ANEURYSMS OF THE THORACIC AORTA

Multi-detector computed tomography findings of atypical blunt traumatic aortic injuries: a pictorial review

Traumatic injuries to the aorta are a significant source of morbidity and mortality in trauma patients, which highlights the importance of rapid diagnosis and treatment. Multi-detector row computed tomography has become the primary imaging modality for the imaging assessment of the polytrauma patient because it is fast, noninvasive, and the data sets can be used to create tailored multi-planar reformatted images that optimally display the location and morphology of aortic trauma and its relationship to adjacent structures. Although the classic location of blunt injury to the aorta occurs just distal to the left subclavian artery, aortic injuries may occur at any location along the aorta and in any patient population. Radiologists should be prepared to evaluate these types of injuries in nontraditional planes that are tailored to each examination and to present the data to clinicians using commercially available 3D software for purposes of surgical planning. Here, we review in pictorial form atypical aortic injuries with emphasis on multi-planar reformations.

Methods of cerebral protection in surgery of the thoracic aorta

During the last decade, a considerable increase in the number of operations on the thoracic aorta has been observed. Although patient's outcomes have improved considerably, this surgery is still associated with significant morbidity and mortality due to neurological complications. Various methods have been proposed and widely used as means to protect the brain from ischemic damage. This review summarizes the principal methods of cerebral protection, describes the advantages and disadvantages of each method and their impact on patient outcomes, and discusses the different surgical techniques proposed to minimize the risk of cerebral injuries.

The safety and usefulness of cool head-warm body perfusion in aortic surgery

OBJECTIVE

To determine the safety and usefulness of antegrade hypothermic cerebral perfusion in conjunction with mild hypothermic (tepid) visceral perfusion (so-called cool head-warm body perfusion; CHWB) in aortic surgery; the clinical outcomes and perioperative data on this new technique were retrospectively analyzed.

METHODS

From January 1990 to March 1999, 59 patients underwent ascending aorta or aortic arch surgery using antegrade selective cerebral perfusion (SCP). Three perfusion techniques, differentiated by perfusion temperature, were used, those being deep hypothermia (DH; nasopharyngeal temperature of 20 degrees C, n=14), moderate hypothermia (MH; nasopharyngeal temperature of 28 degrees C, n=17) and CHWB (nasopharyngeal temperature of 25 degrees C and bladder temperature of 32 degrees C, n=28). Selection of the technique largely followed a chronological pattern, in this order: DH, MH and, more recently, CHWB. The three groups were retrospectively compared in terms of operative outcome, duration of cardiopulmonary bypass (CPB) and operation, and intraoperative blood loss.

RESULTS

The early (within 30 days after surgery) mortality/hospital mortality (including operative mortality) was 7.1/21.4, 5.9/11.8 and 3.6/7.1% in the DH, MH and CHWB groups, respectively. The rate of stroke was 7.1, 6.3 and 3.6% in the DH, MH and CHWB groups, respectively. No statistical difference was found in early or hospital mortality, or in the rate of stroke among the three groups. The CPB time, especially the time for rewarming, was significantly shorter in the CHWB than in the DH group. Likewise, the operation time, especially the time after CPB, was significantly shorter in the CHWB than in the DH and MH groups. Blood loss was significantly less in the CHWB than in the DH group.

CONCLUSION

Our data suggest that CHWB perfusion in aortic surgery is a safe and useful technique in shortening the operation time and reducing blood loss, but further prospective study is necessary.

Neurological outcome in a porcine model of descending thoracic aortic surgery. Left atrial-femoral artery bypass versus clamp/repair

BACKGROUND AND PURPOSE

In a porcine model of thoracic aortic cross-clamping (AoXC), we compared the incidence and severity of paraplegia with two surgical techniques: left atrial-femoral artery (LA-FA) bypass (BP group; n = 9) and clamp/repair (CR group; n = 8). The descending thoracic aorta was clamped near its origin and distal to the third intercostal artery for 30 minutes. The intervening three intercostal arteries were ligated and divided.

