What is your blood pressure (BP)?

Central arterial blood pressure

(What is it, don’t like it. Pay attention it could save your life)

It is a pressure that is measured, almost exclusively, by placing a cuff around one arm – usually the left. The cuff is then inflated to a point whereby all blood flow is stopped. If you have placed a stethoscope over the brachial artery (artery in the arm) you will hear nothing at this point. Because there is no blood flow, and nothing to hear.

As the pressure in the cuff is lowered, a noise will be heard as the blood first starts to squeeze through. This is defined as the systolic blood pressure i.e. the point of highest arterial pressure, just after the heart contracts. A sharp tapping noise would be the best description.

As you lower the pressure in the cuff, the noise changes and muffles. Eventually, there will come a point where the blood is flowing through the brachial artery all the time …the point of ‘lowest’ blood pressure. Once this pressure is reached, the noises in the brachial artery cease. This is defined as the diastolic blood pressure. (The pressure does not reach zero, because the heart pumps once again to boost the pressure again).

All of this means that your blood pressure is presented as two figures. The highest recorded pressure (systolic) over the lowest (diastolic).

Historically, blood pressure measured in millimetres of mercury. Because, in the good old days, blood pressure meant how many millimetres of mercury could be pushed up a tube by the force of the cuff being inflated round the arm. If you used water in the tube, instead of mercury, we would measure in metres, not millimetres.

Despite the fact that mercury has nothing to do with the process any more, the measurement is still called mmHg (millimetres of mercury that can be pushed up a narrow tube). A normal blood pressure is around 120/70. If you are an Olympic weightlifter, the blood pressure can reach over 300mmHg during a lift. Which is pretty high.

In a nutshell that is what your blood pressure is…. but what does it mean? The pressure in your arm is certainly not the same as the pressure in your finger, or your brain. The pressure will be different in the right and left arms, as the blood has further to go before it reaches your right arm. It will be different if the cuff is put in a slightly different place on the arm. It will also be different if you are stressed, if the cuff is a bit small – or slightly too big.

In short, your blood pressure can be all over the place. Which is why a single measurement is not used to define high blood pressure. You need at least three. In fact, this is not nearly enough either. To diagnose someone with high blood pressure you really need to monitor the blood pressure over a twenty four hour period – using ambulatory monitoring. This helps to get rid of ‘white coat’ hypertension (high blood pressure). A phenomenon whereby the act of a healthcare professional wrapping a cuff round your arm sends your blood pressure sky high.

Because of the difficulties of measuring the blood pressure, it is estimated that around twenty five per cent of people diagnosed as having hypertension – do not actually have high blood pressure at all. Which means that they are taking drugs that they do not need. Costing the NHS at least a billion a year, and a great deal more around the world (yes, this truly is an international blog).

The other major problem with measuring the blood pressure at the arm is that it may not reflect the blood pressure just after the blood leaves the heart. The central arterial pressure. This is important, because this is the most critical pressure of all. There are a number of reasons why this is so.

Firstly, the central arterial pressure is the pressure in the aortic arch (the U bend in the aorta (biggest artery in the body)). This represents the pressure that sends blood straight up the carotid arteries and into the brain, which is clearly important with regard to stroke risk. [This where two, critically important, small BP sensing organs sit]

It is also the pressure that has the greatest impact on the kidneys. The renal arteries branch directly from the aorta itself. Therefore the central arterial pressure is closely monitored by the kidneys, which are the primary organs of blood pressure control. In addition, the central pressure has the greatest impact on the aorta itself. A relatively common cause of death is a ‘ballooning’ of the aorta (aortic aneurysm).  Such aneurysms can burst, with obviously catastrophic results.

Now, there is no doubt that the pressure at the arm is related to the central arterial pressure. It must be – to a certain degree. And for most people measuring at the arm is probably a good enough estimate of the ‘true’ blood pressure.

However, if your blood pressure measurement is high, or low, or you are on blood pressure medication….then the pressure measured in the arm becomes increasingly unreliable. It can even become misleading i.e. your pressure seems to be going down in the arm – but it is not going down as much centrally1. (It may even be going up.)

‘The results of the Conduit Artery Functional Endpoint (CAFE) study also suggest that the central aortic blood pressure may be more predictive of cardiovascular events, such as stroke and heart attack, than traditional peripheral (brachial) blood pressure measurements. CAFE was the first study to repeatedly measure central aortic pressure in a major clinical outcomes trial and the first to show that central aortic pressure is a plausible mechanism to explain the better clinical outcomes seen in patients treated with amlodipine-based therapy in ASCOT.’

Of course, central arterial blood pressure is somewhat difficult to measure. Up till fairly recently you had to insert a catheter, with a measuring device, into to the femoral artery, and push it up to the aortic arch. This would not be highly practical during a consultation with a GP. So central BP is very rarely measured. But it would be best if it could…

The anomalies of blood pressure trials

Now to introduce another thread to this discussion. Which is the fact that, if you choose to look at the clinical trials on blood pressure lowering with an objective eye, there is almost no correlation between the amount the blood pressure is lowered (at the arm) – and any clinical outcomes. By which I mean that the rate of heart attacks and strokes do not relate to the degree of blood pressure lowering.

