Non-penetrating traumatic injuries of the aortic arch

Abstract

Background

In severely injured trauma patients, non-penetrating aortic arch injuries (NAAI) have a remarkable incidence and mortality. Both diagnostics and therapy of NAAI recently underwent significant changes.

Purpose

To assess mortality, morbidity, and the risk factors associated with NAAI in severely injured patients (Injury Severity Score [ISS] ≥16) under the light of recent technical and procedural advances in trauma care.

Material and Methods

A total of 230 consecutive trauma patients with ISS ≥16 admitted to our level-I trauma center during a 24-month period, were prospectively included and underwent standardized whole-body computed tomography (CT) in a 2 × 128-detector-row scanner. Incidence, mortality, patient and trauma characteristics, and concomitant injuries were recorded for patients with NAAI. Localization of NAAI was described referring to Mitchell and Ishimaru; severity was graded according to the proposal of Heneghan et al.

Results

Thirteen of 230 patients had a NAAI, yielding an incidence of 5.6%. Mean age and ISS was not elevated in NAAI (44.4 ± 14.8 years, ISS = 38 ± 12.4). Mortality was 23.1%. One patient had severe neurologic sequelae from a stroke; all surviving patients had to undergo (transient) anticoagulant therapy. Trauma mechanism was of high kinetic energy in all cases. Concomitant injuries were predominantly thoracic (rib fractures = 76.9%, thoracic spine fracture = 38.5%).

Conclusion

Whenever an individual possibly encountered a deceleration–acceleration trauma mechanism, a high level of suspicion for NAAI should be maintained. It remains to be determined whether recent advances in mortality are due to changes in trauma care or due to improved vehicle and road safety.

Keywords

Aorta computed tomography (CT) angiography trauma adults dissection

Introduction

Despite recent advances in prehospital care, diagnosis, and therapy, non-penetrating injuries of the aortic arch (NAAI) remain having high morbidity and mortality (1). Fortunately, these injuries are not encountered very frequently. While patients with open ruptures of the aortic arch seldom reach the emergency room, dissections and sealed ruptures can be found on a regular basis in severely injured patients (2). Imaging artifacts and anatomic variations are common pitfalls in the diagnosis of aortic injury (3). While contrast-enhanced computed tomography (CT) today is the imaging modality of choice in most trauma centers, inter-institutionally standardized whole-body CT protocols are sparse. Survival benefits have clearly been demonstrated for seamless integration of contrast-enhanced CT imaging into emergency room patient handling (4). With CT scanners being at the edge of further gains in acquisition speed and imaging resolution, a more homogenous technical environment can be expected in the near future urging for and enabling integration of evidence-based imaging protocols, balancing fast acquisition, low radiation, and high diagnostic sensitivity. Endovascular aortic repair (EVAR) now is available in most trauma centers 24/7 and effectively add up to the treatment strategies previously being limited to conservative or open surgical therapy (5). Thus, hospital care providers face a rising incidence due to refinement of diagnostic sensitivity while being capable of offering new minimally-invasive approaches (6). Yet, it remains unclear how these changes affect overall morbidity and mortality of NAAI, since devastating injuries were less prone to be missed even with inferior imaging techniques, and not suitable for minimally invasive EVAR.

Material and Methods

The Independent Ethics Committee at Regensburg University confirmed that for this scientific project, no ethics approval or commission’s opinion was necessary because according to our applicable laws and guidelines such observational study without any study-related clinical intervention or use of patients’ personal data does not have to be submitted to the ethics committee. A total of 230 consecutive multiple-injured trauma patients admitted to our level-I trauma center during a consecutive 24-month period were prospectively included. All patients underwent a standardized whole-body CT scan in a 2 × 128-detector-row scanner (Siemens SOMATOM Definition Flash, Siemens Healthcare AG, Forchheim, Germany), consisting of a non-contrast head CT and a one-phase contrast-enhanced whole-body (skull vertex to middle of thigh; non-ECG-triggered) CT including head and neck.

CT scan

Initially, a non-contrast-enhanced scan of the head was acquired in 0.75 mm slices (360 mAs, 120 kV, pitch = 0.55, increment = 0.75 mm, field of view [FOV] = 230 mm).

