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Red River Anthology

1997; Lippincott Williams & Wilkins; Volume: 42; Issue: 3 Linguagem: Inglês

10.1097/00005373-199703000-00001

1529-8809

Kenneth L. Mattox,

Trauma, Hemostasis, Coagulopathy, Resuscitation

Serving as President of the American Association for the Surgery of Trauma has been the pinnacle of my professional career to this point. Many have helped me reach this point: most important are my wife June and daughter Kimberly, my surgical mentors at Baylor, Doctors George Jordan, Arthur Beall, and Michael E. DeBakey, and my office assistants, especially Ms. Mary Allen. This presentation summarizes three decades of an abiding and driving special interest. Figure 1Figure 1: Kenneth L. Mattox, MD President, American Association for the Surgery of Trauma.TEXAS RIVERS AND TEXAS TRAUMA Rivers provided the access, traverse, and barriers to what was to become the State of Texas. More of Texas's borders are defined by rivers than any other state in the United States. Explorers, priests, outlaws, adventurers, teachers, renegades, farmers, ranchers, and doctors sought solace, retreat, riches, and opportunity in the land east of the Sabine River. This land initially did not belong to the United States. It was claimed by Spain, France, Mexico, and the Indians. When Cabeza de Vaca landed on Galveston Island and continued via the Brazos River, the land and its inhabitants were hostile, even cannibalistic. Near the Pecos River in 1535, this explorer/shaman performed the first recorded operation in North America. "Doctor" Cabeza de Vaca and his assistant, Estefan, successfully removed an arrowhead from the sternum (and pericardium (?) and ascending aorta (?) of an Indian. This feat earned the Spaniards the respect of the Indians, who then supplied the naked and starving Spaniards with food and clothing, which allowed them to get to Mexico City and back to Spain, where de Vaca later published his diary. Another river, the San Antonio, was adjacent to the massacre at the Alamo, where seven physicians, two of them surgeons, perished. One survivor, who, because he had a wounded leg, was dispatched early as a courier, was also a surgeon. Doctor John Sutherland met up with the beleaguered residual army of Texans led by General Sam Houston, a rugged male chauvinist who enjoyed consuming two carbon fragments. General Houston took his tattered army ahead of the aggressive Mexican Army, led by the Napoleon of the West, General Santa Anna. East of the current city of Houston on a swampy island near the San Jacinto River, the Mexicans were invaded and routed by the Texans during the peak of the siesta hour. Santa Anna surrendered and Sam Houston, the victor, sustained only a broken leg. Because of this single victory won in a single afternoon, one of the largest land acquisitions in the history of the United States took place. A Texas river again was both witness to and vehicle for history-altering events. Each of the Texas rivers has a similar anthology. The Red River separates Texas from our northern neighbors. Except for the Grand River in the south, forming the border with Mexico, the Red River constitutes the longest border between Texas and any of his neighbors. For me, a Texas surgeon, the name of this long "artery" is also symbolic of what has been and continues to be one of the greatest challenges in trauma-the aorta. Just as Texas history has always been of great interest to me, I also have been fascinated with injuries to the aorta since my beginning days of medical school. I take this opportunity to share with you some of my biases and observations and how they have evolved over the years. In my quest, I have discovered over 3,000 scientific articles and book chapter citations. I have also discovered that almost every institution represented in American Association for the Surgery of Trauma has at least one article on aortic trauma in the literature, many of which are single case reports or contain aortic injuries hidden within a report of a series of other wounds. In Doctor Arthur Beall's classic 1960 review of aortic injury [3], he noted that only four abdominal aortic injuries had previously been successfully repaired, two of which were gunshot wounds. Three years later, in November 1963, the world watched as three shots rang out at Dealey Plaza, quite near the Trinity River in Dallas, where President Kennedy sustained a fatal gunshot wound to the head. Three days later, his accused assassin, Lee Harvey Oswald, sustained a gunshot wound to the suprarenal aorta and expired of hypothermia, coagulopathy, and acidosis. These two operations are recorded in The Warren Report and clearly establish the challenges of prehospital transportation, resuscitation, control, and exposure. On reading the Warren Report in 1964, just before starting my surgery internship, my fascination with Texas history and the injured aorta merged into a life-long personal quest I refer to as Red River Anthology. The rivers of Texas-the