To quote a series of bullet point in the European Journal of Cardiology entitled ‘There is a non-linear relationship between mortality and blood pressure’:

  • Drugs that lower the blood pressure by about the same amount have very different effects on outcomes
  • Cardiovascular benefits of ACE-inhibitors (Angiotensin Converting Enzyme – Inhibitors), independent of blood pressure, are not observed with calcium antagonists, despite the latter having more pronounced effects on blood pressure.
  • HOPE (Heart Outcomes Prevention Evaluation study) demonstrated that ACE inhibitors provided diverse and profound cardiovascular benefits, with only trivial differences in blood pressure between the treatment and control groups
  • ALLHAT (Antihypertensive and Lipid Lowering treatment to prevent Heart Attack Trial) showed a dramatic difference in cardiovascular risk between alpha blockers and diuretics, with essentially no difference in their effect on blood pressure. The investigators of ALLHAT concluded ‘blood pressure lowering is an inadequate surrogate marker for health benefits in hypertension.

This is extremely important, because for many years, most of the ‘evidence’ on blood pressure treatment has been based on a statistical model known as the ‘log-linear’ model. This model states that ‘the relation of blood pressure to risk of death is continuous, graded, and strong, and there is no evidence of a threshold.’ (Stamler). The model itself, and that statement, were almost entirely based on evidence from the Framingham Heart Study. The study that your doctors will use to calculate your risk of dying of heart disease.

Essentially, according the log-linear model, the lower your blood pressure (measured at your arm), the better. And the more that drugs lower it, the better. At least this is the thinking that is currently used.

However, thirty years ago Ancel Keys (yes, him) concluded that the linear model, in terms of the relationship of overall and coronary heart disease death to blood pressure was ‘unjustified’. Ten years ago, the authors of the article ‘There is a non-linear relationship between mortality and blood pressure’ further concluded (after reviewing the Framingham data – the data upon which your doctor will determine your future risk of dying of CVD)…the following:

‘Shockingly, we have found that the Framingham data in no way supported the current paradigm to which they gave birth. In fact, these data actually statistically rejected the linear model. This fact has major consequences. Statistical theory now tells us that the paradigm MUST be false ….’ (Their italics and capital letters).

In short, the blood pressure model that is used worldwide is simply, plain damned wrong. The reality is that the amount the blood pressure is lowered in the arm bears little, or no, relationship to any benefit on heart attacks and stroke.  How can this be? Well, there are two major reasons for this. One of which I am covering in this article. The other, later. Now to introduce another thread.

How do blood pressure lowering drugs work?

I am going to avoid being too technical here – which is tricky. I am also, only focussing on the four most commonly used blood pressure lowering agents/classes.

1: Diuretics. These drugs make you pass more urine, by blocking sodium re-absorption by nephrons in the kidney. This means that you pass a lot of urine (diuresis). This puts you into a state of mild dehydration, thus reducing blood volume. Exactly why this lowers your blood pressure is a moot point. (You may think you know. However, it is almost certainly far more complicated that what you are thinking – I certainly don’t understand it)

2: Beta-blockers: These, effectively, slow your heart rate and also decrease the pumping force of your heart. An unwanted effect is that they also cause peripheral blood vessel constriction.

3: Calcium channel blockers: These reduce the force of contraction of the heart, dilate blood vessels (arteries not veins), and slow the heart rate at bit. All of which lowers the blood pressure.

4: ACE-inhibitors: (a bit more explanation is required to explain how they work). The kidneys are the primary organs that control blood pressure. If they pick up that the BP is too low, they release a substance called renin. Renin triggers a whole series of other hormones into action. Ending up with increased angiotensin II levels.

This hormone has multiple effects. It reduces urine production, by increasing sodium absorption. It causes constriction of arteries, and stimulates the pituitary gland to produce anti-diuretic hormone (ADH) – thus reducing urine output.  It does several  other things too, all of which result in the blood pressure going up.

As is the complex way of the body, the kidney doesn’t actually produce angiotensinogen II  when the blood pressure drops(which would seem logical). The kidney produces renin, the liver produces angiotensinogen. When these two hormones met, angiotensinogen is converted into angiotensin I. Then angiotensin I is further converted to angiotensin II by an enzyme called Angiotensin Converting Enzyme (ACE). (There will be an exam later)

All of this means that angiotensin II is the main, active, substance. Once it has been produced, angiotensin II goes off to do all its blood pressure raising things. If, however, you give an ACE-inhibiting drug (ACE-inhibitor), angiotensin II production is blocked, and the blood pressure will fall.

Anyway, as I hope has now become clear, the blood pressure lowering classes of drugs all work though very different mechanism. They all lower the blood pressure at the arm, but what else are they doing?

Beta blockers tend to constrict peripheral blood vessels. Calcium channel blockers and ACE-inhibitors tend to dilate them. Diuretics are mainly neutral on blood vessel diameter.  ACE-inhibitors also do something else that is extremely important. They stimulate Nitric Oxide synthesis in the blood vessels themselves, which both dilates arteries, and increases blood vessel flexibility.

In short, the effect on central and peripheral blood pressure of various BP lowering medications will be very different.

Bringing these thoughts together

You may think, why now? Why is he quoting articles, and research, from many years ago? Well, you have to bear in mind that it is a long time since anyone did a placebo controlled blood pressure lowering study. It would be considered unethical to do so now (such are the alleged enormous benefits of BP lowering). So, there isn’t really any fresh information. Just the monitoring of one drug vs. another, and assuming benefit based on the degree of BP lowering – using the log-linear scale.