Aiming at a scanning time as short as possible in the setting of a routine integration of CT into emergency room algorithms, we use a single contrast-enhanced scan from head to toe with 120 mL of contrast agent (Accupaque 350; GE Healthcare Buchler GmbH & Co. KG, Braunschweig, Germany) injected automatically followed by a flush with 30 mL saline, both at injection rates of 3 mL/s. The scan is started at a fixed delay of 55 s after contrast-agent injection is completed. The FOV is 500 mm, slice thickness 5.0 mm, increment 5.0 mm, pitch 0.6; kV and mAs are calculated and set automatically (CARE kV and CARE Dose; Siemens Healthcare AG) based on the topogram. A soft-tissue kernel with medium edge attenuation (B26f medium ASA) was used for calculation of axial, coronal, and sagittal views of the head and neck. Additional thick-slab axial maximal intensity projections (MIP) were rendered (10 mm) in axial, sagittal, and coronal views. Additional reconstructions were rendered using a B60f kernel for lung tissue (axial), B60f sharp kernel for bones (axial and coronal, additional sagittal for spine), and B30f for soft tissue (axial, additional coronal for abdomen). Further reconstructions were calculated on the radiologist’s discretion depending on the findings or suspicions drawn from the standard datasets.

A radiologist consultant and a radiologist resident performed image interpretation using a standard three-monitor workstation using Syngo and SyngoVia PACS (picture archiving and communication system; Siemens Healthcare AG).

Patient data were anonymized; patient and case characteristics including therapy and outcome were recorded. Localization of NAAI was encoded using the published scheme for endovascular aortic repair by Mitchell and Ishimaru (7): zone 0 comprises the ascending aorta; zone 1 the sector of innominate artery; zone 2 the left common carotid artery; zone 3 the Ductus Botalli; and zone 4 the descendent aorta. As proposed by Heneghan in 2016, NAAI-severity was graded accordingly (8): “minor” (=1) comprises SVS grade 1 and 2 injuries, or no external contour abnormality and an intimal tear or thrombus, or both, sized <10 mm; “moderate” (=2) comprises SVS grade 3 injuries; and “severe” (=3) comprises SVS grade 4 injuries (5).

Statistical analysis

For statistical calculations, analysis, and plotting, GraphPad Prism version 5.00a for Mac (GraphPad Software, San Diego, CA, USA) was used. Arising from the observational character of this study, mainly descriptive statistics were used. Groups were compared using two-sided student’s t-test, paired when suitable. Fisher’s exact test was used when appropriate. Statistical significant differences were regarded at P < 0.05.

Results

We enrolled 230 consecutive patients, of whom 13 were diagnosed with a traumatic NAAI (5.6%). Complete details on baseline patient characteristics are given in Table 1. Patients without NAAI were aged 44.3 ± 22.8 years and patients with NAAI were aged 44.4 ± 14.8 years. Mean Injury Severity Score (ISS) of individuals with NAAI was 38 ± 12.4 compared with 32 ± 14.9 in non-NAAI patients. Mortality in patients with NAAI was more than double (23.1% versus 11.5%; *P < 0.05). Only one major bleeding (0.5% versus 14.7%; *P < 0.05) was observed in NAAI, however, with a fatal outcome.

Table 1.

Baseline characteristics of individuals with and without NAAI.

	Non-NAAI	NAAI	P
n	217	13
Age (years) (mean ± SD; range)	44.3 ± 22.8; 2–91	44.4 ± 14.8; 19–73
Sex (M/F)	153/64	11/2
ISS (mean ± SD)	32 ± 14.9	38 ± 12.4
Major bleeding	32 (14.7%)	1 (0.5%)	*
Mortality	25 (11.5%)	3 (23.1%)	*

P < 0.05.

Trauma mechanism included a car accident in five cases (38.5%), motorcycle accident in five cases (38.5%), fall from height (>3 m) in two cases (15.4%), and hit by a car as pedestrian in one case (7.7%).

