Traumatic rupture of the aorta

Journal of Clinical Forensic Medicine (1996)3,

123-127

© APS/PearsonProfessionalLtd 1996

ORIGINAL C O M M U N I C A T I O N

Traumatic rupture of the aorta J. Kim, A. Busuttil Forensic Medicine Unit, University of Edinburgh Medical School, Edinburgh SUMMARY. The aim of this study was to determine the incidence and mortality from traumatic ruptures of thoracic aortas (TAR) in a well defined population over a 7 year period. The study provides a retrospective analysis of case files of all deaths from road traffic accidents and falls from heights, the usual causes of TAR, filed in the Forensic Medicine Unit of the Pathology Department of the University of Edinburgh, for Lothian and Borders Region. Of the 276 fatal road traffic collisions and falls from heights identified in archival material, 66 traumatic aortic ruptures were found in the period between 1988 and 1994. Only 11% of these patients were alive on arrival to a hospital or an emergency department. To decrease the high mortality rate the following are required: an earlier, more sustained and vigorous, on site resuscitation; efficient screening methods for the diagnosis of TAR in multi-traumatised patients; identification of the specific characteristics of those traumatic episodes which are likely to be associated with a high risk of rupture, and an increase in the number of surgical interventions for ruptured aortas. Journal of Clinical Forensic Medicine (1996) 3, 123-127 The frequency with which aortic rupture is encountered in patients dying of major trauma has prompted a study of the lesion. 1Accidents causing dosed ruptures of the thoracic aorta may be separated into three groups: a) those associated with direct crushing forces; b) vertical deceleration and; c) horizontal deceleration injuries? Crushing forces usually result in multiple injuries, so that the torn aorta becomes only one of many findings elicited post-mortem. Vertical deceleration injuries are usually associated with jumps or falls from heights or in elevator falls. The factors which bring about traumatic aortic rupture can be summarised as follows: torsion stress and the stress from a 'waterhammer effect' due to compound intraluminal blood which is produced during blunt trauma, appear to be predominantly responsible for rupture of the ascending thoracic aorta, whereas shearing and bending stresses appear to cause rupture of the aortic arch and descending aorta. 3,4 The incidence of ruptures of the thoracic aorta appears to be related to vehicular collisions at high speeds of impact. The number of road traffic accidents and the number of individuals sustaining thoracic injuries have risen sharply over the last few years; acute aortic rupture occurs in 15 to 20% of individuals killed

in vehicular accidents. 3 Therefore, a history of a severe and sudden deceleration incident should immediately arouse the suspicion of acute aortic transection. 5 Death usually occurs immediately from exsanguination after aortic rupture, but 10-20% of the injured survive tong enough for potential reparative treatment, provided a rapid diagnosis, active resuscitation and rapid transfer of the patient to a n operating theatre take place. 4 Of the 10-20% who do survive to be hospitalised, 66% will be dead by 2 weeks, 82% by 3 weeks and 90% by 10 weeks. 5 Survivors of the initial injury appear to fall into two groups: those in whom the haemorrhage is contained in a peri-aortic haematoma within the first few days after injury, and those surviving the initial and delayed threat who develop a 'false' aneurysm due to organization of the peri-aortic haematomas which may remain stable for months or years.

MATERIALS A N D M E T H O D S

The study comprises all known cases of ruptured thoracic aortas in road traffic accidents and falls from heights in the years 1988 to 1994 that could be identified from the archives of the Forensic Medicine Unit of the University of Edinburgh. All death in road traffic accidents and falls from heights in the Lothian

Professor A. Busuttil, J. Kim, Forensic Medicine Unit, University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG, U K Correspondence to: A. Busuttil 123

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Journal of Clinical Forensic Medicine

and Borders region of Scotland are referred by the Procurator Fiscal's office to this Unit; thus this series is complete for this population as every death from an accident is submitted to a fully autopsy and these are all carried out by this Unit. All the case files for those fatalities resulting from falls from heights and road traffic collisions were analysed, and all case files for those deceased identified at post-mortem examination as having sustained an aortic injury were selected for in-depth analysis. In addition to the autopsy report and reports of specialised examinations such as neuropathology examination of the brain, toxicology, each file contained a detailed police report made to the Procurator Fiscal concerning the actual incident. From these selected case files, various details were transferred on to a pre-prepared protocol, including personal details, mode of injury, a report of the incident, extra-thoracic and thoracic injuries sustain, location and exact type of injury to the aorta, time interval between traumatic incident and death, any resuscitation and operative procedures carried out, place and time of death. The records were re-evaluated for all those individuals who survived to reach a hospital but were shown at autopsy to have sustained an aortic rupture.