However, it has now become possible to measure central blood pressure by simply using a cuff placed round the arm. I have had this process explained to me many times, and cannot really understand how it is done. But the results are repeatable, and accurately reflect central blood pressure. Which is all that really matters.

When you do this, you can also measure the velocity of the pulse wave, which is an accurate indicator of arterial flexibility – and thus arterial health. If your arteries are stiff this is a worrying sign, and reflects poor arterial health. The more flexible your arteries are, the better.

At last, hoorah, instead of wrapping a simple cuff round people’s arms, we can use a complicated cuff to look at two more, really important things. The central blood pressure, and arterial flexibility. This gives us far more information.

Perhaps most importantly, we can monitor the effects that different blood pressure lowering medications have, beyond their impact on the BP measured at the arm. We can see if central pressure is increased, or decreased, or if arterial compliance (flexibility) is improved.

I think that this is a major breakthrough in medical practice. So much so, that I have acquired a machine for myself, and will be using it on a regular basis. I fear it will take the wider medical profession about twenty years or so for this to become an accepted way of measuring blood pressure. This is about the normal lead time for new ideas to become standard practice.

Sweden 1967

Sweden in 1967

It may, of course, take longer. Or never happen at all. At the risk of going off on a major tangent, I remember looking at pictures of roads Sweden in 1967. This was when they switched from driving on the left, to driving on the right. 3rd Sept 1967

As you can see from the picture, a bit of a mess. But imagine if any country tried to do it now, with the extra number of cars and lorries, and roads, and signs. This would probably be just too difficult.

How about changing the way we look at measuring blood pressure. We have always measured blood pressure using a simple cuff on the arm. All the clinical studies on BP lowering were done using this technique. All the data, all the guidelines….everything, is now based on doing BP measurement in this way.

Just imagine what happens if someone now says. Hold on, this is not good enough. The measurement is inaccurate and potentially confusing, and it doesn’t’ really tell us what we need to know. Let us start again. Let us drive on the right, not the left.

In the meantime, whilst the medical world grapples (or chooses not to grapple) with a trillion dollar problem, you can do yourself a favour and get your blood pressure measured centrally.

More on this later.

1: http://www.medscape.org/viewarticle/518570

2: Port S, et al: ‘There is a non-linear relationship between mortality and blood pressure.’ European Heart Journal (2000) 21, pp. 1635 – 1638

84 thoughts on “What is your blood pressure (BP)?

  1. Richard Gibbs

    Well that was interesting and informative. I was not aware of most of this. I must ask my Johns Hopkins cardiologist about this next time I go!

  2. Valerie


    Thanks for this article. I like the way you put it all together. It took me sooo much time to understand what you wrote here (Wikipedia is great for many things, but not so much for synthesis).

    Two things:
    1- Do the benefits of ACE-inhibitors extend to ARBs?
    2- You wrote:
    “All of this means that angiotensin II is the main, active, substance. Once it has been produced, angiotensin II goes off to do all its blood pressure lowering things.”
    You surely meant the opposite “… all its blood pressure increasing things.”

    My doctor (an internist specializing in hypertension) insists that the lower the blood pressure, the better. I tried to explain to him that trends in the healthy, unmedicated population are not necessarily good targets for pharmaceutical treatment of hypertensive patients. I also tried to discuss the Cochrane results regarding the lack of evidence for treating hypertension down to 140 vs. 160. We argued a lot and got nowhere. Sigh…


    1. Tim

      My doctor also insisted that the lower the better, so I said as I work in a Hospice we have some very low Bp patients as in 60/40 is that low enough for you? There was no comment! Perhaps I should have said 50/35?

    2. Odette Hélie

      It’s always very stimulating to read your chronicles. My companion has been struggling with hypertension for years. Coktails after coktails on various drugs accompanied by serious side-effects like chronic loss of energy, mood disorder, bad sleep, etc. All those side effects for moderate gain : it’s like his body has its own arterial pressure and finds a way, after some time, to get back to it whatever pills he takes. We are aware of the “u” relation (instead of the usual linear relation we get lectured about by physicians) between hypertention and morbidity/mortality, but still were a bit frightful to see his pressure reach 170/100 when he did not take those d… pills. So, we will now try to put our hands on one of these machines (does not seem to be available yet in Quebec or Canada). At least, the decision to stop the medication will be based on real data!!

      1. Odette Hélie

        Already done and negative. However, I read that results of such a test can be misleading if the patient is already on anti-hypertensive drugs and that a salt load test can help to confirm/infirm. However, I am wondering, as you imply in one of your replies if, considering the poor outcomes in various clinical trials, hypertension is only a symptom and thus, reducing may not be very useful. On the other hand, it can do some damages to organs so…

  3. Ulrik

    Thank you for bringing our attention to this; I’m looking forward to more posts on BP. I searched for a device that measures central arterial pressure and arterial stiffness and found pulsecor.com – however, I couldn’t find anything aimed at the consumer market. How would I go about acquiring a pulsecor (or similar) device?

      1. Ulrik

        I’ve sent an email to the Uscom sales address; then we’ll see what they say. In the US, many medical devices are only sold to licensed physicians due to regulations.

      2. Ulrik

        I got a reply from Uscom; they do sell the CardioScope II to consumers in the US, but at a price that’s almost 2 orders of magnitude above entry-level BP monitors, so I’ll wait until the price comes down before getting one.

