Don’t Be Fooled by the Great Masquerader
Jennifer Nofar Boukouris, M.D.
Co-Chief Resident, St John Hospital and Medical Center
You are in the middle of a busy shift when you pick up a chart that lists a
chief complaint of chest pain. As you enter the patient room, you observe a
middle age African American female in mild distress. She appears tachypneic. A
quick look at the other triage vital signs reveals that she is tachycardic,
hypertensive, and has a low grade temperature. The nursing staff has already put
her on the cardiac monitor and performed the ECG which was remarkable only for
sinus tachycardia. During the patient interview you discover that she has had a
dry cough and pluertic chest pain over the past 2 days. Review of systems is
positive for dyspnea on exertion and orthopnea. She denies any past medical
history, drug use, or sick contacts. You decide to pursue a cardiac workup and
check a chest x-ray. The x-ray revealed a left lower lobe infiltrate. So, you
attribute her chest pain to pleurisy from the pneumonia and start IV antibiotics
and give her a bolus for the tachycardia and morphine for the pain. After the
therapies have been instituted you reassess the patient and notice she is still
tachycardic, hypertensive, and uncomfortable. Things just are not adding up in
your mind. You wonder how pneumonia could cause so much discomfort and such a
systemic response in a previously healthy woman...
Aortic dissection is a rare but life-threatening emergency that often goes
undiagnosed to even the sharpest clinician. Some studies have quoted a near 50%
miss rate. Each hour that an aortic dissection goes undiagnosed, the mortality
rate increases 1-2%. Therefore, it should always be part of the differential
diagnosis for patients complaining of chest pain. Incidence of aortic dissection
is estimated to range from 2.6 to 3.5 per 100,000 person-years. This may be an
underestimate because of the underreporting of the condition. The International
Registry of Acute Aortic Dissection (IRAD) reviewed 464 patients who were
diagnosed with aortic dissection, and found that65% were men and the mean age
was 63 years.
Two mechanisms exist for creating an aortic dissection. First, increasing
hydrodynamic stress tears the intimal wall of the aorta and a column of blood
slips in between the intimal and medial layers creating a false lumen.The other
less common type of aortic dissections are intramural hematomas. They develop
without tearing the intimal wall. They are proposed to be instigated by
hydrodynamic forces damaging the vaso vasorum which eventually ruptures and
bleeds into the medial wall. The Stanford classification has become the more
popular way to describe aortic dissections. Type A dissections involve the
ascending aorta while Type B includes all others. Ascending aortic dissections
are twice
as common as descending dissections.
Keeping the following risk factors and scenarios in mind will help aid in the
diagnosis. The most predisposing factor for aortic dissection is uncontrolled
hypertension. In the IRAD study 72% for patients had a history of hypertension.
Another important risk factor is previous history or aortic dissection. One
third of those patients will re-dissect, rupture, or extend their dissection in
the next 5 years. Other risk factors include: atherosclerosis, connective
tissues diseases such as Marfan Syndrome and Ehler’s Danlos, vascullitis such as
giant cell arteritis, cocaine use, pregnancy, sleep apnea, Turner’s syndrome,
bicuspid aortic valve, polycystic kidney disease, trauma, cardiac
catheterization, and a family history of aortic dissection. We should document
lack of the above risk factors in the medical record.
Patients with aortic dissection classically present with severe, sharp, or
tearing chest pain that is worst at onset, radiating to their back (73% of cases
according to the IRAD study). Signs and symptoms of an aortic dissection are
related to the location and extent of the dissection. Clues to an ascending
aortic aneurysm are new aortic insufficiency murmur, inferior ST elevation MI
secondary to extension into the right coronary ostia, cardiac tamponade,
hemothorax, asymmetrical radial or carotid pulses, and difference in systolic
blood pressure between the two arms of 20mm of mercury or more. Patients with
Type B dissections are more likely to be hypertensive than Type A dissections.
They may present with migrating pain, back pain, and asymmetrical pulses. Think
of this disease if you have complaints above and below the diaphragm such as
chest pain and abdominal pain.