Frio, Blanco, Colorado, Medina, Grande, Red, and many others-have names also typically used when discussing vascular injuries, i.e., Cold, White, Color, Middle, Grand, and Red. At times even the Angelina-the little angel-enters the operating room or intensive care unit. HISTORICAL OVERVIEW Ninety-seven percent of the knowledge base on aortic trauma has been written since I began medical school 36 years ago this week. Much of this history has been written by members of this organization, in this audience, and often from this city. Before 1960, aortic injury was typified by either instant or early death from exsanguinating hemorrhage or development of chronic complications such as central arteriovenous fistulae, false aneurysms, aortic occlusion among others. Stranahan, in 1953, first successfully repaired a chronic traumatic aneurysm of the thoracic aorta. Passaro, in 1959, reported the first successful repair of an acute blunt injury to the descending thoracic aorta performed by Klassen (37 years ago). Until 1973, the year I first attended an American Association for the Surgery of Trauma meeting, only 44 successfully treated cases of penetrating injuries, most secondary to stab wounds, of the thoracic aorta, had been reported (Ramanathan 1975). In 1974, when I was discussing a paper by your Vice President, Doctor Bob Lim, I stated that he had identified an unmet challenge in vascular surgery-aortic trauma. Ironically, in 1996, that still exists. MILITARY AND AORTIC INJURY No aortic injuries were reported from World War I, and the classic review by DeBakey and Simeone [7] after World War II reported only three injuries to the aorta. In a separate report, 24 injuries to the thoracic aorta without a single death were cited (Harkin 1949). From a follow-up of World War II military experience, Goyette (1954) reported three chronic posttraumatic thoracic aneurysms, one of which resulted in a surgical death, whereas the remaining two were observed for up to 10 years. During the Korean War, 2.4% of the injuries were arterial wounds, and only two aortic injuries were reported in country. Valle (1955) cited eight patients transferred to Japan had thoracic aortic injuries repaired with 0000 silk and with no deaths. Despite an extensive vascular trauma registry from the Vietnam War, Billy and Rich (1971) [5] reported only 99 autopsied and 39 treated cases (total, 138) of aortic injury. Eleven of the treated patients died before surgery (four patients) or postoperatively (seven patients). All had Dacron prostheses. No injuries to the aorta have been reported from the Lebanon, Afghanistan, Croatia, Panama, Somali, or Desert Storm military conflicts. EPIDEMIOLOGY/NATURAL HISTORY Aortic injury may be secondary to penetrating, blunt, and iatrogenic trauma. Aircraft accidents are the epitome of energy transfer, and aortic tears are found in up to 30% of patients in fatal aircraft accidents (Hess 1944, Dulchavasky 1993). A transected aorta is the cause of death in 12 to 30% of adults who die from blunt trauma (Parmley 1958, Greendyke 1966, Kirsh 1976, Kart 1976) [31]. Gunshot wounds to the aorta are more uncommon than blunt injury. In 1970, Symbas reviewed gunshot wounds to the thoracic aorta and reported that only 43 cases had been successfully managed. Of these, 67% developed a fistula between the aorta and a heart chamber or an adjacent great vein. Population based studies for penetrating and iatrogenic injury to the entire aorta are not available, as is also true for blunt abdominal aortic injury. Oller (1992) in reviewing 39 months of data in a North Carolina statewide database found that of 26,617 injured patients, 1,148 vascular injuries were sustained in 978 patients, and were seen in eight trauma centers. Among these vascular injuries were 58 thoracic aortic injuries and 16 abdominal aortic injuries. Using these percentages as a general guide, and roughly extrapolating from these statistics for a population base of 1,000,000, 45 patients would annually sustain 53 vascular injuries, of which 2.7 would be to the thoracic aorta and 0.75 would be to the abdominal aorta. This extrapolation is borne out by reports from trauma centers indicating an average of 2.6 to 2.9 cases seen per year. If one of six automobile accident deaths is caused by aortic rupture and approximately 50,000 traffic deaths occur annually, aortic injury accounts for approximately 8,000 deaths/year in the United States alone (Greendyke 1966). Beattie (1952) reported that before 1950, 90 cases of thoracic injury had been reported, and only seven lived more than 18 hours after injury. Only four patients had survived, and all four had intrapericardial lacerations. Beattie reported the fifth successfully managed case, a stab wound to the ascending aorta. Feczko (1992) in a review of 142 autopsied patients with traumatic thoracic injury, reported that only 2% survived more than 8 hours. Abdominal vascular injury occurs in 15% of all abdominal trauma patients (Feliciano 1984). Except for the