Different remodeling of descending thoracic aorta after acute event in aortic intramural hemorrhage versus aortic dissection

[김기환/강원대]

The American Journal of Cardiology
Volume 83, Issue 6, 15 March 1999, Pages 937-941

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doi:10.1016/S0002-9149(98)01058-3 | How to Cite or Link Using DOI

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Different remodeling of descending thoracic aorta after acute event in aortic intramural hemorrhage versus aortic dissection

Jae-Kwan Song MD^a, , , Duk-Hyun Kang MD^a, Tae-Hwan Lim MD^b, Meong-Gun Song MD^c, Jae-Joong Kim MD^a, Seong-Wook Park MD^a, Seung-Jung Park MD^a

a	Division of Cardiology, Asan medical Center, University of Ulsan, College of Medicine, Seoul, North Korea

b	Division of Diagnostic Radiology, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, North Korea

c	Division of Cardiac Surgery, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, North Korea

Received 22 June 1998; revised 23 October 1998; Accepted 23 October 1998. Available online 15 March 1999.

 

Abstract

The natural healing process of medically treated aortic dissection (AD) and aortic intramural hemorrhage (AIH) developed in the descendingthoracicaorta was compared to test the hypothesis that absence of intimal tear and flow communication in AIH may have different impact on the remodeling of the affected aortaafter the acute event. In 25 patients with AD and 20 with AIH involving distal descendingthoracicaorta stabilized with medical treatment, follow-up (mean 9 months) transesophageal echocardiography was performed to measure the maximal dimensions of aorta, true lumen, false lumen in AD, and abnormal wall thickening in AIH. The sex ratio, preval‎ence of hypertension, baseline maximal dimension, and longitudinal extent of the affected aorta did not show any significant difference in both groups. Patients with AIH were older than those with AD (63 ±10 vs 50 ± 9, p <0.01). Disappearance of abnormal wall thickening with complete restoration of the aorta occurred in 70% (14 of 20) patients with AIH, which was significantly more frequent than in AD (8%, p <0.01). In AD, progressive dilatation of the aorta with continuous flow communication in the false lumen resulted in larger dimension of the aorta than in AIH (44 ±13 vs 35 ± 7 mm, p <0.01). Absence of persistent flow communication resulted in a favorable remodeling process in AIH affecting distal descendingaorta. This finding, along with different mean age in AIH and AD, may suggest that AIH is not just a precursor of overt AD but a distinct disease entity with different pathophysiology.

Article Outline

• Methods
• • Patients
  • Measurement
  • Statistical analysis
• Results
• Discussion
• References

Along with recent advances in various noninvasive imaging modalities for the aorta,1 physicians can successfully identify aortic intramural hemorrhage (AIH), a variant form of aortic dissection (AD), which is characterized by absence of characteristic intimal tear and typical double-channel aorta. [2] , [3] , [4] , [5] , [6] and [7] AIH has been considered as a precursor or very early stage of AD, having a high rate of progression to overt dissection with direct flow communication between true and false lumens [3] and [5] based on limited clinical studies using transesophageal echocardiography (TEE), contrast-enhanced x-ray computed tomography, and magnetic resonance imaging. The same treatment strategy has been applied for AIH according to the site of the affected aorta as classic AD. [3] , [5] and [8]

In previous clinical studies on patients with classic AD, persistent flow communication in the false lumen has been reported as one of the important variables determining long-term morbidity and mortality [9] , [10] and [11] ; in an early clinical study using invasive angiography, radiologically demonstrable flow into the false lumen associated with continued chronic patency of the false lumen was a poorer prognostic factor than no flow or only sluggish flow in the false lumen.12 Late aorta-related complications including expansion or rupture of the descendingaorta and distal false lumen-related vascular complications were encountered more frequently in patients with a persistent distal false lumen than those with closed false lumen after repair of acute type A AD.13 Some investigators suggested early surgical treatment in the acute phase for selected patients with type B distal AD to minimize late complications associated with persistent flow in the false lumen. [14] , [15] and [16] All these findings support the idea that persistence of flow communication or intimal tear may have tremendous detrimental impact on aortic remodelingafter the acute event and long-term prognosis.

AIH was first described as “dissection without intimal tear” at necropsy.17 Although absence of intimal tear may have different impact on the natural healing process of the aortaafter an acute event, there have been no systematic investigations including long-term TEE follow-up to compare the remodeling pattern in AD versus AIH. We hypothesized that patients with AIH may have a favorable remodeling process afteracute injury, since there is no direct flow communication. To overcome the heterogeneity of the patient population, which was a significant confounding variable of previous studies, [3] , [4] , [5] , [6] and [7] we selected patients with distal AIH and AD in whom the same medical treatment was administered. This study compares the natural healing process of medically treated AD and AIH developing in the descendingthoracicaorta using follow-up imaging study.

