Eur J Cardiothorac Surg 1998;13:230-239
© 1998 Elsevier Science NL
Intramural hematoma of the thoracic aorta
Yukinori Moriyamaa,
Goichi Yotsumotoa,
Kazumi Kuriwakib,
Shunichi Watanabea,
Kouichi Hisatomia,
Shinji Shimokawaa,
Hitoshi Toyohiraa,
Akira Tairaa
a Second Department of Surgery, Kagoshima University, Faculty of Medicine, Sakuragaoka 8-35-1, Kagoshima City 890, Japan
b First Department of Pathology, Kagoshima University, Faculty of Medicine, Sakuragaoka 8-35-1, Kagoshima City 890, Japan
Received 4 September 1997;
received in revised form 1 December 1997;
accepted 9 December 1997.
Corresponding author. Tel.: +81 99 2755368; fax: +81 99 2658177.
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Abstract
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Objective: This study was designed to clarify the optimal treatment mode of patients with intramural hematoma (IMH) of the thoracic aorta. Methods: From 1992 through 1997, 51 patients underwent surgical repair or medical treatment of IMH of the thoracic aorta. There were 36 male and 15 female patients, aged between 49 and 79 years with a mean of 67 years. The ascending aorta and/or aortic arch was involved in 18 patients (group I), whereas the descending thoracic aorta was affected in 33 (group II). The presence of intimal disruption in IMH was confirmed in 10 of group I and 13 of group II patients. Results: For group I patients 13 required aortic arch repairs and the remaining 5 underwent conservative therapy including anti-hypertensive medication. Primary indications for immediate surgery were: cardiac tamponade in 5 patients, aortic dissection superimposed on IMH in 2, and persistent pain with an aortic arch aneurysm in 1, respectively. Early elective operations were done for enlarged ulcer in 3 patients and aneurysmal dilatation in 2 of which 1 had a coexisting aortic arch aneurysm. The 2-year survival rate after diagnosis was 94% with an operation-free rate of 25%. Nine of the group II patients experienced surgical intervention of which 8 had intimal disruption, 4 patients received urgent replacement of the descending thoracic aorta for massive pleural effusion and 1 had the aortic arch replaced for a coexisting aneurysm with persistent pain. All other patients underwent conservative treatment and 4 of them had to be shifted to early surgery during the initial hospitalization because of an enlarged ulcer. The 5-year survival rate in group II patients was 63% with an operation-free survival rate of 66%. Conclusions: On the basis of our experience early operation is recommended for almost all patients with ascending aortic IMH, and medical therapy for those with descending aortic involvement unless complication developed. However, the presence of intimal disruption may require early surgical treatment even in the patients with descending thoracic IMH.
Key Words: Intramural hematoma • Optimal management • Intimal disruption
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Introduction
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Intramural hematoma (IMH) of the thoracic aorta
[1]
[2] may derive from spontaneous rupture of aortic vasa vasorum
[3] or penetrating atherosclerotic ulcer
[4]. Improved imaging techniques have led to strict definition of IMH that is characterized by aortic wall hematoma without demonstrable intimal disruption or ulcer, although there may still be a limit to detection of all intimal lesions. Furthermore, the optimal management of patients with IMH has not been established yet. At our institution medical treatment was first applied to these patients irrespective of the presence or absence of intimal defect or ulcer, and surgical intervention was reserved for those who sustain complications such as impending rupture, cardiac tamponade, uncontrollable pain, and compromise of a major arterial branch. Hence, we reviewed here our experience with treatment of extensive aortic wall hematoma according to the site of involvement and the presence or absence of intimal disruption following this policy.
