S A Scandal in Bohemia: You see, but you do not

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1 Aortic Injury in Vehicular Trauma James S. Williams, MD, Jonathan A. Graff, MD, Justin M. Uku, MD, and Jeffrey P. Steinig, MD Department of Surgical Education, Memorial Medical Center, Savannah, Georgia, and Department of Surgery, Millard Fillmore Hospitals, Buffalo, New York A 5-year retrospective study of 530 motor vehicle fatalities revealed 105 aortic injuries occurring in 90 victims. These were reviewed to determine the injury patterns, circumstances, and mechanisms involved. In addition, the survival time, the driver s age and sex, the time of day of the accident, and the blood alcohol level were considered. The aortic injuries consisted of 61 transections and 44 tears (13% were multiple). Sixty-five percent of the injuries were located in the proximal descending aorta (66% of these were transections), 14% were in the ascending aorta and arch (33% of these were transections), 12% were in the distal descending aorta (more than 1 cm distal to the subclavian artery) (46% of these were transections), and 9% were in the abdominal aorta (56% of these were transections). Associated injuries consisted of multiple rib fractures (78%), liver lacerations (61%), head injuries (42%), first rib fractures (42%), splenic lacerations (36%), heart lacerations (34%), sternal fractures (28%), cervical spine fractures (26%), and thoracic spine fractures (20%). Death occurred within 1 hour in 94% and within 24 hours in 99%. The impact was head-on in 62% of the accidents. The victim was the driver 74% of the time and male in 77% of the cases, and the blood alcohol level exceeded 0.1 mg/dl in 43%. Most aortic disruptions were complete transections of the proximal descending aorta, associated with serious injury to the thorax, and occurred in head-on collisions. Findings support a compression and upward thrust of the heart as a mechanism responsible for the aortic disruption. (Ann Thorac Surg 1994;57:726-30) herlock Holmes noted in an aside to Dr Watson in S A Scandal in Bohemia: You see, but you do not observe. On the roadways and in hospital emergency rooms, we continue to see death resulting from motor vehicle trauma, but we are frequently unable to observe diagnostic signs that may indicate the presence of covert trauma [l-31. Recognition of aortic injury in patients involved in violent motor vehicle accidents is imperative to ensure their survival [2-61. A very small number of these victims reach the operating room. This study attempts to discern injury patterns, accident mechanisms, For editorial comment, see page 530. and pertinent variables in the setting of motor vehicle fatalities caused by aortic trauma. Knowledge of these factors may facilitate the diagnosis of aortic injury in live patients. Methods The postmortem reports of 530 consecutive victims of motor vehicle accidents whose autopsies were performed at the Erie County Medical Examiner s office over a 5-year period (January 1980 through December 1985) were studied retrospectively. In Erie County, New York, all trauma deaths are referred to the medical examiner s office for Accepted for publication June 30, Address reprint requests to Dr Williams, Department of Surgical Education, Memorial Medical Center, PO Box 089, Savannah, GA postmortem examination. In 90 cases, aortic disruption was found to have caused or contributed to the death. These cases were reviewed in detail. The number of patients who were treated in the hospital and who survived was not determined. Deaths resulting from other causes of aortic injuries were not included in the study. Factors considered were the description of the aortic injury, accompanying anatomic injuries, the mechanism of injury, the survival time, road conditions, whether the victim was the driver or a passenger, the victim s age and sex, the time of day and month of the accident, and the presence of blood alcohol. Results In the 90 cases studied, we found 105 aortic injuries consisting of 61 transections and 44 tears. (A transection is defined as complete disruption of the intima and media layers; a tear is defined as partial disruption of a varying length of the same two layers. The adventitia remained intact in most cases.) In examining the distribution of aortic injuries (Table l), we found that 65% of the tears and transections were in the descending portion within 1 cm of the origin of the subclavian artery (66% of these were transections); 14% were in the ascending and arch portions (33% of these were transections); 12% were in the descending thoracic portion more than 1 cm dislal to the origin of the subclavian artery (46% of these were transections); and 9% were in the abdominal aorta (56% of these were transections). Multiple aortic injuries were present in 13% of the cases. No significant difference was found by The Society of Thoracic Surgeons /94/$7.00

