UKH

I have a lower than average pulse rate (resting is low 40s, occasionally in high 30s).

Assuming my blood is normal, I'll still be needing to pump the "same" volume of blood around my body.

One way this could be achieved is if my heart's stroke volume is larger than normal. But if it too is normal, does that inevitably imply that my blood pressure must be higher to keep the necessary volume circulating?

Reason for asking is my BP is slightly higher than normal and it would be nice to get it down a bit, am I inevitably handicapped because of the slow pulse rate (not significantly overweight ~5kg, reasonably fit, don't smoke, <10 units alcohol/week).

Have you had your low pulse rate investigated at all previously?

No expert whatsoever, but your body will compensate for blood pressure variations by constricting blood vessels etc - the heart can vary pumping effort to a degree too. Unfortunately any similarities to a hydraulic circuit are only on the face of it

Could it be that your "flow rate" is also lower than normal, ie your circulation is also affected? Your assumption about needing to pump the same volume seems to dismiss this idea.

Has your resting HR changed at all?  When you say blood pressure is up, is it still within the bounds of what’s considered normal and healthy? Did you measure blood pressure yourself or was it in a medical setting?  White coat syndrome can raise the measured value above daily norms.  Not that blood pressure is a static thing, it varies throughout the day.

A resting heart rate of 40 or below is highly unusual in anyone other than highly trained athletes. The body adapts by various mechanisms including increasing cardiac stroke volume, reducing blood vessel diameter, altering blood pressure, increasing RBC/Haemoglobin etc. 

There are lots of other reasons for bradycardia (slow heart rate, less than 60bpm) some of which are harmless, some could be a risk factor for more serious problems. 

Get checked by.a GP before doing anything to try to change your blood pressure!

Mine is low too. Regularly about 40, sometimes just below. I'm 58, fit, non smoker as per you.

Health check about 2 years ago told me I had slightly elevated blood pressure. There didn't seem to be much concern so I just lowered my coffee intake and didn't change anything else really. It was checked again 12 months ago, BP now normal and my RHR is steady at 40ish. No symptoms from that other than I have been a bit of a fainter all my life. First time in the village shop and comprehensively destroyed their display of tinned foods...! 

Edited to add that advice to get it checked anyway is good advice

I'm not a fluid dynamics expert, but I have designed pumping stations and water distribution network, so I think that basically makes me a doctor. Pretty sure that's how it works.

I have no idea what causes high blood pressure (I didn't say I'm a good doctor), but if I think of it as a pumping station, the three obvious things are:

• Longer pipe (more internal friction)
• Smaller pipe diameter (this means higher flow velocity and therefore more friction losses)
• Higher pump rates (means higher flow velocities and therefore more friction losses)

Now with my new doctor hat on if you are overweight you presumably have more blood vessels (so a longer pipe), you may not be doing much exercise (smaller diameter pipe, I think artery size varies with fitness level) and your body probably needs more oxygen to feed your excess tissue (higher pump rate). So high blood pressure and weight correlating appears to make a lot of sense.

Since your heart pumps by chambers there are two ways for it to increase flow rate:

• Beating faster (obviously)
• Larger stroke

I've heard your stroke gets larger as you get fitter which is one of the contributing reasons why fitter people have a lower heart rate for a given load.

But I would expect your heart would reduce it's stroke during rest periods.

It makes sense to me that high blood pressure could be a symptom of a large heart stroke which is the equivalent to a higher pump rate.

Why your heart doesn't just pump at a slightly faster rate at a reduced stroke volume to reduce the pressure on your organs and blood vessels is a mystery to me. I would get it checked (actually, I would ignore it, but that's bad, I'm better at giving advice to others than myself).

From only a fluid dynamics standpoint pressure shouldn't influence the "volume circulation" (i.e blood flux through the heart) if the stroke volume / rate is kept the same. So low heart rate and normal stroke volume is enough to say less blood is getting to the rest of your body. Obviously this does not prove there is a "problem" with low heart rate because I've ignored all the biology.

Don't think of it as a pump thing as much as a plumbing issue. Unlike pumping stations pumps/pipes, the big pipes in the bodies flow side of the system (not return) are muscular and do stuff, they don't just sit there passively being pipes.

Been helping my wife revise this stuff (she's the clever one, certainly not me!)

