Daniël du Toit

Long-term results of stent graft treatment of subclavian artery injuries: management of choice for stable patients?

BACKGROUND The management of penetrating subclavian artery injuries poses a formidable surgical challenge. The feasibility of stent graft repair is already established. General use of this modality is not widely accepted due to concerns regarding the long-term outcome in a generally young patient population. We review our stent graft experience to examine long-term outcomes. METHODS All patients with penetrating subclavian artery injuries were evaluated for stent graft repair. Patients were excluded when hemodynamically unstable or unsuitable on other clinical and angiographic grounds. Patients were followed prospectively for early (<30 days) and late (>30 days) complications. Clinical and telephone evaluation, Doppler pressures, duplex Doppler, and angiography (when indicated), were used to asses patients at follow-up. Outcomes were recorded as technical success of procedure, graft patency, arm claudication, limb loss, the need for open surgical repair, the presence or absence of other complications, and death. RESULTS Fifty-seven patients underwent stent graft treatment during the 10-year period. Mean age was 34, and 91% were men. There were 53 stab wounds and four gunshot injuries. Pathology included false aneurysms (n = 42), arteriovenous fistula (n = 12), and three arterial occlusions. Early complications: One patient (2%) had a femoral puncture site injury which was managed with open surgical repair. One patient died early due to multiple organ failure related to concomitant injuries. Three patients (5%) presented with graft occlusion and nonlimb threatening ischemia in the first week after treatment. All three patients were managed successfully with a second endovascular intervention. Late complications: Twenty-five (44%) of the 57 patients with subclavian artery injuries were followed-up with a mean duration of 48 months. Two patients died as a result of fatal stab wounds months after their first injuries. Five patients (20%) and three patients (12%) presented with angiographically significant stenosis and occlusions, respectively. The stenotic lesions were successfully managed with endovascular intervention, and the occluded lesions were managed conservatively. No patient experienced life or limb loss or any incapacitating symptoms at the end of the study period. There was no need for conversion to open surgery. CONCLUSIONS This study has reaffirmed the feasibility and safety of stent graft repair in treating stable patients with selected penetrating subclavian artery injuries. The results of this study also confirmed acceptable long-term follow-up without any limb or life threatening complications. We conclude that endovascular repair should be considered the first choice of treatment in stable patients with subclavian artery injuries.

Duodenal injuries: surgical management adapted to circumstances

OBJECTIVES To evaluate the results of an evolving policy of primary repair of duodenal injuries, when considered feasible and safe, complemented by pyloric exclusion if any doubt as to the integrity of the repair existed. PATIENTS AND METHODS A prospective analysis of all patients with surgically identified duodenal injuries treated at a single institution over a 3-year period. RESULTS In 30 patients studied, there were four deaths (13%) and an overall complication rate of 47%. There were 68 associated intra-abdominal injuries in 29 patients. Primary duodenorraphy was employed in 18 patients (60%), pyloric exclusion in 11 (37%) and pancreatoduodenectomy in one patient (3%). No failures of duodenal repair were recorded. CONCLUSION Adverse results in patients with duodenal trauma are largely a reflection of frequent associated injuries and their consequences. Selective, liberal employment of pyloric exclusion, based on individualized intra-operative assessment, can minimize duodenum-related morbidity.

Endovascular management of traumatic cervicothoracic arteriovenous fistula

This study evaluated a single‐centre experience with endovascular repair of traumatic arteriovenous fistula in the cervicothoracic region.

Neurologic outcome after penetrating extracranial arterial trauma

PURPOSE We undertook this study to determine factors that adversely affect outcome in patients with penetrating injury to the extracranial cerebral vasculature. Patients and methods Medical records were reviewed for all patients who had undergone surgical intervention to treat penetrating injury to the extracranial cerebral arteries between January 1989 and December 1999. Forensic autopsy findings were also reviewed for all patients who died as a result of their injury. RESULTS One hundred fifty-one patients with injury to the brachiocephalic artery (n = 21), common carotid artery (n = 98), or internal carotid artery (n = 32) were identified. Overall mortality was 21.2%, and stroke rate in surviving patients was 15.1%. Twenty-five of 32 deaths (78.1%) were stroke-related. Brachiocephalic artery injury was associated with the highest mortality (38.1%), and survivor stroke rate was highest in patients with internal carotid injuries (22.7%). Hemodynamic instability at presentation led to both higher mortality (30.7%) and stroke rate (19.2%). Preoperative angiography did not influence mortality or stroke rate in hemodynamically stable patients. Procedural mortality associated with arterial ligation was 45% (9 of 20 patients), and no surviving patient experienced a change in pre-ligation neurologic state. Nine patients remained neurologically intact after ligation, and 2 patients with preoperative localized neurologic deficit were unchanged postoperatively. In 131 patients, mortality after arterial repair was 17.6%, and in 5 surviving patients (5.4%) an ischemic neurologic deficit developed. Twelve of 15 surviving patients (80%) with preoperative neurologic deficit who underwent arterial repair had improved neurologic status. Cerebral infarcts were confirmed at autopsy in 23 patients; 18 infarcts were ischemic (10, repair; 8, ligation), and 5 infarcts were hemorrhagic (all, repair). No factor was identified that was predictive of ischemic versus hemorrhagic infarction in patients undergoing repair. CONCLUSIONS The presence of hypovolemic shock, internal carotid artery injury, complete vessel transection, and arterial ligation are associated with unfavorable outcome. Penetrating injury to the brachiocephalic, common carotid, or internal carotid artery should be repaired rather than ligated when technically possible. Subsequent ischemic or hemorrhagic cerebral infarction is unpredictable, but overall outcome is superior to that with ligation of the injured artery.