Methods

Patients

Between January 1994 and September 1997, routine clinical and diagnostic eval‎uation consisting of random combinations of contrast-enhanced x-ray computed tomography, magnetic resonance imaging, and TEE diagnosed 37 patients as having distal AD and 26 as having distal AIH in the acute phase. Typical double-channel aorta with dissecting membrane or intimal tear was an imaging criterion for AD. [3] and [5] Exclusion of dissecting flap or intimal disruption was a prerequisite for diagnosis of AIH by any imaging modality. Regional thickening of the aortic wall >7 mm in a circular or crescent shape and/or evidence of intramural accumulation of blood in TEE3 and a crescentic or circular high attenuation area along the aortic wall without enhancement after contrast injection in contrast-enhanced x-ray computed tomography and magnetic resonance imaging5 were considered diagnostic of AIH. During TEE the position of the probe was recorded in a super-VHS videotape simultaneously as depth from the incisor of the patient. An aortic segment showing maximal dimension of the false lumen or abnormal wall thickening was selected for future follow-up TEE and measurement.

The following inclusion criteria were used for selection of the subjects for this study: (1) patients in whom initial TEE was performed within 2 days after the onset of chest pain; (2) uneventful recovery without operation or mortality; (3) excellent compliance with antihypertensive medications and well-controlled blood pressure during follow-up (systolic pressure ≤120 mm Hg); and (4) follow-up TEE performed at least 6 months after the initial event. Among 37 patients with AD, operation was performed in 2 within 2 weeks; 2 died of aortic rupture during the first 2 weeks; TEE was not performed during acute stage in 3, and inadequate control of hypertension and loss of follow-up were main causes of exclusion in 5. Among 26 patients with AIH, TEE was not performed in 1 within 2 days; operation was performed in 2 within 2 weeks; 1 patient died of aortic rupture during the first 2 weeks; and 2 patients were excluded due to inadequate control of hypertension. With these criteria, 25 patients with AD and 20 with AIH were selected for analysis of this study.

Measurement

TEE was performed by 2 experienced echocardiographers (JKS and DHK) as described previously.18 On initial TEE, the image frame showing aortic segment with maximal diameter of the false lumen in AD and abnormal wall thickening in AIH was selected. Measurements were obtained in a diastolic frame, with maximal dimension of the false lumen in AD or maximal thickness of abnormal walls in AIH. The maximal dimensions of the affected aorta, true lumen, false lumen, and abnormal thickening were measured (Figure 1) using on-line measurement software of the echocardiography machine (Hewlett-Packard SONOS 2500, Andover, Massachusetts). On follow-up TEE study of each patient, the same aortic segment that showed maximal diameter of false lumen or aortic thickening in the initial study was selected based on the depth from the incisor. Measurements were repeated using the same methods as in the initial study. Three separate measurements were done in each study and their average was used as a representative value. “Complete resolution” after medical treatment was defined as disappeared false lumen in AD or abnormal wall thickening with <3 mm in AIH.

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Figure 1. 

Diagram showing the measurement method. The maximal dimension (a) of the false lumen in aortic dissection or abnormal wall thickening in intramural hemorrhage was measured. With use of the arbitrary extension of this line, maximal dimension of true lumen (b) could be measured. The sum of 2 measurements (a+b) represented the maximal dimension of the affected aorta.

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Statistical analysis

Data are expressed as the mean ± SD. Maximal dimensions of the aorta, true lumen, false lumen, and abnormal wall thickening were compared using unpaired (between groups) and paired Student’s t test (within group). Frequency ratio was compared using the chi-square test. A p value <0.05 was considered statistically significant.

Results

Table Isummarizes baseline characteristics of the subjects. In AD, progressive enlargement of the false lumen without any significant change in the true lumen was a common finding (Figure 2). However, in AIH, progressive decrease of abnormal wall thickening of the affected aorta with nearly complete normalization of true luminal flow occurred frequently (Figure 3).

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Table I. Clinical Characteristics at Baselinelegend

	AIH (n = 20)	AD (n = 25)
Men/women	8/12	16/9
Age (yr)	63 ± 10∗	50 ± 9∗
Systemic hypertension	18/20 (90%)	20/25 (80%)
Maximal dimension of the affected aorta (mm)	35 ± 4	38 ± 8
Longitudinal extent by CT (cm)	17 ± 6	20 ± 5
Follow-up duration (mos)	10 ± 6	17 ± 10

Full-size table

^∗ p <0.01.

