(Circulation. 1996;93:380-386.)
© 1996 American Heart Association, Inc.
Articles |
A 73-Year-Old Man With Hypertension and Syncope
Presented May 8, 1995, as Clinical Case Conference, Section of Cardiology, Department of Medicine, University of Chicago, University of Chicago Medical Center, Chicago, Ill.
From the Section of Cardiology, Department of Medicine (A.P., R.S., C.K., P.V., J.B., T.F., R.M.L.), the Department of Pathology (S.G.), and the Department of Surgery (B.K.L.), University of Chicago (Ill) Medical Center.
Correspondence to Athena Poppas, MD, Noninvasive Cardiac Imaging and Physiology Lab, Section of Cardiology, University of Chicago Medical Center, 5841 S Maryland Ave, MC5084, Chicago, IL 60637.
Key Words: Clinicopathological Conference • aorta • syncope • echocardiography • cardiovascular diseases
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Case Presentation (R. Sawyer and A. Poppas) |
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 Top Case Presentation (R. Sawyer... Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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A 73-year-old man presented to the University of Chicago Hospital Emergency Department on April 9, 1995, with a syncopal episode. The patient had been in his usual state of health until earlier that morning when he experienced an acute loss of consciousness during micturition. He fell and hit the left side of his head but sustained no other injuries. He was unable to tell how long he had been unconscious, although he thought that it had only been a few seconds. The event was not witnessed. He did not remember any premonitory symptoms such as palpitations, chest pain, dyspnea, headache, visual changes, or olfactory sensations or any confusion, grogginess, or bowel incontinence after the event. The patient had not noted any recent or remote episodes of dyspnea on exertion, orthopnea, paroxysmal nocturnal dyspnea, dizziness, numbness or weakness, nausea, vomiting, diarrhea, fever, chills, cough, abdominal pain, back pain, or lower-extremity claudication. One month before this admission, the patient had experienced a similar episode of micturition syncope, but he had not sought medical attention. The previous episode also occurred immediately after awakening and was not preceded by any unusual symptoms.
His past medical history was significant for long-standing systemic hypertension, chronic atrial fibrillation, a cerebral vascular accident in 1983 without any residual defects, and a bowel obstruction due to volvulus that required surgery in 1992. He was a retired maintenance worker and part-time minister. He did not smoke, drink alcohol, or use recreational drugs. He was not taking any prescription or over-the-counter medications. His family history is significant for atherosclerosis, with his mother and father dying of myocardial infarction at ages 60 and 70 years, respectively.
On physical examination, the patient was alert and oriented. He was 6 ft tall and weighed 69 kg. His vital signs included a temperature of 38.1°C, an irregular pulse of 90 beats per minute, a respiratory rate of 18 breaths per minute, and a blood pressure of 160/88 mm Hg in both arms that did not change with positioning. Oxygen saturation on room air was 95%. The left forehead revealed a small abrasion and hematoma. His neck was supple and there was no Brudzinski's sign. There was no cervical adenopathy or thyromegaly. The pupils were equal, round, and reactive to light and accommodation. The extraocular movements were intact, and the sclera were anicteric. The lungs were clear to both auscultation and percussion.
His cardiac rhythm was irregularly irregular, with slight variation in the intensity of the first heart sound with a physiologically split second heart sound. No extra heart sounds, thrills, or murmurs were heard on auscultation while standing or squatting or during the Valsalva maneuver. The point of maximal cardiac impulse was palpated in the sixth intercostal space displaced lateral to the midclavicular line. The carotid, radial, femoral, and dorsalis pedis pulses were equal bilaterally, with normal upstrokes and no bruits.
The abdomen was soft and nontender with normal bowel sounds, no bruits, and no hepatosplenomegaly. There was no clubbing, cyanosis, or edema noted in the extremities. The neurological examination revealed a normal gait and a negative Romberg test. There were no abnormalities of cranial nerves II through XII. There was no muscular wasting, and motor strength was normal. The deep tendon reflexes were symmetrical and 2+ throughout, and there was no Babinski sign.
