HYPERTENSION

This is the word used to describe a rise in the blood pressure in the arterial circulation. This condition was unknown until Riva Rocci invented a machine to measure blood pressure (sphygmomanometer) in 1896. Since then hypertension has been the object of intense study, as it has been found to be a major risk factor for cardiovascular disease (heart attacks, stroke, heart failure, kidney disease and accelerated atherosclerosis).
 
In the early sixties, Sir George Pickering in Oxford devised a method of measuring blood pressure continuously by putting a little tube or catheter into an artery, and linking it to a gauge, which could record and inscribe the pressure values on paper. This technique has been refined and modified to a more practical and non-invasive method known as ambulatory blood pressure monitoring (ABPM), which uses an automatic and intermittent self inflatable cuff which through a portable sensor records the pressure values at random intervals during day and night for 24 hours.

Many thousands of articles have been published on this subject, and it is generally accepted that the specific cause for the rise in blood pressure cannot be established in 95 % of cases. In the remaining, it may be a consequence of diseases of the kidneys, of the adrenal glands, to some illnesses during pregnancy, or to drugs such as contraceptives, amphetamines or cocaine to mention the most significant. Nevertheless, in the large group of ‘essential’ hypertensive patients where no specific cause has been identified, there is often a familial trait.
 
Though there is controversy as to the exact figure, systolic blood pressure equal or greater than 140 mmHg (millimeters of mercury) and diastolic blood pressure equal or greater than 90 mmHg is considered high (140/90 mmHg)) Starting from 115/75 mmHg the risk of cardiovascular disease doubles with each increment of 20/10 mmHg.  Blood pressure is considered normal or optimal when it is lower than 120/80 mmHg and blood pressures between 120-139/80-89 mmHg are now considered to be pre-hypertension and require initiating health promoting lifestyle modifications to prevent cardiovascular disease. During sleep, the accepted cutoff is 10% lower. As there are moments when the body requires delivery of nutrients and oxygen at a higher pressure, in the 24 hour studies it is accepted that one may have up to a 30 % of recordings higher than the limit, and still be considered normal. Therefore, a single high recording does not necessarily mean hypertension. This is quite frequent in doctors consulting rooms, where higher than normal figures may be recorded and is commonly known as ‘white coat hypertension’, probably due to anxiety at that moment. Therefore repeated controls, and sometimes home self-monitoring and ABPM, are called for before beginning treatment.
 
It has been demonstrated beyond any doubt that even in the normal range, the lower the blood pressure, the less chance of having “organ damage”: heart attacks, heart failure, kidney disease and stroke.  Conversely, the risk probability rises dramatically as the figures go above normal.  In spite of the popular belief that diastolic blood pressure is the more important marker in terms of risk, in persons over 50 years-old, a systolic blood pressure of more than 140 mmHg is a much more important cardiovascular risk factor.

In North America it is estimated that 50 million people are hypertensive. For individuals aged 55 to 65, the lifetime probability of developing hypertension is around 90 %.  Figures from a very solid source, the well known Framingham Study, have shown that hypertensive patients have a fourfold increase in strokes, and a sixfold increase in heart failure, when compared to persons with normal blood pressure.

Many factors play a part in the causation of hypertension, and in everyday practice it is hard to decide which is or are the factors in any one single person. Initially the heart output is sometimes increased; later on, constriction of peripheral blood vessels contribute to the maintenance of elevated blood pressure. Salt also has an important role in some individuals, especially in African-Americans, black Africans, elderly people and diabetics. Chemical substances released from the adrenal glands such as adrenaline and other catecholamines play a part, as does renin, an enzyme released by the kidney which controls the synthesis of angiotensin, indirectly causing arterial constriction and release of the adrenal salt retaining hormone called aldosterone.  There are other hormones and chemicals, which are source of extensive investigation and research, in the hopes of finding newer and better drugs to control or cure hypertension.

Contrary to popular opinion, most people with hypertension are not aware of their situation because it does not give any symptoms: a very small group do get headaches at the back of the skull, though this symptom can also be seen with people having low blood pressure. A famous TIME magazine cover a few years ago read “Hypertension, the silent killer”, which is to the point. Not withstanding, symptoms are prominent in cases of acute and severe elevation of the blood pressure, such as in accelerated hypertension and in malignant hypertension, which constitute emergencies requiring immediate reduction of the blood pressure to avoid organ damage. Fortunately in latter years these situations have become infrequent.

As sodium is the main salt in the circulating blood, until the fifties the only weapon against this condition was a strict salt-free diet. Only then effective medicines began to appear, such as diuretics, which eliminate sodium through the kidneys, and beta-blockers, which act on the heart. Some have fallen by the wayside, such as ganglionic blocking agents and reserpine, having been replaced by much more effective and well tolerated medicines, all very much in use today: the angiotensin converting enzyme inhibitors, the angiotensin receptor blockers and the calcium channel blockers, all which help dilate the small arteries, and thus lower the pressure.
Lifestyle modifications such as dietary salt reduction, stopping smoking, regular exercise and reduction of excess weight are called for in all cases and in some persons may be sufficient to reduce blood pressure to normal. Permanent medication must be added for all those who do not respond. The goal of treatment is to achieve blood pressure levels below 140/90 mmHg, excepting those persons with diabetes or chronic kidney disease where a more stringent goal of 130/80 mmHg is recommended.
By keeping to a proper follow up with your physician, which should be repeated at regular intervals, this modern day scourge can be completely brought under control, and the serious consequences avoided.
 
 
John D. Humphreys, MD, MTSAC, FACC.
John Emery, MD.
 
References:
  • Harrison’s “Principles of Internal Medicine”
  • Lock S, Last JM & Dunes G (Editors). “The Oxford Illustrated Companion to Medicine”, Oxford University Press, 2nd Ed., W.B. Saunders, 1998.
  • Chobanian AV, Bakris GL, Black HR, et al. Natioal High Blood Pressure Education Program Coordinating Commission. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. The JNC 7 Report. JAMA 2003; 289: 2560-2572.