inferior vena cava and iliac arteries, the abdominal aorta is the most common abdominal vascular injury (Mattox 1988) [18] Pairolero, in discussion of a paper by Duhaylongsod (1992) [9], pointed out that the mortality from blunt thoracic aortic injury had improved only 10%, at best, during the last 30 years. The mortality from penetrating injury to both the thoracic and abdominal aorta remains in excess of 50%, even among patients who arrive alive at a hospital. At least three patient populations exist. One group dies at the scene. The second group is hemodynamically unstable on arrival or becomes unstable within the first hour and has only a 2% survival rate. The third group lives to undergo aortography (usually exceeding an in-hospital time of 2-6 hours) and has a 75% survival (Maggisano 1995). Traditionally, reports show that 85% of patients with aortic injury die before arrival at the hospital. Of the remaining 15%, the traditional reports indicate that the unoperated mortality is 1% per hour for the next 48 hours. With changes in resuscitation, evaluation, and available treatment options, including nonoperative acute management, this natural history is changing. Among patients arriving alive at a hospital, two distinctly different groups of patients are identified. One group arrives with hemodynamic instability and/or multisystem injury, including central nervous system and orthopedic trauma. The mortality among this group is more than 50%, and most of these deaths occur within 4 hours, including aorta related deaths. The second group of patients appear hemodynamically stable, remain stable, have rigid control of their blood pressure and fluid management, and undergo an orderly evaluation and operative planning for all injuries, including that to the thoracic aorta. In this group of patients, operation is often delayed for several hours, days, weeks, or even months. Aorta-related death or complication is rare to infrequent in this group of patients. The natural history of thoracic aortic injury has been based on historic data. Often cited as having a 1% per hour in-hospital mortality, death from the thoracic aortic injury actually usually occurs within the first 2 to 4 hours, even if undergoing operation very urgently. For patients without early surgery, fistulae and false aneurysms are not unusual complications. Even in 1967, Bennett, with limited numbers of patients, demonstrated that development of chronic aneurysms was not uncommon, and may develop after more than 10 years after the injury, supporting the traditional philosophy that aortic injury requires an operation as soon as the diagnosis is made. Williams (1994) reported a 5-year review of 530 motor vehicle crash fatalities. Ninety patients had 105 aortic injuries, 44 in the descending thoracic aorta (65%), 15 in the ascending aorta (14%), 12 in the distal descending thoracic aorta (11%), and nine in the abdominal aorta (12%). Death occurred within 1 hour in 94% of the patients, and 99% of the patients were dead at 24 hours. In further support of this philosophy, Rodriquez (1990), in discussion of Eddy's paper (1990) [10], reports a 67% mortality when patients with thoracic aortic rupture were transferred to a second institution before definitive treatment, resulting in an injury to operation mean time of 10.5 hours. However, patients transported directly to the trauma center had a 4- to 6-hour injury to operation time, and mortality decreased to 27%. BIOMECHANICS "Points of attachment" explanations (Keen, 1972; Bowen, 1962), "torsion theories" relating to continuing forward movement of the aorta filled with blood (Coermann 1972, Sevitt 1977), and a postulated aortic hydrostatic pressure increased to more than 578 to 660 g's of force (Lundevall 1964) have all been suggested as the mode of injury. Most recently, blunt aortic trauma at all points on the aorta has been proposed to be secondary to an osseous pinch (Cohen 1992, Crass 1990). Using animal, human, and computed tomography enhanced data, Cohen presents convincing support that an "osseous pinch" is significantly more responsible for aortic injury than was originally thought. The aortic arch may be pinched between the spinal column and the manubrium. The descending thoracic aorta may be pinched between the spine and the lower rib cage. LOCATION/PATHOLOGY Two or more sites of injury occur in 6 to 15% of the autopsied cases. Multiple tears occur in 7.8% of autopsy series versus only 1% in surgical series (Rabinsky 1990). When ejected from an automobile, a 27% incidence of aortic rupture is seen, compared with 12% when not ejected. Aortic injury site was 3% ascending, 64% proximal descending, 21% at the diaphragm, 9% abdominal aorta, and 3% at the abdominal bifurcation. Attempts have been made to compare blunt aortic tears with dissecting aneurysms and postulate (incorrectly) that the aortic adventitial wall is intact, with the media and intima ruptured. Actually, all three layers of the aorta are torn, and it is the surrounding tissue