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Patients and methods
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From January 1992 through March 1997, a total of 51 patients underwent surgical repair or medical treatment of IMH of the thoracic aorta at Kagoshima University Hospital. All patients presented with severe chest and/or back pain mimicking that of classic aortic dissection. IMH was defined as a circular or crescent shape, extensive aortic wall hematoma with no evidence of intimal flap or false lumen noted by contrast computed tomographic (CT) scan (n=51), digital subtraction aortography (n=51), or magnetic resonance imaging (MRI) scan (n=9). Focal aortic wall hematoma with deep ulcer formation was excluded from this study. There were 36 male and 15 female patients, aged between 49 and 79 years with a mean of 67 years. IMH involved the full length of the aorta in 11 patients, and was confined to the ascending aorta and/or aortic arch in 7 and the bulk of the descending thoracic aorta in 33 patients. All patients were admitted to our hospital with a mean interval of 3.2±4.7 days from the episode of onset. Hypertension was present in 39 of the 51 patients, most had severe hypertension at the time of admission, and 11 patients had concurrent or previously repaired atherosclerotic aneurysms in the thoracic (n=3) or abdominal aortic segments (n=8). The patients were initially placed on medical treatments while various diagnostic studies were carried out. Once acute aortic dissection was excluded the medical therapy was continued since operation was initially deferred in this series unless specific complications developed.
The patients were divided into two groups according to the aortic segment afflicted with IMH, whether it was on the ascending aorta and/or aortic arch (group I, n=18) or the descending thoracic aorta (group II, n=33). A comparison between the clinical features of the two groups is given in Table 1. Predominance of men over women was seen in group II as compared with that in group I. The maximum diameters of the ascending aortas measured on CT scan were 49±13 and 37±6 mm in groups I and II, respectively, with a significant difference (P<0.05) between them. However, no significant differences were found in other variables such as age, incidence of associated aneurysm, and the presence of a small ulcer or calcified intima.
Complete follow-up was conducted on all 51 patients, ranging from 2 days to 64 months with a mean of 25 months. Follow-up data were obtained by review of medical records, hospital visits and telephone interviews with the patients, their families, or their physicians. All continuous variables are presented as the mean±S.D. Discrete variables were compared with a 
2-test or Fisher’s exact test, and the continuous variables were analyzed by Student’s t-test. Actuarial survival rates were estimated by the Kaplan–Meier method, and the log-rank test and the generalized Wilcoxon test were used to compare survival curves. Statistical significance was confirmed when the probability value was less than 0.05.
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Results
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Group I
Of the 18 patients in group I, 13 required surgical treatments for the following complications: cardiac tamponade in 5 patients, enlarged ulcer in 3, aneurysmal dilatation in 2 of which 1 had preexisting aortic arch aneurysm, aortic dissection superimposed on the IMH in 2, and persistent pain with aortic arch aneurysm in 1, respectively (Table 2). Representative imaging studies were shown in
Fig. 1
Fig. 2
. All these patients underwent replacement of the ascending aorta and aortic arch with a collagen-impregnated woven Dacron prosthesis through a median sternotomy under deep hypothermic circulatory arrest; total arch repair in 4 and proximal hemiarch repair in 9. Selective cerebral perfusion was used in all patients to prevent cerebral ischemia during arch repair. All of them had markedly dilated ascending aorta with a mean transverse diameter of 52±13 mm. Of the 13 patients who had operations, 8 were found to have small ulcers in the mid to distal segments of the ascending aorta, whereas 5 had no ulcer detectable. Trivial to mild degree of aortic regurgitation was confirmed by transesophageal echocardiogram in 6 patients, and all valves were preserved in the operation. Aortic tissue for histologic study was available from 10 of the 13 cases, where the hematoma was demonstrated in the outer one-third to one-fourth layers of the media with no significant myxoid degeneration (
Fig. 3
). Definite atherosclerotic change was found in only 2 patients with aortic arch aneurysm. In the remaining 5 patients who did not have an operation, 2 were found to have small ulcers in the proximal descending thoracic aorta. Among these 5 patients, 2 had cardiac tamponade relieved by pericardiocentesis and 1 of them also had paraplegia caused by spinal cord ischemia due to medial hematoma involving entire segment of the aorta. The 18 patients who had ascending aortic IMH are all alive except 1 who died of brain damage 2 months after operation. The mean follow-up interval for these patients was 13 months, ranging from 2 days to 37 months. The actuarial survival rate at 2 years after diagnosis was 94% with an operation-free survival rate of 25% (
Fig. 4
).
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Fig. 1. MRI scan on admission demonstrates IMH (arrows) in the ascending aorta (a), which showed regression 2 months later (b). Patient was treated conservatively.