Concomitant injuries suggest a predominant pattern of thoracic deceleration and/or acceleration traumata with an elevated count of thoracic spine fractures (38.5% versus 25.3%; *P < 0.05), rib fractures (76.9% versus 46.1%; **P < 0.01), and upper extremity fractures (53.8% versus 32.2%; *P < 0.05) (Table 2). Also, abdominal organ injuries (53.8% versus 25.8%; *P < 0.05), lumbar spine fractures (30.8% versus 20.3%; *P < 0.05), and carotid artery dissections (30.8% versus 3.9%; **P < 0.01) are encountered more often in combination with NAAI. Severe injuries to the head are less frequent in NAAI, as seen with traumatic brain injury (46.2% versus 64.5%; *P < 0.05) as well as midface and skull fractures (23.1% versus 42.9%; *P < 0.05).

Table 2.

Concomitant injuries of individuals with and without NAAI.

	Non-NAAI	NAAI	P
Cervical spine fracture	43 (19.8%)	3 (23.1%)
Thoracic spine fracture	55 (25.3%)	5 (38.5%)	*
Lumbar spine fracture	44 (20.3%)	4 (30.8%)	*
Midface and skull fracture	93 (42.9%)	3 (23.1%)	*
Rib fractures	100 (46.1%)	10 (76.9%)	**
Pelvic ring fracture	58 (26.7%)	4 (30.8%)
Upper extremity fracture	70 (32.2%)	7 (53.8%)	*
Lower extremity fracture	58 (26.7%)	3 (23.1%)
Traumatic brain injury	140 (64.5%)	6 (46.2%)	*
Lung injury	119 (54.8%)	7 (53.8%)
Heart injury	4 (1.8%)	1 (7.7%)
Abdominal organ injury	56 (25.8%)	7 (53.8%)	*
Carotid artery dissection	8 (3.9%)	4 (30.8%)	**

P < 0.05.

P < 0.01.

EVAR was performed in seven out of 13 patients, open surgery in three patients, hybrid (EVAR and surgery) in one patient, and conservative management in two patients (Table 3). While one patient happened to survive a stroke, two patients with EVAR and one with open surgery died. All surviving patients had to undergo anticoagulation therapy (100%).

Table 3.

Therapy and outcome of individuals with NAAI.

Patient (sex/age)	Localization (7)	Severity (8)	Therapy	Outcome
1 (F/44)	2	2	EVAR (26 × 100 mm)
2 (M/73)	3	3	EVAR (34 × 152 mm)	Deceased
3 (M/59)	4	2	EVAR (28 × 100 mm)
4 (M/47)	3	3	EVAR (26 × 100/9 × 38 mm)
5 (M/35)	0	3	Surgery	Deceased
6 (M/34)	3	2	EVAR (26 × 100 mm)
7 (F/50)	0	2	Surgery
8 (M/54)	1	2	Hybrid: ACC (9 × 38 mm) + Surgery	Stroke
9 (M/19)	3	2	Surgery
10 (M/56)	4	1	Conservative
11 (M/33)	3	3	EVAR (28 × 134 mm)	Deceased
12 (M/22)	4	2	EVAR (26 × 134 mm)
13 (M/52)	3	1	Conservative

Severity was graded according to the proposal of Heneghan et al. (8), our cohort had four severe cases, three of whom died. Seven had a moderate-type injury and two had a minor-type NAAI. When looking at the localization of NAAI using the Mitchell and Ishimaru scheme, zone 0 was affected twice, zone 1 once, zone 2 once, zone 3 (Ductus Botalli) six times, and zone 4 three times (7).

Discussion

Non-penetrating injuries of the aortic arch are among the less frequent entities in trauma care, but have a high mortality and morbidity (2,9). Recently, both diagnostic work-up and therapy of NAAI underwent significant changes, with CT scanners reaching the edge of further gains in speed or spatial resolution, and evaluation and homogenization of scan protocols is of rising interest (9). EVAR has also become available 24/7 in most trauma centers, being a suitable therapy in a variety of aortic arch injuries, even as hybrid in combination with open surgical repair (10). Diagnostic and therapeutic developments do not, however, seem to have an impact on devastating aortic arch injuries. It is therefore arguable whether recent changes of in-hospital care substantially influence morbidity or mortality in NAAI.

