Question
Do CHF patients improve aerobic capacity primarily through heart rate?
Answer
No they do not. Here is the bottom line. Because the central function, meaning the heart itself or the central mechanism. Because of rate limitations. Because of contraction limitations. The improvement in someone with CHF does not come through changes in central mechanism because we cannot count on that. It comes through a second mechanism. Oxygen uptake is a function of stroke volume times heart rate times the AVO2 difference. If my heart is shot, forgive me for that rather dramatic term, but if it is not going to be rehabable - it is not once the scar is formed - what mechanism homeostatically do I have to improve a patient's function? Why not just say to them, "I am sorry, you have 3 to 5 years. You are just going to have to get your affairs in order." How can we and why should we work with these patients? Because it has been shown that when the central mechanism of the heart cannot function, the periphery's ability to extract oxygen picks up and helps make up for the deficit of the heart itself. I had a physician one time say to me, "this patient is here to die. They have an ejection fraction of 17. Just make them comfortable." I said, "you keep them stable. I will get them stronger." This patient was on a transplant list. We got into a rehab program, and that patient was taken off the transplant list because we progressively exercised him. We could not change the scarred heart. The damage had been done, but the periphery, the muscles, improved their extraction of oxygen. That patient enjoyed an enhanced quality of life again due to the training that had improved oxygen extraction in the periphery. That is our whole rationale for working with these patients. That is a great question and provides the rationale for what it is that we do. You may be backed against a wall one day being asked why are you working with that patient if their heart is bad? Their periphery is not bad. We can still make a difference that way.
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