A young man 27 years of age, presented to the out-patient clinic with general
fatigue and difficulty in climbing even two flights of stairs. He was diagnosed to have
systemic hypertension five years back and had been on antihypertensive drugs ever
since. Besides his fatigue, he also complained of episodic headache with dizziness.
These episodes were often related to undue physical exercise, emotional upset or
to missing of his medication. There was no history of cyanotic spells or fleeting joint
pains during childhood. He denied abusing tobacco, alcohol or illicit drugs.
On examination, there were no facial features of an endocrine disorder such as
thyrotoxicosis, acromegaly or Cushing’s syndrome, but his lower limbs were unusually
thin. The radial pulse was 84 beats/min. and bounding in nature. The BP in his right
arm was 170/100 mm Hg. Pulse amplitude over the femoral arteries was reduced
in volume and delayed compared to the brachial pulsation. Also, there were visible
pulsations in the suprasternal notch. The cardiac apex beat was heaving in nature
and slightly displaced towards the left axilla. On auscultation, S1
was normal, A2
was
loud and a presystolic S4
was audible. An ejection systolic murmur was heard at the
upper left parasternal area. Incidentally, the same murmur was also audible over the
interscapular region. Soft continuous murmurs were also heard over the scapulae.
On abdominal auscultation, there was no bruit heard over the renal arteries.
CLINICAL DISCUSSION
When confronted with a young patient with moderate to severe systemic
hypertension, the clinician should be alert to the possibility of secondary
hypertension. Incidentally, secondary hypertension constitutes less than 5% of
all hypertensive patients, while most have primary or essential hypertension.
Usual causes of secondary hypertension are:
• Endocrine disorders
• Renovascular disease
• Coarctation of aorta.
In this patient, ECG showed tall R waves in leads V5 and V6
with deep S
waves in leads V1 and V2
, indicating the presence of left ventricular hypertrophy
(Fig. 18.1). X-ray showed mild cardiomegaly with a rounded contour of the left
heart border. There was “notching” of the undersurface of the 4th to 8th ribs and a “figure-of-3” appearance of the aortic arch. ECHO revealed concentric left
ventricular hypertrophy with normal ejection fraction. Aortic valve was bicuspid
with thickened leaflets and an insignificant gradient across the valve. The mitral
valve was normal and there was no ventricular septal defect. Doppler signal from
the suprasternal notch showed a pulsatile aortic arch with a distal aortic gradient
that tapered into diastole. A mosaic jet was seen in the descending aorta, directed
away from the transducer Coarctation of aorta is the most likely cause of hypertension in this case.
There was clinical, radiological and cardiographic evidence of left ventricular
hypertrophy. There were brachio-femoral delay, suprasternal pulsations, a
parasternal and interscapular systolic murmur (coarctation itself) and continuous
intercostal murmurs (collateral vessels). All these auscultatory findings are
pathognomic of aortic coarctation. The murmur of coarctation itself may be
continuous if the narrowing is severe, while presence of an ejection click indicates
an associated bicuspid aortic valve. On X-ray chest, notching of the lower border
of ribs indicates arterial collateralization, to by-pass the aortic obstruction. The
“figure-of-3” appearance is produced by indentation of the aorta at the site of
coarctation, with dilatation on either side of the narrowing. The suprasternal high
velocity Doppler signal is characteristic of aortic coarctation.
Coarctation of the aorta is a localized narrowing of the aortic arch (Fig. 18.3),
due to a fibrous ring encircling the wall or a shelf projecting into the lumen. The
narrowing is in the region of the ligamentum arteriosum (juxta-ductal) and may
be pre-ductal or post-ductal. The aorta distal to the narrowing is often dilated
and aneurysmal. Coarctation may present in the neonatal period (infantile type)with heart failure, in which case the narrowing is diffuse, tubular and severe
(hypoplastic aorta). In adult type coarctation, the narrowing is discrete, ring-like,
less severe and detected during evaluation of systemic hypertension.
Some patients may complain of pain and/or weakness in the legs
(claudication), due to reduced femoral blood flow. Brachio-femoral delay pertains
to the difference in amplitude and timing between the brachial and femoral
pulsations. Therefore, the blood pressure is higher in the upper limbs than in the
lower limbs. If the left subclavian artery is also narrowed by coarctation, the blood
pressure is only elevated in the right arm. In Takayasu’s aorto-arteritis (pulseless
disease), which is also called “reverse coarctation”, the blood pressure is reduced
in the upper limbs compared to the lower limbs, because there is stenosis at the
origin of aortic arch branches.
Hypertension in coarctation of aorta is multifactorial. The aorta proximal to
the narrowing is stiff and the carotid sinus baroreceptors are set at a higher level.
Additionally there is a renal component, due to narrowing proximal to the renal
arteries. Coarctation of aorta is associated with a bicuspid aortic valve in half the
patients. Other cardiac anomalies are ventricular septal defect and mitral valve
prolapse (Table 18.1). In 10 to 20% patients, there are intracranial aneurysms
around the circle of Willis. Aortic coarctation may be associated with Turner’s
syndrome, characterized by a short-statured female with broad chest and a webbed neck. Long-term complications of coarctation are heart failure and stroke
due to hypertension, dissection of proximal aorta and ruptured aneurysm of the
sinus of Valsalva. The bicuspid aortic valve can develop stenosis or regurgitation
and be the site of endocarditis. Finally, sub-arachnoid hemorrhage can occur due
to ruptured intracranial aneurysm
Management of secondary hypertension due to aortic coarctation, is governed
by the same principles that apply to the treatment of essential hypertension. This
involves the judicious use of a combination of antihypertensive agents. Several
drugs are used including diuretics, beta-blockers, calcium-antagonists and ACEinhibitors (or ARBs), since the hypertension is generally moderate to severe in
grade and severity. Definitive treatment of aortic coarctation (systolic gradient >
30 mm Hg) is surgical excision of the area of aortic narrowing with an end-to-end
anastomosis. A prosthetic tubular Dacron graft may also be interposed. Another
technique is patch aortoplasty at the site of coarctation.
RECENT ADVANCES
Recently,the technique of percutaneous balloon aortoplasty has been developed.
It is most suitable for discrete stenosis or if narrowing has recurred following
surgical correction of coarctation. The incidence of restenosis after aortoplasty is
reduced by stenting.