In comparison to the results reported by Heneghan et al. in 2016, mean ISS of cohorts was leveled (39.5 versus 38.0) and the mortality of all causes was reported to be 20.9% overall, with 26.7% before (1999–2005) approval of TEVAR (8) in the USA, centering around our mortality rate of 23.1%. With 53.7% of endovascular repair in NAAI, reported numbers match our statistics (53.8%). These numbers have to be considered under the light of 80% of traumatic NAAI not even reaching the emergency room (2), as well as under the recent advances in vehicle safety and road-safety campaigns. Accordingly, the gain of 5.8% in the mortality rate in Heneghan’s study is paralleled with n = 7 severe aortic injuries in the 26.7% mortality group, and threefold lower count of severe cases (n = 2) in the era past 2010, compared with four severe cases in our cohort. Counter-wise, the number of minimal aortic lesions developed from n = 0 before 2005 up to n = 22 past 2010 in the Heneghan cohort. In our cohort, two individuals died following EVAR, one following open repair, and the other following a hybrid procedure. From our study, the conclusion can neither be drawn nor denied, that routine inclusion of EVAR as therapeutic option improved mortality. Thus, to us it is of doubt whether there was a true improvement of mortality in NAAI attributable to technical advances in one or both, diagnosis and therapy. With one patient having survived a stroke following dissection at the origin of the left common carotid artery, morbidity is rather low (7.8%). Taking into account the risks of an anticoagulation therapy, all patients had to cope with a relevant (transient) limitation (11).

Recent and upcoming advances in vehicle safety (12) are results of analysis of, for example, injury patterns. Biomechanistic considerations thus should be of major concern in the analysis of NAAI. The theory of “aortic whiplash” being the leading underlying cause of aortic arch injuries is backed by the observation of 6/13 (46.2%) of lesions located at the Ductus Botalli (Fig. 1a–c). Its adhesion to the arch makes it a point of minor stability, because mobility in the deceleration–acceleration sequence is severely limited, leading to shear forces at the aortic wall. The concept of a “whiplash”-type of motion is primarily known from the cervical spine (13,14), but applies to the aortic arch as well. All cases of NAAI in our cohort have in common a trauma mechanism, where suddenly becoming stationary is the key finding. Further safety engineering could evaluate the turning point of motion as an approach to further technical advances in vehicle equipment. On the contrary, our observations of trauma mechanism and concomitant injuries in NAAI should lead to a high level of suspicion for NAAI whenever encountering individuals with a possibly sustained “aortic whiplash.”

Fig. 1.

(a–c) Example of a rupture of the aortic arch at the Ductus Botalli with EVAR. (a) Axial CT shows sealed rupture of the aortic arch at the Ductus Botalli in a 47-year-old man after a motorcycle crash. (b) Sagittal CT. (c) Sagittal CT of EVAR with stent in the left subclavian artery.

With only two “minor” NAAI according to Heneghan et al., our CT scan protocol not being ECG-gated might be of relevance (15). While the latest recommendations do not specifically advise in using ECG-gating in CT, it can be subject to debate (9). On the other hand, ECG-gating likely will not have a substantial impact on sensitivity for moderate or severe NAAI.

Limitations of our study have to be considered: the cohort size from this single-center report is limited, which can be of relevance in statistical matters. We encountered this fact by primarily showing descriptive statistics. Transferability of our observations might be restricted by inhomogeneous and non-standardized emergency room handling in different trauma centers, as well as different preferences and availability of surgeons and/or interventional radiologists in charge. Furthermore, due to the level-wise organizational structure of German trauma care, our study only comprises individuals being primarily taken to our level-I-trauma center; secondary admissions from second- or third-level centers are not considered in our cohort.

In conclusion, it remains of doubt whether observable small advances in mortality compared with the pre-EVAR era are attributable to technical progress in diagnostics and therapy, or are due to advances in road and vehicle safety. Aortic whiplash seems to be the predominant cause of NAAI; a high level of suspicion has to be maintained whenever an individual possibly encountered a deceleration–acceleration trauma mechanism.

Footnotes

Declaration of Conflicting Interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

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