Heart rate and bp

[Ari1584]

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are heart rate and blood pressure inversely related? when blood pressure is high, heart rate decreases and when blood pressure is low, heart rate increases? or do i have this completely wrong

 

[161927]

the simple trend is HR and BP are related linearly -- not inversely

 

[rocuronium]

This is a difficult topic because there are many things involved with blood pressure. You have to consider stroke volume, systemic vascular resistance, as well as blood volume.

I think, however, that if everything else were maintained (SV, SVR, preload, afterload etc.) an increase in HR would cause an increase in BP, hence a linear relationship.

 

[calimed214]

When blood pressure is low due to volume depletion or what-have-you, the tissues/organs may not be adequately perfused. The body tries to compensate by increasing the heart rate. This may lead to an increase in blood pressure, but it's not a 1:1 ratio -- in other words, just because your heart rate doubles, doesn't mean your blood pressure does as well. Normal vessels dilate to allow more blood to flow through, and there may be no rise in blood pressure at all. I think that other factors such as systemic vascular resistance have a more direct impact on blood pressure.

 

[bobsagat]

I think you need to look at cause/effect relationships here to make sure you don't get confused.

Increasing HR will increase BP.

Does that mean that a high BP comes with a high HR? Not necessarily. Just from feedback loop logic, you would expect that if hi HR causes hi BP, a hi BP would result in a lo HR to compensate through some feedback mechanism.

If the cause of hi BP is hi HR, then yes they're directly (rather than inversely) relatd. If the cause of hi BP is some other thing, HR could be lower to compensate, in which case they might be inversely related.

I'm just pulling this out of my @** since I really have no idea how that feedback would occur, but an important point in these relationships is cause and effect. Which one, if either, is the independent variable, and which is the dependent?

 

[Vihsadas]

As other have said, it's really dependent on just how you are changing your heart rate and blood pressure. There are many other effects in play here that have to be considered.

A useful thing to know is that you can make a pretty solid analogy between the current flowing in a circuit and the cardiovascular system. In a circuit, V = IR. V is the "pushing potential" for current to flow and is alikened to BP, I is the current itself and is likened to Cardiac Output (CO), and R is the electrical resistance which is likened to Total peripheral resistance.
So you can rewrite V = IR as the "heart equation" as follows:
V = I x R
BP = CO x TPR

which can be further rewritten:

BP = (HR x SV) x TPR

So *if* you hold resistance and stroke volume constant, then as HR increases you increase BP (linear increase) and the same vice versa. That is BIG "if", though. As we've said there are many other factors in play in the cardiovascular system that could alter how CO changes in relation to BP and vice versa.

 

[bsteven2]

sign of shock is increased hr decreased BP thus it really depends on the situation i.e equilibrium and so forth. You can also relate it to "Cushings triad"