An essential part of any health check-up is getting a blood pressure reading. But when the doctor inflates that cuff around your arm and then releases it, what exactly is being measured?
A feature of mine in the Daily Mail today sets out a radical new picture of hypertension. It explains why some people on blood pressure pills may not need them, while others could be getting types that aren’t likely to work for them.
The reason you may not be getting optimal treatment is because there are actually two different blood pressure (BP) measurement. The familiar sort taken from your arm and another that is the actual pressure of the blood being pumped out of your heart and they are not necessarily the same. However for decades, for a perfectly good reason, doctors have assumed that for practical purposes they are.
There is growing evidence (Professor Bryan Williams of University College London is one of the pioneering researchers) that central pressure is the most important and the most reliable predictor of your chances of developing heart disease or stroke.
Sticking a catheter up from your groin
As the article explains, the reason arm BP has been assumed to be identical to BP in the main artery exiting the heart (aorta), is because until recently the only way accurately to measure central pressure was by sticking a catheter with a sensor attached into a blood vessel in your groin and threading it up into your heart. Not appropriate for a five minute health check.
However that all looks set to change thanks to a technological breakthrough. A new generation of portable or even wearable BP devices can take the data gathered from your arm and by running it through some clever new software, provide an accurate measure of central pressure at the touch of a button,
The new machines can also report how flexible and healthy the arteries around the heart are. A New Zealand firm called PulseCore is selling them in the UK for £2000. If you want to know more about central pressure and possibly have it measured or even take part in a trial, these are two numbers you can ring:
Wales Heart Research Institute 02920 742 352
Institute of Cardiovascular Science, University College London 0203 108 2357
Drugs to avoid
The article has a lot more details about how and why arm and central measurements differ. What I want to do here is to add a few points and draw out some of the implications.
The new findings about central pressure highlight an inconvenient truth . While all hypertension tablets effectively lower BP measured at the arm, some are very poor at cutting your risk of heart related problems. So just lowering BP isn’t necessarily beneficial.
This was first studied in a controlled trial by Professor Williams six years ago in the journal Circulation. One of his key findings was that beta-blockers (then regularly given to lower blood pressure) had no beneficial effect on central pressure. NICE now recommends they only be used as a last resort; not surprisingly since Williams was the lead author.)
This fact seems to have escaped the designers of the dreadful polypill – supposed to cut cardiovascular risk by combining several types of heart pill in one. The current model includes the beta-blocker used in Williams’s study called atenolol. The other drug the study identified as ineffective was one of the widely used diuretics.
The two types of drug that did have an effect were the ACE inhibitors and the calcium channel blockers. Only this week, however, a study found an association between long term use of calcium channel blockers by women and a significantly raised risk of breast cancer.
Trying natural compounds makes sense
For more detailed information about the different effects of of the drugs and central pressure in general, see the latest posting on Dr Malcolm Kendrick’s, blog. He has been investigating it for some time and has just paid for one of the new machines out of his own pocket; they aren’t officially approved yet.
The new technology undoubtedly offers the possibility of more accurate diagnosis and monitoring – given the usual caveats about more research being needed. But they also pose a considerable headache for the authorities. The cost of changing over would be huge and how much clinical impact would it actually have and how long would it take to gather the evidence? But in the meantime they may encourage some non-drug approaches.
This is because research using central monitoring so far suggests that one of the most effective ways of improving what is going on there is to reduce arterial stiffness, especially by encouraging release of nitric oxide which relaxes the arteries. This is is one of the effects of the ACE inhibitor drugs, identified by Williams as being effective at the centre.
What’s interesting, as the Mail article describes, is that several natural compounds, notably L-Argenine can also do this. This is an area that Kendrick is investigating, notably with a new product called Prokardia which, he declares, he has an interest in. This is how much drug researcher is done too.
And of course there are plenty of ways to bring down blood pressure without taking anything extra at all.