Deck 5: The Blood Vessels of the Thorax

Question 1

A 16-year-old girl, on examination in the doctor's office, was found to have absent pulses in both femoral arteries. In addition, her blood pressure was higher in both upper limbs than in both lower limbs. An anteroposterior radiograph of the chest showed notching of the necks of the upper ribs on both sides. What is your diagnosis? Why is there notching of the ribs?

Answer 1

Coarctation of the aorta is a narrowing of the aorta just proximal, opposite, or distal to the site of attachment of the ligamentum arteriosum. It is believed to result from the presence of an unusual quantity of ductus arteriosus muscle tissue incorporated in the wall of the aorta.
When the ductus arteriosus contracts after birth, the ductus muscle in the aortic wall also contracts and the aortic lumen becomes narrowed. Later, fibrosis occurs and permanent narrowing takes place. The notching of the lower borders of the ribs is caused by the opening up
of the collateral circulation through the subclavian, internal thoracic, and posterior intercostal arteries to carry blood from above the coarctation to the distal part of the aorta ; it is the dilated posterior intercostal arteries that notch the ribs

Question 2

Name the common sites on the thoracic aorta where damage occurs in blunt trauma. Between 80\% and 90\% of such injuries result in immediate death. Explain in anatomic terms the path commonly taken by the escaping blood in cases of traumatic rupture of the thoracic aorta. Name the tissues that can sometimes temporarily control the leak, thus permitting the patients to be taken to the emergency department alive.

Answer 2

Blunt traumatic injury to the thoracic aorta involving horizontal deceleration occurs most commonly just distal to the origin of the left subclavian artery. This site is vulnerable since the heart and the aortic arch are mobile and the descending aorta is fixed. Sudden vertical deceleration, as in a fall, may result in an intimal tear at the root of the ascending aorta; the momentum of the heart filled with blood is sufficient to produce the tear.
Rupture of the ascending aorta occurs into the pericardial cavity, producing immediate cardiac tamponade and death. Rupture of the descending thoracic aorta frequently occurs into the left pleural cavity. The tear initially occurs in the tunica intima; the tunica media and adventitia and the surrounding connective tissue and the pleura may delay the complete rupture or temporarily control the leak. If untreated, delayed rupture and death usually occur in these cases within 2 weeks.

Question 3

A 56-year-old man was seen in the emergency department complaining of swelling of both arms. On questioning, he said that he first noticed that his hands were swollen 3 weeks earlier. He admitted being a heavy smoker and had on several occasions coughed up bloodstained sputum. On examination, his face looked puffy,especially around the eyes. Pitting edema was present in both the upper limbs, the face, and the neck. With the patient in the recumbent position, numerous dilated superficial veins were seen over the chest wall and abdomen. Later a chest radiograph revealed a large opacity in the upper lobe of the right lung. A diagnosis of advanced bronchogenic carcinoma of the right upper lobe was made. Can you explain the presence of edema in both the upper limbs, the face, and the neck? What is the cause of the dilated superficial veins of the chest and abdominal walls? Is there normally communication between the main veins draining the upper part of the body and those draining the lower half of the body?

Answer 3

The swelling of both upper extremities and the head and neck, caused by edema, and the engorgement of the superficial veins of the chest and abdominal walls clearly indicate the presence of a superior vena caval obstruction. This obstruction was caused by the expanding metastases in the mediastinal lymph nodes secondary to the bronchogenic carcinoma. The dilated superficial veins included the lateral thoracic vein, a tributary of the axillary vein; lumbar veins, tributaries of the inferior vena cava; and the superficial epigastric vein, a tributary of the great saphenous vein of the leg
that drains into the femoral vein. These venous channels provide an alternative pathway in superior vena caval obstruction, permitting superior vena caval blood to return to the heart via the inferior vena cava. The superior vena cava normally communicates with the inferior vena cava through the azygos veins. However, in this case the tumor was pressing on the superior vena
cava proximal to the entrance of the azygos vein

Question 4

A fourth-year medical student was asked by a pediatrician what factors are responsible for the closure of the foramen ovale in the atrial septum at birth. The student also was asked if oxygenated or deoxygenated blood normally passes through the foramen ovale during fetal life. How would you answer these questions?