# Blood pressure queries

I did a bit of research on the systole and diastole stages of the heart cycle and I know that 120/80 is the average blood pressure. However most websites I look at concentrate on what high blood pressure is so what I was wondering is:

What does it mean when the difference between the systole and diastole is great e.g. 103/51 and what does it mean if they’re close to each other e.g. 107/75?

Thanks.

IANAD, but I am an EMT. Diastolic (upper number) pressure is a measure of how hard your heart works to push the blood through your body; systolic is the pressure with the heart at rest.

I do not know except at a very broad level of fluid mechanics what the difference between the two numbers signifies. WRT fluid mechanics, the difference would be an indication of the overall resistance to flow, analogous to a voltage drop across an electrical load. Obviously, the lower the numbers, the less your heart has to work.

Someone who knows more will be along shortly, and can probably fill both of us in on the physiological implications.

Anybody? I’m really surprised that people know more about how much testicles weight than this lol.

I think what you’re talking about is the pulse pressure.

The difference between the two numbers should be around 40

If it’s low you might be going into shock. If it’s high… (somebody help me on this one)…

As a rule of thumb the pulse pressure varies with the compliance of the arterial tree and the stroke volume of the heart. While it is usually around 40 or so, it can vary under normal physiologic conditions and many pathologic ones. The heart rate can also affect pulse pressure, because a faster heart rate leaves a short run-off time before the next beat creates another systolic wave.

It’s hard in the context of a simple post to give you all the possible permutations, but here are some examples.

Suppose a person has a weak heart muscle and is unable to eject a very large volume of blood with each heartbeat. The pulse pressure will be narrow, and generally speaking both the systolic and diastolic pressures will be low.

Sometimes the ability of the heart to expand will be limited, producing a narrow pulse pressure. Example conditions that produce this are fluid around the heart (a pericardial effusion of some type) and an acutely collapsed lung (a tension pneumothorax); both of these create an abnormally high pressure in the chest cavity and keep the heart from filling, as well as create a faster heart beat (a reflex tachycardia).

People with stiff arteries (from arteriosclerosis, for example) can have high systolic pressures and more normal diastolic pressures, widening the pulse pressure. You might see a pressure of 170/95, say. We see this in the elderly a lot. The reason is obvious–when the heart beats the systolic wave peaks high and rapidly because the arterial system is not very compliant. Think of adding a wave of water into a stiff bag with only a small exit versus adding the same pulse of water into a softer bag. In the first case the pressure peak is higher.

Many physiologic conditions will affect pulse pressure by affecting the underlying parameters of heart rate, stroke volume, and peripheral resistance. Exercise would be a common example, and depending on the person, vigorous exercise might narrow a pulse pressure. One of the effects of regular exercise is an amelioration of some of the acute responses.

Hope this sends you in the right direction. Generally speaking–very rule of thumb here–a wide pulse pressure in healthy people is not worrisome except in some unusual conditions and circumstances, but a narrow pulse pressure is a little more bothersome. In the two examples you give, neither would raise my eyebrow if you were otherwise healthy, and I would not be surprised if the 103/51 person was simply aerobically fit with good arteries, although it’s a very crude indicator.

If the individual is acutely sick, both wide and narrowed pulse pressures can be diagnostically helpful, and both are potentially ominous signs.

I am not sure what a testicle weighs, although I could guess. Should be pretty easy to look up, though…

In hypovolemic shock, peripheral vaso-constriction will keep you systolic pressure high while shunting it to the all important heart/lungs/brain. But the lack of circulating volume will give you the low diastolic that reads as widened pulse pressure.

Thank you Chief, that was along the lines of what I was looking for, all the permutations etc.

You got that backwards- it’s systolic/diastolic. Systole= contraction of the heart, diastole= relaxation of the heart.

In addition to what’s been posted already, there are a number of other conditions which can lead to a widening of the difference between the top (systolic) and bottom (diastolic) numbers of the blood pressure.

Things like anemia and fever will widen the gap.

So too will hyperthyroidism and aortic insufficiency (leaky aortic valve in the heart). A rarer cause includes so-called arteriovenous malformations.