  4. Sue Richardson

    Very interesting article. If we aren’t being told to keep an eye on our cholesterol and lower it as much as possible, we are being told to keep an eye on our BP with a view to keeping that as low as possible as well. In the light of the new machine you mentioned, would you say that the devices sold to laypersons like me to measure BP are in reality a waste of time?

  5. dearieme

    Recently a nurse slipped the cuff on my arm, pressed the button, and sat back. Her eye fell on the list of my medications on her computer screen. “It’s a wonder you have a blood pressure at all”, she said. Which makes me wonder.

  6. Stephen Rhodes

    This is a very confusing field for the layperson. So as a 63 year old male someone who has recently stopped taking Ramapril I would like to share a couple of thoughts and what I have managed to glean – mainly from articles on http://www.ncbi.nlm.nih.gov
    Over the last year my blood pressure (both arms similar – taken daily same time of day same chair etc with an Omron MX3 Plus) typically varied from 130/70 to 190/95 from day to day and could be as much as 15/4 different when taken minutes apart. Pulse typically low 50s to mid 70s.
    In early July after yet another high ‘white coat’ (neurogenic hypertensive) BP reading I agreed with my GP that I would take some time trying to control my BP – my intention being to do it through weight loss, exercise, and a more ‘unrefined’ diet.
    Over the previous 9 months I had dropped a 20 pounds to hold at 12.5 stone, so I dropped another 8lb to just below 12 stone and increased my cycling and by mid August my BP was only slightly less extremely erratic and temporarily much lower after exercise – but that is the natural response I understand.
    I then experimented for a month stopping the Ramapril with the result that my BP rose significantly higher at the lower end, never below 150/80 (except after cycling it drops to 130/70 for a while).
    I now intend to restart Ramapril and monitor for a month to see if the lower values return.
    But, and here are the thoughts;
    1) There is an increase reporting of Angioedema in the US among those being treated with ACE Inhibitors, considered due to the higher persistence of Bradykinin in the endothelium (that results from taking the ACE Inhibitors and, I think ARBs too) making arteries ‘leaky’. Am I weakening my arteries by prolonged use of Ramapril?
    2) There isn’t just one ACE, there is ACE2 (http://www.ncbi.nlm.nih.gov/gene/59272) which acts on Angiotensin II – which is strongly inhibited by the action of ACE Inhibitors – to produce Angiotensin 1-9 (still being researched for its effects!) and the vasodilator Angiotensin 1-7 . Is it advisable to block the production of a ‘natural’ vasodilator by blocking the production of Angiotensin II by taking the Ramapril?
    3) If my BP can drop by over 30 points systolic and over 15 points diastolic during and after exercise, and vary minute to minute by up to 15 systolic and 4 points diastolic, can I assume that my hypertension is neurogenic and effectively – in view of the wide variation – beyond treatment?
    4) Why does cardiology steadfastly use a single diagnostic tool before medication when there are so many potential problems with the patient that remain to be eliminated, e.g. “Single atom mutation in protein kinase G (PKG) eliminated oxidant sensing induced by H2O2 a major component of EDHF which leads to hypertension” Prysyazhna et al.

    Sorry for the verbosity.

    1. Dr. Malcolm Kendrick Post author

      Firstly, to quote Bob Marley. Don’t worry…be happy. You are clearly fit and well, with a good (reactive) BP. Perhaps you want to try 24 hour monitoring to see what happens over a day. This is more useful than single measurements. Why does the medical profession use a single diagnostic tool? Because it is easy to do

      1. Glynis Mitchell

        What is your view of at home monitoring, using the NICE protocol which does not rely on a single reading in a doctor’s office? I know that this is still peripheral rather than central, but it is all we have right now.

        I will be investigating the availability of Central Arterial Monitoring here in Houston Texas, but if there is little or no money in it for “them” I may not find a doctor who is interested enough to offer it.

      2. Blacksmith

        I was told by my doc NOT to take lots of BP measurements, presumably to avoid my obsessing over the changing numbers. I did it anyway to see how things change over time. Glad I did – it started me questioning the “experts” and got me on the road to LCHF/ paleo.

        BTW – you are quoting Bobby McFerrin.

      3. Glynis Mitchell

        The UK National Institute for Clinical Excellence has a protocol for home monitoring, over either 4 or 6 days–two close-together readings am and pm. They are very specific about your physical and environmental comfort during the readings. Also, they map out a pathway depending on results. According to their criteria, if the averaged BP is fine BP does not need to be taken again for five years. I found the “five year” period very surprising, and I choose to do the protocol at least once a year. I like to insist my doctors here in the US (who are always on my case to get on their drugs based on a clinic reading) put a copy in my notes. To quote a quotable quote “Stick that in your pipe and smoke it.”

        In the light of Dr. Kendrick’s research any system of peripheral BP monitoring may be obsolete, but it is all we have and at least provides data to protect ourselves (I hope) from being part of the 25% should not be on BP meds.

        NB: I would also have said Bob Marley–good to know–good one for the Pub quiz!!

    2. Sue Richardson

      I agree, it is all very confusing for the layperson. That is why I wondered if there is any point in the machines we can purchase and use in our oŵn homes. Your BP is up and down – so is mine. But as Dr K says you are obviously a fit person. I am a similar age, can’t claim to be as fit, although I am not on any medication for anything, but I would really like to know if I should bother with my Omron if it is so prone to variance.