2 Ann Thorac Surg lyy4;57:72&30 WILLIAMS ET AL 727 Table 1. Location of Aortic lnjurv Percentage Percentage of Specific of Anatomic Location (n = 105) Injuries Injuries Ascending aorta (including arch) Descending thoracic aorta (within 1 cm proximal to the origin of the subclavian artery) Descending thoracic aorta (more than 1 cm distal to origin of subclavian artery) Abdominal aorta Multiple aortic injuries were present in 13% of the YO cases between the percentage of tears versus transections in the descending thoracic aorta more than 1 cm distal to the origin of the subclavian artery, and in the abdominal aorta. Associated anatomic injuries (Table 2) included multiple rib fractures (78%), liver lacerations (61%), head injuries (42%), first rib fractures (42%), splenic lacerations (36%), heart lacerations (34%), sternal fractures (28%), cervical spine fractures (26%), and thoracic spine fractures (20%). Forty-four percent of the fatalities occurred at the accident scene; 50% occurred during the ensuing hour. Thus, Table 2. Associated Anatomic Injuries Injury Multiple rib fractures Liver Head First rib fracture Spleen Heart laceration Sternal fracture Cervical spine fracture Thoracic spine fracture (n = 90) Percentage The 90 victims all had multiple associated anatomic injuries Table 3. Death After lnjury Time (n = 90) Percentage Immediate Within 1 hour Between 1 and 24 hours 4 5 Greater than 24 hours % of the victims died within 1 hour of injury. Five percent died between 1 and 24 hours of injury. Therefore, 99% of the victims died during the first 24 hours (Table 3). It was not possible in this autopsy series to determine which of these patients would have been salvageable. The direction of impact was head-on in 62% of the accidents; the collision was lateral in % and unknown in 20% (Table 4). Dry road conditions existed in 63% of the accidents. The victim was the driver of the automobile in 74% of the accidents and male in 77% of the accidents (Table 5). Analysis of the time of day when the accident occurred revealed that 40 (44%) took place between the hours of 11 PM and 7 AM, 30 (34%) between 3 and 11 PM, and 20 (22%) between 7 AM and 3 PM. The time-of-year distribution exhibited a trimodal curve, with peaks in the spring, summer, and fall. The blood alcohol level was greater than 0.1 mg/dl (the legal limit in New York State) in 43% of the victims. Information on the apparent speed on impact, the amount of vehicular deformation, and the use of a seat belt restraint system was not consistently available in the case files reviewed. Comment Aortic disruption resulting from blunt trauma remains a very devastating injury. Parmley and associates [5] have commented: That anyone survives complete transection of this major artery is most unbelievable. Death frequently occurs abruptly at the site of the accident, or within 1 hour of the injury [5, 7, 81. Those who reach the emergency room are suffering from polytrauma, which is very distracting and makes the diagnosis of a ruptured aorta extremely difficult [l, 3, 91. Although trauma victims may reach the emergency department alive, a very small number of them reach the operating room. If a delay in the diagnosis of aortic rupture or lack of response to resuscitation efforts occurs, cardiac arrest and death will eventuate [2, lo]. Of those operated on, survival depends Table 4. Direction of lmaact Direction (n = 90) Percentage Head-on Lateral Unknown

3 728 WILLIAMS ET AL Ann Thorac Surg 1994;5772&30 Table 5. Breakdown of the Victims by Sex and by Driver Versus Passenger Status Variables (n = 90) Percentage Sex Male Female Driver versus passenger Driver Passenger on the nature of the associated injuries, and complete recovery depends on an uncomplicated postoperative course [2, 11, 121. In this autopsy series, as in others in the literature, the site of the most aortic damage resulting from blunt trauma is in the descending portion 1 cm from the origin of the left subclavian artery at the insertion of the embryonic ductus arteriosus (duct of Botallo) [2, 3, 5, 7, 131. Most injuries at this site are complete transections. Fewer aortic injuries occur in the ascending aorta (including the arch), the distal descending aorta, and the abdominal aorta. s are found in approximately half of the descending and abdominal injuries, but only a third of the ascending aortas are transected. Multiple sites of aortic tears are found in approximately 10% of the cases. In our series, one of the tears was in the proximal descending aorta just distal to the subclavian artery origin in 11 of 12 victims. Three theories of aortic rupture have been advanced to explain the mechanism