The laboratory values on admission are shown in the
Table
. The ECG showed coarse atrial fibrillation, poor
R-wave progression, and ST- and T-wave abnormalities consistent
with anterolateral ischemia and/or digitalis effect. On the
chest radiograph, there were clear lung fields and mild cardiomegaly,
and the aorta was mildly tortuous (Fig 1). A noninfused
head computed tomogram (CT) showed mild atrophy and small vessel white
matter disease within the subcortical, periventricular
white matter and anterior limb of the right internal capsule. The
patient was admitted to the cardiac telemetry unit for observation.
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Clinical Discussion (A. Poppas) |
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TopCase Presentation (R. Sawyer...Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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Syncope can be defined as the sudden, transient, and spontaneously reversible loss of consciousness with simultaneous loss of postural tone. The differential diagnosis and prognosis of syncope is exceptionally broad and can be focused by the early separation of cardiac from noncardiac etiologies. A number of studies have emphasized the importance of history and physical exam in determining the pathophysiology underlying the syncopal episode.1 2 3
This elderly gentleman presented to the emergency room with his second episode of micturition syncope. Unfortunately, these events were not witnessed; therefore, crucial details to help differentiate cardiac from neurological etiologies of syncope can only be inferred. The patient's description of the event was not consistent with a seizure; there was no postictal state and no loss of bowel or bladder control. Acute cerebrovascular disease rarely presents with an abrupt loss of consciousness. Occasionally, bilateral carotid occlusion or isolated midbrain infarction may present in this manner. Structural abnormalities such as tumor, subdural hematoma, or intracranial bleeds were excluded by the head CT findings. His physical examination was remarkable for the absence of any residual neurological deficit or vascular findings (carotid bruits, double impulses, or pulse deficits). His mild confusion at the time of admission was chronic according to his family and internist; the small vessel white matter disease noted on his CT is consistent with the diagnosis of multi-infarct dementia.
The patient had cardiovascular disease with poorly controlled, long-standing hypertension and atrial fibrillation with a slow ventricular response. He had hypertensive heart disease as evidenced by his physical examination, which revealed a dynamic left ventricular impulse. This finding was also supported by the presence of cardiomegaly on chest radiograph and ECG changes consistent with left ventricular hypertrophy. The ECG lacked evidence for myocardial ischemia or infarction as a cause for his syncope. Physical examination revealed no abnormal heart sounds, murmurs, or peripheral pulse changes suggestive of aortic stenosis, left ventricular outflow tract obstruction, mitral stenosis, pulmonic stenosis, or obstructive left atrial myxoma to explain his syncope. He had no evidence of orthostatic changes by blood pressure or pulse measurements. His syncope could have been the result of a cardiac dysrhythmia. Given his intrinsically slow atrial fibrillation on presentation, a bradyarrhythmia or tachyarrhythmia may have occurred. Finally, a vasovagal reflex phenomena seems equally likely because both of his syncopal events occurred with micturition. Intrinsic rhythm disturbances may accentuate the vagus-induced bradycardic effects of cough or micturition.4
The differential diagnosis of syncope should also include carotid sinus hypersensitivity (cardioinhibitory, vasodepressor, or mixed), aortic dissection (associated with great vessel involvement or tamponade), metabolic disturbances (hypoglycemia, hyperventilation, toxic ingestion), and psychiatric disorders (anxiety and panic disorders, major depression, and somatization). Finally, depending on the individual characteristics of the population studied, the etiology of syncope still remains undetermined in 30% to 50% of cases.1 2 3
A transthoracic echocardiogram was performed to better define the hypertensive heart disease suggested by the history and physical examination, and an electrophysiology consultation also was obtained.