      1. Glynis Mitchell

        Sue, I was wondering the same thing. I am of a similar age, and I have been steadfastly opposed to BP meds based on clinic readings. Doctors here in the US put you under pressure to start medicating.
        So I bought the cuff monitor and followed the NICE protocol (I am Scottish). I have done this three times over the last 18 months and my BP average always comes out as “normal.” This, despite having several huge readings (but not as huge as when I go to the doctor). Is it not normal for the BP to go up if we are worried, scared, angry, in pain or discomfort etc. Perhaps we should be worried if this did not happen. For now, the cuff and the protocol are all I have (I have not tried the ambulatory method), but I would rather put my money on home monitoring than what occurs in the doc’s office with the associated implications of lifetime medications and their not insignificant side effects. After all, I do not live my life at the doc’s office or the dentist’s office!

  7. Sue Richardson

    Good point – we are bound to get a more normal reading at home, where we are relaxed – apart from staring at the machine and hoping it registers ‘normal’ that is! I’ll carry on with my Omron for the time being.

  8. Carol Colestock

    I was always under the assumption that if the two numbers were farther apart, the arteries were more flexible. But the total of the two should be 200 or lower. So a 120/80 wouldn’t be as healthy as 140/60. Is there any truth to this?

      1. Glynis Mitchell

        Dr. Kendrick,
        I know that your original post focuses on the possible disparity between peripheral BP readings and the actual condition of the aorta and the central BP in folks who are taking anti hypertensive medications. They may be lulled into a false sense of security, thinking that their meds are working well and their troubles are over.
        But what of those folks who are not taking any BP meds and believe that their peripheral, traditional readings are fine? Is there any evidence that demonstrates a negative correlation between “normal” readings and arterial/aortal rigidity? Or do we just assume that if we have such rigidity, it will show up as persistent rather than intermittent hypertension? And what criteria do we use in the diagnostic decision pathway? Is the NICE recommendation of 140/90 or lower adequate? I ask this because here in the US the pressure is on to go lower and lower, especially for those already on treatment. Your article at least allows us to make some informed choice if ever we are deemed in need of BP meds.

        1. Dr. Malcolm Kendrick Post author


          Simple questions, without very simple answers. My own view is that – firstly – there is little or no evidence for the lower is better mantra. This excludes those with BP higher than 160/90 (at the arm). Above this and risk clearly escalates rapidly. Whether or not lowering it reduces risk rapidly – or by very much – is a moot point.

          Secondly, there have really been very few placebo controlled studies on blood pressure lowering done. Those that were, were pretty unimpressive in their ability to improve significant end-points e.g. heart attacks, strokes, or death. In fact the first big study MRC, demonstrated no benefit, at all, on heart attacks. Whether this is because of the agents chosen. Or, that we are not measuring BP in the right place. Or, that lowering BP merely sweeps a measurement under the carpet and does little actual good…… I don’t know.

          My own view is that beta-blockers are rubbish, and should not be used. Calcium channel blockers have many other problems associated with them, and can raised mortality, diuretics are neutral but pretty useless. ACE-inhibitors (if you can deal with the cough, and don’t suffer angioneurotic oedema) provide good benefits – many of which have nothing to do with BP lowering.

          Are the guidelines adequate? Absolutely not. They rely on a mathematical model and are wrong, because the model is wrong.


          On Fri, 13 Sep 2013 18:27:31 +0000

      1. dearieme

        “Whether or not lowering it reduces risk rapidly – or by very much – is a moot point.” A word of warning: our American cousins use “moot” with a different meaning, something like ‘trivial’ or ‘unimportant’.

      2. Glynis Mitchell

        Malcolm Kendrick, youn indeed a gem. Your response to my “simple” questions was exquisite and entirely logical.
        One further question: how does “white coat symdrome” effect central BP? I know there may not be enough data to answer this question, but it is a significant one, since the technology is in limited supply and usually only available in doctors’ offices.

      3. Glynis Mitchell

        Dr. Kendrick,
        I wanted to mention my husband’s doctor’s rationale for first doubling his ACE Inhibitor and then throwing in a calcium channel blocker because his BP was not 110/70 at the office visit! (his BP was 146/90 or similar at different visits. Colin is so anxious about going that he holds his breath during the procedure, which does not help.) The doctor, a very cheery chap, said that any stressful situation causes a spike and therefore taking more meds to go lower should prevent him he “stroking out.” All I know is that when he was put on BP meds here in the US, his BP was nowhere near 160/90. Certainly his dad died prematurely of long established heart disease and this fact has to be considered, but he was a lifetime smoker and Colin has never smoked.

        At least I have some small reassurance that the ACE Inhibitor may be beneficial for Colin and his unknown aortal pressure, until we can get a better method of evaluation.

        Anyway, your communications have been very helpful.
        Thank you,

  9. Stephen Rhodes

    Is there any evidence to demonstrate the mechanism(s) by which high blood pressure – higher than the 160/90 at the arm that you note – causes damage to particular organs?
    Having seen a link proposed between the persistence of elevated bradykinin and angioedema (presumably this is the US version of angioneurotic oedema), might it be the case that it is not high BP per se, but rather the response of the body to the raised BP that causes the damage, and that this will inevitable depend on the individual’s endocrine system and endothelial cells?

