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Thorax Board Review Cases


Case 1. A 55 yr. old man enters the emergency room after sudden onset of excruciating pain in his chest that radiates down the medial aspect of his left arm – classic symptoms for a heart attack. Explain why the man feels pain in his left arm. What nerves would the pain fibers travel in?


Case 2. An MRI shows that your patient’s right coronary artery is blocked just distal to the SA nodal branch. What areas of the heart would be affected by this blockage? (for each area you mention, name the main branch that supplies it) A heart block occurs and your patient’s ventricles begin to contract erratically. Explain how the heart block occurred and how the conduction system has been interrupted. How could this problem be corrected?


Case 3. Your 65 yr. old patient has a tumor near the posterior aspect of the root of the right lung. Which of the following structures could be affected by the tumor: phrenic nerve, vagus nerve, azygos vein? While removing the tumor during surgery, you notice that it has caused inflammation of the visceral pleura on the posterior aspect of the lung. Would your patient feel pain from this inflammation? What if the inflammation had spread to the parietal pleura in this location? What nerves do pain fibers from the parietal pleura travel in?


Case 4. Routine examination of a newborn baby detected an atrial septal defect. This developmental defect is usually caused by ______ or ______. (two possible answers) In the fetal heart, what is the name of the “normal” ASD? What is the function of this structure? What normally happens to this structure at birth? There is another structure in the fetal heart that performs a function similar to that of the structure you named above. What is this structure and what is its remnant called in the adult heart?


Case 5. A man enters the emergency room with a knife sticking out of his chest. The knife is located in the third right intercostal space, just lateral to the junction of the rib and its costal cartilage. Based on what you know about surface anatomy, is the knife piercing the heart? Name the layers that the knife is passing through, starting with skin and ending with visceral pleura.


Case 6. Your patient has fluid in her pleural cavity. Where should you insert the needle (thoracocentesis) to enter the pleural cavity, but avoid the lung? If you wanted to perform a pericardiocentesis where would you insert the needle?

 


Practice questions

1. Where is the best place to listen to the aortic valve with a stethoscope?

A. 5th LICS
B. 2nd RICS at RSB
C. 4th LICS
D. 2nd LICS at LSB


2. Which of the following anomalies is NOT commonly seen with Tetralogy of Fallot?

A. VSD
B. hypertrophy of the R ventricle
C. pulmonary stenosis
D. ASD


3. A tumor in the upper inner quadrant of the breast would most likely drain to the:

A. parasternal nodes
B. clavicular nodes
C. axillary nodes
D. abdominal nodes


4. Which of the following is found within the right atrium:

A. crista terminalis
B. moderator band
C. chordae tendineae
D. trabeculae carneae


5. Which of the following is NOT associated with the sternal angle:

A. tracheal bifurcation
B. start of the aortic arch
C. T2 vertebral level
D. junction of 2nd rib and sternum


6. Your patient has a tumor in the middle lobe of the right lung. If the tumor spread via the lymphatics, which of the following describes the path it would travel through the lymph nodes?

A. tracheobronchial nodes, bronchopulmonary nodes, paratracheal nodes, pulmonary nodes
B. pulmonary nodes, bronchopulmonary nodes, paratracheal nodes, tracheobronchial nodes
C. bronchopulmonary nodes, pulmonary nodes, tracheobronchial nodes, paratracheal nodes
D. pulmonary nodes, bronchopulmonary nodes, tracheobronchial nodes, paratracheal nodes

 

Thorax Board Review Answers

Case 1. Whenever you need to determine the path of afferent nerves, first think about the efferent nerves (afferent nerves travel along the same path as the efferent nerves only in the opposite direction). The general rule is that afferent PAIN fibers travel with sympathetics, and afferent REFLEX fibers travel with parasympathetics. In the case of the heart, pain fibers travel with sympathetics. Sympathetic fibers originate in the lateral horn of the upper thoracic segments (T1- T5), will either synapse at these levels of the chain or ascend into the cervical region of the chain to synapse (this is because the heart developed higher in the chest and initially the nerves had to travel up to reach the heart). The post-ganglionic fibers that leave the chain are known as cardiac nerves, and they enter the cardiac plexuses. Pain afferents therefore would travel backwards in the cardiac nerves and would enter the spinal cord between T1-T5, the same area where cutaneous GSA nerves from the T1-T5 dermatomes enter. These afferents enter the dorsal horn, and use the same pain pathways (ALS) to get to the brain (there is not a separate pain pathway for visceral nerves). Therefore, the brain knows it is receiving information from the ALS, but can’t distinguish between GSA and GVA information; it interprets the fibers as pain impulses from the heart AND the skin. Therefore, dull visceral pain is felt in the chest, and more localized pain is felt along the distribution of the T1-T5 dermatomes (upper chest, medial arm).