that limits the developing false aneurysm (Snedenaa 1990). In the case of the descending thoracic aorta, the parietal pleura contains the hematoma from the aortic tear. Moore (1953) reported the pathologic changes of penetration and "bursting," which occurred with experimental gunshot wounds to the aorta. On rare occasion, trauma may produce injury to an already diseased aorta, as was reported by Gammie (1996) ASSOCIATED INJURIES Fifty percent of patients subsequently found to have aortic injury have no initial clinical findings, but have either mechanism of injury or radiographic findings suggestive of vascular trauma. Upper body hypertension signifying blunt injury to the thoracic aorta was recognized in the early 1960s (Laforet 1965). First rib fractures indicate severe chest wall energy transfer, but are not associated with any higher incidence of aortic injury (Fisher 1982). Combined aortic arch and tracheal injuries have been reported by O'Neill (1982). Sternal fractures are not associated with an increased incidence in aortic injury. Hills (1993) reviewed 172 patients with sternal fractures out of 2,226 motor vehicle crash victims over a 6.5-year period. NO patient with sternal fracture had an aortic transection. Ostremski (1990) and Brookes (1993) found no correlation between sternal fracture and aortic rupture. Ochsner (1989 and 1992) has presented two reports suggesting that pelvic fracture, especially anterior-posterior compression, should elicit suspicion for associated aortic injury. The association between thoracic spine fracture and aortic injury has been documented by Sturm (1990) and Bakker (1996). Woodson (1989) reaffirmed hoarseness (laryngeal paralysis) as a presenting sign of aortic trauma owing to the often associated injury to the left recurrent laryngeal nerve. Howanitz (1990) has reported cardiac injury associated with aortic trauma. IMAGING The presence of one or more of over 20 diagnostic clues appearing on initial or early supine, semierect, or erect chest x-ray films elicits suspicion of thoracic great vessel injury and indicates the need for special imaging. Only 8.3% of patients subsequently found to have an aortic injury did not have one of these suggestive clues (Woodring 1990). Using accessory clinical and radiographic signs an additional 5.6% of patients with aortic injury might have suspicion of an injury. For 1.7% of patients, the only presenting indication of aortic injury is mechanism of injury, which, unless used as an indication of imaging, may lead to missed injuries. Evaluation of serial chest x-ray films obtained at close intervals for the first months after the trauma will detect a mediastinal abnormality in this small percentage of patients. The addition of transesophageal echocardiography (TEE) to the initial screen should also eliminate this initial diagnostic dilemma. Traditional computed tomographic (CT) scans, and now enhanced helico CT scans, are often ordered to evaluate a known mediastinal hematoma. Although this procedure is sensitive for such hematomas, it has historically had a 17% false-positive and 39% false-negative rate (Tomiak 1993). Numerous authors have stated that the aortogram is the standard and that CT scanning delays treatment, and, further, that CT findings are misleading. It has been suggested by others that CT scans might reduce the need for an aortogram (Marvis 1987, Moregan 1992, McLean 1991, Fisher 1994, Gavant 1995, Hills 1994). CT scanning increases costs and almost always leads to angiography; therefore, immediate angiography is recommended (Hunink 1995). However, in 1986, White demonstrated that in his experience with computed tomography alone, 91% of patients subsequently demonstrated to have an aortic tear would go to surgery and that with aortography alone, 91% would go to surgery. With a sensitivity of 100% and a specificity of 75%, TEE is becoming an excellent screening tool (Le Bret 1994). TEE takes an average of 27 minutes compared with aortography, which takes 76 minutes (Kearney 1993). TEE can be performed during laparotomy and repeated as often as indicated (Brathwaite 1994, Catoire 1995, Vignon 1995). On occasion, especially in penetrating trauma, TEE may detect injuries missed with aortography (McIntyre 1994). For these reasons, TEE must become an evaluation tool of the trauma surgeon. Aortography remains the best tool for specific aortic injury diagnosis, except in penetrating injury to the thoracic aorta, where an injury may be missed unless the radiographic beam is exactly perpendicular to the injury. Secondary aortic injuries and vascular anomalies, such as remnant of vascular ring anomalies, are best detected by aortography. Intravascular ultrasonography is in development and soon to be a tool of the vascular and trauma surgeon. All diagnostic tools have advantages and disadvantages. Arteriography is often delayed because of nonavailability of personnel and equipment. Ultrasound studies are often overread. Both CT and TEE do not pick up congenital vascular