  10. Glynis Mitchell

    I found this article very interesting, especial the funding and the comment that the CASP may be as much as 30mmHg lower than the pressure measured in the arm! Also the comment that for younger people, their arm systolic BP is ‘exaggerated’ in comparison with their actual CASP.
    Also note that a home monitor has also been developed, though there is no comment on its testing. Great for people like me, who hate going to the doctor because of pressure to take meds based on a stressful clinic reading.
    With all the investment surely these machines should be adopted. I think the benefit far outweighs the potential harm especially in this non-invasive procedure.


  11. Glynis Mitchell

    For those of us stateside, here is a link to the company with the monitors mentioned in the above article I sent earlier. They have contact information to call and find someone in your area who is offering Central Aortic Systolic Pressure measurement. I am also trying to find out the cost of the home monitor. I will report back, when I have any useful information.


  12. mec76

    Try this UK link for the CASP device, no prescription neededhttp://www.medscope.co.uk/cart.php At £441 incl VAT (£73 odd) and pp. Expensive. Might buy me a C’mas present. Meantime, Omron m3 will just have to do. The 2K model you were looking at Dr Kendrick, is the professional model with soft ware to link to one’s PC, and where one can get a print out – a useful feature.
    Keeping to approximately the same times of day I take three times per arm, L & R, three times per day, a.m., midday and p.m. I chuck the first readings of each set of three, – leaving two readings per set of three readings – then average each set, then at the end of the day aggregate. Then, a final aggregate at day three of taking readings. I do this for sets of three days, times five = 15 days. Bit of a pain, but keep to the protocol and one ends up with a good spread of BP results. **Don’t fixate. If one misses summat, so what – not the end of the day !
    My BP tends to be all over the place, from 225/120 down to a 135/55, pulse runs at a reasonably steady 65 – 77. Yes, do also have ‘some’ abnormal heart rhythms, not too violent, but always evident. Having thrown wobblies to 16 anti-hypertensive medications, my BP is now unregulated. No, am not particularly concerned. Pointless. I have PAD. Am recovering from a horrendous stasis dermatitis with full blown lower limb oedema (9lbs of it); have a swollen left side carotid artery that has ended up playing with eye sight (double vision, R. eye and severe retinal damage – also have NTG, no tension glaucoma) and very painful cerebral spasms, again, R. side. Have wicked cramps – feet, calves, thighs, fingers and wrists (never knew that one could get cramps in so many different places). All a bit dragsy.
    I did look at the denerving procedure, but with only some two years of track record, am hesitant to go ahead – though it might be my answer. The method was developed in France where trials have been most successful and where CHU (university teaching hospitals) use it (do not like to use the word ‘practice’…!) Denervation has also been trialed in the UK with similar success – though not widely available.
    Am going back to trying L’Arginine, AAKG, Alpha Arginine KetoGlutamate, with Jiagolum (herb). The ‘J’ herb bolsters the good effects of the AAKG. Vaso dilation is what I am looking for. I also take a range of supplements – for eyes, BP and vasodysregulation.
    Enough – Have probably bored the pants of everyone…!
    Reply ↓

  13. greenjersey

    Dr Kendrick, you say that beta blockers are “useless”. Are you referring to their effect on blood pressure alone? Do you feel they have any merit post M.I.? i have been taking 25mg (half a tablet) twice a day since my NSTEMI seven years ago and I am now wondering why, particularly as the last cardiologist I saw snorted dismissively when I told him of this!

  14. Steve Morrissey

    Thank you for this posting.
    I am working on a module for an M.Sc in Medicinal Chemistry and I learnt that for cardiovascular disease it was just going to look at hypertension and heart failure. I was concerned that this was looking at the symptoms of the problem and not the actual problem. I have seen a good deal of evidence that the main cause of these problems are arterial stiffening, especially of the aorta. And therefore the solution to the problem should address arterial stiffening not just the question of the brachial artery pressure.
    Whilst searching for information I came across your posting on this question and it is extremely helpful article.
    As you mention the blood pressure in the aorta is a more useful piece of information. And definitely the pulse wave velocity in the aorta is a vital piece of information since it provides a measure of how stiff the arteries are. One cannot solve a problem by creating a solution to the wrong question.
    If a drug just reduces the blood pressure then the diastolic pressure can drop too low and that is bad news. Such a drug is not fixing the problem.
    I have read papers indicating that Isolated systolic hypertension is all down to arterial stiffness, and this makes a good deal of sense.
    On my course I will be looking at proposing a solution for arterial stiffness since in theory that should prevent/treat high blood pressure and also heart failure.

    Best Wishes


    Just to note that I have posted previously on your site, and as you might remember I am extremely interested in the potential of vitamin K2, so you might be able to guess what I hope to put forward. 🙂

  15. Pete

    I had a heart attack followed by a by-pass op 13 years ago, I was 42 at the time. I was put on statins, aspirin & beta blockers, switching too to ace inhibitors a few years later.

    I had all sorts of problem with statins, fatigue, muscle and joint pain, memory and mood problems. After reading your book I came off statins for a long period but went back to them due to constant pressure from my GP.

    I now find that I cannot tolerate any of my medication due to stomach upset/pain and bloating. It started with the aspirin but now anything I take disagrees with me. Due to my age the ace inhibitor was recently switched to some other drug which has the added effect of making my feet swell.