Diastolic pressure (the top number during heart pump) is affected  by many things and is as much to do with the resistance of the rest of the system as it is to do with the heart itself. As the blood exits the heart (from the left ventricle) to go round the body it enters a very big artery that is sort of walking stick shaped called the aorta. It is muscular. It should tense and relax a bit, in sympathy with the heart, to assist pumping. As a rule of thumb, the big arteries are muscular and the small arteries are elastic. The stiffness of the muscular and elastic arteries has the bigger input into persistent diastolic hypertension. Kidney hormones like adrenaline are also of interest 

The lower pressure number, when the left ventricle is relaxed is the systolic pressure, and of the many things that effect it are the amount of fluid in the system and the function of the kidneys (and the balance of sodium/potassium) and action of corticosteroids/hormones produced around the kidneys such as aldosterone plus a whole spiders web of other hormones. Some of these affect the diastolic blood pressure too, such as adrenaline mentioned (adrenaline = epinephrine to Americans, like epi pen, epinephrine pen)

I know enough to realise I don't have a clue and haven't even scratched the surface of what's going on.

But I do know enough to tell people here that considering it like just a pump and pipes and fluid mechanics isn't going to give an effective understanding of blood pressure. 

It's tricky (giant understatement!!) and needs a real doctor, not random internet weirdo like me to examine and consider all sorts of stuff.

Step away from the fluid mechanics thinking and go and check with your doc

Interesting read.

One thing I took from it is how many problems in hydraulic engineering could be solved if we could just have stretchy pipes and variable diameter pipes.

Think you might have those the wrong way round. 

https://teachmephysiology.com/cardiovascular-system/cardiac-output/heart-ra...
 

Bottom line is it’s complicated, and that’s when everything is working normally.

If you are worried about your HR and blood pressure, random climbers on the internet are no substitute for a history and examination by a trained professional (same applies to the person with a low heart rate, high blood pressure who collapses in shops). 

I’m not a doctor either but I have studied fluid dynamics, so that’s good enough. I also have moderately high blood pressure, which annoys and baffles me. I don’t drink, reasonably fit, don’t smoke, no family history of hypertension, good cholesterol numbers, don’t drink warm lard for breakfast, not fat, don’t have a stressful life, resting heart rate 50 to 60. 
Is it your systolic or diastolic pressure which is high, or both?

Orthostatic Syncope if occurs from sitting to standing up quickly.

https://www.ncbi.nlm.nih.gov/books/NBK537285/

An apochryfal tale of a cardiology conference in the ?early 80's.

Speaker shows chest x ray with huge heart and an ECG with a very slow heart rate and asks for suggestions.  All concerned even suggesting possible heart transplant - speaker then says they belonged to Sebastian Coe!

One of the issues is stiffening of arteries due to sedentary lifestyles.  That stiffening leads to higher blood pressure, plus also linked to narrowing as they fur up.  This stiffening isn’t an inevitable consequence of age and an active lifestyle can keep the arteries flexible.  At least that’s what the ageing researchers discovered when they looked at lifelong regular exercising people in their 50s to 80s compared to sedentary peers and those in their 20s.

Maybe your blood pressure is elevated by your annoyance about your high blood pressure!

You’re probably right. That’s annoying. 

😂

Eeekk! Yes, as long as my wife doesn't too. Thankfully it's her exam coming up not mine, I'd just have failed!

No, that doesn't happen to me, it's more like..completing 100milers,  tearing big toe nail off while running on the coast path barefoot, having a plaster cast removed, having blood taken, and after having a wee....only once thankfully! 

Crikey.  I think most of us would be likely to fall over after a day like that!

🤣

Hi Mike, would be interested to know what your BP normal is, and what sort of HR range you have access to. I'm a good bit older than you, and my resting HR by Garmin is upper 40s rather than lower, and I'm of a similar opinion to you in that I suspect pressure must be higher at low HR. Just checked mine, having been on the Wattbike doing intervals a couple of hours ago, and got an average of 141/76 at a 53 rate. Some would say that is a highish Systolic value (and indeed did, 50 years ago) but testing recently after a steady few miles running I got a much more acceptable 126/75 when my HR was still around 60. I am slightly underweight but drink more to compensate...

PS - Waxwings in Wigston this morning - just a handful, and poorly lit, but no matter - only my second sighting of them, really chuffed!

