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1. Venous Relations in the Thoracic Cage
To recall the position of major venous structures in relation to the sternum and costal cartilages:
Behind sternoclavicular joints → Brachiocephalic veins begin
Behind 1st right costal cartilage → Superior vena cava begins
Behind 2nd right costal cartilage → Azygos vein ends
Behind 3rd right costal cartilage → Superior vena cava ends
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2. Branches of Arch of Aorta — “Know your ABC’S”
A – Arch of aorta
B – Brachiocephalic trunk
C – Left Common Carotid artery
S – Left Subclavian artery
3. Lung Lobes and Heart Valves — “Right is Tri, Left is Bi”
Right side: Tricuspid valve and Tri-lobed lung
Left side: Bicuspid (Mitral) valve and Bi-lobed lung
A teenage girl presented with breathlessness. On auscultation, the physician detected a machine-like murmur and a continuous thrill at the second left intercostal space near the sternal margin.
Chest radiographs and angiocardiography confirmed the diagnosis of Patent Ductus Arteriosus (PDA)
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1. What is the ‘machine-like’ murmur?
It is the continuous murmur produced by shunting of blood from the aorta (higher pressure) into the pulmonary artery (lower pressure) through a patent ductus arteriosus.
2. How can the shunting of blood be prevented?
By surgical ligation or catheter-based closure of the ductus arteriosus to stop the abnormal communication between the aorta and pulmonary artery.
3. What is the function of ductus arteriosus in prenatal life? When does it close?
During fetal life, the ductus arteriosus diverts right ventricular blood from the pulmonary artery directly into the aorta, bypassing the non-functional lungs.
It connects the left pulmonary artery to the arch of aorta, distal to the left subclavian artery.
Normally it closes shortly after birth due to increased oxygen tension and decreased prostaglandin levels, becoming the ligamentum arteriosum.
If it remains patent (about 1 in 3000 births), backflow from aorta to pulmonary artery produces a continuous murmur.
Persistent PDA leads to left-to-right shunt, pulmonary hypertension, right ventricular hypertrophy, and eventually heart failure if untreated
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Case:
A 45-year-old man presents with facial puffiness, prominent neck veins, and superficial chest wall veins visible up to the costal margin. He complains of difficulty in breathing when bending forward.
Explanation:
These are signs of SVC obstruction, commonly caused by bronchogenic carcinoma or mediastinal lymphadenopathy compressing the SVC.
Anatomical Correlation:
If obstruction is above the entry of the azygos vein, venous blood drains via the azygos system → veins dilated only on chest.
If obstruction is below the azygos entry, blood drains through thoracoepigastric veins to the IVC → veins dilated on chest and abdomen.
Clinical Note:
Engorgement of veins in upper body with downward blood flow direction is diagnostic.
Case:
A 16-year-old boy presents with headache, weak femoral pulses, and radio-femoral delay. X-ray shows rib notching due to enlarged intercostal arteries.
Explanation:
Coarctation = congenital narrowing of the aorta just distal to the ductus arteriosus (near the ligamentum arteriosum).
Anatomical Correlation:
Blood flow bypasses the constriction via collaterals:
Subclavian → Internal thoracic → Anterior intercostal → Posterior intercostal → Descending aorta.
The enlarged intercostal arteries erode ribs, producing notching on X-ray.
Clinical Note:
Upper limb BP is higher than lower limb BP; treated surgically.
Case:
A 55-year-old man complains of hoarseness of voice, dysphagia, and dyspnea. Radiograph shows widened superior mediastinum and aortic knuckle prominence.
Explanation:
Due to aneurysmal dilation of the arch of aorta compressing adjacent structures.
Anatomical Correlation:
Left recurrent laryngeal nerve (around ligamentum arteriosum) → hoarseness.
Trachea and esophagus → dyspnea and dysphagia.
Left bronchus and phrenic nerve may also be affected.
Clinical Note:
This constellation of findings = Mediastinal Syndrome.
Case:
A 20-year-old athlete experiences breathlessness and palpitations. Echocardiography reveals mild right atrial dilation and left-to-right shunt through a patent foramen ovale.
Explanation:
Failure of fusion between septum primum and septum secundum.
Increased pressure in left atrium due to aortic hypertension causes left-to-right shunt, increasing pulmonary flow.
Clinical Note:
Prolonged condition can lead to Eisenmenger’s syndrome (reversal of shunt).
Case:
A 30-year-old woman with long-standing mitral stenosis develops progressive dyspnea and right-sided heart failure.
Explanation:
Mitral stenosis increases left atrial pressure → back pressure transmitted to pulmonary veins → pulmonary trunk dilation.
Anatomical Correlation:
The pulmonary trunk, normally anterior and left to the aorta, enlarges and may compress the left recurrent laryngeal nerve, leading to hoarseness.
Case:
A 25-year-old undergoing cardiac catheterization is found to have the catheter entering the coronary sinus instead of the right atrium.
Explanation:
Due to persistence of the left anterior cardinal vein, forming a left SVC draining into the coronary sinus.
Clinical Note:
Usually asymptomatic but important during central venous access or pacemaker placement.
Case:
A 58-year-old hypertensive patient presents with sudden severe chest pain radiating to the back.
Explanation:
A tear in the intima of the ascending aorta creates a false lumen between tunica layers.
Blood tracks along the wall, potentially rupturing into the pericardial cavity, leading to cardiac tamponade.
Clinical Note:
This is a surgical emergency with high mortality.
Case:
A driver involved in a car crash develops massive hemorrhage into the mediastinum. Autopsy reveals rupture of aorta just distal to ligamentum arteriosum.
Explanation:
The aorta is fixed at the ligamentum arteriosum; sudden deceleration causes shearing stress at this point — a classic site of traumatic aortic rupture.
Case:
A patient with SVC obstruction above azygos entry shows a dilated arching vein in the right paratracheal region on chest X-ray.
Explanation:
The azygos vein provides an alternate venous route to the heart when the upper SVC is obstructed.
Case:
A 5-year-old boy presents with difficulty swallowing and noisy breathing since birth.
Explanation:
Persistence of both right and left dorsal aortae forms a vascular ring around the trachea and esophagus, causing compression.
Clinical Note:
Surgical division of one arch relieves symptoms.
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