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Electrophysiological Evaluation (C. Kinder) |
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TopCase Presentation (R. Sawyer...Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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Although the incidence of micturition syncope in the general population is not known, some reports suggest that of all episodes of syncope as many as 9% may be related to micturition.5 This form of syncope was initially described in otherwise healthy young men in association with predisposing factors such as alcohol ingestion, dehydration, and recent upper respiratory tract infection.6 As might be expected, the prognosis in this group of young, healthy patients was excellent. Recently, Kapoor et al5 described a group of 25 older patients (mean age, 60 years) with multiple medical problems and micturition syncope. In this study no cause for micturition syncope could be found, but the majority (88%) of patients had orthostatic hypotension. Therapy was directed at improving orthostasis, and over a mean follow-up of 15.3 months there were no episodes of recurrent micturition syncope or sudden death.
The pathophysiology of micturition syncope is likely multifactorial, and the exact mechanism remains controversial. It has been suggested that physiological changes occurring during micturition may lead to a decline in cerebral blood flow and syncope. These changes include vagal stimuli associated with micturition7 ; Valsalva's maneuver, leading to decreased venous return6 ; and a poorly characterized reflex related to sudden decompression of the bladder, causing sympathetic nervous system withdrawal and an additional excessive vagal response.8 Preexisting orthostatic hypotension may also be aggravated by one or more of the aforementioned physiological changes leading to micturition syncope. In addition, impaired baroreceptor reflexes and sinus node dysfunction may play a role in the elderly population.9 Finally, mild hypotension induced during micturition may initiate the well-described cascade of events leading to neurocardiogenic syncope.10
In general, if one isolated episode of micturition syncope occurs and the patient has no evidence of underlying heart disease based on history, physical examination, ECG, echocardiogram, and (possibly) exercise testing, then correction of potentially reversible contributing factors such as volume depletion or excessive medication coupled with close clinical follow-up is usually all that is necessary. If there is evidence of underlying structural heart disease, as for example decreased left ventricular function, bundle-branch block, or a positive signal-averaged ECG, then even a single episode of syncope, despite being associated with micturition, merits investigation for other cardiac mechanisms of syncope, including both tachyarrhythmias and bradycardia. Those with structural heart disease or multiple episodes of micturition syncope may benefit from electrophysiological evaluation to clarify the potential mechanism of syncope.11 Finally, the presence of atrial fibrillation, especially if paroxysmal, can be associated with sick sinus syndrome.12 Thus, sinus and/or AV node dysfunction could be an alternative cause of the syncope noted in this patient.
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Echocardiographic Findings (P. Vignon, J. Bednarz, and R.M. Lang) |
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TopCase Presentation (R. Sawyer...Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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A transthoracic echocardiographic study was performed shortly after the patient's admission. The aortic root was dilated (4.5 to 5.0 cm) and contained an intraluminal oscillating flap that appeared to originate 1.5 cm above the right coronary aortic cusp. With the use of color-flow mapping, no entry tear could be located in the ascending aorta (Fig 2
).
The descending thoracic aorta appeared normal in the
parasternal, subcostal, and suprasternal views. With the use of
color-flow mapping, moderate aortic regurgitation
was noted across a trileaflet aortic valve. A small pericardial
effusion was observed but was not associated with any adverse
hemodynamic findings. Additional findings consisted of
mild concentric left ventricular hypertrophy
together with preserved systolic performance and no
regional wall motion abnormalities. A transesophageal
echocardiographic (TEE) examination was performed using
a multiplane 5-MHz probe to identify the entry tear and determine the
extension of the dissection. The presence of a mobile intimal flap in
the ascending aorta was confirmed (Fig 3). This flap
extended to the arch at which an entry tear was observed and confirmed
with color-flow mapping. A thick, nonorganized mural thrombus
layered the false lumen of the aortic arch, and no mediastinal hematoma
was visualized. The descending thoracic aorta appeared normal despite
the presence of a small left pleural effusion. No evidence for
extension of the dissection into the arch vessels was noted.
