keepgoing
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On physical examination of a 7-year-old boy, the child's upper body appears much more developed than his lower body. Blood pressure in the upper extremities exceeds that of the lower extremities. On cardiac examination, there is a midsystolic murmur over the anterior chest and back. The child's lower extremities are cold, and femoral pulses are absent. The part of the vascular system that is affected in this disorder is derived from which of the following embryologic structures?
A. Bulbus cordis
B. Ductus arteriosus
C. Left horn of sinus venosus
D. Right common cardinal vein
E. Right horn of sinus venosus
F. Third, fourth, and sixth aortic arches
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| indidoc1
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F
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"Whether you think you can or whether you think you can't, you're right!" ~ Henry Ford
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| keepgoing
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agreed indidoc1 
The correct answer is F.
Explanation:
This patient has coarctation of the aorta (constriction of the ascending aorta), which is suggested by a midsystolic murmur over the anterior part of the chest and back, hypertension in the upper extremities, and absent or delayed pulsations in the femoral arteries. The upper extremities and thorax may be more developed than the lower extremities. Patients with coarctation of the aorta may experience symptoms such as cold extremities as a result of tissue ischemia.The truncus arteriosus gives rise to the proximal portions of the ascending aorta and the pulmonary trunk. The third, 4th, and 6th aortic arches and the right and left dorsal aortae contribute to the remainder of the aorta.
The bulbus cordis (choice A) gives rise to the right ventricle and the aortic outflow tract.
98% of cases of coarctation of the aorta take place immediately distal to the offshoot of the left subclavian artery, close to the junction of the ductus arteriosus (choice B) with the aorta.
The left horn of the sinus venosus (choice C) gives rise to the coronary sinus.
The right common cardinal vein (choice D) gives rise to the superior vena cava.
The right horn of the sinus venosus (choice E) gives rise to the smooth part of the right atrium.
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| lq2006
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F
aorta coarctation
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| po
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Preductal coarctation is associated with an increased incidence of cardiac defects, and the patient may present with congestive heart failure (CHF) if a VSD is present. A preductal defect does not change normal fetal blood-flow patterns. As a result, no collaterals form in utero. If blood flows through the patent ductus arteriosus, pulses are often palpable in the lower extremities. Symptoms develop as the ductus closes, leading to a clinically significant obstruction.
On clinical examination, the infant often is irritable and disinterested in feeding. Tachycardia is often present. Few findings may be apparent on physical examination in a healthy-appearing infant. However, in the uncompensated patient, differential cyanosis may be observed between the upper body and the lower body. A systolic murmur may be present over the left precordium or between the scapulae on the patient's back. An infant who is compensating (ie, one with a left-to-right shunt through a patent foramen ovale) should have a substantial systolic blood-pressure gradient between the arms and the legs.
Physical findings in a neonate who is decompensating and critically ill may differ substantially. The blood-pressure gradient is often absent secondary to diminished cardiac output. Hypotension, oliguria, and severe metabolic acidosis are concurrent with severe coarctation, as blood flow to the kidneys and all distal structures is drastically impaired. In severe obstruction or in IAA, diagnosis by physical examination can be obscured as long as the ductus remains patent because the pulmonary artery pulse is palpated in the femoral arteries.
Paraductal and postductal anomalies
Paraductal and postductal anomalies are often isolated defects, and the incidence of associated anomalies is low. Later in life, patients may present with headache, epistaxis, or visual disturbances. Exertional dyspnea and stroke are other presenting symptoms (Shearer, 1970).
Coarctation can be clinically diagnosed depending on the available evidence, as described above. To summarize, hypertension or a systolic blood-pressure gradient between the arms and legs may be observed. Checking the patient's blood pressure in both arms is important because an anomalous origin of the right subclavian distal to the coarcted segment may be present. A systolic murmur over the left precordium or between the scapulae may be heard, and the femoral pulses may be absent or diminished with a delayed upstroke. In children older than 5 years, look for the signs of collateral circulation, ie, enlarged and palpable collateral vessels, audible bruits, and dilatation of the intercostals (rib notching)
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