Then potentially that could be dehydration and reduced blood volume combined with being knackered. Anyway if only the once not a big worry for you I’m sure.

Its probably happened 7 or 8 times now....but probably only once in the past 10 years. I think you are spot on with the link to dehydration. Following a big run or ultra the fainting feeling happens almost every time as the body decides to slow down. Normally a bit of a lie down and recovery time is all that's needed!

There’s also stopping too quickly and not doing a cool-down.  During more intense exercise the blood vessels in active muscle are dilated to maximise flow.  The heart is beating fast and the dilation means the blood can get where’s it needed more easily.  Because the muscles are active they act as a pump to push the blood back to the heart against gravity.  If you suddenly stop your heart is still beating fast, and blood vessels dilated but the active muscle is no longer acting to pump the blood back.  This blood can pool a little in the previously active muscle. A cool down allows the heart to slow down and vessels begin to constrict in the active muscle preventing that blood pooling and another potential cause of fainting.

Hi Pete,

First things first, Waxwings somehow look far too exotic to be a "British" bird - saw my first one last winter and several in G Manchester a few weeks ago, and Monday I was properly Chuffed at South Stack - plenty flying about, I always like watching them, it looks like they're basically messing about in the wind.

HR - so sitting totally relaxed it would typically be around 45, lying down in bed is when it gets lower and is when I've seen it below 40 on an oximeter (in the middle of the night). No idea what my maximal HR is.

BP - typical is in the range 135-140/85-90, sometimes a bit more, never over 160/100, but also unusual for me to be below 130/80. So not excessively high, just a bit higher than I (and my consultant) would like.

Thanks everyone for the medical advice, I should have made clear that I wasn't after that. I'll explain the background to my question.

Basically I sometimes get an arrhythmia, one of the supra-ventricular tachycardias and I may end up having an ablation if it becomes enough of a nuisance (*). But I also have a thickened left ventricle wall (IIRC without finding the hospital letters), and the most common cause of thickened heart muscle is high BP although being an "athlete" can also cause this. So the cardiac consultant would ideally like my BP to be down in the 120/80 range (at home) and none of the quick wins (lose weight, stop smoking, cut down on alcohol, exercise) give much opportunity to help.

So I wondered if I was going to be disadvantaged in any quest to lower my BP by having a low resting PR - I've had this low resting PR for as long as I can remember so it's not an issue in itself. I thought there might be a fairly easy theoretical answer (for an appropriate expert) but from what people have posted it appears that the multiplicity of factors makes this impossible to say theoretically - sounds like it would need empirical studies, etc.

(*) - the slow PR means treatments like beta-blockers are non-starters.

And some general advice, don't mess around with oximeters in hospitals if your PR is likely to go below 50, it sets an alarm off 😁

Non medic here.

Your blood pressure is higher than you want.  Normal is below 120/80.

This video (actually a podcast, no vid) from minute 11 or so, looks at the risk of such high numbers.  I think he goes on to advocate drugs over diet, I disagree with that approach.

Blood pressure

youtube.com/watch?v=3T9gIkAXI2c&

Apparently the relationship between the systolic blood pressure measured at your arm using a cuff and the pressure at your heart and internal organs isn’t straightforward. This relationship depends in part on your heart rate. It’s discussed in this paper: https://www.futuremedicine.com/doi/full/10.1517/14796678.1.1.69

The downloadable pdf is easier to read. 
I’d be curious to have my blood pressure measured using one of the pulse wave devices. Anyone know where that can be done? I think the suggestion is that some people who have a high bp measured at their arm don’t actually have a high bp where it matters, and conversely some people whose bp appears normal do. Well, that’s my understanding after skimming through a few papers. Maybe a cardiologist will be along shortly. 

Can’t answer with any knowledge, but for me I have a RHR down at it’s lowest between 42-45, and at the same time have seen my BP down as low as 100-115/73-75 with that pulse rate. Always had a low RHR, but my norm during a lazy day (ie not exercising) would be in the 50-60s. On the other hand I’ve never been able (even when a lot younger and doing strenuous exercise) to get a high pulse rate, ever. I used to max out at 133 when younger.

Overall, my GP has said repeatedly I have slightly high BP and has been wanting me to take tablets over the years since my normal BP is just in the high blood pressure range.  I do have white coat syndrome and so we agreed rely on my home monitoring instead of surgery readings.

Don’t know if that is of any help.