anomalies such as diverticulum of Kommerell (Knight 1991), remnant of interrupted aortic arch, ductus diverticulum, coarctation, and right sided aortic arch and descending thoracic aorta. The trauma surgeon must use expertise and judgment in determining the best tool for each clinical situation. TREATMENT ADJUNCTS Lopez-Viego (1992) reported 14% of 129 patients with abdominal aortic injuries required an emergency department (ED) thoracotomy, with no survivors. Among 46 patients requiring operating room (OR) thoracotomies, there was a 20% survival. Jackson (1992) reported that of six patients with aortic injury requiring ED thoracotomy, none survived, and, of the patients requiring OR thoracotomy, 17% survived. Pierce (1966) recommended the use of balloon tamponade in cardiovascular trauma. Walt (1975), in discussion before this Association of my paper on suprarenal aortic injury, suggested intra-aortic insertion of a Foley balloon to achieve control. Low (1986) used a transfemoral retrograde aortic occluding balloon in 15 trauma patients that presented hypotensive. Of the survivors, one had a gunshot wound to the abdominal aorta and had a 30-minute balloon occlusion time. Another patient who had balloon occlusion of the abdominal aorta for 90 minutes survived surgery but subsequently died of ischemic bowel. Fifteen other trauma patients had similar injuries but did not have balloon occlusion, and all 15 patients died. These authors were able to insert the aortic balloon via the femoral artery in 58% of patients. Ammons (1990) used an intra-aortic balloon pump (IABP) in patients with both cardiac contusion and ruptured aorta. Use of two or more balloons has been reported by several authors (Gomez 1973, Schwab 1996, Linker 1989). A new generation of large intra-aortic balloon occluders can be inserted via the femoral artery into the thoracic or abdominal aorta for hemorrhage control (Gupta 1989, Low 1985). Twenty-one patients, ten with abdominal aortic injury (four to the suprarenal aorta), had insertion of this device. All patients who arrived at the hospital with no blood pressure but with a cardiac rhythm expired. Of the five patients with an initial blood pressure (BP) between 50/- and 80/- in whom the balloon was inserted, all but one died initially and the survivor died on the third postoperative day. Of the five patients with an initial BP > 80/- and aortic injury, three expired, one in the operating room and the other two many days postoperatively. Lafani (1991) recommended removal of intravascular-retained foreign bodies with the use of balloons. Multiple authors have used balloon tamponade for nontraumatic conditions, especially ruptured abdominal aortic aneurysms (Buhren 1989, Ng 1977, Howard 1971, Senseniz 1981, Lapin 1973, Smith 1972, Hesse 1962, Heimbecker 1964, Robicsek 1970, Hyde 1982, Edwards 1953, Hughes 1954). Other authors have used balloons in trauma, but not for aortic injury (Scalea 1991, Feliciano 1990, Hughes 1954, Berkoff 1971, Belkin 1988). Application of pneumatic antishock garments increase afterload and, therefore, increases blood pressure in areas of aortic injury, which, in turn, increases the sheer forces on the tear. Pneumatic antishock garments are not recommended in cases of potential aortic injury. Except in patients who are heparinized, for many years the graft choice of the Ben Taub Trauma Service has been knitted Dacron. In a report from Brazil, a spiral saphenous vein graft was used only once, out of necessity, and that graft became aneurysmal and was subsequently replaced with a Dacron prosthesis. AORTIC ROOT/ASCENDING AORTA Parmley (1959) [31,32] and Arajarvi (1989) suggest that blunt injury to the ascending aorta is 50 to 72% as common as blunt injury to the isthmus, but because it is more likely to be associated with fatal heart injury or pericardial tamponade, only 7% of patients with this injury reach a hospital, compared with 15 to 24% of the patients with isthmus ruptures. Over a 30-year period at the Ben Taub General Hospital, 33 of 5,760 cardiovascular injuries seen were to the ascending aorta. Many articles in the literature are single case reports, including those presenting as complications, such as aortic fistula (Heller 1903, Gomez 1927, Hubener 1938, Kaufman 1929, Parmley 1958, French 1994) [31,32]. Blunt injury may require aortic root reconstruction (Cleveland 1976, Charles 1976, Kirsh 1976, Violon 1982, Cuadros 1984, Jannelli 1985, Sadow 1988, Marzelle 1989, Boruchow 1991). Successful management of a penetrating injury to the ascending aorta was first reported by Dshanelidze in 1922, although one must question just what caused the stream of blood to be thrown over the shoulder of Cabeza de Vaca in 1535. Others have described their management of such injury (Blalock 1934, Elkin 1941, Elkin 1944, Beattie 1950, McCann 1958, Diveley 1961, Phillips 1979). During an 11-year period, French (1994) treated 17 acute and five chronic traumatic thoracic aneurysms, one of which (chronic) was to the ascending