Case 2. Areas affected by the blockage of the right coronary artery: right atrium (by right coronary directly), right ventricle (marginal and posterior interventricular branches), left ventricle and interventricular septum (posterior interventricular branch), and the AV node (AV nodal branch). Lack of blood to the AV node disrupted its function. Impulses from the SA node are not transmitted to the AV bundle- ventricles therefore do not receive the impulse- heart block occurs (heart block is just defined by any blockage in the conduction system). Problem can be corrected by inserting a pacemaker into the ventricular wall (provides electrical impulses which stimulate ventricular contraction at the correct time in the conduction cycle).


Case 3. The tumor could affect the vagus nerve and azygos vein, both of which are located posterior to the root of the right lung. The phrenic nerve travels anterior to the root of the lung. The patient would not feel pain from inflammation of the visceral pleura because it is insensitive to pain – its afferent fibers relay stretch sensations only. However, the parietal pleura is very sensitive to pain due to the somatic afferent fibers that innervate it. The GSA fibers that innervate the costal parietal pleura (and the most peripheral parts of the diaphragmatic pleura) travel with the motor nerves that innervate it – the intercostal nerves. From the intercostal nerve (VPR) they would travel through the spinal nerve and dorsal root to enter the spinal cord (between T1-T12); pain would be felt along the trunk. GSA fibers that innervate the diaphragmatic and mediastinal pleura would travel with the phrenic nerves and enter the C3-5 spinal nerves; pain would be referred to the neck and shoulder (dermatome territories for C3-5).


Case 4. If development of the atrial septum does not proceed normally, an atrial septal defect (ASD) can occur. The most common developmental problems with this defect are failure of the septum secundum to form, or excessive resorption of the septum primum. Normally the fetal heart has a “hole” in the atrial septum called the foramen ovale. The function of the foramen ovale is to shunt blood from the right atrium to the left atrium so that it bypasses the non-functioning lungs (by avoiding the right ventricle and pulmonary trunk). The foramen ovale closes at birth; the remnant in the adult heart is called the fossa ovalis. The other structure that helps to shunt blood away from the lungs is the ductus arteriosus between the pulmonary trunk and the aorta. Blood entering the heart through the SVC flows inferiorly into the right ventricle, and then through the ductus arteriosus rather than the pulmonary trunk. This structure also closes at birth and its remnant is called the ligamentum arteriosum.


Case 5. The knife is not piercing the heart – the right heart border runs along the 3rd - 6th costal cartilages. The layers the knife is passing through are: skin, superficial fascia, pectoralis muscles (with deep fascia around them), external intercostal (could be membrane or muscle at this point- knife is right near the junction of the two), internal intercostal muscle, innermost (muscle or membrane), endothoracic fascia, costal parietal pleura, visceral pleura.


Case 6. To remove fluid from the pleural cavity you should place the patient in an upright position (so fluid flows inferiorly) and insert a needle into the costodiaphragmatic recess. This can be accessed through the 9th ICS at the midaxillary line – the needle should be placed directly in the center of the ICS to avoid the VAN on the inferior aspect of the 9th rib, and the collateral branches on the superior aspect of the 10th rib. To perform a pericardiocentesis (i.e. for cardiac tamponade), the needle could be inserted through the 5th or 6th LICS close to the lateral border of the sternum (the so called “bare area” of the pericardium). The pericardial sac is not covered by the lung (or pleura) here because of the cardiac notch in the left lung. Another approach is to insert the needle via the infrasternal angle, however the internal thoracic vessels are at risk during this method.


Practice questions:

1. B
2. D
3. A
4. A
5. C
6. D

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