of thoracic aortic injury [3, 4, 1%]. The first theory is that at the moment of impact, the heart and aorta remain fixed, while the descending aorta continues forward [14]. This explanation is unlikely, however, because the descending aorta is fixed by the intercostal vessels and the ductus arteriosus [15]. The second theory is that the descending aorta remains fixed to the posterior thoracic wall, while the heart, arch, and ascending aorta swing forward, resulting in a shearing force at the isthmus. In support of this theory, Coermann and associates [13] proposed the existence of a shoveling mechanism, in which a cranially directed blow on the lower chest displaces the heart and mediastinum cranially, thus stretching and tearing the aorta at a point fixed by the ductus arteriosus. This is the most common site of injury noted in the present and other series [ 131. Coermann s group performed cadaver experiments in 1972 in an attempt to find evidence supporting this theory. Additionally, Sevitt [16] proposed that the superior aorta stretches cranially, thus tearing the aorta just proximal to the ligamentum arteriosum. This effect is exacerbated by rapid chest compression, as shown in his animal experiments. Further, Bowen and e [15] and Keen [14] postulated that a combination of deceleration and direct impact is necessary to rupture the aorta. The third theory of aortic rupture is that hydrostatic pressure rapidly elevates at impact, and the aorta bursts and tears at its weakest points [17]. In support of this theory, Lundevall [17] described a water hammer effect that occurs when the aorta ruptures, in which only 5788 to 6608 of force is delivered rapidly and causes a tear or transection through the effect of inertia alone. These forces can be generated by an auto crash in which the vehicle is going approximately 40 mph, where the deceleration occurs in milliseconds. In Coermann and associates [ 131 cadaver experiments, the intraluminal aortic pressures that were recorded ranged from 3008 to greater than 1,OOOg. The findings from these two studies indicate that rapidly increasing intraaortic pressure exerts a water hammer effect. Experimentally, Zehnder [ 1 slowly stretched the aortic walls, but found that high bursting pressures were required to produce rupture. A combination of the second and third theories may constitute the most plausible mechanical explanation for traumatic aortic injury. The impact was head-on in 62% of the accidents in this series (perhaps more, as the direction of impact in 20% of the cases is unknown). With concomitant chest compression, the pressures could be sufficient and the displacement of the heart, arch, and ascending aorta great enough to produce a water hammer effect and a shearing force. The source of abdominal aortic injuries must include direct injury as well, as Parmley and associates [5] noted that 29 of their 34 patients had spinal fractures associated with an abdominal aorta injury. However, the location of the abdominal aorta injury was not recorded in the Parmley report, nor was this information consistently available for the subjects in our series. Not all trauma victims with aortic injury die as a direct result of the injury to the aorta. An estimated one third [2] to two thirds [7] of the persons with aortic injury actually die of associated causes. Sturm and colleagues [9] found in their study that 41% of the victims who had injury to the aorta also had associated injuries that were considered fatal. In the present study, we found that death was due to aortic injury, or aortic injury was considered a major factor in the fatal outcome, in 90 of 530 (17%) of the consecutive autopsies. This finding is similar to the 16% cited in Greendyke s [7] study. Severe thoracic trauma, as manifested by multiple rib fractures, was seen in more than three fourths of the cases, sternal fractures in more than a fourth, and first rib fractures in almost half. With so much violence directed at the thoracic cage, it is not surprising that the heart and spleen were injured in more than a third of the cases in our series, and the liver in more than half. These findings are similar to others reported in the literature [l, 5, 7, 101. However, when the injuries sustained by the passenger and driver were compared by Greendyke [7], 80% of the passengers and only 47% of the drivers were found to have suffered liver injuries, whereas 47% of the drivers and only 20% of the passengers had splenic injury. One would expect the driver to suffer more liver lacerations from the impact against the steering wheel. Although 74% of the victims in this study were drivers in whom the steering wheel could be a contributing source of injury in chest compression, 26% of the victims who sustained aortic injury were passengers.