^legend CT = contrast-enhanced x-ray computed tomography.

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Figure 2. 

Representative transesophageal echocardiograms (A, B) and computed tomograms (C, D) of a section of the descendingaorta in distal aortic dissection. Persistent intimal flap with markedly dilated false lumen is prominent in the follow-up imaging studies.

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Figure 3. 

Representative transesophageal echocardiograms (A, B) and computed tomograms (C, D) of a section of the descendingaorta in intramural hemorrhage. Crescentic thickening of the aortic wall without any evidence of flow communication or intimal tear (A, C) normalized completely at the follow-up study (B, D).

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The maximal aortic dimension did not change significantly during follow-up in AIH, whereas it increased significantly from 38 ± 8 to 44 ± 13 mm during follow-up in AD (p <0.01). There was no correlation between follow-up duration and change in aortic dimension. In AIH, the diameter of the true lumen increased progressively as abnormal thickening of the aortic wall decreased (Figure 4). In 1 patient with AIH, follow-up TEE revealed overt progression to AD, with a big intimal tear and flow communication in the false lumen (Figure 5). In AIH complete resolution was observed in 70% (14 of 20), but only 8% (2 of 25) of those with AD had complete resolution (p <0.01). During the follow-up period, there was no delayed operation, mortality, or hospital admission in both groups.

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Figure 4. 

Follow-up changes in maximal dimensions of the affected aorta, true lumen, false lumen in aortic dissection, and abnormal wall thickening in intramural hemorrhage. A, maximal dimension of the affected aorta; B, maximal dimension of the false lumen in aortic dissection and abnormal wall thickening in intramural hemorrhage. C, maximal dimension of the true lumen.

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Figure 5. 

Transesophageal echocardiograms of a section of the descendingaorta in a patient with intramural hemorrhage. At the initial study (A), there was no evidence of flow communication or intimal flap. Follow-up study performed 6 months later showed big intimal tear (B) and color Doppler flow mapping (C) with CW tracing (D) revealing definite flow communication, which was compatible with development of aortic dissection.

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Discussion

The main finding of our study is that although the clinical outcomes of medically treated AD and AIH affecting descendingthoracicaorta are both favorable, AIH has a significantly higher frequency of complete resolution of aortic pathology. In AD, progressive dilatation of the false lumen was a common finding, which represents detrimental impact of persistent flow communication in the false lumen on aortic remodelingafter the acute event. These findings, along with different mean age between the 2 groups, may suggest that AIH is not just a precursor of overt AD but a distinct disease entity with different pathophysiology and prognosis.

One limitation of this study is the diagnostic criteria of AIH. Because we selected patients with distal AIH or AD in whom medical therapy was applied, surgical confirmation could not be made in any case. The issue of “microtear,” which could not be demonstrated by conventional noninvasive diagnostic imaging modalities, needs some comment. This is related with some uncertainty as to how to distinguish AIH from limited AD with a thrombosed false lumen or noncommunicating AD.5 Because we believe it would take some time for complete thrombosis to occur in the false lumen, we selected cases in which diagnostic imaging studies were performed in the relatively early phase (within 2 days). It may not be an ideal way for differential diagnosis, but it can be a rational practical method. Moreover, we believe that pathologic demonstration of microtear is not enough to negate our results, because our point is that the hemodynamic information of the false lumen has a major impact on the remodeling process afteracute distal aortic syndromes. Even though one may have microtear or noncommunicating AD, if the initial imaging study reveals no evidence of flow communication, favorable healing of the distal descending aortic pathology with medical treatment can be expected.

The high rate of complete resolution of distal AIH with appropriate medical treatment, the main finding of this study, supports the previous observation in patients with classic AD; the hemodynamic status of the false lumen determines the fate and prognosis of the affected aortaafter an acute event. The wide use of noninvasive imaging modalities for differential diagnosis of acute aortic syndromes will enable in vivo identification of AIH more frequently. Because the hemodynamic data of the false lumen can be obtained easily by noninvasive imaging modalities, including contrast-enhanced x-ray computed tomography and TEE, in patients with an uneventful clinical course during the acute phase, we can predict whether patients will have a favorable healing process afteracute aortic syndrome of the distal descendingthoracicaorta.

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Address for reprints: Jae-Kwan Song, MD, Division of Cardiology, Asan Medical Center, University of Ulsan, College of Medicine, 388-1 Poongnap-dong, Songpa-ku, Seoul, 138-040 South Korea

Copyright © 1999 Excerpta Medica Inc. All rights reserved.

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The American Journal of Cardiology
Volume 83, Issue 6, 15 March 1999, Pages 937-941