METHODS

All animals received methohexital anesthesia and were hyperventilated to a Paco2 of 28 to 32 mm Hg. Animals in the CR group received mannitol, and after AoXC, proximal hypertension was controlled with phlebotomy. In the BP group, proximal hypertension was controlled with LA-FA bypass using a centrifugal pump (Biomedicus 520C). Proximal mean arterial pressure, distal mean arterial pressure, central venous pressure, and cerebrospinal fluid pressure were measured; radioactive microspheres were injected at baseline, at AoXC + 5 minutes, at AoXC + 20 minutes, at AoXC off + 5 minutes, and after resuscitation. Neurological function was assessed at 24 hours. The animals were killed, and the spinal cord was removed to determine spinal cord blood flow. Histological cross sections of the lumbar spinal cord were stained with cresyl violet/acid fuchsin and then examined with light microscopy to determine the ratio of altered to total spinal cord neurons.

RESULTS

Fifteen animals survived (one death in each group) and were assessed neurologically at 24 hours after AoXC. Despite better distal perfusion and lumbar spinal cord blood flow in the BP group, during AoXC, and at AoXC off + 5 minutes, there was no significant difference in the severity of spinal cord ischemic injury between groups as assessed neurologically by Tarlov score (P = .90, Mann-Whitney U test). As well, the ratio of altered to total lumbar spinal cord neurons did not differ between groups (P = .24).

CONCLUSIONS

In this chronic porcine model, distal circulatory support with LA-FA bypass afforded better distal perfusion and improved lumbar spinal cord blood flow but did not influence the severity of spinal cord ischemic injury when compared with a clamp/repair technique.

Use of left heart bypass in the surgical repair of thoracoabdominal aortic aneurysms

The purpose of this study was to assess the usefulness of left heart bypass in thoracoabdominal aortic aneurysm surgery. Data from 50 patients who underwent thoracoabdominal aortic aneurysm repair between July 1987 and October 1993 were retrospectively reviewed. In all of them a left heart bypass (left atrium to left femoral artery) with a centrifugal pump (without systemic heparinization) was used. Patient-, disease-, and operation-related variables were analyzed using univariate methods. There were no intraoperative deaths. The in-hospital mortality rate was 8% (n = 4). Survival rates were 77% (+/- 6.5) at 2 years and 62% (+/- 8.7) at 5 years. Renal failure requiring dialysis occurred in five (10%) patients and paraplegia in five (10%). Sixteen (32%) patients had respiratory insufficiency requiring prolonged (> 8 days) ventilation. After univariate analysis, the risk factors for developing a need for postoperative dialysis were found to be the preoperative creatinine level (p = 0.002) and the presence of preoperative arterial hypertension (p = 0.018). A history of peripheral vascular occlusive disease (p = 0.008) was an important risk factor for predicting late death. No factors retained significance in the univariate analysis of hospital deaths and postoperative paraplegia. Renal and spinal ischemic times were substantially reduced in comparison to the theoretic times calculated if cross-clamping had been used. Bypass-related complications were completely absent. The use of a left heart bypass during thoracoabdominal aortic aneurysm surgery may not reduce the global complication rate; the results were similar to those achieved using simple cross-clamping. However, this technique appears to be the method of choice for protecting organ systems at risk during difficult repairs.

Evolution of surgical techniques for aneurysms of the descending thoracic aorta: twenty-nine years experience with 659 patients

Between 1953 and 1993, 659 patients underwent descending thoracic aneurysm resection. The most common etiology was atherosclerosis. Pain was the main presenting symptom. Perioperative mortality fell from 24.2% between 1953 and 1964 to 14.3% between 1970 and 1993. Paraplegia occurred in 4.1% (27/659) patients overall and was little affected by time of operation or use of atriofemoral bypass. Paraparesis occurred in 5.9% (39/659) patients and was reduced by use of atriofemoral bypass. The low rate of paraparesis in the earlier experience was offset by the higher perioperative mortality from hemorrhage, attributable to the use of systemic heparin. The use of heparin-free circuits with centrifugal pumps should be considered in patients likely to have a clamp time greater than 30 minutes. The major source of perioperative morbidity and mortality was cardiac causes (48%) followed by perioperative hemorrhage (14.4%), pulmonary complications (14.4%), and rupture of another aneurysmal segment (12.0%). Late mortality occurred most commonly from cardiac causes (30.6% of deaths) and rupture of another aneurysm (16.3% of deaths). Improvement in results was due to general refinements of management in all areas rather than any single factor. These results indicate that complete preoperative assessment of the patient and the entire aorta is essential and that regular life-long follow-up is critical in order to avoid unnecessary morbidity and mortality from cardiac, cerebrovascular, or subsequent aneurysmal complications.

