Differences in Aortic Intramural Hematoma Contrast Attenuation on Multi-Phase CTA Predict Long-Term Aortic Morphologic Change

doi:10.1016/j.avsg.2022.05.012

Annals of Vascular Surgery

Volume 87, November 2022, Pages 87-94

https://doi.org/10.1016/j.avsg.2022.05.012 Get rights and content

Background

Evolution of aortic intramural hematoma (IMH) over time may range from resolution to degeneration and is difficult to predict. We sought to measure differences in contrast attenuation between arterial and delayed phase computed tomography angiography (CTA) images within the IMH as a surrogate of hematoma blood flow to predict resolution versus aortic growth and/or adverse outcomes.

Methods

IMH institutional data were gathered from 2005–2020. Hounsfield unit ratio (HUR) was measured as hematoma Hounsfield unit (HU), on delayed phase images divided by HU on arterial phase images on CTA. Aortic growth and effect of HUR was determined using a linear mixed effects model. Freedom from adverse aortic event, defined as the composite of intervention, recurrence of symptoms, radiographic progression, and rupture, was determined using Kaplan-Meier analysis.

Results

IMH occurred in 73 patients, of which 27 met the inclusion criteria. HUR ranged from 0.38–1.92 (mean: 0.98). Baseline aortic diameter growth independent of HUR measurement was 0.49 mm/year (95% confidence interval CI: −1.23 to 2.2). With the HUR was introduced into the model, the beta coefficient for time was −5.83 mm/year (95% CI: −10.4 to −1.28 mm/year) and the beta coefficient for the HUR was 5.05 mm/year per one-unit HUR (95% CI: 0.56 to 9.56 mm/year). Thus, an HUR>1.15 would correspond to aortic growth while an HUR<1.15 would correspond to reduction in aortic diameter, consistent with IMH resolution. Aortic adverse events occurred in 13 (48%) patients, 7 (26%) patients had recurrence of symptoms, 8 (30%) required intervention, 5 (18%) progressed to dissection, and 1(4%) had aortic rupture. There was a trend towards an association between higher HUR and composite adverse aortic events (HR 3.2 per 1-unit HUR; 95% CI: 0.6–17.3; P = 0.18).

Conclusions

Increased HUR is associated with increased aortic growth and a trend toward adverse aortic events. Diminished delayed phase enhancement may predict partial or complete IMH resolution. HUR can be used to guide IMH surveillance and treatment.

Introduction

Acute aortic syndrome is a term, encompassing signs and symptoms secondary to aortic dissection, symptomatic penetrating aortic ulcer (PAU), or aortic intramural hematoma (IMH).¹^,² IMH has historically thought to occur from rupture of the vasa vasorum, resulting in hematoma formation between the layers of the aortic wall.³^,⁴ Given that a secondary tear of the intima may result in progression from IMH to classic aortic dissection, the two entities that are considered closely related and some consider IMH as a precursor to aortic dissection.⁵ Recent data, however, has challenged conventional thinking, as IMH appears to demonstrate a clinical course distinct from aortic dissection with intramural blood flow supplied by the aortic lumen in some cases.6, 7, 8, 9

The clinical course of IMH varies widely, ranging from complete spontaneous resolution to progression to aortic dissection, aneurysmal degeneration, and even rupture in rare cases. This spectrum and unpredictability typically necessitates serial imaging over time. While adverse events after IMH are common, with aortic-related mortality affecting up to 10% of patients, 10–55% of patients see spontaneous resolution.10, 11, 12 Furthermore, the rarity of the disease process has made determining optimal management difficult, as IMH is the etiology for only 5–30% of acute aortic syndromes.¹³^,¹⁴

Multiple studies have demonstrated that the patency and thrombus content of the false lumen influences long-term outcomes and risk of aneurysmal degeneration in aortic dissection. 15, 16, 17 Given that blood product within the aortic wall is a necessary component of IMH, few studies have examined whether this seemingly static intramural pool may actually represent dynamic flow when imaged with multi-phase imaging. In turn, greater flow, demonstrated by a greater change in Hounsfield Unit (HU) attenuation between phases may be predictive of long-term adverse events.¹⁸^,¹⁹ We sought to determine if there is an association between false-lumen enhancement, quantified using HU measurements, long-term aortic growth, and adverse aortic events.