No, I have a sitting resting heart rate pretty much same as you, sometimes little lower, sometimes little higher, but in the 40s. No idea overnight I haven’t worn a watch for 30 years, let alone a fitness tracker. My blood pressure when measured sits around 107 / 67 ish.  

Yours and CP's posts are making me think not too much empirical studies needed to get an answer; ho-hum.

Just checked my readings which I record on the GP practice app. Last reading was Oct 2023 and resting HR was 43 and BP 107 / 69. Pretty much in my baseline.  

Yes they are the wrong way round

If you want to keep your BP down, stop checking it!

Ignorance is bliss approach 

... .... Maybe a cardiologist will be along shortly. 

Not really, if anyone reading this actually was a cardiologist, they'd be compelled to *not* give internet advice. Unless they had read patient notes examined the patient etc etc and had the facts, it'd professional misconduct for them to give out advice beyond saying something generic and go see your doc. 

The only advice people can get on forums like UKC is going to be from unqualified random internet-weirdos like me. Which for a subject where you need to get it right, like cardiology, means that forum advice is going to be a bit lacking... (Understatement!)

But, on the bright side, due to the white-collar nature of endurance sports (triathlon for example) a consultant cardiologist is more likely to be sympathetic to very fit people and how they differ from average Jo couch potato. I'd hope they'd be able to answer all these questions about low pulse and BP and the like. To regurgitate (and nauseam) ... OP really needs to speak to a cardiologist about all this!

There's some good stuff in this thread - and some less good stuff but mostly good!

In summary, you are right to say that cardiac output is stroke volume x heart rate. So if stroke volume is fixed and HR falls, CO falls. But stroke volume is very rarely fixed, so the relationship between HR and BP is far more subtle. 

The poster who mentioned the pipes not behaving like pipes is bang on. BP is a result of cardiac output and systemic resistance (SVR) - so HR is involved, but at rest is a minor player compared to changes in vascular resistance. If you actually have high BP (and the numbers you have quoted are indeed a bit high, irrespective of your age) then that almost certainly reflects your SVR being high at the point of measurement - for which there's a whole heap of causes, including white coat hypertension (usually easily identified by a 24hr automated BP recording when going about your normal daily stuff). 

SVR is under very complex control with assorted complex mechanisms, which might involve circulating volume (e.g. dehydration) or apparent overload (salt/water retention) amongst many (including your genetic inheritance, and the advice to 'choose your parents wisely' still applies!). Salt exclusion is almost impossible in the western diet - if we exclude all salt from the diet then BP almost always falls, but a proper salt excluded diet is unbelievably bland and extraordinarily difficult to stick to and would mean never having a meal out, or someone else cooking or anything made in a packet/wrapper ever again....

If your BP remains persistently high then there's a no shortage of effective treatments out there which don't affect HR meaningfully but do improve SVR (and hence BP) including the ACE inhibitors and their more modern cousins, the ATRAs (who am I kidding - I'm old enough to remember admitting people to hospital to start them on a very new and potentially dangerous drug where we were so worried about causing catastrophe they came in to hospital and had their obs done every 15 minute after the first dose for 4 hours - when ACEi first came out in the late 90s). 25 years later we are much more relaxed about ACEi!

Good luck and discuss with your consultant - especially if you have a bit of LVH as a fit outdoor type whose pushed their heart reasonably hard over the years and now has some rhythm disturbance. I agree, don't take medical advice from strangers over the internet!

Also: ignore HR when asleep, it's irrelevant (well I get a bit nervous below 30 but the point stands). 

cheers

(Dr) b

DOI: not registered with the GMC as overseas!

Thanks for all that. Firstly I should just point out that I'm not at all concerned about the HR, always been thus.

It's not white coat hypertension (although I get that too), taking readings at home.

Unlikely to be salt, I never add it to food, very rarely to cooking and I don't have huge amounts of processed food.

Probably some genetic factor, both parents had heart issues but both lived into their 90s, Dad to 99 after a triple bypass and aortic valve replacement at 91.

I am being seen by a cardiac team. The OP was me just wondering if there was a HR v BP theoretical relationship between far apart NHS appointments.

I suspect I shall end up on another drug. 

Choosing your parents is important, mine were both on a raft of drugs. My mother in law, who also lived into her 90s, and led a much less healthy lifestyle, was on 1.