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The presence of two vascular lumens separated by an undulating intimal flap is considered to be diagnostic of aortic dissection.13 When complete thrombosis of the false lumen occurs, a central displacement of intimal calcifications (when present) may be used as an alternative diagnostic criterion. In this case, partial thrombosis of the false lumen was observed only in the aortic arch. This finding was confirmed during surgery and was consistent with our inability to detect blood flow in the false lumen of the aortic arch with color-Doppler imaging. The entry site of the dissection is commonly defined as a tear of the dissected membrane with blood flow demonstrated by color-Doppler imaging between the two aortic lumina.14 The direction of blood flow across the entry tear of the aortic dissection follows the pressure gradient between the false and true lumina. In the present case, blood flow entering the false lumen through an entry tear was only observed during systole; no other rupture sites of the intimal flap ("reentry tears") were visualized. Since the tear arose proximal to the left subclavian artery and extended proximally to involve the ascending aorta, this aortic dissection should be classified as type A.15 Aortic regurgitation and pericardial effusion, as seen in this patient, are findings frequently associated with proximal aortic dissections.16 17
Conventional transthoracic echocardiography has limited diagnostic value in the evaluation of the thoracic aorta, particularly in its descending segment, because of a limited field of view and the need for optimal imaging quality.17 The excellent sensitivity of TEE for the diagnosis of acute aortic dissection has been widely reported.16 17 False-positive results secondary to artifactual images or extensive plaque formation in patients with severe aortic atherosclerotic changes sometimes may be encountered, accounting for the lower specificity of TEE in the ascending aorta.16 Although the current case was a spontaneous aortic dissection, this condition may sporadically occur after traumatic chest injuries secondary to abrupt deceleration accidents.18 The differential diagnostic TEE findings between aortic dissection and traumatic aortic rupture are as follows.19 (1) In traumatic lacerations, the aortic contour is deformed due to the formation of a localized pseudoaneurysm, whereas the dissected aorta is usually enlarged in a symmetrical manner. (2) Since the flap of the ruptured aorta involves the entire depth of both intimal and medial layers, it usually appears thicker than the intimal flap commonly observed in aortic dissections. (3) With the use of color-Doppler mapping, blood flow velocities are generally similar on both sides of the "medial flap" of the disrupted aortic wall, whereas blood flow is usually slower in the false lumen of the aortic dissection. (4) TEE findings are usually confined to the region of the aortic isthmus in cases of traumatic aortic rupture, whereas lesions associated with aortic dissections are usually more extended.
Among the alternative noninvasive diagnostic modalities, magnetic resonance imaging (MRI) has been demonstrated to be accurate for the diagnosis of aortic dissection. Advantages of this imaging modality include localization of the entry site, visualization of intra- and extraluminal thrombi, and pericardial effusion as well as the extension of dissection to the branch vessels.17 However, MRI is less sensitive than TEE to diagnose the presence of aortic regurgitation and is time-consuming and cumbersome to perform in hemodynamically unstable patients. On the other hand, chest CT is less reliable than both TEE and MRI for the diagnosis of acute aortic dissection, with the added disadvantage of being unable to depict the entry site.17 Accordingly, Nienaber et al17 have proposed using MRI to diagnose acute dissection of the thoracic aorta in hemodynamically stable patients and TEE in unstable patients who are unable to be transported safely.
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Cardiac Catheterization Findings (T. Feldman) |
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TopCase Presentation (R. Sawyer...Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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Coronary arteriography was performed via the right femoral artery. Mild, diffuse coronary artery disease, with a dominant right coronary artery system and average distribution, was demonstrated. The worst focal stenosis was a 60% lesion noted in the mid-right coronary artery trunk. Noticeably, the left Judkins coronary catheter first traversed the dissection flap, and a test injection demonstrated the false lumen. It is usually possible to cross from the false to the true lumen by withdrawing the catheter proximal to the dissection flap and manipulating a floppy, steerable guide wire across the false and into the true lumen. Left ventriculography showed a small, mildly hypokinetic left ventricle without regional wall motion abnormalities. There was 1+ mitral regurgitation. The true aortic root appeared dilated. The pigtail catheter was pulled back from the left ventricle to a position just proximal to the aortic valve. Aortography demonstrated the presence of moderate aortic regurgitation and a large flap extending from the right coronary sinus to the origin of the right brachiocephalic trunk. The origins of all the arch vessels were widely patent and no evidence of a dissection flap was seen in the arch or descending aorta. Aortography was performed with a 7F catheter. Although it is attractive to use small catheters and floppy wires, the greater viscosity of low osmolarity contrast requires larger catheter size for good quality aortography. The relative safety of low osmolarity contrast agents in these hemodynamically unstable patients is important.