Toward a durable and safe aortic root reconstruction

The development of acceptable and durable aortic root operations has been interesting. With trial and error there has been a progressive intrusion on the aortic valve and coronary arteries. Many surgeons have contributed to this progression, with the final step being taken by Dr Bentall in 1968. Since that time has come a gradual application of this more complete operation and a better understanding of its advantages.

Digital subtraction spinal cord angiography in patients undergoing thoracic aneurysm surgery

Thoraco-abdominal aortic replacement can be associated with a high incidence of paraplegia. Because the major source of blood supply to the thoraco-abdominal spinal cord is through the anterior spinal artery of Adamkiewicz, reimplantation of intercostal and lumbar arteries could reduce the risk of this operation. We used intraarterial digital subtraction angiography (DSA) for preoperative localization of the anterior spinal artery in 12 patients. This vessel was successfully located in 9 patients, with DSA providing good quality images in all patients. Preoperative knowledge of the origin of this vessel was helpful in the planning of the operation in all patients, but its efficacy as a routine procedure was not established.

A reconsideration of cerebral perfusion in aortic arch replacement

Ten patients underwent aortic arch replacement for aneurysmal disease from 1970 to 1985 using a simplified cardiopulmonary bypass (CPB) technique with partial brachiocephalic perfusion, low CPB flow (30 to 50 ml/kg/min), moderate systemic cooling (26 degrees to 28 degrees C), and topical hypothermic myocardial protection. The arterial line from a single pump head has a Y shape to perfuse the femoral artery (20F cannula) and either the innominate or left carotid artery (14F). Of the 10 patients (mean age, 58 years) with arch aneurysm (6 atherosclerotic, 2 dissections, and 2 degenerative), 3 had previously undergone major cardiovascular operations. Concomitant procedures included aortic valve replacement in 4 and coronary artery bypass grafting in 3. Eight patients survived the procedure, and 1 died three weeks after operation of a ruptured abdominal aneurysm. Among the survivors, CPB time was 119 +/- 36 minutes (+/- standard deviation), myocardial ischemia time was 79 +/- 32 minutes, and intraoperative blood requirement was 5.9 +/- 3.4 units. There were no postoperative strokes. Neurological complications were only minor and included an asymptomatic miosis and ulnar nerve paresthesias in 1 patient and transient vocal cord palsy in another. Applicable in most patients undergoing elective resection of degenerative and atherosclerotic arch aneurysms and in selected patients with arch dissections, this simplified technique of brachiocephalic perfusion without circulatory arrest provides an attractive and safe alternative; the potential advantages are technical simplicity, reduced CPB and operating times, and satisfactory cerebral protection.

Surgery of descending aorta. A method of autotransfusion and intercostal artery preservation

Paraplegia is a tragic complication of surgery of the descending aorta. It is unpredictable and occurs with a similar incidence with or without distal circulatory support. Hypotension, prolonged aortic cross clamp time, and ligation of intercostal arteries have been considered causative factors. Recent experience with ten consecutive patients undergoing descending aortic surgery without shunts employed a method of autotransfusion and intercostal preservation. There were no deaths, renal failure, or paraplegia. The perioperative blood requirement per patient was 2.4 units of blood.

