Geldorp et al., 2011).
- The latest study compared results across illness severities. This revealed that the cardiac abnormalities could not be due to deconditioning.
What were the two key measures found to be different?
Cardiac output = The volume of blood pumped by the heart per minute.
Stroke Volume = The volume of blood pumped by the left ventricle of the heart per heartbeat.
Both of these measures usually decrease upon standing. However, they were found to decrease more in the patients with ME/CFS, compared to the healthy controls.
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