RESULTS

During the 7 year period under study, 1988 to 1994, 276 cases of road traffic accidents and falls from heights were discovered (Table 1) with a total of 66 traumatic ruptures of the thoracic aorta. There were 49 male and 17 female patients and they ranged from 10 to 84 years of age (mean: 41 years). A further analysis of incidence rates with respect to age and sex is shown in Table 2. Thirty-six of the 66 patients were involved in automobile collisions, 15 were pedestrians struck by automobiles, 3 were riding motor-cycles and 1 was riding pillion; 14 were injured in falls from a height. Thus, the majority of traumatic ruptures of the aorta occurred in drivers, pedestrians and persons falling

Table 1 - Year and sex distribution of traumatic aortic rupture (n:66) Year 1988 1989 1990 1991 1992 1993 1994 TOTAL

Male

Female

12 8 8 4 2 7 7 48

0 3 3 0 2 4 6 18

Table 2 - Age and sex distribution of Traumatic Aortic Rupture (n:66) Age(yrs) 0 20 21-30 3140 41-50 51-60 61-70 71 >

Male

Female

Total

9 8 7 6 8 4 5

4 2 3 3 1 2 4

13 10 10 9 9 6 9

from a height. In several different accidents, both the driver and passenger in the same automobile sustained aortic injuries. Clinical findings are noted in Table 3. The incidence of associated thoracic and extrathoracic injuries was high. Fifty-five patients had associated rib fractures, 59 of whom had lung injuries and 15 had sustained a fracture of the sternum. Nineteen had thoracic vertebral fractures, 22 had associated heart injuries, 41 had a right haemothorax whilst 51 had a left haemothorax. Fifteen patients had also sustained a haemopericardium of the extrathoracic injuries, 30 patients had pelvic fractures and 34 had sustained limb fractures. The liver was injured in 42 cases and the spleen in 34 cases (Table 4). In studying the police reports and descriptions of the incident in which aortic rupture took place, it was impressive to note repeatedly a frequent association with excessive vehicle speed, unexplainable, bizarre driving manoeuvres and disregard for the Highway Code by vehicular occupants. The violence of impact as judged by the destruction of the automobile and areas of impact was usually very substantial. However, there were several cases in which minor collisions or accidents occurring at low speed eventuated an aortic disruption. Data regarding the use of seat belts was impressive; for drivers they were invariably worn but not for passengers. There are no apparent differences in patterns of distribution or number of lesions in the passenger, driver and pedestrian group.

Table 3 - Incident in which traumatic aortic rupture took place Incident

Male

Female

Fallfrom a height Road traffic incident

9 17

5 6

Driver Front passenger Rear passenger side Rear driver's side Motor cyclist Pillion rider Pedal cyclist Pedestrian

4 0 4 3 3 1 0 11

2 1 2 0 0 0 0 4

Traumatic rupture of the aorta Table 4 - Injuries associated with Traumatic Aortic Rupture Number Rib fracture < 6 > 7 Sternum fracture Body Manubrium Both Thoracic vertebrae fracture Lungs - lacerations a n d contusions Heart Haemopericardium Haemothorax Skull fracture Brain injury Liver injury Splenic injury Fractured pelvis Fractured lumbar Vertebrae Haemoperitoneum Limb

