Study author Satish Raj, a heart rhythm cardiologist at the University of Calgary, and his colleagues have often seen these sorts of patients at their dysautonomia and fainting clinic. And they wondered if there was something more they could offer these patients besides lifestyle changes like drinking more water or medications.
As he explains it, when people stand up, blood flow normally shifts downward to below our chest. But in IOH, this change seems to be accompanied by a reflex, triggered by the activation of muscles as we stand up, that causes blood vessels to open widely — and it’s this combination that then causes the rapid but temporary drop in blood pressure. Based on Raj’s team’s earlier work, as well as other research, they hypothesized that people with IOH could short-circuit this process by activating the reflex early or by tensing the lower limb muscles as they stood, somewhat mitigating the blood pressure drop.
To test this out, they recruited 22 volunteers with IOH to try out both of the techniques they developed. One method involved pre-activating the muscles behind the reflex from a sitting position, done simply by raising the knees one at a time for up to 30 seconds. The other asked people to stand and then tense up their lower limbs, by crossing their legs and clenching their thighs and butt. As a control, the volunteers would also stand up normally. Compared to the control condition, on measures of both the volunteers’ circulation and their self-reported symptoms, people’s IOH improved after doing either technique. And Raj’s patients in the clinic have anecdotally reported similar success after adopting the strategies. The team’s findings were published Wednesday in the journal Heart Rhythm.