aorta and it was successfully reconstructed with a Dacron graft. Weaver (1989), from the very busy LA County Hospital, reported a 10-year experience of thoracic outlet injuries and found only four patients with injury to the ascending aorta; two required cardiopulmonary bypass for repair. No deaths occurred in this series, and no aortic arch injuries were seen in this series. The mortality of injury to the ascending aorta is difficult to calculate, but appears to be in excess of 50%. AORTIC ARCH In 1989, Bladergroen reported a 12-year experience of cervical and thoracic vascular injuries seen at their trauma center or at autopsy. Although "aorta" was excluded from their query, 112 persons were found to have vascular injury, 48% of whom were pronounced dead in the field or upon arrival at the hospitals. No aortic arch injuries were presented. Penetrating Injury to the Aortic Arch Penetrating wounds to the aortic arch were the earliest such inquiries to be successfully managed, and both reported injuries had arch to innominate vein fistulae (Proctor 1950, McCook 1952). Perkins (1958) noted that until 1958 only five previous instances of successfully managed stab wounds to the thoracic aorta had been reported. He reported an additional case, a 2-cm laceration of the aortic arch at the innominate. The patient presented 2 hours after injury and surgical management was approached via a "trap door" incision. Beall (1962) reported a single case of stab wound to the aortic arch and reviewed ten previously successfully managed cases: one ice pick wound, four stab wounds, and five gunshot wounds. Beall's reported case was through-and-through the aortic arch and had a fistula to the left pulmonary artery. Symbas (1969) reported a reconstruction of the arch secondary to a rupture between the left carotid and left subclavian arteries. Tector (1974) reported repair of a disinsertion of the left carotid artery (secondary to blunt trauma) from the arch using multiple perfusion technique. Vosloo (1990) used inflow occlusion in the surgical management of a stab wound to the aortic arch. Pate (1993) [36] reported an 8-year experience with penetrating injuries to the aortic arch and its branches. Ninety-three patients were treated, 27 had injuries to the aortic arch. Nine were not resuscitated, and of the 11 operated on, 7 died (38.9%). At operation, these authors used innovative temporary shunts in four patients and deep hypothermia and circulatory arrest in one patient. Blunt Injury to the Aortic Arch The first two reported successfully managed blunt aortic arch injuries were wrapped with cellophane (Weisel 1951, Hollingsworth 1952). Bahnson (1953) was the first to resect a post-blunt traumatic aneurysm of the arch by tangential excision with resection of aortic continuity. He was promptly followed in 1954 by DeBakey who successfully repaired a recurrent traumatic arch. Parmley reported 296 cases of blunt aortic injury, 22 of which had arch injury, only one of which was operated on and died. Other early single case reports of blunt injury to the aortic arch include those by Piwnica (1971), Mittal (1972), Tector (1974), and Reyes (1975). Ellison (1977) was apparently the first to successfully use deep hypothermia and circulatory arrest for an acute blunt injury to the aortic arch. Blunt injury to the proximal innominate artery is considered to be an aortic arch injury and is approached by simple bypass procedures without pump, shunts, or heparinization. More than 50 references exist for innominate and thoracic outlet vascular injury (exclusive of aortic arch injury). DESCENDING AORTA Undoubtedly, more articles are written addressing injury to the descending thoracic aorta than the combined literature for the entire remaining aorta. At the aortic arch, the left carotid artery arises from the innominate artery in at least 12 to 15% of the population. In Houston, up to 30% of African-Americans have this anomaly. Kieffer (1994) and Knight (1991) have discussed aberrant subclavian artery anatomy as a variant of a residual vascular ring. This anomaly leads to a diverticulum of Kommerell. These two anomalies when encountered in patients with trauma create both diagnostic and treatment challenges. Penetrating Injury to the Descending Aorta Between 1922 and 1969, only 43 successfully treated cases of gunshot wounds to the thoracic aorta had been reported (Symbas 1970). death usually occurred within 1 hour of injury (Parmley 1958) [32]. Between 0.3 and 1.5% of civilian penetrating thoracic injuries account for 3% of civilian arterial injuries (Sergent 1970). Drapanas reported that 5.3% of 226 patients collected over 27 years had penetrating thoracic aortic injury. Eiseman (1955) presented a case of delayed posttraumatic descending thoracic aneurysm, which was repaired 10 years after injury, but the patient was left paraplegic. The lesion was successfully repaired but postoperative paraplegia occurred. Eiseman cited items that might reduce paraplegia, including shortened cross cl