For the diagnosis of aortic dissection, cineangiography has a number of advantages over cut film. It allows structures to be viewed both in motion and time. Panning may be performed during the aortogram to demonstrate the arch and descending aorta. Of course, aortic insufficiency and coronary anatomy may be demonstrated as well. The major disadvantages of cineangiography are that the field of view is smaller and it lacks the resolution of serial cut film for fine detail, especially when a large field of interest exists.20
Should all patients undergo cardiac catheterization in the setting of aortic dissection? Catheterization alone may be used to establish the diagnosis of aortic dissection. Occasionally, in addition to the diagnosis of a dissection by noninvasive techniques, there is a clear need to look for coronary artery disease or establish the relationship of the arch vessels to the dissection flap. An especially important clinical situation requiring aortography exists when myocardial infarction presents together with aortic dissection.21 Recognition of the presence of an aortic dissection in this setting is critical to avoid the administration of thrombolytic therapy.22 23
Patients with type B aortic dissections (those arising beyond the take-off of the left subclavian artery) may undergo percutaneous catheter fenestration of the intimal flap to decompress the dissection plane and allow re-establishment of distal patency. This is a recently described, useful emergency technique for patients with occluded renal, femoral, or mesenteric vessels.24
Patients with unstable, acute aortic dissection are optimally cared for in the cardiac catheterization laboratory. Unstable patients can be managed even while TEE and cardiac catheterization are simultaneously performed. Patients who are hemodynamically unstable, in whom the diagnosis of aortic dissection has been established using noninvasive imaging and in whom there is little concern regarding the presence of coronary artery disease should undergo urgent operation without prior catheterization. In summary, performing a cardiac catheterization is of particular importance when noninvasive evaluation results in an inconclusive diagnosis or when further definition of the extent of the dissection and/or involvement of the arch vessels is required. Cardiac catheterization should be considered complementary to noninvasive diagnostic methods to maximize the information available to the surgical team before operation.
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Operative Findings (B.K. Lee) |
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TopCase Presentation (R. Sawyer...Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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The patient remained hemodynamically stable during anesthetic induction. A segment of saphenous vein was harvested and the left femoral vein and artery exposed. A median sternotomy was performed and the pericardium opened. The pericardial fluid was xanthochromatic, consistent with recent but not acute hemorrhage. There was no evidence of cardiac tamponade. The aorta was dilated and ecchymotic, with hemorrhage extending into the epicardial fat overlying the right ventricle. The exposed surfaces were covered with an inflammatory exudate that was subacute in appearance.
The right atrium and left femoral artery were cannulated and total cardiopulmonary bypass instituted. The femoral artery was normal in appearance. The ascending aorta was cross-clamped and retrograde cardioplegia administered. During systemic cooling the aorta was opened. The aortic valve was tricuspid and normal in appearance. The aorta was dissected to the level of the sinuses of valsalva. The thrombus filled the large false lumen. No tear was identified. The aortic valve commissures were resuspended with pledgetted sutures and the proximal aorta reinforced with polytetrafluoroethylene felt. A segment of saphenous vein was placed end to side to the right coronary artery.
