428
U N I T 5
Circulatory Function
diuretics, such as spironolactone, which is an aldoste-
rone antagonist, often are used in the medical manage-
ment of persons with bilateral hyperplasia.
Pheochromocytoma.
Pheochromocytomas are rare
catecholamine-secreting tumors of adrenal chromaffin
cells.
30
They can occur at any age, including infancy, but
are uncommon after 60 years of age. They can occur as
part of hereditary syndromes, but most are sporadic. Of
the sporadic tumors, about 10% are malignant.
46
Like adrenal medullary cells, the tumor cells of a pheo-
chromocytoma produce and secrete the catecholamines
epinephrine and norepinephrine. The hypertension that
develops is a result of the massive release of these cat-
echolamines. Their release may be paroxysmal rather
than continuous, causing periodic episodes of head-
ache, excessive sweating, and palpitations. Headache
is the most common symptom and can be quite severe.
Nervousness, tremor, facial pallor, weakness, fatigue,
and weight loss occur less frequently. Marked variability
in blood pressure between episodes is typical.
Diagnostic methods include urinary and blood assays
for catecholamines and their metabolites and CT and
MRI studies to locate tumors and possible metastases.
Surgical removal of the tumor or tumors is the treat-
ment of choice. If the tumor is not resectable, treatment
with drugs that block the action or synthesis of cate-
cholamines can be used. When correctly diagnosed and
treated, most pheochromocytomas are curable. When
they are undiagnosed or improperly treated, they can
be fatal.
30–46
Coarctation of the Aorta.
Coarctation of the aorta or
aortic coarctation is a congenital condition in which
a narrowing or constriction of the lumen of the aorta
exists.
47
In the adult form, narrowing most commonly
occurs just distal to the origin of the subclavian (see
Chapter 19). The ejection of a large stroke volume into
a narrowed aorta results in an increase in systolic blood
pressure and blood flow to the upper part of the body.
Blood pressure in the lower extremities may be normal,
although it frequently is low. It has been suggested that
the increase in cardiac output and maintenance of the
blood pressure to the lower part of the body is achieved
through the renin-angiotensin-aldosterone mechanism
in response to a decrease in renal blood flow.
Coarctation of the aorta should be considered as a
cause of secondary hypertension in young people with
an elevation in blood pressure. Because the aortic capac-
ity is diminished in coarctation of the aorta, there usu-
ally is a marked increase in pressure (measured in the
arms) during exercise, when the stroke volume and
heart rate are exaggerated. Pulse pressure in the legs
almost always is narrowed, and the femoral pulses are
weak. It is important that blood pressure be measured
in both arms and one leg when coarctation of the aorta
is suspected. A pressure in the arms 20 mm Hg or more
higher than in the legs suggests coarctation of the aorta.
Treatment consists of surgical repair or balloon
angioplasty. Although balloon angioplasty is a relatively
recent form of treatment, it has been used in children
and adults with good results. However, there are few
data on long-term follow-up.
Oral Contraceptive Drugs.
The use of oral contracep-
tive pills is probably the most common cause of second-
ary hypertension in young women. Women taking oral
contraceptives should have their blood pressure taken
regularly.
30
The cause of the increased blood pressure is
largely unknown, although it has been suggested that the
probable cause is volume expansion because both estro-
gens and synthetic progesterones used in oral contracep-
tive pills cause sodium retention. Various contraceptive
drugs contain different amounts and combinations of
estrogen and progestational agents, and these differences
may contribute to the occurrence of hypertension in
some women but not others. Fortunately, the hyperten-
sion associated with oral contraceptives usually disap-
pears after the drug has been discontinued, although it
may take as long as 3 months for this to occur. However,
in some women the blood pressure may not return to
normal, and they may be at risk for development of
hypertension. The risk for hypertension-associated car-
diovascular complications is found primarily in women
older than 35 years of age and in those who smoke.
Target-Organ Damage
Hypertension is typically an asymptomatic disorder.
When symptoms do occur, they are usually related to
the long-term effects of hypertension on other organ
systems, termed
target organs
, such as the kidneys,
heart, eyes, and blood vessels
29
(Chart 18-2). The excess
morbidity and mortality related to hypertension is pro-
gressive over the whole range of systolic and diastolic
pressures, with target-organ damage varying markedly
among persons with similar levels of hypertension.
Hypertension is a major risk factor for atheroscle-
rosis; it predisposes to all major atherosclerotic cardio-
vascular disorders, including coronary heart disease,
heart failure, stroke, and peripheral artery disease. The
risk for coronary artery disease and stroke depends to
a great extent on other risk factors, such as obesity,
smoking, and elevated cholesterol levels. In clinical
CHART 18-2
Target-Organ Damage
Heart
■■
Left ventricular hypertrophy
■■
Angina or prior myocardial infarction
■■
Prior coronary revascularization
■■
Heart failure
Brain
■■
Stroke or transient ischemic attack
Chronic kidney disease
Peripheral vascular disease
Retinopathy
From the National Heart, Lung, and Blood Institute. The
Seventh Report of the National Committee on Detection,
Evaluation, andTreatment of High Blood Pressure. Publication
No. 03–5233. Bethesda, MD: National Institutes of Health; 2003.
