Is There Evidence to Show That HEFFF Patients Have a Normal Cardiac Output?

At rest, most patients with HEFFF have a normal cardiac output and normal cardiac index. These patients lack cardiac output reserve because they're unable to increase their heart rate with exercise. So if neurohormonal pathway activation is sort of the key step to lead to sodium retention inHEFFF, is there evidence to suggest that this lack of cardiac output reserve with exercise, it's enough to activate that neuroh hormonal pathway? It's a great question and it's one that I tried to find a clear answer to. And so the short answer is I don't know.