Atypical presentations make the diagnosis more challenging. One study quoted
that 15% of dissections present pain free. A good rule is to consider aortic
dissection if you have chest pain and another complaint. Rare and interesting
presentations include chest pain and voice hoarseness secondary to left
recurrent laryngeal nerve palsy, chest pain and dysphagia secondary to
compression of the esophagus. There have been case reports of aortic dissection
leading to neurologic deficits including altered mental status, seizures, and
strokes. These deficits can be due to direct extension of the dissection into
the carotid arteries or diminished carotid blood flow. Moreover, if a patient
presents with sudden lower extremity paralysis and mentions that they had some
chest and back pain as well, they could have had an aortic dissection that
occluded the spinal artery. Another way that aortic dissection can present is
with syncope. The IRAD study found that 13% of the patients with aortic
dissection had syncope as their only complaint, and no pain. Needless to say,
always approach each patient with a high clinical index of suspicion and wide
differential.
Chest x-ray is indicated if an aortic dissection is suspected. Abnormal CXR
findings related to aortic dissection are numerous and include mediastinal
widening, “calcium sign” which is a calcium deposit 5mm or more from the wall of
the aorta, and a left sided pleural effusion. However, up to 12% of patients
with aortic dissection have a normal chest x-ray. Multiple advanced imaging
modalities are available to confirm the diagnosis, but most physicians chose
helical CT if the patient is stable because it is readily available.
Transesophageal echocardiograms are useful in Type A dissections when the
patient is not stable enough to leave the emergency department.
It is imperative that patients suspected of having an aortic dissection be
treated while diagnostic tests are performed. Medical management is necessary to
reduce heart rate and blood pressure. A beta blocker should be used in
conjunction with vasodilator therapy. Target heart rate should be between 60 and
80, and target systolic blood pressure should be between 100 and 120. Labetalol
is recommended in cocaine associated aortic dissection. Type A aortic
dissections require prompt surgical treatment. Type B dissections only require
surgery in certain instances: if a major vessel is blocked and oftentimes this
is corrected by interventional radiology, uncontrolled hypertension, frank
aortic leaking or rupture, or development of a localized aneurysm. Therefore,
surgery should be consulted for all aortic dissections.
Reviewing the chest x-ray again, you notice that the mediastium could be
widened. As you finish telling the patient and her spouse that you plan on
checking a CT scan to rule out other causes for her pain, her husband follows
you to the desk and asks you if his wife is going to die. In your astonishment
to his question you ask “Why do you say that?” He responds by telling you that
her sister and niece were both diagnosed with pneumonia and then died suddenly
after. You reassure the man and call CT to take the lady next. So although you
almost fell into the trap of “tunnel vision” your gestalt was correct, the lady
had an aortic dissection.
References:
Eagle KA, Isselbacher EM, DeSanctis RW: International Registry for Aortic
Dissection (IRAD) Investigators: Cocaine-related aortic dissection in
perspective. Circulation 105:1529, 2002.
Hagan PG, et al: The International Registry for Aortic Dissection (IRAD): New
insights into an old disease. JAMA 283:897, 2000
Ankel, F Chapter 84 Aortic Dissection. Rosen’s Emergency Medicine Concepts and
Clinical practice 6th edition1324-1329, 2006
Soddeck G, et al: D-Dimer in ruling out acute aortic dissection: a systematic
review and prospective cohort study. European Heart Journal 2007
28(24):3067-3075
Swahney N, et al: Aortic Intramural Hematoma – An increasingly recognized and
potentially fatal entity. Chest. 2001;120:1340-1346.
Manning, W: Clinical Manifestations and diagnosis of aortic dissection.
UptoDate.2008
Elefteriades, J, et al: Management of descending aortic dissections. Ann Thorac
Surg 1999;67:2002-2005
Rogers, R. “Aortic Dissection”. Audio Lecture from EMRAP April 2008.
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Posted: Sunday, October 26, 2008