USMLE UWorld Step 1

6968 Pages·2014·615.296 MB·English

by  coll.

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Q. Id: 8332 (549201] Previous Next
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The following vignette applies to the next 2 items.
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A 52-year-old man is brought to the emergency department for evaluation of fever, chills, and malaise.
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Cardiac examination reveals a new holosystolic heart murmur that radiates toward the axilla. Blood cultures
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are obtained and he undergoes transesophageal echocardiography. The ultrasound probe is placed in the
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mid-esophagus facing anteriorly and cardiac chambers are interrogated.
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Item 1 of 2
Anatomically, which of the following chambers is closest to the probe?
O A. Left atrium
O B. Left ventricle
O C. Right atrium
O D. Right ventricle
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Item: 1 of12 ll f'Mark
Q. Id: 8332 (549201] Previous Next
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The following vignette applies to the next 2 items.
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A 52-year-old man is brought to the emergency department for evaluation of fever, chills, and malaise.
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Cardiac examination reveals a new holosystolic heart murmur that radiates toward the axilla. Blood cultures
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are obtained and he undergoes transesophageal echocardiography. The ultrasound probe is placed in the
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mid-esophagus facing anteriorly and cardiac chambers are interrogated.
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Item 1 of 2
Anatomically, which of the following chambers is closest to the probe?
~ @ A. Left atrium [75%]
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B. Left ventricle [6%]
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C. Right atrium [13%]
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D. Right ventricle [6%]
Explanation: User Id: 549201
Transesophageal echocardiography (TEE)
Trachea
TEE probe
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Aortic arch
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Q. Id: 8332 (549201] Previous Next
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Transesophageal echocardiography (TEE)
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Trachea
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TEE probe
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Aortic arch
Pulmonary trunk
Pulmonary valve
--
Descending
aorta
t---Left atrium
Right
ventricle
Ventricular
septum
Left ventricle
Mitra! valve
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This patient's presentation suggests acute endocarditis, with confirmation pending the results of the blood
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cultures and cardiac imaging. Transesophageal echocardiography (TEE) uses ultrasound waves generated
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from within the esophagus to produce clear images of the neighboring cardiac structures. The left atrium
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makes up the majority of the heart's posterior surface, with the esophagus passing immediately posterior to
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the heart. Therefore, the esophagus lies within clo:sest proximity to the left atrium. This allows the left
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atrium, atrial septum, and mitral valve to be particul'arly well visualized on TEE. Due to its adjacent proximity,
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conditions that result in left atrial enlargement (eg, atrial fibrillation, mitral stenosis) can cause dysphagia
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through external compression of the esophagus.
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(Choice B) The left ventricle forms the apex and left border of the heart on frontal chest x-ray.
(Choice C) The right atrium, along with the superior vena cava, forms the right lateral cardiac border on
frontal chest x-ray.
(Choice D) The right ventricle forms the anterior (sternal} surface of the heart and the majority of its inferior
border.
Educational objective:
The left atrium forms the majority of the posterior surface of the heart and resides adjacent to the esophagus.
Enlargement of the left atrium can compress the esophagus and cause dysphagia.
Time Spent: 9 seconds Copyright© USMLEWorld,LLC. Last updated: [7/14/2014]
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Item 2 of 2
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• 8 In the same mid-esophageal position, the probe is rotated so that it now faces posteriorly. Anatomically,
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O A. Descending aorta
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O B. Pulmonary artery
O C. Pulmonary veins
O D. Superior vena cava
O E. Tricuspid valve
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Item 2 of 2
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• 8 In the same mid-esophageal position, the probe is rotated so that it now faces posteriorly. Anatomically,
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"' @ A. Descending aorta [69%]
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B. Pulmonary artery [8%]
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C. Pulmonary veins [10%]
0 D. Superior vena cava [11 %]
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E. Tricuspid valve [2%]
Explanation: User Id: 549201
Transesophageal echocardiography (TEE)
Trachea
TEE probe
~
!..---Esophagus
Aortic arch
Pulmonary trunk
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ltem:2 of12 ll P'Mark
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Trachea
TEE probe
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~
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1----Esophagus
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Aortic arch
Pulmonary trunk
Pulmonary valve
__D escending
aorta
--Left atrium
Right
ventricle
Ventricular
septum
Left ventricle
Mitra! valve
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The aorta has four major divisions: the ascending aorta, the aortic arch, the descending thoracic aorta, and
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the abdominal aorta. The ascending aorta lies posterior and to the right of the main pulmonary artery. The
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aortic arch travels above the right pulmonary artery and the left bronchus. The brachiocephalic, left common
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carotid, and left subclavian arteries originate (in that order) from its superior aspect. The descending thoracic
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aorta abuts the left anterior surface of the vertebral column and lies posterior to the esophagus and the left
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atrium. This permits clear visualization of the descending aorta during transesophageal echocardiography
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(TEE), allowing for the detection of abnormalities s1Uch as dissection or aneurysm. The descending thoracic
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aorta continues to travel down the left anterior surface of the vertebral column, becoming the abdominal aorta
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as it crosses the diaphragm and eventually branching into the common iliac arteries.
a- I •I •
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as n crosses tne aiapnragm ana evemua11y orancrnng into tne common mac anenes.
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