The subject of high blood pressure is both confusing and hugely anxiety-provoking for patients. The unfortunate thing is that many medical practitioners also don’t quite understand blood pressure and this shows in how blood pressure is managed in modern-day medicine.
What is a complex underlying process has now been simplified to a set of 2 numbers and if those 2 numbers are higher that what a bunch of experts thinks is normal (and every so often this so called bunch of experts change their minds (and there is a difference in expert opinion from continent to continent)), then the patient is told that they have high blood pressure and consigned to a lifetime of anxiety and an ever-increasing set of expensive and potentially harmful pills.
If we think about it, it is a very clever way to use fear to generate profits. Tell everyone whose number is above a certain value that they are at high risk of something bad happening to them, strike the fear of god into them, give them a label so that insurers can start charging them more, get them on medicines for life so that the pharmaceutical industry can benefit, let them have side -effects from the medications and then give them more medication to counter those side-effects and the best thing about it all is that the if and when something bad does happen to the patient blame it on the fact that they had blood pressure without even questioning why the patient was subjected to treatment in the first place if it did not prevent the thing that they were taking the medications for.
Most amazingly, the patient will continue to comply and never ever even know whether the medications have actually prevented something bad from happening to them or not.
To my mind, this is bad medicine. This kind of medicine uses fear to enfeeble and enslave patients. This is not the kind of medicine I want to practice. Good medicine enlightens the patient, Good medicine is based around logic, common sense and good science and should serve to empower and liberate the patient.
I am not saying that blood pressure is not important and at least in some patients, lowering of excessively high blood pressure is definitely a good thing. What i am saying is that we should be more sophisticated in trying to work out an individual’s risk and managing the individual rather than subjecting a whole population to the indignity of taking tablets in the hope that someone somewhere may benefit.
High blood pressure to my mind reflects a process. A process which suggests that the body is in some way stressed. It is also true to say that if the body is chronically stressed then indeed, it is associated with worse outcomes for the patient in the long term. The difficult thing however is to recognise this stress at an early stage. One of the measurable manifestations of that stress is an increase in blood pressure and in that sense numbers may help recognise the presence of this underlying process. However we are all different and therefore we all have different numbers. Furthermore our numbers change all day long. Our numbers go up when we are stressed or anxious or exercising and they are lower when we rest. So when you have constantly varying numbers like this, which set of numbers should we be relying on? Is the best set of numbers taken first thing in the morning? Or last thing at night? Or should it be an average of two separate recordings? And even if those numbers are high, the more important question is – are they high for you? You can see how confusing it is.
The answer is that the important numbers to rely on are the numbers that have been shown to be the most predictive of harmful events in the future. In this video i will talk to you about the best numbers to use to work out whether your blood pressure may be high for you or not.
Ambulatory blood pressure monitoring
We recognise that isolated blood pressure recordings are entirely useless. They can not be used to make a diagnosis. They can not be used to predict prognosis and they can not be used to monitor a patient’s response to treatment. They are a waste of time.
The best way to get a good understanding of blood pressure is to use something called ambulatory blood pressure monitoring. Here a blood pressure machine is strapped to the patient for 24 hours and the machine will automatically measure the blood pressure twice every hour during waking hours and once every hour at night and then calculate 3 sets of average from all the readings. It will give you a 24 hour average, a day-time average and a night time average. All research studies on the subject of blood pressure have found that ambulatory blood pressure monitoring is the most reliable non-invasive method for an accurate assessment of blood pressure. The results are far more reproducible because all the variability tends to get averaged out. An ambulatory blood pressure monitor can be helpful to give you an accurate representation of blood pressure numbers, it is more accurate in terms of predicting prognosis and it can reliably assess response to treatment.
One of the most useful bits of information that an ambulatory BP monitor can give you (which no other non invasive BP monitor gives) is that it can tell you about your blood pressure at night. In many ways, knowing the blood pressure levels at night can be very useful. For one, the patient is at rest and many of the confounders such as stress, exercise etc are minimised and therefore you expect a much cleaner number. Secondly if there is a process going on in the body then that would be going on all the time and therefore you would expect to see it reflected at night too.
Nocturnal blood pressure
Our blood pressure should normally follow a circadian pattern. This means that when we are sleeping our average blood pressure should fall by 10-20% compared to our daytime values. This is called nocturnal dipping.
If you take a population of patients with a diagnosis of high blood pressure and then do an ambulatory blood pressure recording, you will see two groups.
- Patients in whom the blood pressure at night falls by 10-20% who are known as dippers
- Patients in whom the blood pressure doesn’t drop by that much or paradoxically goes up. They are known as non-dippers or reverse-dippers.
When you follow these two groups, it is commonly observed that it is the non-dippers and the reverse-dippers who have the worst prognosis. They have a higher risk of strokes, heart failure, heart attacks, and even cardiovascular death. This is particularly useful because it allows you to work out if the blood pressure is high for you rather than relying on a pre-determined set of numbers.
In addition some patients will have elevated numbers at night irrespective of whether they dip or not and these patients are termed as having nocturnal hypertension. Current american guidelines say that night-time blood pressure average readings should not be above 110/65 and Europeans say that night time BP average should not be above 120/70. About 30-50% of patients with high blood pressure during the day will also have high blood pressure during the night and these patients also have a worse outcome in the future.
Older patients, patients with diabetes, kidney dysfunction, elevated calcium levels, elevated uric acid levels and homcysteine levels are more likely to have nocturnal hypertension.
In addition, some patients may have normal blood pressures during the day so they are not diagnosed with high blood pressure but when you do an ambulatory blood pressure monitor, you may make a couple of interesting observations – 1) Some don’t dip and they tend to have worse outcomes. 2) Some have a condition called isolated nocturnal hypertension.
Some patients may just be non dippers and others may just have isolated nocturnal hypertension and we are still not sure as to which is more important but it is likely that they offer independent information about overall prognosis.
Many experts now feel that perhaps the best information about prognosis from BP is determined from what the BP does at night when the patient is asleep.
So why is this important:
- Nocturnal hypertension and even dipping status unfortunately can only be diagnosed with ambulatory BP monitoring and if you have not had a 24 hour BP monitor then you may be at risk without even knowing about it.
- There may be a cause for the blood pressure being high at night such as sleep apnoea and sometimes the way we may suspect it and treat it, would be through looking at the night-time blood pressure profile.
- There are some medications which seem to work better at restoring dipper status and reducing night time blood pressures. There is some evidence that calcium channel blockers and another medication called Aliskiren which seem to be more effective compared to medications such as beta blockers.
- Finally there is quite a lot of evidence that suggests that changing the timings of when you take your medications can be very helpful and have a measurable impact on prognosis. So taking the medications at night before bed-time may be preferable to taking the medications in the morning.
In my practice I rely heavily on ambulatory BP monitoring to diagnose and manage patients and perhaps the only reason it is not used as often is because of cost. If you want to understand your blood pressure, then I would highly recommend a 24 hour BP monitor – and they are not even that expensive. We are now able to post them out to patients and who can then put them on for 24 hours and then post the device back and we can download the BP recordings. This is a service that I have started offering many of my patients and if you are interested please contact me.