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Fig. 2. Contrast enhancement CT scan of patient number 12, taken on the day of onset of pain, revealed extensive non-enhancing crescentic IMH (arrows) in the ascending aorta (a). A repeat CT scan 2 weeks after diagnosis showed localized dissection of the ascending aorta. Intimal flap (*) was clearly seen (b).
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Fig. 3. Histologic study of the ascending aorta taken from patient number 10, where the hematoma (arrows) was demonstrated in the outer one-third to one-fourth layers of the media with no significant degeneration. (Elastica van Gieson stain; original magnificationx6.)
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Fig. 4. Survival rate of patients with IMH involving the ascending aorta. The actuarial survival rate at 2 years after diagnosis was 94% with an IMH-related complication-free rate of 25%.
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Group II
Of the 33 patients with descending thoracic aortic involvement, 9 experienced complications related to IMH, and required surgical intervention (Table 3). Of the 9 patients who had operations 8 were found to have ulcers in the proximal to middle segments of the descending aorta, whereas only 1 had no ulcer detectable. Eight patients had their atherosclerotic descending thorcaic aorta replaced via left lateral thoracotomy under mild hypothermic femoro-femoral cardiopulmonary bypass. Four of them were complicted by massive pleural effusion and underwent emergency surgery (
Fig. 5
). In 4 patients elective repair of the descending thoracic aorta for enlarged ulcers was carried out with a mean follow-up interval of 3.4 months after the episode of onset. The remaining 1 patient had replacement of the aortic arch for a coexisting atherosclerotic aneurysm. Unfortunately, however, this patient was found to have a typical intimal flap in the descending aorta after arch repair. After operations 2 patients died of coagulopathy and brain damage, respectively. All but 2 patients survived the acute phase of the disease and were discharged from the hospital. There were 4 deaths during the follow-up period; rupture of a coexisting abdominal aortic aneurysm (AAA), sudden death, acute myocardial infarction, and cerebrovascular accident in 1 each at 6 and 8 months, and 2 and 5 years after diagnosis, respectively. Although the patient who died of ruptured AAA was found to have an extensive IMH involving AAA, operation was denied because of her advanced age and severe debility. The remaining 27 patients are alive at present with a mean follow-up interval of 47 months (range, 6 days–64 months). Therefore, actuarial survival rate at 5 years after diagnosis was 63% with an operation-free survival rate of 66% (
Fig. 6
).
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Fig. 6. The actuarial survival rate of patients with IMH involving the descending thoracic aorta was 63% at 5 years after diagnosis with an IMH-related complication-free survival rate of 66%.
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In view of late results according to the presence or absence of ulcer, there were no significant differences in the 2-year survival rates between the two patients groups; 88 and 87% in ulcer (+) and ulcer (-), respectively (
Fig. 7
a). However, operation-free survival rates of patients with ulcer (+) and ulcer (-) were 23 and 76% at 2 years after diagnosis with a significant difference (P<0.05) between them (
Fig. 7b). Of the medically treated patients, 26 had repeat CT scan at a mean of 7 months after diagnosis, which demonstrated regression of medial hematoma in all cases.
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Fig. 7. The actuarial survival rates of patients with IMH according to the presence or absence of ulcer. There were no significant differences in the 2-year survival rates between the two patient groups; 88 and 87% in ulcer (+) and ulcer (-), respectively (a). Operation-free survival rates of patients with ulcer (+) and ulcer (-) were 23 and 76% at 2 years after diagnosis with a significant difference (P<0.05) between them (b).
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Discussion
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Recently two variant forms of aortic dissection are recognized; one is IMH
[1]
[5]
[6] and the other is penetrating atherosclerotic ulcer
[4]
[7]
[8]. Patients with these variants cannot be distinguished reliably from those with aortic dissection on the basis of clinical grounds alone. Aortic dissection is generally known to originate from a primary intimal tear, which then allows propagation of blood into the aortic media to create a false lumen
[1]
[2]
[9]
[10]. In the past patients with IMH have been grouped together with aortic dissection, although recent advance of imaging modalities such as CT scan or MRI has made it possible to distinguish between them. On the other hand penetrating ulcer derives from the continued erosion of an atherosclerotic plaque
[4]
[7]
[8]
[11]
[12]
[13] and often affects the mid to distal portion of the descending thoracic aorta with coexisting localized medial hematoma
[6]
[8]. However, several cases of IMH were reported to originate from an ulcer in an atherosclerotic aorta
[1]
[14]. Furthermore some uncertainty also exists concerning how to distinguish IMH from limited aortic dissection with thrombosed false lumen. Thus, the cause of IMH appears to be multifactorial at present. Characteristics of various aortic pathology involving the thoracic aorta were compared in Table 4. Even if high-resolution imaging studies are used, it seems difficult to detect all intimal lesions including a small ulcer
[15]
[16]
[17]
[18]. Hence, all patients with extensive aortic wall hematoma, irrespective of the presence or absence of intimal disruption, were included in this study to elucidate the clinical characteristics and prognosis of the patients.