Right

Left

23 26

24 26

59

59

41

51

14 7 7 19

22 15 13 33 42 34 30 2 4 34

Alcohol was present in either the blood, urine or vitreous humour in 5 of the 23 deceased drivers tested, with values ranging from 18-262 mg of alcohol/100ml of blood. Of the pedestrians tested for alcohol, 6 exhibited alcohol intoxication (104-259 mg of alcohol/100ml of blood). No drugs were looked for routinely in body fluids. Of the total 66 cases studied, aortic rupture was considered to be the major morbid anatomical explanation for the death in 20, while in the remaining 46, multiple other traumatic lesions also of sufficient magnitude to explain death were encountered. Injury occurring between the junction of the arch and the descending part of the aorta was seen in 44 patients, in the ascending aorta in 5 patients, distal to the arch in 10 patients, in lower descending thoracic aorta in 9, in the abdominal aorta in 5 and in root of the aorta in one (Table 5). In the 66 patients with traumatic aortic rupture, 20 patients exhibited at least one point of complete transection with varying degrees of retraction of the lacerated ends of the severed vessels, leaving 15 cases with lacerations which were not circumferential. Ten of the latter exhibited no full thickness lacerations. In essentially all cases, the lacerations were transverse. There was no predilection for any part of the circumference of the aortas which the cases in this study exhibited. Apart from their lacerations the pathological features in these aortae were compatible with the findings to be expected in them in terms of the degree of atheromatous changes and calcification present, appropriate to their age groups; significant atherosclerotic changes were present in 10 of the 66 ruptured aortas and

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Table 5 - Sites of Traumatic Aortic Rupture Root of the Thoracic Aorta Ascending Thoracic Junction between arch and descending thoracic aorta Thoracic distal to the arch Lower thoracic descending Abdominal aorta

1 5 44 10 9 5

appeared to be unrelated to the traumatic lesions. No other disease (e.g. cystic medial degeneration, vasculitis) of the ruptured aortas was demonstrated. Thirty-eight patients died instantaneously or within 1 hour of sustaining traumatic injuries, with 21 patients dying while being resuscitated or in transit to hospital. Seven of the 66 were alive on arrival at an emergency hospital: 2 of these died within 24 hours after admission, 4 died after being transferred from Accident and Emergency to a ward. One patient died whilst being operated on in the theatre (Table 6). Of the 7 patients surviving to reach hospital 5 were road traffic accidents and 2 were falls from a height. Four patients were subjected to a thoracotomy whilst 2 required a laparotomy: the other patient had no operative treatment. Significantly, 6 of the 7 patients had superficial lacerations or partial ruptures or tears with only one case of full transverse rupture. Two of the 7 had multiple lacerations or tears of the aorta.

INITIAL SURVIVORS A brief account on each of the subjects who survived the initial traumatic episode follows. Subject 1:19-year-old male, front seat car passenger, died 17 h 20 min after incident. Cardio pulmonary resuscitation (CPR) and thoracotomy, almost complete tear (3/4 circumference or aorta) at junction between arch and descending part; also left femoral fracture, pelvic fracture and injuries to lungs and liver. Subject 2:31-year-old male, fell 50 ft, died 2 h 27 rain after incident, taken to Accident and Emergency department and later transferred to a surgical ward, CPR and thoracotomy. Very superficial transverse

Table 6 - Time interval between traumatic incident and death Time of death Death from injuries Death after hospitalisation Death on the ward Death in theatre

Male < 1h 14 h < 24 h > 24h < 24 h > 24h

29 25 2 0 2 0 1

Female 9 6 0 0 0 2 0

126 Journal of Clinical Forensic Medicine intimal tears in descending aorta, also rib fractures, left humerus fracture, bilateral haemothoraces, haemoperitoneum, injuries to spleen, liver, lungs and heart. Subject 3: 73-year-old female pedestrian hit by van at 60 mph, died 4 days after incident. CPR, horizontal tear in posterior lateral descending aorta (involving the intimal and partial thickness of media) and 2 horizontal intimal splits in lower descending aorta, rib and sternum fractures, pelvic fracture, left haemothorax and haemopericardium. Subject 4:31-year-old female, fall from 140 ft, died 6 h after incident. Partial transverse rupture of junction of arch and descending part. CPR and laparotomy, associated rib and sternum fractures. Subject 5: 54-year-old male driver, died 12 h after incident, ITU after resuscitation, laparotomy, several roughly horizontal tears present in intima immediately distal to the arch. Associated rib fractures, transverse fracture of thoracic vertebrae, pelvic fracture, bilateral haemothoraces, spleen and liver injuries. Subject 6" 34-year-old female driver, 4 h after incident, multiple cardiac arrest but could not be revived on fourth occasion. Horizontal laceration of aorta at junction of arch and descending thoracic part (above this there are multiple parallel horizontal tears), bilateral haemothoraces. Thoracotomy and aorta clamped. Associated rib fracture and injury to spleen, lungs and heart. Subject 7: 20-year-old male car driver, died after 4 h 40 min. CPR, thoracotomy, tear involves 1/4 diameter of aorta at junction of arch and descent part. Associated rib fracture, limb fracture, pelvic fracture. Liver and lungs injured. In reviewing these seven cases with prolonged survival, there appears to be little difference in terms of the multiplicity and severity of associated injuries which they have sustained in comparison with the rest of the series. However, there appears to have been a much earlier access to more vigorous resuscitation which enabled these patients to survive longer. It is important to note that some of these cases had incomplete tears which had resulted in a slower rate of external blood loss and a bigger window of opportunity in terms of their potential survivability.