4 Ann Thorac Surg 1994;5772&30 WILLIAMS ET AL 729 Hartford and associates [ 101 compared the distribution of injuries between survivors and nonsurvivors and found the patterns to be fairly similar. In an effort to determine the causes of death at the accident scene, Sturm and colleagues [8] noted that the death rate was significantly greater for patients with head injury (p < 0.01), a second intrathoracic injury (p < 0.025), and abdominal injury ( p < 0.001). Those who survived had a lower injury severity score ( ) than did nonsurvivors ( standard deviation [SD]; p < 0.001). Similarly, the injury severity scores of patients without rupture of the aorta (19.9 -C SD) were significantly less than those in patients who suffered rupture (42.1? 11.6 SD; p < 0.001). These findings reflect a less violent accident and lower deceleration forces. In addition, although cardiac contusion is difficult to diagnose, its presence may adversely affect the outcome of these patients [12]. The survival time in patients with aortic injury has varied from immediate death to complete recovery after operative intervention. Ninety-four percent of the victims in this series died within the first hour after injury; 44% of these victims died at the scene. Only 5 patients (6%) survived more than 1 hour. Studies conducted by Strassman [19] and Parmley and associates [5] in the 1940s and 1950s revealed an early survival rate of 15% to 20%. In 1966, Greendyke [7] reported on an autopsy series consisting of 40 trauma victims who died with an aortic rupture; only 3 survived more than 1 hour. Coermann and colleagues [13] noted that auto design promoted chest, aorta, and cardiac injury resulting from intrusion of the steering wheel into the passenger compartment. Deceleration forces were absorbed by the chest, so that the speed of impact was sufficiently reduced to allow for initial survival in about 17% of these victims. In the setting of the high speeds noted by Greendyke [7], survival was minimal. The advent of regional trauma centers, the better training of emergency medical technicians, and changes in auto design have led to improved survival rates. In our study, 44% of the victims were dead at the scene, compared with the 50% reported by Sturm and associates [8] in Although the 1958 study of Parmley and colleagues [5] revealed that death occurred at the accident scene in 80% of their victims, these data were obtained from the Armed Forces Institute of Pathology; only two thirds of the accidents were vehicular, whereas one third consisted of pedestrian, plane crashes, falls, and other accidents. In Hartford and coworkers [lo] 1986 series of 86 patients who sustained aortic injury, 70 were dead at the scene or on arrival at the hospital. Of the remaining patients, 16 were evaluated in the emergency room, 9 patients came to operation, and all survived. Similarly, in the series of Bodily and colleagues [2], 26 patients were potentially salvageable and 12 (46%) survived. No information was available regarding how many victims with aortic injury were seen in the emergency department of Erie County Hospital during the period of this study. Violent vehicular accidents were the cause of 79% of the aortic injuries in our series. In other studies, the injuries caused by motor vehicle accidents have accounted for 73% of the reported cases, versus pedestrian accidents in % [2, 5, 8, lo]. Other reported causes of injury have been falls (5%) and motorcycle accidents (3%); compression, truck accidents, direct blows, and snowmobile accidents altogether account for less than 1%. Other contributing factors include the blood alcohol levels and time of day. Forty-four percent of the accidents occurred between 11 PM and 7 AM. Similarly, Hartford and associates [lo] found that 55% of the accidents in their series occurred between 6 PM and 6 AM. The fact that 43% of the victims with aortic injuries had positive blood alcohol levels indicates that intoxication may have played a role in these deaths. Incomplete accident data prevented further analysis, however. The time-of-year distribution showed a trimodal curve with peaks in the spring, summer, and fall when higher speeds are possible on the roadways. The road conditions were dry in most (63%) of the accidents. The age of the victims with aortic injury ranged between 12 and 87 years (mean, 36 & 16 years SD) [l, 2, Male patients dominanted in a ratio of from 3:l up to 8:l [l, 2, 6, 8, 10, 111. These findings are similar to those in this study. Accurately diagnosing an aortic injury in a victim brought to an emergency room after extraction from a demolished automobile is extremely difficult. The most consistently accurate diagnostic test continues to be aortic angiography [l], although computed tomography and digital subtraction angiography are emerging as viable alternatives where available [4]. The finding of a widened mediastinum on a chest radiograph obtained with the patient in the upright position still remains the most sensitive criterion for aortic rupture [l, 201. Sturm and colleagues [20] reviewed 26 anteroposterior chest radiographs from patients with subsequently proven traumatic aortic rupture, and determined the mean mediastinal width in this setting is 9.4 cm, measured at the superior border of the anterior fourth rib [ZO]. The observation of right-sided tracheal and nasogastric tube deviation (typically at the T4 level), depression of the left main bronchus below 40 degrees from the horizontal, and blurring of the aortic arch contour are further findings that should make one suspect an aortic injury [20]. When the diagnosis is made expeditiously, survival is remarkably improved. The aorta ruptures as a result of rapid deceleration and most commonly tears just distal to the ligamentum arteriosum, leading to rapid demise. The ability of the patient to survive rests on the extent of accompanying injuries and the speed with which an aortic injury can be identified and treated. The history of a force of sufficient magnitude; head-on impact; a male driver; multiple rib fractures, particularly first rib fracture; sternal fracture; thoracic spine fracture; the presence of associated injuries; and characteristic radiologic findings are all factors that point to a diagnosis of aortic rupture. We thank Davey Volkhardt for editorial assistance.

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