Sunday, September 3, 2000		Keeping fit

THE heart is the centre of the cardio-vascular system and it pumps a few litres of blood every minute so that oxygen and other nutritional requirements reach every cell of the body. This force of the strong left chamber of the heart (left ventricle) and the resistance offered by the small thread like conduits (arterioles) generate the force defined as blood pressure (BP). BP is measured during the contraction of the left ventricle called the systolic pressure (upper reading) and during relaxation of the heart known as diastolic pressure (lower reading).

The blood pressure at birth is as low as 65-70 mmHg and rises gradually during the childhood to the adult level of 140/90 mmHg, which is now defined as the upper limit of the normal. Blood pressure reading varies under different physiological conditions but in general it is kept fairly constant by the regulatory forces in the body.

Our knowledge of blood circulation in general and high blood pressure in particular is relatively recent. Although fragmentary information was available earlier, it was only in 1628 that William Harvey demonstrated the full circulation of blood. It starts its journey from the strong left ventricle of the heart, goes through the tissues and returns to the right side of the heart, via venous system from where it goes to the lungs for its refill of the oxygen and then travels back to the left side of the heart for the next round.

It took nearly 100 years more when Stephen Hale, in 1733, put a glass tube into the crural artery of a mare and measured the force of its flow when the blood rose to a few feet of the column. This was the first clear demonstration of the physical force of circulation or the blood pressure. Another 100 years later, various devices to measure the blood pressure in experimental conditions and then in clinical situations were devised. In 1894, Riva Rocci devised the present mercury manometer. In this instrument BP is measured in terms of millimetres of mercury. Now we have all kinds of devices, including the spring based dials and electronic devices of all shades which the patient himself can use. Instruments are now available for continuous recording of blood pressure of a patient when required.

It has not been easy for the epidemiologists and the physicians to define what high blood pressure is. As mentioned earlier, normally it starts increasing from the very birth and reaches the adult level somewhere in midteens. Earlier it was believed that it goes on increasing with the age and a formula was prevalent where the upper blood pressure was considered to be 105 + age as the upper normal limit. The studies over the last few decades have shown that that is not true and that the blood pressure beyond certain range is harmful at any age. The definition of the blood pressure in an adult at present is 140 mmHg systolic and 90 mmHg as the diastolic. Of course, this will be lower in children depending upon the age. This limit has been gradually brought down from 180/100 mmHg to 160/95 mmHg to the present 140/90 mmHg in my own lifetime. Already people are talking of bringing it to 130/85 mmHg. This is not based on any fashion or whim, but on continuous epidemiological observations and long-term studies. Hypertension is classified in various stages as mild, moderate and severe depending upon the degree of pressure. For the present purpose it is enough to say that higher the pressure or the stage of hypertension worst are the consequences.

What causes the blood pressure? Only in about 5 per cent to 10 per cent of the patients, the cause of hypertension is precisely known and that is known as secondary hypertension — secondary to some known cause. In our studies conducted at the PGI, Chandigarh, we found that not more than 5 per cent of the patients of blood pressure fell in this category. The known causes include kidney diseases including the diseases of the arteries supplying blood to the kidneys (renovascular hypertension), hormonal disorders including those of adrenal, thyroid and pituitary, various disorders of pregnancy, disorders of autonomic nervous system and one produced by various drugs, including harmones. In a majority of the patients, the cause is not known. For want of a better definition, this is known as primary or essential hypertension. Basically, it means we do not know the precise cause. Some of the factors mentioned are the genetic predisposition, obesity, high intake of salt, heavy drinking of alcohol, disorders of the regulatory function of the kidneys, resistance to insulin and so on. Consistent research during the 20th century has clarified many aspects of this disease. But the exact cause or the "Holy Grail" is still missing as remarked by a very famous British physician, Sir George Pickering, who spent a life time in doing research on high blood pressure.

This disease just have no symptoms and the patient may feel nothing abnormal. This has earned this disease

a dubious label of "silent killer". Irrespective of lack of symptoms, it keeps on damaging vital organs even during the mild stage. At numerous occasions one has seen patients with a blood pressure of 250/130 mmHg or more who are absolutely unaware of it. They cannot be convinced that they need any help or treatment. They may have come just for a trivial illness or a pre-operative check up. In fact some of the symptoms may appear for the first time when the patient learns about his high blood pressure. The symptoms may be heaviness of the head, especially the nuchal headache at the back of the head, flushing of the face, blurring of the vision, bleeding from the nose, palpitation and a general sense of fatigue. Some of these symptoms occur because some of the vital organs have already started getting affected. The organs specifically affected by high BP are called "target organs". They include the heart, the kidneys, brain and the eyes. Once any one or more of these organs are involved, then there can be a plethora of symptoms, including palpitation, breathlessness, pain in the chest, swelling of the feet, blurring of vision going on to severe visual problems including blindness, brain stroke with its various presentations and symptoms of kidney and heart failure. Numerous studies have shown that involvements of these important organs is proportionate to the degree of both systolic and diastolic blood pressure. The old myth that only diastolic blood pressure is important has been laid to rest.

The present knowledge of the disease therefore demands that we should not wait to treat the blood pressure when it has already done the damage and produced symptoms. The time to treat the blood pressure is therefore when you are symptom free. All programmes about the hypertension in the developed countries are based on detection, treatment and follow-up. You should look for hypertension and treat it when you find it. A lot of professional as well as public education is needed to bring this point home.

Hypertension is the number two cause of chronic renal failure in the USA (Diabetes mellitus being No 1) and our own studies in the PGI, Chandigarh, showed that this may be the case in our country too. It is a great contributor to the causation of strokes, coronary artery disease and damage to the eyes.

Achieving of better control of blood pressure in the USA has also shown the converse, that is, with the bringing down of hypertension, the incidence of coronary artery disease has come down. Admittedly, there would be other factors contributing to this decline including the decreased smoking and general awareness of physical exercise.

In our country we still do not have an effective public health programme for detection of high blood pressure in the community, although various surveys including done by us in the PGI have shown its presence all over. Till then we need to be acutely aware of this disease and every patient who comes to the hospital for anything should have his blood pressure recorded.

Everyone should become conscious and get blood pressure measured at least once a year, after the age of 25 and may be more frequently, if there is a family history of hypertension or if there is a rise in blood pressure at any age. Once there is detection of hypertension, it requires continuous monitoring and treatment which may not necessarily be the drug treatment. It can be said that once a hypertension, always a hypertensive. There, however, may be phases when he needs no active treatment. Yet the potential for trouble remains.

Non pharmacological measures or changes in lifestyle may be enough to control mild hypertension. But the most important thing is the awareness and monitoring. The lifestyle changes like controlling of body weight, salt restriction, cessation of smoking, no alcohol intake or taking in moderation, regular physical exercise, relaxation techniques and general management of stress can be helpful either in postponing or decreasing the requirement of drug therapy.

There are very effective, safe and reasonably priced medicines available for the control of blood pressure. Nobody needs to suffer from the consequences of hypertension any more. The causes of secondary hypertension, as mentioned above, need detailed investigation for its diagnosis and management. But, blissfully, the number of these cases is very few. High blood pressure is relatively silent in the beginning but makes very loud noises later on. It is so eminently diagnosable (all that you need is to record the blood pressure), treatable and so easily monitored.

All we need is a certain degree of will and discipline. I vaguely remember somebody telling a gathering after a lecture, "You are all brave people. Do a death-defying act today. Get your blood pressure checked".

Let us do it today, if not already done recently — symptoms or no symptoms.