Hypertension 1996 : One Medicine, Two Cultures
Guidelines and new prospectives of the hypertension therapy
A. Stella
Centro di Fisiologia Clinica ed Ipertensione
Università degli Studi di Milano
Introduction
A hundred years ago, it was published on the “Gazzetta Medica di Torino”
(1), the article of Scipione Riva-Rocci in which there was the characteristic
of a new measurement method of the arterial pressure: a Mercury Sphygmomanometer.
Differently from the complicated laboratory instruments, utilised during
that period, this simple discovery permitted a great improvement of the
knowledge on the arterial hypertension as, since then, it has been possible
to measure the arterial pressure on a wide scale, and mostly in the common
clinical practice. With the perfectioning of the technique, occurred thanks
to the observation of Nikolai Sergeyevich Koroktoff (2), the auscultatory
method was introduced, achieving the actual measurement system of the arterial
pressure. In fact, nowadays, the same method is used and the arterial pressure
values obtained are those used as a reference, not only in major clinic
studies but also in the guidelines.
In the passing of the century, the experimental studies and the clinical
observation followed each other with an increasing intensity, allowing people
to know all the arterial pressure mechanical regulations in both the physiological
and the pathologic conditions. Parallel, the statistics given by USA insurance
companies, highlighted that life expectation is lower, due to the major
risks of the high arterial pressure values. Therefore, it has been established
that arterial pressure is a risk factor.
Nowadays, we know that arterial hypertension is one of the most important
cardiovascular risk factor and also for the progression of renal chronic
insufficiency. Nevertheless, there are some other cardiovascular risks.
Factors as obesity, diabetes mellitus, lipoidoproteinosis, and sedentary
activity that must be appropriately estimated when the therapy of arterial
hypertension has to be decided. This concept has largely been emphasised
in the guidelines published in 1993 by Joint National Committee (3) and,
separately, by both the World Health Organisation and the International
Society of Hypertension (4).
As clarified by WHO and ISH, we have to remember that guidelines don’t have
to be intended as an arrangement or an imposition to the doctors, but as
a useful and practical, critical reference that can allow the doctor to
make up his own decision the best of ways.
In other terms, the doctor will have to select the general knowledge, expressed
in the guidelines, for each single hypertensive patient, considered in his
own specific clinical condition.
The innovative aspect of the recent guidelines is the admission of the prognostic
importance of the isolated arterial hypertension, of the positive effects
of the anti- hypertensive therapy in the old age, and of all the cardiovascular
risk factors role, when it has to be decided the therapeutic conduct.
Arterial hypertension classification
Many different classifications criteria of arterial hypertension can
be used: an etiologic one, that distinguishes the primary from the secondary
form, whose aetiology is known; a clinical one which evaluates the involvement
degree of target organ’s functionality or the malignancy degree of the hypertension;
at last the most commonly used method based on arterial pressure values.
As stated above, this method is based on the arterial pressure values, obtained
with the Riva-Ricci’s device and with the auscultatory method. The guidelines
recommend these values to be the result of two or more measurements, made
at the same time and confirmed, at least, in a successive measurement. The
guidelines, furthermore, establish the normal arterial pressure values:
diastolic one, inferior to 90 mmHg and the systolic one, inferior to 140
mmHg. Hypertension diagnosis is established when just one, or both the values
of arterial hypertension are firmly superior to those mentioned above. The
arterial pressure increase fixes the different degrees of hypertension:
light, mild, severe and very severe.
It’s quite easy to decide to start the pharmacological treatment when the
hypertension is medio-severe. In this cases the therapy’s benefits are clearly
evident. When the arterial pressure values are only slightly increased it
is much harder to estimate the opportunity of starting an anti-hypertensive
therapy. The limit values of diastolic arterial pressure are the expression
of this doubt. Beyond these limits, different from country to country, changing
from 90 to 100 mmHg for the diastolic pressure it is advisable to start
the anti-hypertensive therapy. Opportunely the guidelines emphasise the
importance of valuing the arterial pressure levels in each single case,
as the concomitant presence of other cardiovascular risk factors and complications,
diabetes mellitus or renal insufficiency, can strongly influence the decision
to start the anti-hypertensive therapy.
Hypertension therapy
Life habits’ changes: This term has been introduced in the last guidelines
and it points the non-pharmacological approach to the hypertension therapy.