    My BP is between 130-140 over about 87, do I really need BP meds? my GP is insistent that I need them due to my history, and of course the compulsory statin. I am very inclined to stop all my medication as they just cause me discomfort, pain & stress. Its really a quality of life issue.

    If I hadn’t had any side effects I would happily continue taking the prescribed cocktail in the hope I would live a little longer. I am posting my dilemma as I can find little sensible advice for people like myself who have had a CV event.

    Are statins and BP meds really that much more important to some one in my position?

    1. Siew Walton

      Hi Pete,
      I know your post was a while ago and wonder how you are doing. I have high blood pressure for several years, but have managed to control it and gradually cutting down the dosage of my medicine.
      I would suggest that you read the book, ” NO More Heart Disease” by Dr Ignarro and consider taking a good quality L arginine/L Citrulline based supplement, together with sensible diet and moderate exercise.


      1. robert lipp

        hi Siew,
        what is “sensible diet and moderate exercise”? in your understanding?

        in my world it is following LCHF and 40 mins brisk walking 5/7 days. it has worked wonders for me – blood pressure (old style left arm cuff) down with no meds.


  16. James

    Hello Dr. Kendrick,

    Very interesting article, but it left me, as a layman, somewhat confused.

    My cardiologist firmly informed me that “normal” blood pressure is in the 120-130 range, irrespective of age. He explains that with age the arteries become increasingly “calcified” or hardened, and thus it is usual for elderly patients to have higher blood pressure. However, according to the Dr., that does not mean that a 70 yr. old with bp of 170 has “normal” bp. He should be taking bp medication to get nearer the 130 ideal. Perhaps at least get to 140. The few lucky elderly people who naturally have low bp are exceptions that prove the rule. Do you agree with this Dr.’s point of view regarding age and blood pressure?

    At any rate, since I am 69, and do not have bp of 120-140, he has prescribed bp meds–we tried several, which I did not tolerate too well, and finally settled on 5 mg. amlodipine daily.

    My question is: should I not worry about bp unless it gets really high, say 190-200? By the way, my resting pulse is around 59-60 beats per minute.

    I should add I had a heart attack last year and had a stent placed. Stress. I’ve been on plavix for a year, and the Dr. wants to go another 6 mos. to be on the safe side. I now feel quite normal and have good energy. I was also given statins, which I dutifully took for 6 months and then stopped. I don’t trust them.

    Thank you!

  17. James

    I should perhaps add that when I took Telmisartan (one of the last ones we tried), the cough bothered me (I have some asthma), so I was put on the Amlodipine (unforunately it also has the side effect of shortness of breath). Frankly I wish I could get off all of them. I was quite struck by your remark on another post that potassium, perhaps 2g daily would probably work as well as any bp medicine–all the more so in that if one is taking bp medicine one has to be careful of taking potassium supplements!

    I rather doubt that my classically trained cardiologist would take kindly to a suggestion that I drop the bp meds to take potassium, but I am very tempted to do so–after gradually lowering the meds while gradually increasing the potassium to some 2 g, say, over a month’s time.

    Also, I’ve eliminated sugar and all white flour from my diet and also the usual cookies or other sweet bread while I work at my desk; also walking every day, sometimes even doing sprints. I was too careless of the amount of time sitting without getting up.

      1. James

        Thanks for the reply, Dr. Kendrick!
        If ever you get the time, I would still be very interested in your view of what does cause the higher blood presssure as one ages–assuming that is a fact, and more especially whether you assign much importance to getting the bp below, say, 155 or so in people my age or thereabouts. In short, whether you consider that such higher blood pressure can be perfectly normal or whether you think that anything about the 120-30 range is necessarily a symptom of an underlying problem, irrespective of age.

        I would also be very interested in knowing whether you consider that a substitution for some 2gm. potassium daily could be a viable substitute for a bp medication, even in cases such as mine, of a prior heart attack. Mine was actually a thrombosis. Hence the statin prescription–which quit after 6 mos., given my dietary changes.

        Thanks again, and all the best,


  18. mec76

    There is a new’ish BP monitor that was in the news back in 2011, and touted to measure central pressure. Was developed between Univ Leicester and scientists in Singapore. My own BP is all over the place, from hypos to alarming spikes. Have tried 15 antihypertensive drugs so far, but the side effects were too dire to continue further. I rely on life style to control.

    As usual, an excellent article Dr Kendrick – and good comments. Thanks.

  19. Sutton

    I was told my blood pressure is 120/0 and the nurse did that was ok. I’m concerned as I’m overweight and have never had a reading like this, it’s usually 120/80 or 130/90 As high as 145/90. I’m hypothyroid on medication for it. Lately my heart feels as if it’s galloping at times… Is there an explanation for this and should I be concerned?
    Thank you.

  20. Steve Morrissey

    Many thanks for raising these questions on established beliefs.

    I have been looking around at blood pressure studies and mortality, and trying to find studies looking at the effectiveness of BP medication (ie effectiveness in mortality, strokes,etc not in reaching a target). I have just seen that there appears to be new guidelines in the US:-



    The guideline seem to have moved to a target of 150/90 for people over 60 from 140/90. I haven’t read the paper yet, but I aim to since I am curious as to what studies they used for their recommendations.

    Best Wishes and thanks again for your work.