Successful resection of an aortic arch aneurysm using a temporary trifurcation bypass graft

Resection of a syphilitic aortic arch aneurysm in a 62-year-old woman was accomplished using a trifurcation temporary bypass system. The bifurcation graft was sutured end-to-side to the ascending thoracic aorta, to the brachiocephalic trunk and to the left common carotid artery, respectively. The attached third limb end was anastomosed end-to-side to the infrarenal abdominal aorta. This technique enabled a large shunt into the abdominal aorta. Occlusion of the iliac arteries proved to be effective in coping with hypotension while attending to the bypass and the volume replacement. The post-operative recovery was uneventful and the patient has remained well after 43 months.

Descending aortic aneurysmectomy without adjuncts to avoid ischemia

Encouraged by reports on the safety of simple aortic cross-clamping for resection of descending aortic aneurysm, we began utilizing this technique more liberally in 1976. This study was undertaken to examine the results of operation in 36 patients, equally divided into two distinct groups. In Group 1, either extracorporeal circulation or indwelling temporary shunts were employed during the period of aortic occlusion. In Group 2, simple aortic cross-clamping was utilized to manage the lesion. No adjuncts were used to avoid ischemia in the latter group. The only 2 early deaths and two instances of paraplegia occurred in Group 1. In general, there were fewer complications in Group 2, with approximately two-thirds of the patients experiencing an uneventful postoperative course. These differences are considered important since the two groups were similar in respect to the extent and nature of the lesions and other factors contributing to operative risk.

Ischemic myelopathy

Ischemic myelopathy and Angiology of the Spinal Cord have recently drawn the attention of both paraplegists and angiologists, and their details are now fairly well known. Ischemic myelopathies increased with the rise of vascular surgery, but the means of prevention have been carefully studied and the incidence is now decreasing. Twenty-five hundred cases of cord injury have been reviewed, and among 92 nontraumatic cases, 16 ischemic myelopathies have been tabulated. The anatomy and physiology of the spinal cord circulation have been described.

Natural history of arteriosclerotic thoracic aortic aneurysms

Out of 28 patients with arteriosclerotic aortic aneurysm seen between 1965 and 1975, 22 were not surgically repaired. Of these 22 patients, 9 subsequently died of rupture and 7 of unrelated cardiovascular disease, and 6 are living at the time of this study. Mean survival for the group is less than 3 years. All but 1 rupture occurred in aneurysms larger than 10 cm, and recent increase in size preceded rupture in all patients for whom serial roentgenograms were available. This study documents the high risk of rupture of arteriosclerotic aortic aneurysms of the descending thoracic aorta and suggests a more uniform use of surgical management depending on the patient's age and underlying state of health.

Techniques of reinforcing the ascending thoracic aorta

Two techniques of reinforcing the ascending thoracic aorta with Dacron vascular prosthetic material are described. Circular reinforcement has been used patients with fusiform dilatation of the ascending thoracic aorta in whom it was considered that graft replacement was unsuitable, and also in patients with a thin-walled aorta, where reinforcement was thought to be beneficial in preventing dehiscence of an aortic suture line. The techniques are described in two patients who underwent aortic valve replacement and who had aneurysmal dilatation of the ascending thoracic aorta.

Angiographic differentiation of thoracic aneurysms and neoplasms

The distinction between nondissecting aneuryms of the thoracic aorta and thoracic neoplasms may be difficult. The aortographic findings associated with aneurysms may be subtle. However, when the aortogram is properly performed and interpreted and the findings correlated with the plain chest roentgenograms the distinction between aneurysms and neoplasms may be made consistently. The thoracic aortogram should be filmed in at least 2 projections and abdominal aortography and ultrasonography should be performed. With aneurysms the aortographic signs include widening (often slight) of the aortic lumen, thickening of the aortic wall, small ulcer-like collections of contrast and non-filling of regional intercostal arteries. With neoplasms none of these radiological features is to be anticipated, while the aorta will be normal, displaced or narrowed.

Ruptured non-traumatic aneurysms of the descending thoracic aorta

Two cases of ruptured non-traumatic aneurysm of the descending thoracic aorta and a third in which rupture was imminent are discussed with regard to two simple operative techniques, both of which were employed with success. Partial aneurysmectomy was employed in one case and a temporary to permanent shunt graft in the other two. The simplicity of the techniques is such that they may be used in hospitals which are not equipped for extracorporeal perfusion.