14.MALIGNANT HYPERTENSION

Question 1

Pathogenesis?

Answer 1

Malignant hypertension is considered a renin-mediated type of hypertension because of the, often
marked, activation of the renin-angiotensin aldosterone system (RAAS).
In experimental models it has been demonstrated that,
apart from angiotensin II, other blood pressure stimulating factors, such as deoxycorticosterone,
noradrenalin or decreased NO, may result in malignant hypertension. In humans, this is best
demonstrated by patients with an aldosterone producing adenoma (Conn’s syndrome) or
pheochromocytoma. In Conn’s syndrome, renin secretion is suppressed because of an increased
autonomous production of aldosterone. Despite an initially suppressed renin secretion, these
patients may develop malignant hypertension and profound activation of the renin-angiotensin
system. In patients with a pheochromocytoma, surgical removal of the tumor may result in
normalization of blood pressure despite an initial presentation with malignant hypertension. These
data suggest that a single blood pressure increasing stimulus, not directly related to the reninangiotensin system, may lead to malignant hypertension and RAAS activation. Therefore, it is likely
that the activation of the renin - angiotensin system in malignant hypertension is a secondary event.

Question 2

Risk factors and causes?

Answer 2

A history of poorly controlled or untreated hypertension is the most important risk factor of
malignant hypertension. In the Malignant Hypertension Register from West Birmingham, only 29% of
admitted patients had received one or more antihypertensive drugs prior to admission, whilst 45%
were previously diagnosed with hypertension. Left ventricular hypertrophy was present on the
electrocardiogram in 77% at admission suggesting that hypertension was present in more patients
before they presented with malignant hypertension.
Malignant hypertension is more frequently observed among patients from sub-Saharan African
descent. This may be explained by differences in hypertension awareness and control in this
population.
Previous studies have suggested an association with smoking and
malignant hypertension, patients with malignant hypertension being more likely to smoke than
hypertensive or normotensive controls irrespective of their age, sex or ethnic background.

Question 3

Secondary causes?

Answer 3

Basically any drug or condition that increases blood pressure can contribute to the development of malignant
hypertension. Yet, there are some drugs
and secondary causes that may accelerate
blood pressure to such an extent that
malignant hypertension follows. Several
retrospective studies have shown that
primary renal and renovascular disease
account for most of the secondary causes
of malignant hypertension
In populations
with more vigorous blood pressure
control patients with essential
hypertension are more likely to be
detected, treated and controlled thus
preventing them from developing
malignant hypertension.
The prevalence of endocrine causes of malignant hypertension such as pheochromocytoma, Conn’s
and Cushing’s syndrome is invariably low.
Although rare, oral contraceptives seem to be involved in the development of malignant
hypertension in some women.
In some
cases normal blood pressure values have been recorded just prior to the prescription of anticontraceptives.