Hypertension 1996 : One Medicine, Two Cultures
Nephrovascular hypertension: Angioplasty of the stenosis of the renal artery
L. Inglese
“E. Malan” Department of Haemodynamic and Cardiovascular Radiology
San Donato Milanese Hospital, Milan.
Nephrovascular disease is one of the commonest causes of secondary hypertension.
It can be related to a renal hypoperfusion that causes an increase in the
systolic-diastolic values of systemic arterial pressure. It must be taken
into account that not all rein-vascular diseases cause hypertension (diabetes
for example) but only those which cause local or global renal hypoperfusion.
The ligature of the renal artery in the laboratory animal (Goldblatt's experiment)
provokes a sudden increase in reninemia with activation of the angiotensin
system and consequent systo-diastolic hypertension. The early removal of
this obstacle restores pressure to normal values whilst delayed removal
is not usually able to produce a similar effect.
Nephrovascular hypertension is present in 1-4% of the hypertensive population
but its preponderance shows a clear increase of up to as much as 34% in
the subgroup of elderly patients with little response to medical therapy
diffused atherosclerosis and comprised renal functioning. Nephrovascular
hypertension is therefore caused in the first place by a hypoperfusion of
the renal artery. Twenty-five percent of the patients suffering from nephrovascular
hypertension show a bilateral obstructive pathology of both renal arteries.
The cause of renal artery stenosis is, in the majority of cases, of an atherosclerotic
nature and mainly affects subjects of the male sex in the 50-60-age range;
it is frequently accompanied by another localisation of atherosclerotic
damage more often at coronary, carotid or lower limb level. Another cause
of renal artery stenosis is represented by fibromuscular dysphasia of the
renal artery itself, which appears in the younger age range (twenties and
thirties) and more frequently in the female sex. It is due to a miopragia
of the renal artery wall, which may be congenital or induced by hormonal
factors (estrogens).
Clinically, nephrovascular hypertension classically appears with a sudden
increase in the telediastolic pressure in subjects who had been normotensive
up to then or in the sudden deterioration of the pressure homeostasis in
a subject who, up to that moment, had responded constantly to anti-hypertensive
treatment. In addition to this factor of anamnesis and the instrumental
collation of a significant increase in the telediastolic pressure (>90 mmHg),
the presence of a systo-diastolic murmur may be found in the paraumbilical
region in the presence of a renal function which usually is not compromised.
The clinical suspicion of nephrovascular hypertension may be confirmed by
the sequential scintigraphic scan with a test using Captopril (paying attention
to the bilateral pathology), with the ascertainment of increased reninemia,
with the semeiological duplex scan, with the spiral CT and lastly with the
selective renal angiography during which a confirmation not only of the
presence of a critical stenosis (>60%) must be sought, but also a transtenotic
pressure gradient which, together with the angiographic aspect, represents
the point of reference for the evaluation of the success of the possible
planned operating procedure.
Until not many years ago, surgery was compulsory, especially for patients
non-responding to medical therapy and, from the examination of various case
histories, surgery was not without mortality and morbidity rates which were
not indifferent (5-10%).
In 1977, Andreas Gruentzing was the first to carry out the transluminal
angioplasty of the renal artery (PTRA) which, with a mechanism similar to
that of coronary angioplasty, using wall barotrauma by means of a balloon
catheter, succeeded in restoring an almost normal endoluminal channelling
and therefore the restitution of the renal perfusion pressure. Clinically,
the evaluation of effectiveness of the therapeutic procedure, whether it
is surgical or by intervention (PTRA) is assessed according to the criteria
of the collaborative study on nephrovascular hypertension (JAMA, 1972, vol.
