Download A 60 year old man presents with a complaint of chest pain that

A 60-year-old man presents with a complaint of chest pain that began as he was driving.
He describes it as sudden in onset to the center of his chest with radiation to his abdomen.
At the time of arrival to the ED, he states the pain is somewhat less than it was at onset.
He denies any nausea, vomiting, diaphoresis, or shortness of breath. His past medical
history is significant for HTN. He does not smoke or drink alcohol and denies any illicit
drug use. On exam, he is in no acute distress. His VS are BP 220/115, HR 70, RR 16, T
98.6. He has clear bilateral breath sounds and his cardiovascular exam reveals no
murmurs or gallops. His abdomen is soft and non-tender without any masses. His
extremities are warm without edema, but his femoral pulse feels slightly stronger on the
left than the right.
The patient is placed on the monitor and two large bore IVs are started. An EKG shows a
normal sinus rhythm without any acute ST changes. A portable CXR is significant for a
slightly widened mediastinumm.
An echo performed at the bedside is shown below:
Parasternal long axis
After performing the echo, the ultrasound exam is continued into the abdomen, where the
following is seen:
Transverse image of abdominal aorta
Longitudinal image of the abdominal aorta
Finally, a suprasternal view of the aorta is viewed:
Question 1:
Which of the following are not considered risk factors for development of an aortic
dissection?
a. Hypertension
b. Bicuspid aortic valve
c. Tobacco use
d. Tertiary syphilis
Question 2:
When evaluating the aorta with ultrasound, which of the following is correct?
a. Transthoracic echocardiography is the most sensitive imaging modality for
evaluating the ascending aorta
b. Transesophageal echocardiography enables the examiner to evaluate both the
thoracic and abdominal aorta
c. Ultrasound of the aorta may be limited by patient factors such as habitus or
the presence of bowel gas
d. Transthoracic echocardiography can only evaluate the ascending aorta; the
descending aorta is not visualized on standard views
Question 3:
Which of the following is most commonly seen in the presentation of aortic dissection?
a.
b.
c.
d.
Syncope
Slurred speech
Hypertension
Pulse deficit in an extremity
Question 4:
Which standard transthoracic echo view offers a view of both the aortic root and
descending aorta?
a. Parasternal long axis
b. Parasternal short axis
c. Subcostal
d. Apical
Question 5:
In the treatment of aortic dissection, which of the following is correct?
a. A myocardial infarction (MI) resulting from aortic dissection is treated
identically to an MI without concomitant dissection
b. In hypotensive patients, fluid resuscitation should be avoided to prevent
disruption of clot
c. Medications that aggressively lower systemic blood pressure may cause a
reflexive increase in heart rate, resulting in an increase in shear stress on the
aorta
d. Dissections involving the descending aorta are typically treated surgically
Diagnosis: Aortic Dissection, DeBakey Type I (Answers to questions at the end of the
discussion)
Aortic dissection most commonly originates from a tear in the intimal layer of the vessel.
This causes a false passage and can propagate to involve branches of the aorta, including
the coronary arteries, renal arteries, and carotids.
The majority of patients with aortic dissection are men between the ages of 60 and 80
years. The most common risk factors in this group are a history of hypertension and
atherosclerosis. In younger patients, predisposing factors include a history of vasculitis
involving large vessels, collagen vascular disease (such as Marfan syndrome or EhlersDanlos syndrome), biscuspid aortic valve, aortic coarctation, and Turner syndrome.
Cocaine use or other agents causing a rapid rise in blood pressure have been reported as
risk factors. Rarely, dissection can be iatrogenic in etiology, such as following a cardiac
catheterization.
Aortic dissection is classified by two main systems, the DeBakey and Stanford systems.
The DeBakey classification is based on the origin of the dissection. Type I originates in
the ascending aorta and extends to at least the aortic arch. Type 2 originates and is
confined to the ascending aorta. Type 3 originates in the descending aorta and extends
either distally or proximally. The Sanford system is based on the region of the aorta
involved regardless of the site of origin of the tear. Type A involves the ascending aorta
and type B refers to all other dissections not involving the ascending aorta.
The presentation of aortic dissection is classically described as chest pain that is sharp or
“tearing” chest pain that is sudden in onset with radiation to the back. However,
depending on the location of the intimal tear, the patient may present with pain in the
chest, back, or abdomen. The pain may radiate to the back or to the abdomen or groin.
Syncope is a relatively common presenting symptom. As the dissection can propagate
into the branches of the aorta, the patient may present with symptoms of a
cerebrovascular accident, myocardial infarction, or heart failure.
Physical exam typically reveals a hypertensive patient, although hypotension may also be
present. Hypertension is more common in dissections involving the descending aorta.
Signs of symptoms of decreased blood flow to an organ or limb may be present.
Dissection involving the coronary arteries or aortic valve may present with acute aortic
insufficiency or heart failure. Dissection may propagate into the pericardium resulting in
tamponade. When the carotid arteries are involved, the patient may have weakness of a
limb or slurred speech. A pulse deficit (including a greater than 20mmHg difference in
the upper extremities) may be noted in the extremities, although this is an unreliable
finding and is not seen routinely in aortic dissection.
Although dissection can be predicted from history and physical exam, most cases require
that further imaging be performed. A standard chest x-ray may reveal widening of the
mediastinum, pleural effusion, loss of aortic contour, apical capping, or displaced
calcification. It may appear normal if the dissection originates in the descending aorta.
Computed tomography has a high sensitivity and specificity for identifying an aortic
dissection. However, it requires the use of intravenous contrast and requires a potentially
unstable patient to leave the emergency department.