This kind of approach is recommended in the light hypertension forms, because
it is often sufficient to normalise the arterial pressure. It consists in
reducing a possible excess of weight, in stopping smoking, in sodium and
alcohol restriction, in practising a light exercise and in promoting a diet
that can eventually reduce cholesterol levels. It is necessary to observe
that these precautions are not much valid and they take a long time to be
set up. That’s why the actual pharmacological option is maintained also
for the light hypertension forms.
Pharmacological therapy: On the base of their main action mechanisms, the
drugs used in the hypertension therapy can be classified in wide groups:
diuretics, sympathicolytics, ACE inhibitors, Ca-antagonists, and vasodilators.
The diuretics and the sympathicolytics include subgroups with specific pharmacological
qualities. Diuretics, increasing the urinary excretions of water and sodium,
reduce the extracellular volume. Sympathicolytics can reduce the sympathicus
system’s activity (central action drugs), they block its effects on the
cardiovascular system (alpha and beta blockers). ACE-inhibitors block the
angiotensin II synthesis (both on plasmatic and tissue level), that is a
powerful vasoconstrictor. Ca –antagonist promote peripheral vasodilatation,
blocking the passage of calcium inside the unstried muscular cells. At last,
vasodilators act directly on resistance vessels, inducing the arteriolar,
or venous, or both, vasodilatation.
Guidelines suggest starting the anti-hypertensive therapy with only one
kind of drug, gradually raising the dosage, if necessary, to obtain an adequate
hypotensive answer. In case it is totally or partially unvalid, it is suggestible
to modify the drug, using it in monotherapy. If both drugs have a scarce
therapy effect, guidelines recommend starting the therapy with two or more
anti-hypertensive drugs. Some associations are advised as diuretics + another
first choice drug (see beyond), or Ca-antagonists + ACE-inhibitors or B-blocker.
The JNC guidelines indicate diuretics and B-blockers as first choice drugs,
since only for these drugs, it has been demonstrated the reduction of cardiovascular
mortality and morbidity. Alternatively, Ca-antagonists, ACE-inhibitors and
the alpha 1-receptors blockers. The WHO-ISH guidelines put on the same level
all the first choice drugs: adrenergic receptor blockers, ACE inhibitors,
Ca-antagonists and diuretics.
The very conservative position of the JNC guidelines has been strongly criticised
by an editorial published on the same journal (5). In the editorial it is
underscored that ACE- inhibitors and Ca-antagonists have an important hypotensive
effect and also their sufficiency to favour the metabolic processes that
lead to the structural reshaping of the cardiovascular system. On the other
side, the choice of a drug of first application is more linked to the valuation
of the side effects than to the tested demonstration of reducing cardiovascular
mortality and morbidity. As stated on WHO-ISH guidelines, the benefit of
anti-hypertension therapy depends exclusively on the reduction of arterial
pressure value rather than the type of drug used.
New therapeutic prospects
The recent physiopathologic acquisitions have given some indications
to develop new drugs able to reduce the arterial pressure. Some of them
are still in a proximal studying phase. Some others are in a clinical testing
phase and others are already on sale.
While the rennin inhibitors and the angiotensin receptor blockers interfere
with the rennin-angiotensin system, as the converting enzyme, the other
drugs have new action mechanisms. Particularly, they are studying some substances
that can interfere with serotonin and andotheline receptors, with prostaglandin’s
synthesis, and with biological activity of Natriuretic Atrial Factor.
The aim of these researches is to obtain the ideal drug for the hypertension
therapy. It has to be valid, devoid side effects and that can be applicable
cheaply. In the next years this last aspect (cost/benefit) could become
an important characteristic.
Bibliography
- Riva-Rocci Scipione “Un nuovo sfingomanometro” Gazzetta Medica di Torino 1986, anno XLVII, No 50.
- Korotkoff N.S. “Kvoprons o Metodoach eczidovania krovuanovo davlenia” Izv Imperator Vorenno Med Akad 1905, 11: 365-367.
- “The fifth Report of the Joint National Committee on Detection, Evaluation and Treatment of High Blood Pressure (JNC V)” Arch Intern Med. 1993; 153: 154-183.
- “1993 Guidelines for the management of mild hypertension: memorandum from a World Health Organisation/ International Society of Hypertension meeting” J Hypertens 1993; 11: 905-918.
- Weber Ma, Laragh Jh “Hypertension: steps forward”. The Joint National Committee fifth report. Arch. Intern. Med. 1993; 153: 149-152.
Edited by Aldo Campana,