Last week mine was 120/80 and today it is 130/90. You will immediately recognise these sets of numbers as my blood pressure readings. But how much do you really know about them?
There are two phases in a cardiac cycle — the pumping phase or systole, when the heart pumps blood out of the heart into the circulation, and the relaxation phase or diastole, when the empty heart gets refilled with blood.
Blood pressure readings are represented by two numbers, one on top of another as in a fraction. The top number is called systolic blood pressure and represents the maximum force exerted by the heart against the blood vessels during the heart’s pumping phase and the bottom number, which in turn is the diastolic blood pressure, the resting pressure during the heart’s relaxation phase.
In a normal situation, our blood pressure level is dependent on a few factors such as body activity (higher when active) and emotion (higher when angry or upset). Therefore, blood pressure readings are rarely the same each time you take it. Although the blood pressure varies, the human body functions well at a certain level — less than 140/90 mmHg. If the blood pressure persistently exceeds this value, complications such as heart attack, stroke and kidney disease can arise.
When the heart contracts, it pushes a large amount of blood forward to the arteries. Like an elastic band, the arteries are supposed to expand to accept the blood and prevent the pressure within from rising.
The formation of arteriosclerotic plaques in the arteries from various factors such as high cholesterol and smoking stiffens them and prevents them from expanding when the heart contracts. This causes the blood pressure to increase.
The stiffer the arteries, the higher the blood pressure rises. It thus becomes a vicious circle — high blood pressure continues to cause plaque buildup, which narrows the arteries and increases blood pressure
further.
As a person ages, there will be a greater chance of these stiffening factors being present. The blood pressure, therefore, appears to rise with age. This led to the simple formula of person’s normal systolic blood pressure is “100 plus the age”. For instance, if you are 60 years of age, you are apparently allowed to have a systolic blood pressure of 160 mmHg. However, this idea of age-adjusted blood pressure targets has long been discarded.
The current consensus on the management of hypertension from countries all over the world including Malaysia states that blood pressure should be maintained below 140/90 mmHg throughout one’s lifetime. Above this level, early therapy is essential to protect against organ damage.
Regarding which is worse — systolic or diastolic hypertension, a question I am often asked, my short answer is — both are bad. However, there have been a number of trials comparing the two and they have shown that the systolic blood pressure is more important than the diastolic blood pressure in estimating the risk for heart attacks and strokes, especially in the elderly. In a trial published in the Annals of Internal Medicine in 2003, almost 8,000 people participated in a survey from 1976 to 1992.
It was found that rising systolic blood pressure was the clearest indicator for increased risk of death compared to increased diastolic blood pressure easurements. For all intents and purposes, both systolic and diastolic blood pressures are important and should always be kept in the normal range.
Dr Haizal Haron Kamar
Consultant Cardiologist
Tropicana Medical Centre
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