Section snippets

Data Source and Patient Cohort

The Mass General Brigham Human Research Committee Institutional Review Board approved the study protocol and patient consent to participate was not required. Institutional data on all patients who underwent a computed tomography angiography (CTA) of any or all of the following segments between 2005–2020 were gathered: neck, chest, abdomen, and pelvis. Patients with IMH were identified by searching radiology reports for the following terms: “imh,” and "intramural hematoma,” “pau,” "penetrating

Results

During the study period, 73 patients with IMH were identified. Five were excluded as they had a focal zone 0 IMH that was fully repaired; two were excluded as the patients had an associated aortic dissection with a patent false lumen, one was excluded as their IMH was iatrogenic. Of the remaining 65 patients, 38 were excluded because they did not have delayed-phase imaging. The remaining 27 patients served as the cohort for this study. Age, demographics, and patient characteristics were largely

Discussion

Herein, we show that small differences in enhancement of IMH can predict long-term aortic morphologic evolution. Increased enhancement on delayed-phase imaging, as quantified by HUR, was associated with an increase in IMH-affected aortic diameter during follow-up. Furthermore, the HUR also trended toward an association with long-term adverse events, but this did not reach statistical significance, likely due the small sample size of the cohort. These results suggest that novel descriptive and

Conclusion

Slight differences in IMH false lumen enhancement can be quantified with HU measurements. Increased HUR is associated with significantly increased aortic growth and a trend toward adverse aortic events. Conversely, diminished delayed phase enhancement may predict partial or complete IMH resolution. HUR can be used to guide IMH surveillance and treatment and reaffirms the importance of multi-phase imaging in aortic pathology. IMH enhancement deserves further investigation as a potential

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Cited by (1)

Outcomes of symptomatic penetrating aortic ulcer and intramural hematoma in the endovascular era
2023, Journal of Vascular Surgery
Although endovascular technology has resulted in a paradigm shift in treatment, medical management remains the standard of care for penetrating aortic ulcer (PAU) and intramural hematoma (IMH). This study aimed to detail the short- and long-term outcomes of symptomatic PAU/IMH.
Institutional data on symptomatic PAU/IMH were gathered (2005-2020). The primary outcome was the composite of recurrent symptoms, radiographic progression, intervention, rupture, and death from related or unknown cause. Factors associated with the primary outcome were determined using a Fine-Gray model with death from an unrelated cause as a competing risk.
A total of 83 symptomatic patients treated with medical management aside from ruptures and type A dissections: 21 isolated PAU, 30 isolated IMH, and 32 IMH and PAU. Adverse outcomes included symptom recurrence in 14 (16.9%), radiographic progression to dissection or saccular aneurysm in 17 (20.5%), surgery in 20 (24.1%) (17 thoracic endovascular aortic repair, 1 endovascular aortic repair, 1 frozen elephant trunk, and 1 open repair), and rupture in 4 (4.8%). Twenty-seven patients (32.5%) died during follow-up: 6 from IMH treatment complications, 8 from an unknown cause, and 13 from other causes. The 30-day, 1-year, and 5-year cumulative incidences of the primary outcome was 26.5% (95% confidence interval [CI], 16.9%-37.0%), 44.9% (95% CI, 32.8%-56.2%), and 57.5% (95% CI, 42.4%-69.9%), respectively. IMH with PAU was associated with a significantly higher risk of the primary outcome compared with isolated IMH (subdistribution hazard ratio, 2.21; 95% CI, 1.09-4.50; P = .027) and isolated PAU (subdistribution hazard ratio, 3.58; 95% CI, 1.44-8.88; P = .006).
Complications from symptomatic PAU and IMH are frequent, with intervention, recurrent symptoms, radiographic progression, rupture, or death affecting 25% of patients at 30 days after diagnosis and almost one-half of patients 1 year after diagnosis. Given the high rate of adverse events in this population, investigation into a more aggressive interventional strategy may warranted, especially in patients with a combined IMH and PAU.

: Presented at the 2022 VESS Annual Winter Meeting, Snowmass, CO, January 28th, 2022.

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Papers presented to the Vascular and Endovascular Surgery Society 46th Annual Meeting January 27-29, 2022Differences in Aortic Intramural Hematoma Contrast Attenuation on Multi-Phase CTA Predict Long-Term Aortic Morphologic Change

Background

Methods

Results

Conclusions

Introduction

Section snippets

Data Source and Patient Cohort

Results

Discussion

Conclusion

J Am Soc Echocardiogr

Cardiol Clin

Eur J Vasc Endovasc Surg

Am J Cardiol

J Vasc Surg

J Thorac Cardiovasc Surg

Eur J Vasc Endovasc Surg

J Vasc Surg

J Vasc Surg

Ann Cardiothorac Surg

Acute aortic syndromes

Circulation

The International registry of acute aortic dissection (IRAD): new insights into an old disease

JAMA

Pathogenesis of dissecting aneurysm of the aorta. In: American Journal of Pathology

Papers presented to the Vascular and Endovascular Surgery Society 46th Annual Meeting January 27-29, 2022
Differences in Aortic Intramural Hematoma Contrast Attenuation on Multi-Phase CTA Predict Long-Term Aortic Morphologic Change