After 30 minutes of cooling, blood was collected in the venous reservoir and the circulation arrested. During circulatory arrest, retrograde cerebral perfusion via the superior vena cava was maintained at 250 to 500 mL/min. The cross-clamp was removed and the arch inspected. There was a large, complex tear in the intima of the undersurface of the arch extending past the level of the subclavian artery. There was a large amount of thrombus present within the aortic wall, with ecchymoses extending into the surrounding tissue, which were inflamed and extremely friable. A synthetic polyester graft was fashioned to replace the undersurface of the aortic arch and ascending aorta. The distal anastomosis was completed with polytetrafluoroethylene reinforcement. The cross-clamp was replaced and circulation restarted. Almost immediately, copious bleeding was noted distal to the anastomosis requiring a second period of circulatory arrest. On inspection through the graft, it was noted that the distal intima had pulled away from the graft. The graft was removed and replaced further distally. A side graft was placed to this graft and circulation commenced antegrade through the graft. With the rise in pressure, profuse bleeding was again noted. Despite multiple attempts at repair, the patient ultimately succumbed due to uncontrollable hemorrhage.
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Pathological Findings (S. Glagov) |
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TopCase Presentation (R. Sawyer...Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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Histological sections of the surgical samples (Fig 4
)
revealed extensive hemorrhagic dissection of the
aortic media as well as regions of aortic smooth muscle necrosis at
about the same transmural location as the hemorrhagic dissection.
Accumulations of interstitial basophilic material are noted
both deep and superficial to the necrotic hemorrhagic zones. Although
these changes are mainly those of acute dissection of the aortic media,
extension of the hemorrhage into the adventitia is focally
associated with reactive granulation tissue in the adventitia
contiguous with similar changes in the immediately adjacent media.
These changes are indicative of a focal subacute component that may
correspond to a recent episode that resulted in the aortic intimal
changes noted clinically on the day of surgery. However, there is no
evidence of extensive healing of a more remote dissection.
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Aortic dissection is characterized by defective cohesion of the structural elements of the aortic wall. The close association with previous hypertension suggests that chronic tensile stress may be an important factor inducing the structural and compositional changes that render the aortic wall vulnerable to disruption in predisposed individuals. The frequent precipitation of dissection by a crisis that presumably imposes a sudden abrupt rise in pressure is further evidence that the tensile strength of the aortic wall is compromised. The recently demonstrated role of the fibrillin defect in Marfan's syndrome suggests that the integrity of the aortic wall is closely associated with adequate biosynthetic responses to usual physical stresses. In the present case, the aortic wall was extremely friable, resisting attempts at suturing to restore mural continuity. Since the patient did not have any of the usual physical stigmata of Marfan's syndrome, the nature of the near total lack of mural cohesion remains unexplained. Similarly, there is no evidence of a forme fruste of Marfan's syndrome or of a specific toxin that could account for this patient's disorder.
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Clinical Commentary (A. Poppas) |
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TopCase Presentation (R. Sawyer...Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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Our patient's presentation is atypical for acute aortic dissection in a number of respects. First, he presented with syncope as his chief complaint. The patient's syncope seemed to be related to a vasovagal response to micturition in the setting of hypertensive heart disease and intrinsic conduction system disease. Syncope has been reported to occur in association with aortic dissections in
5% of patients.25 26 In this
setting,
syncope is usually associated with a rupture of the dissection into the
pericardium, with resultant hemodynamically significant
tamponade or, occasionally, a rupture into the left thorax with
resultant hemothorax. In addition, acute pericardial stretching may
increase parasympathetic output, causing life-threatening
bradyarrhythmias in tamponade associated with aortic
dissection.27 This patient had a small subacute
pericardial effusion without echocardiographic evidence
of tamponade. More rarely, syncope may occur in dissection secondary to
embolization, occlusion, or propagation of the aortic dissection into
the great vessels, with severe neurological
impairment.25 26 At both cardiac
catheterization and surgery, the dissection did not
appear to involve the great vessels; therefore, there was no evidence