Previous reports have described an older cohort of patients with IMH which had a marked predilection for the descending thoracic aorta
[1]
[6]
[19]. In our experience as well, IMH affected elderly patients (mean age of 67 years) with long-standing hypertension, although one third of them had ascending aortic involvement with a high incidence of coexisting intimal disruption. Histologic study in the operated cases revealed descending aortic IMH to be frequently associated with atherosclerotic change as compared with ascending aortic IMH which usually developed with no significant atherosclerosis. These findings did correspond to those on IMH reported by Harris et al.
[20].
The patients with IMH involving the ascending aorta had a higher incidence of surgical complications despite medical therapy; cardiac tamponade was the most frequent complication requiring urgent surgery irrespective of the presence or absence of ulcer. Enlargement of the affected aorta was the second most important complication to remember, especially in the chronic phase of the disease. Furthermore, we have experienced 2 patients who had spontaneous aortic dissection superimposed on their medial hematoma within a few weeks of onset of IMH. The intimal tears and flaps not found on initial study were clearly confirmed by operation in both of them. There has been some anecdotal data suggesting that IMH can predispose to classic aortic dissection with intimal flap probably by weakening the aortic media and overlying intima
[1]
[2]. The only 3 aged patients who had no ulcer showed favorable response to medical treatment. On the basis of our small series in addition to the previous reports
[1]
[6]
[14]
[20], patients with ascending aortic IMH are clearly at high risk for serious complications, requiring surgical repair.
In contrast, the patients with descending thoracic aortic IMH were managed more favorably with medical treatment than ascending aortic IMH. Nevertheless, 9 patients (30%) ultimately required surgical interventions. Most of them had varying sizes of ulcers. On the other hand, those patients with no ulcer had an uneventful course by medical treatment alone. Only 1 patient underwent an urgent surgery for a juxtaposed atherosclerotic aneurysm in the aortic arch. This patient was initially managed without surgery, although the recurrence of severe pain in the setting of good blood pressure control prompted aortic arch repair. Unfortunately, however, this patient was found to have a typical intimal flap in the descending thoracic aorta after the repair. Considering the clinical course of this patient and those of 2 patients with ascending aortic IMH followed by typical aortic dissection, we have the question of whether IMH truly represents a different pathology or is simply the precursor of the classic aortic dissection.
As strict definition of IMH has not been established yet, it may cause confusion in decision-making for the treatment of IMH to include medial wall hematoma with ulcer into this disease entity. The IMH patients with ulcers in our series had a higher incidence of complications requiring surgery as compared with those having no ulcer. Nevertheless, no significant difference was found in mid-term survival rates between the two. This result was accomplished by means of close follow-up imaging study and prompt surgical intervention whenever complication developed. Mohr-Kahaly and associates
[19] followed up 15 cases of IMH with no ulcer by TEE, and demonstrated progression of IMH to typical dissection in 33% and rupture in 27% with mortality rate of 53%. Robbins et al.
[1] also reported poor late results of 13 cases of IMH. In view of their results in addition to our experience, early operation is recommended for almost all patients with ascending aortic IMH and medical therapy for those with descending aortic involvement unless complication developed according to the management guideline for classic dissection. However, the presence of intimal disruption may require early surgical treatment even in the patients with descending thoracic IMH. IMH may be an important underlying pathology of the aortic dissection, although the clinical data available so far is too limited to draw any definitive conclusion. Further studies and longer follow-up observation of this aortic pathology will be needed not only to clarify the relationship with classic aortic dissection but also to establish the optimal treatment mode.
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Abstract
Introduction