DISCUSSION Archival studies of traumatic ruptures of aorta should offer some assistance in finding their causation and thus decreasing the high mortality rates from such aortic trauma. An important part of this survey was to determine whether there were any specific differences which distinguish patients who managed to survive long enough to reach an emergency hospital

and those who died immediately, but no such criteria could be identified in a careful study of each of the survivors, and by comparison of the various features of the incident and the traumatic damage which they sustained, with those who succumbed. The frequency of trauma to the aorta appears to be increasing in an almost geometric progression as the number of high speed vehicles rise. In the older literature, reports of traumatic aortic rupture were uncommon to the degree as to justify individual case reports. Strassman 6 found only 72 cases of such rupture, 51 of which occurred in automobile accidents, in a retrospective study of 7000 post-mortems conducted in the Office of the Chief Medical Examiner in New York City in the years 1936 to 1942. Lundevall7 discovered 20 instances of traumatic aortic rupture, 19 of which took place in automobile accidents in a 10-year study involving 1200 medicolegal post-mortems performed at the Institute of Legal Medicine in Oslo between 1953 and 1962. In comparison, in the study by Greendyke,8 investigation of 1259 post-mortems performed in only a 4-year period and drawn from a relatively small urban county (under 700 000 population), 42 cases of traumatic aortic rupture were seen, including 35 automobile accident victims. The striking fact emerging from the Greendyke experience is that 1 in every 6 persons dying in a motor vehicle accident in Monroe County, in the past 4 years has sustained a rupture of the aorta. Nor is this experience atypical, Zeldenrust and Aarts 9 have reported 88 cases of traumatically ruptured aorta in 800 road traffic accidents in the Netherlands. The major problem in the rupture of the thoracic aorta from blunt trauma is an early recognition of the lesion preferably before adventitial disruption occurs, closely followed by exsanguination. In the diagnosis of acute traumatic aortic rupture, it is imperative to maintain a high index of suspicion and a constant awareness of the likelihood of this lesion in victims of high speed decelerating injuries, whether or not there is external evidence of chest injuries. A third to half of the patients reported in the literature had no external evidence of thoracic injury at the time of initial physical examination?° Clinical findings of importance are the triad of difference in pulse amplitude between upper and lower extremities, hypertension of the upper extremities as compared with the lower limbs, and a widening of the mediastinum - as the most constant radiological finding. Though it is known that immediate operation is not necessary for all patients with traumatic disruptions of the aorta, prompt diagnosis is mandatory so that appropriate supportive therapy can be instituted.

Traumatic rupture of the aorta

The early accurate diagnosis of aortic rupture is compounded by many problems. The multiply-injured victim presents with various combinations of shock, unconsciousness, respiratory distress, abdominal visceral injury and long bone fractures on to which the attention of the doctors would be concentrated of necessity. As many as 80% of the patients with a rupture of the thoracic aorta die before reaching the hospital. Survival following surgical management of less acute traumatic aneurysm is reported to be better than 80%. 11 Therefore, survival rate should be expected to be between 20 and 80%. In fact, some of the major series of patients with this injury have a survival rate of approximately 50%.12 A mortality rate as low as 20% has been reported after surgical repair after rupture. 13 This rate refers to a highly selective fraction of patients who reached the operating room and had a ruptured aneurysm of the descending thoracic aorta. However, according to the above data even a 100% survival rate after operations for ruptured thoracic aorta would result in an estimated overall mortality rate well over 50%. Advances in pre-hospital transportation of victims of trauma and advances in cardiovascular surgical techniques should provide an opportunity for salvage of patients who, in former years, had a high mortality rate. 14

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