Magnetic resonance imaging is also highly accurate is identifying dissection. However, it
is not as available as other imaging modalities, has limited applicability (cannot be
performed in patients with pacemakers, for example), and also requires a potentially
unstable patient to be relatively inaccessible for a period of time.
Ultrasound is an excellent modality for confirming the presence of an aortic dissection
for several reasons. Primarily, it can be performed at the bedside, negating the need to
transport a potentially unstable patient to the radiology suite. Transthoracic
echocardiography (TTE) is rapid, portable, and well tolerated by patients. Utilizing
standard windows, portions of the ascending and descending thoracic aorta can be
visualized. The parasternal long axis view (Figure 1) shows both the aortic valve and root
and a portion of the descending aorta. Adding a suprasternal view yields an image of the
aortic arch (Figure 2). Views of the abdominal aorta are easily obtained with ultrasound.
Limitations of TTE include inability to visualize the entire ascending aorta and potential
interference by patient habitus, lung tissue, etc. Transesophageal echocardiography (TEE)
is more sensitive for detection of dissection as it places the object of interest closer to the
transducer of the ultrasound. Limitations of TEE include need for sedation prior to the
procedure.
Typically, dissections involving the ascending aorta are treated surgically, while
dissections involving the descending aorta are managed medically with aggressive blood
pressure control. Management of patients presenting with aortic dissection should
proceed as with all patients. If unstable initially, the patient should be aggressively
resuscitated with intravenous fluids and blood products through large bore intravenous
access and emergent surgical consultation should be obtained. An effort should be made
to determine if the cause of hypotension is blood loss or a consequence of the dissection,
such as pericardial tamponade (Figure 3). If the patient is hypertensive initially,
aggressive reduction of blood pressure (BP) should be sought with a goal of a systolic
blood pressure of 100 to 120 mmHg. Of note when attempting reduction of BP, agents
that cause vasodilation may also cause a reflexive increase in the heart rate. An increase
in heart rate increases the shear stress placed on the aorta, potentially worsening an
existing dissection. To blunt this response, an agent that decreases heart rate, such as a
beta-blocker, is typically administered before administration of a vasodilator.
Ultrasound of the Aorta:
Ultrasound of the thoracic aorta is somewhat limited secondary to the presence of
lung tissue and ribs. These structures do not transmit sound waves well and as a result the
thoracic aorta is visible only at three points in the chest: the aortic root, the aortic arch,
and a portion of the descending aorta.
The parasternal long axis view provides a view of both the aortic root and a sliver
of the descending thoracic aorta. This exam is performed with the phased array
transducer on the cardiac setting. The transducer is placed to the patient’s left of the
sternum with the indicator pointing towards the patient’s right shoulder (towards
approximately 10 o’clock). The depth of the image may need to be decreased to focus on
the heart and aorta. A small amount of positioning may be necessary to obtain the optimal
image, seen below:
Parasternal long axis of the heart
In this view, the left side of the heart is seen primarily, with the left atria, mitral valve,
left ventricle, aortic valve, and aortic root visualized. A portion of the right ventricle can
also be seen. In assessing for an aortic dissection, the aortic root should be assessed for
the presence of an intimal flap. Color Doppler can be added to assess for acute aortic
valvular insufficiency if the intimal flap extends to the valve leaflets. Dilation (aneurysm)
of the root can also be assessed by measuring the distance between the walls of the
ascending aorta at the level of the valve tips (not seen in this image). This distance should
be less than 3.6cm. The descending aorta can also be assessed from this view as it is seen
in cross section deep to the heart. If a dissection is present, an intimal flap may be seen.
The arch of the aorta can be assessed by ultrasound as well. To obtain this view,
the phased array transducer is again used, with the cardiac application selected. The
transducer is placed in the patient’s sternal notch with the indicator pointing towards the
patient’s left shoulder. The transducer should be aimed as far anteriorly as possible.
Although this can be a difficult view to obtain, asking the patient to extend their neck
may aid in achieving this view. The following image will be obtained:
The abdominal aorta is usually a bit easier to examine and in select patients may
be clearly visualized from its emergence from the diaphragm to its bifurcation and
beyond. To begin this study, it is preferred to use the curvilinear (or “abdominal”
transducer) on the abdominal setting. In thin patients it may be possible to achieve
adequate views with the phased array transducer. The exam should begin in the
transverse plane, with the indicator pointing towards the patient’s right, just below the
level of the xiphoid process. The aorta is typically located to the patient’s left of the
vertebral body. Knowledge of the anatomy aids in distinguishing it from the IVC, which
is typically to the patient’s right of the vertebral body:
Transverse abdominal aorta
Once identified, the aorta can be followed through the abdomen until its bifurcation at
approximately the level of the umbilicus. In the case of an aortic dissection extending
into the abdomen (as in this case), an intimal flap may be seen. The aorta should also be
measured in this orientation to assess for the presence of aneurysm. It should be less than
3cm at three points: 1. Just proximal to the xiphoid, 2. Midway between the xiphoid and
the umbilicus, and 3. Just proximal to the bifurcation.
Once the aorta is examined in this orientation, views can be obtained in the longitudinal
axis by rotating the transducer so that the indicator points towards the patient’s head. The
vessel can again be assessed for the presence of an intimal flap in this view, but
measurements should not be taken as failure to view the aorta in its midpoint may lead to
false measurements.
It should be noted that this study is limited by both patient habitus and by the presence of
gas in the stomach and/or intestine. Graded compression of the patient’s abdomen may
aid in displacing some of any gas present, but in some patients it may be impossible to
obtain an adequate exam.
Answers to questions with case:
1.
c
2.
c
3.
c
4.
a
5.
c