of neurological involvement to explain the syncope. Second, our patient presented with a painless aortic dissection. In recent series, aortic dissections without associated pain were reported to occur in 10% to 15% of the cases.26 Generally, the pain of aortic dissection is very characteristic; it is often aptly described as tearing or ripping, is most severe at its inception, is unremitting and agonizing, and, ominously, can migrate as the dissection propagates. Severe chest pain with aortic dissection is so characteristic and ubiquitous that it is usually only absent in patients with a decreased level of consciousness and should prompt a search for alternative diagnoses.28 In a Mayo Clinic review of 235 cases of aortic dissection, there were 33 asymptomatic presentations; 19 of these patients had no significant findings on physical examination and all 19 had chronic dissections.25 There are scant reported cases of acute, painless dissections; in two cases there was impaired mental status.29 30 The mechanisms producing pain in aortic dissection are speculative. Putative stimuli include dilation and stretch of the vessel itself or extravasation of blood into surrounding tissue.31
Third, our patient's emergency room chest radiograph revealed a tortuous aorta without mediastinal widening, although the somewhat lordotic view suggested a false shadow along the aortic knob. In 90% of patients with aortic dissection, the chest radiograph reveals an abnormality of the mediastinum, typically with widening of the aortic silhouette. Other radiographic findings can include a greater than 1-cm separation of inner and outer edges of calcification of the aortic knob, a double density, or an aortic bulge.28 A previous radiograph for comparision is often quite helpful. None of the additional radiographic findings were present in our patient.
Next the patient's aortic dissection was discovered incidentally by transthoracic echocardiogram. In the routine evaluation of syncope an echocardiogram is often performed, since the finding of structural heart disease may help guide further diagnostic and/or therapeutic interventions. Our patient demonstrated that transthoracic echocardiography may be useful to visualize the ascending aorta, especially when dilation is noted or symptoms and signs are suspicious. The sensitivity of transthoracic echocardiography for diagnosing acute or chronic dissections of the thoracic aorta is reported to be 59% to 85% with a specificity of 63% to 96%. Its sensitivity is predictably greater for the ascending aorta (78% to 100%) and quite a bit less for the descending aorta (31% to 55%).17 32 The diagnosis of aortic dissection can be made by a variety of invasive and noninvasive modalities, as discussed above. The TEE, catheterization, and even operative suites can provide closely monitored, controlled environments ideally suited to the performance of rapid evaluations of critically ill and unstable patients.
Finally, in our patient the dissected thoracic aorta was found to be
exceptionally friable and beyond repair at surgery. The dissection was
probably subacute, with both acute and subacute changes noted
on histological sections. The latter may well have
contributed to the friability of the tissue noted both grossly by the
surgeon and histologically by the pathologist. The
extreme fragility of the dissected aorta makes the operative repair
technically difficult and sometimes, as in this case, impossible to
complete successfully. Various materials have been use to strengthen
the vessel wall, such as
polytetrafluoroethylene felt, anchoring
pledgets, and glue, and even complete replacement of the ascending
aorta has been attempted with a composite graft.28
Independent predictors of operative mortality include pericardial
tamponade, renal dysfunction, visceral ischemia, and delay in
operation; recent operative mortality remains
10%.33
In our patient, the presence of a type A aortic dissection in conjunction with aortic insufficiency and a pericardial effusion prompted us to recommend immediate surgical repair. Acute thoracic aortic dissection carries an extremely high mortality rate unless surgical treatment is urgently undertaken. A high clinical index of suspicion is required because a correct antemortem diagnosis is made in only half of the cases.28 The diagnosis can be obtained with the use of a variety of modalities; TEE appears to offer the greatest speed without compromising either safety or accuracy. Finally, once the diagnosis of an acute type A aortic dissection is made, the patient should be taken to the operating room posthaste.
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Final Diagnosis |
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TopCase Presentation (R. Sawyer...Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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The final diagnosis is type A subacute thoracic aortic dissection.
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References |
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TopCase Presentation (R. Sawyer...Clinical Discussion (A. Poppas)...Electrophysiological Evaluation...Echocardiographic Findings (P....Cardiac Catheterization Findings...Operative Findings (B.K. Lee)...Pathological Findings (S....Clinical Commentary (A. Poppas)...Final Diagnosis References |
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