    1. Odette Hélie

      We underevaluate the danger of blood pressure over 150-160 and vastly overestimate the danger of BP under 150-160. In other words, the relation between BP and morbidity is not linear (porportional) but would look like an “U” (very low PB being dangerous, moderately high BP not being dangerous and very high BP beoing very dangerous). See rhe HLS curve of Figure 5 of http://www.math.ucla.edu/~scp/publications/mortality.PDF

      From what I understand, this misunderstanding stems from using the wrong stastistical analysis.

  21. Dieter

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    i know how to save you a lot of work, there is an online tool that creates readable,
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  22. Karl

    I was placed on Lisinopril last January for supposed hypertension. I n April whist working on my allotment, I passed out. Went to GP. Had an ECG and was told I have Heart Block. I now have a pacemaker. Prior to going onto Lisinopril I had no symptoms, that I knew of, of heart arrhythmia. I wonder if this drug caused nerve damage in and around the heart. At the time of taking I also experienced tingling in my fingers and down my right leg. I decided I wouldn’t take any more pharmaceutical drugs and have started using transdermal magnesium and various other supplements to lower my BP which I think has worked for me.

  23. Carol

    What happens if you stop bp meds? Who long does it take to get them out of your system and will your blood pressure be all over the place until they are.

    1. Andrew Ward

      Nothing, really. I stopped after many years recently and there seems to be an initial spike over readings taking during the medication and then it goes back to the reading during the medication.

        1. Andrew Ward

          Hi Carol, I was sick and tired of taking them and wanted to be free of conventional drugs. I am seeing a naturopath instead of my useless GP and have been undergoing chelation therapy. My BP is still high, but reading that study, the conventional 120-80 doesn’t seem to be relevant for a 60 year old with cardio vascular disease. In good health, Andrew.

  24. John

    Hello Doctor Kendrick,
    You have affirmed that 160 is the cut-off point for being concerned about high blood pressure.
    Therefore, must one conclude that the pre-2,000 notion that “normal” = age +100 for males and age + 90 for females is not a good guideline?

    Also, is it better to take reduced doses of several kinds of bp medicines rather than the larger dose of one of them?

    1. Sue Richardson

      John, Dr Kendrick has written a lot about blood pressure. Check out his other articles on this blog and also on the THINCS website (The International Network of Cholesterol Sceptics).

  25. JDPatten

    Angiotensin Receptor Blockers (ARBs) are not mentioned, even though they are quite effective and induce less cough than ACEIs.

    Also, ACE “escape” is a phenomenon not mentioned, wherein alternative bodily enzymes are eventually called into play to convert angiotensin I to II. They enable your body to seek the higher BP it seems to want.
    So then your nice beneficial ACE inhibitor no longer works. Nor do others in the class. And it’s not a particularly rare phenomenon.

    What do you do then?

  26. MM

    Hi Dr Kendrick.
    My BP is around 200/120 when I’m off the meds. I do take them though – maximum dose of Ram and Felod and half-max of Dox – but the BP will only go down to 170/100… ish. Hate the idea of lifetime tablets.
    I’d love to know what MIGHT be causing it, as my blood tests/hormones/urine/whatever numbers all look fine. How can I persuade my doc to recommend deeper testing? What do I need to say/ask to get somewhere? All I can see is more Dox on the horizon/next appointment. I refuse a diuretic as, to be blunt, it makes me wet the bloody bed.
    Don’t drink more than a pint of cider a week, never smoked, and I’m a vegetarian/vegan-curious! Was very overweight, lost it all, put most back on. BP never flinched once.
    Cheers, and love the blog.

  27. Robert

    ARB’s … Are these angiotensin II receptor antagonists? My cardiologist put me on losartan 50mg due to ‘spikes’ in bp. Still trying to judge the benefit as my home readings are all over the place – 160/110 in the mornings down to 118/77 in the afternoons, evenings
    The variance of repeated home readings is frightening

    1. lee

      It would be nice to fine an alternative to bp meds. Mine is like yours can change throughout the day. I take two meds to control them but am trying to wean myself off them.

  28. Bill In Oz

    Dr Kendrick, you did this post in September 2013. It is now August 7th 2017 – 4 years later.
    Here in Australia no doctor that I know uses the new ( in 2013 ) technology for measuring BP that you discuss in this post and in the comments. That is a great pity as more accurate method of measuring central blood pressure would be really useful.

    But last week there was a discussion of the problems associated with using the old cuff method, on the Health Report program on ABC’s “Radio National”. It is hosted by Scottish doctor Norman Swan. Here is the link to the transcript.


  29. Peter J Luken

    An engineers perspective is if you get the same measurement standing, sitting or laying down then the measurement is velocity pressure in an artery, not total pressure. The instrument is measuring velocity. The cardiovascular system is made up of two positive displacement pumps operating in series in closed loop. I am speculation that a high reading would be because the left side is trying pumping more/less than the right could receive. In either case it would be an interesting control loop to balance the flow between the two pumps. Control flow of a shear thinning compressible non-neutoin fluid in non-neutoin fluid in an expandable/flexible pipe. Available solutions, exercise, diet, reduce plaque size, improve vain lining, drain some fluild, slow heart(governor) or dialate vein(pie x r squared and pressure squared/velocity) that quite an energy reduction.
    I was surprised your book did not mention calcium, did I miss it


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