Dr. Christopher Quirk

BA Oxon, MA, MBBS Hons, MRCP, FRACP, DDU

Blood Pressure PDF Print E-mail
Thursday, 26 November 2009 07:20

Blood pressure remains one of the silent “destroyers” of the heart, brain, kidneys and vascular system. Unfortunately, because blood pressure is not something we feel, there are to 2 major problems:

1.     We often don’t know about high blood pressure till it has done irreversible damage

2.     Because patients are free of symptoms, it is very difficult to persuade them to take medications to prevent something that may occur in 10-30yrs time, despite the overwhelming evidence for this. 

What Is Blood Pressure?

Blood pressure is the pressure measured within the body’s vascular system.  The best way to think of this is the heart as a pump that pumps a fluid into the arterial system, which is a closed elastic chamber.  Each time the heart contracts and pushes blood into the arterial system it would generate a peak pressure, measured as the systolic blood pressure (top number).  When the heart relaxes, the elastic arterial chamber will relax and there will be a relaxed residual pressure within that system, called the diastolic pressure (bottom number).  This is measured using a conventional blood pressure cuff, usually around the arm.  By occluding the blood flow through the artery and then slowly reducing the pressure of the cuff around the arm, one can assess the blood pressure required to push blood through that obstruction.  Historically, it was felt that the bottom, (diastolic) pressure was the only important reading.  However, it is now appreciated that both the diastolic and systolic pressures are equally as important at leading to Cardiovascular disease. Indeed, as we get older the top (systolic) pressure often rises and the bottom (diastolic) pressure actually falls. This is actually a reflection that hardening of the arteries has already occurred. This is what we are trying to avoid. 

Why Is Blood Pressure Bad?

The Cardiovascular system is not dissimilar to any man made mechanical pump and closed circuit chamber.  Any system like this will be under more stress the higher the pressure within it which will reduce the life expectancy of that system.  However, unlike most man made systems, the heart and arterial system has several major differences.  Firstly, the pressure generated within the system is pulsatile occurring with each heart beat.  Secondly, the arterial system into which the pressure is forced is elastic.  Hence, it is subject to repeated stretch and relaxation, and like any other elastic system over time it will loose its elasticity and stiffen.  If you where to blow up a balloon to high pressure repeatedly, not only might it burst, but over time the balloon will lose its elasticity and not deflate (relax) properly. Thirdly, the heart and vascular system are required to work for twenty four hours a day for periods of around eighty years, without even a moments rest. 

Therefore, if we consider that approximately 60 times a minute, 60 minutes an hour, and 24 hours a day etc a high pressure is forced into the arterial system causing it to stretch to accommodate the blood.  It is therefore not surprising that over time the arterial system looses this elasticity and hardens which is the hallmark of cardiovascular disease, and the higher the pressure it is exposed to the more likely it is to wear out. 

How Do You Detect Blood Pressure?

Unfortunately blood pressure within a very wide range of readings is nearly always completely asymptomatic and it is possible to feel completely normal with very high readings over very prolonged periods.  Therefore, the only way of detecting blood pressure is regular blood pressure screening.  Traditionally, this is done at the Doctors surgery, the frequency of which will be dictated by the blood pressure obtained and the likelihood of developing high blood pressure subsequent to that.  Of course, it is also possible to monitor one’s blood pressure at home to avoid visiting your Doctor and although I do support this approach in many patients I am cautious about recommending it in all people as it itself can induce some degree of anxiety. 

What Defines High Blood Pressure?

This remains a difficult and controversial area and certainly has changed over the past 20 to 30 years.  It also depends very much on individual patient’s characteristics, the presence or absence of known heart disease, the presence or absence of heart muscle thickening, the age of the patient, the presence of diabetes and multiple other factors.  Having said that, we are certainly recommending more aggressive blood pressure targets than 20 to 30 years ago. As a rule, the lower the blood pressure the better subject to that low blood pressure not leading to any adverse symptoms, such as dizziness, light headedness or falls.  There are studies that have demonstrated that using certain blood pressure lowering agents even in patients with ‘normal’ blood pressure further reduces the incidence of heart disease and strokes. I think the notion of ‘High blood’ pressure is misleading. Mostly, any individual’s blood pressure may be a normal characteristic for them, in a similar fashion that some people are tall and others short. However, although normal for them, it is now apparent that blood pressures over a certain level are too high and will lead to premature Cardiovascular ageing if left unchecked.  Too some degree we need to falsely lower that persons blood pressure, which is one of the reasons treating blood pressure can be difficult. Your Doctor will guide you with regards to appropriate blood pressure levels in your case. 

How Do You Treat Blood Pressure?

The treatment of blood pressure can be divided into two broad categories, life style measures and medication. 

1. The affect of life style on any individual’s blood pressure is difficult to predict although one can almost always guarantee at least some response to life styles changes and this should always form part of the treatment of blood pressure.  In particular, exercise and weight reduction probably have the greatest role in reducing blood pressure.  Salt avoidance may impact on the blood pressure, alcohol reduction and certain non-cardiac medications may need to be addressed. To emphasise the point again, it may be possible in some people to avoid or get off medications completely with an appropriate exercise regime. 

2. Although life style issues remain a major part of blood pressure control, and although most people prefer to avoid medications, in my view the commonest mistake we make is to try and avoid medications at the expense of not adequately treating the blood pressure.  In other words, reducing the pressure our heart and arteries are exposed to remains the over riding target.  This may require multiple medications to achieve but the evidence for this reducing Cardiovascular disease is overwhelming. 

Your Doctor will discuss medical treatment of your blood pressure with you.  There are multiple different classes of blood pressure medications, all of which act on the Cardiovascular system in a different fashion, and are often required in various different combinations.  To some degree, control of blood pressure with medications remains trial and error to find the right cocktail that adequately treats youre blood pressure without causing any patient side effects.  This can be tricky and your Doctor may have to work through various different regimes. However, in view of the importance of treating blood pressure you do need to work together with your doctor, accepting that some medications may need to be taken, and undertaking life style measures that will help with the control of your blood pressure.

 

Last Updated on Thursday, 26 November 2009 11:03
 
 
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