230) with the identification of “cured” patients (Ap <90 mmHg without therapy),
patients who show improvement (AP <90-100 mmHg with a bland medical therapy:
monotherapy), stationary patients or whose condition has worsened (AP quo
ante). The dilation of the renal artery is carried out by a coaxial guidance
system and balloon catheter, conveyed locally and dilated to a variable
pressure of 4-8 bar with subsequent measurement of the residual transtenotic
pressure gradient. Of the two etiopathological components, fibromuscular
dysplasia mainly affects the renal artery proper, or its branches of bifurcation
whilst the atherosclerotic process mainly concerns the proximal or often
ostial artery. In the latter case, typical of patients with polylocal atherosclerosis,
simple angioplasty has proven to be ineffective, due to the recidivation
of plaque located on the wall of the aorta. For the treatment of these forms,
endovascular stents were introduced a few years ago, which, by providing
an important wall support can prevent at this level (ostial) the recidivation
of plaque. The application of renal stents has proven to be useful in cases
of PTRA, with hesitation over dissection of the renal artery associated
in varying degrees to plaque recoil.
The evaluation of the therapeutic success of the PTRA, again from the clinical
point of view, may be carried out in the follow-up of the patient by means
of duplex scans and, where necessary, spiral CT.
The prospect of treatment of renal insufficiency, when present in these
patients, has proven to be very interesting. The critical atherosclerotic
lesions of the renal arteries have proven to be rapidly progressive, leading
patients with critical stenosis >90% to serious renal insufficiency which
almost always results in dialysis, with the consequent considerations. The
endoluminal dilation of the renal artery, restoring the flux to the ischaemic
parenchyma, usually determines recovery not only of renal perfusion but
also of renal filtration with impediment of its early or progressive deterioration.
Therefore, treatment by ransluminal angioplasty with the application, where
necessary, of metal vascular endoprosthesis (STENT) has proven to be an
alternative to surgery and increasingly requested as a preliminary treatment
of severe nephrovascular hypertension, of recent onset, accompanied in varying
degrees by a deterioration of the renal function.
We have reviewed the case histories of 156 patients, who underwent transluminal
angioplasty of the renal artery in our hospital between 1990 and 1995 for
the presence of a documented renal hypoperfusion due to mono or bilateral
stenosis (27%) of the renal arteries with subsequent pronounced systo-diastolic
hypertension.
In the cases of fibromuscular dysplasia, the age-range most frequently affected
was between 30 and 40; in the cases of atherosclerosis, the age range most
affected was between 60 and 70. Our statistics show a lower percentage,
compared to literature, of cases of fibromuscular dysplasia as our population
of patients mainly consists of polyvasculopathic patients, with serious
coronary problems and problems of the carotid or iliac-femoral axes. In
these patients we have treated, we have obtained an immediate success from
the PTCA procedure in 145 cases (92%) with the necessity of application
of vascular endoprosthesis in 72 (49%). The immediate rate of complications
was relatively modest: two patients with hospital mortality (1.2%), both
of whom died within four weeks of the procedure, one due to serious renal
failure (starting from a creatininemia of 5 mg/dl) and the second of a cholesterol
embolism, involving the splanchnic and peripheral vessels. In one case we
had to resort to the surgical examination of an axillary hematoma which
required surgical intervention with percutaneous arterial introits. However,
the angiographic success of 92% did not correspond to a similar success
for the recovery of normal homeostasis of the arterial pressure, in the
absence of drugs. Only 22% of the patient population we treated have responded
in this optimal way, whilst 50% showed a significant improvement, in terms
of improved control of arterial pressure, with fewer drugs. Of the remaining
28%, the majority are patients with a compromised renal function in whom
the clinical situation has remained unchanged and only in three have we
noted a progressive deterioration of the renal function compared to the
control. On the basis of our experience, we consider that with transluminal
angioplasty, an effective therapy may be obtained which recovers the calibre
and normal perfusion of the renal artery concerned, with lower morbidity
and mortality rates compared to the analogous surgical solution. However,
it appears decisive to us that the doctor in charge of the case has a greater
possibility regarding the diagnostic sensitivity of this pathology as the
timelines of the invasive therapeutic approach (PTRA) compared to the timing
of the appearance of hypertension, especially if monolateral, is, in our
opinion, essential to link a perfect recovery of the endoluminal channelling
of the renal artery to a good corrective response of the homeostasis of
the renin/angiotensin system which governs the regulation of systemic arterial
pressure.
Edited by Aldo Campana,