The Endovascular Management of Penetrating Carotid Artery Injuries: Long-term Follow-up

OBJECTIVES To review a single-centre experience with stent-graft treatment of penetrating carotid artery injuries and long-term follow-up. METHODS All stable patients with carotid artery injuries presenting between August 1998 and February 2009 were considered for endovascular treatment. Patients were selected based on clinical and radiological criteria and data were prospectively collected. Follow-up was conducted clinically, angiographically and by telephonic contact. Endpoints were stroke, death and any other stent-graft-related complications. RESULTS A total of 128 patients were treated, of whom only 19 were selected for endovascular management. The recorded technical success rate was 100%, with one early stroke and one non-stent-graft-related procedural death. A further four patients were lost to follow-up. The remaining 14 patients had a mean follow-up of nearly 4 years. No stent-graft-related late deaths, strokes or other complications were reported, although one instance of late stent-graft occlusion was documented. CONCLUSION Endovascular management of penetrating carotid artery injuries is safe and the long-term outcomes justify a more liberal application of this technique in selected patients.

Structure of carotid artery in baboon and rat and differences in their response to endothelial denudation angioplasty

BACKGROUND. Most studies dealing with vascular response to injury have been conducted using rodent and rabbit models, although it is expected that the response to injury in these species is dissimilar from man. AIMS. Here we compare the structure of native carotid artery in rat and baboon and the response of these vessels to endothelial denudation angioplasty. METHODS. In both species, the carotid is a musculoelastic artery. Only baboon carotid has a distinct intima, correlating in size with the weight of male baboons. Complete endothelial denudation of left carotid was performed on eight male baboons and 24 male rats by applying an equivalent pull force with a Fogarthy catheter. The animals were sacrificed prior to and 15 min and 2, 3, 4, 7, 14 and 28 days postinjury, one baboon and three rats per time point. RESULTS. Re-endothelialization in the baboon was complete already on day 4, whereas in the rat it was still incomplete on day 28. The proliferative response to injury was far smaller in the baboon than in the rat, the intimal area increased only by 5-fold in baboon compared with 25-fold in rat, and the number of intimal nuclei by 4-fold in baboon compared with 12-fold in rat. Complete compensatory remodelling of the lumen size occurred in the baboon, whereas in the rat remodelling remained incomplete. The cell types participating in the response were, however, similar: deposition of thrombocytes on denuded luminal surface, expression of α-actin by intimal cells, and lack of any significant white cell infiltration in the denuded intima. CONCLUSIONS. Baboon carotids are very different from rat carotids both in their native structure and in their response to injury. With the limited amount of information available from human vessels, baboon carotids closely resemble human carotids in both respects.

Predictive Control of Series Stacked Flying-Capacitor Active Rectifiers

This paper considers the use of back-to-back, full-bridge, three-level flying-capacitor converters in a series-input-parallel-output connected fashion for the implementation of a solid-state transformer. A finite-control-set model-based predictive control algorithm is developed for the control of the active rectifier front-ends. Pulse width modulation is used for the isolation back-ends. A solid-state transformer is constructed with two of the proposed back-to-back converters and experimental results are presented.

Predictive torque control of an induction machine fed by a flying capacitor converter

This paper presents a model predictive control strategy for an induction machine fed by a three-level flying capacitor converter. In order to reduce the calculation effort (64 different switching possibilities for one prediction step) in a first step the best one of the 19 voltage vectors is determined. After that the best switching state which delivers this voltage vector is determined regarding the flying capacitor voltage balancing and the switching effort, making use of a hysteresis-based algorithm. The proposed control algorithm is verified by several simulations which clearly verify that an effective control of speed, torque, flux and of the flying capacitor voltages is possible.

Model predictive control of a flying capacitor converter with output LC filter for UPS applications

This paper presents a model predictive control strategy for a three-level flying capacitor converter with output LC filter for UPS applications. In order to reduce the calculation effort (64 different switching possibilities for one prediction step) in a first step the best one of the 19 voltage vectors is determined. After that the best switching state which delivers this voltage vector is determined regarding the flying capacitor voltage balancing and the switching effort, making use of a hysteresis-based algorithm. A disturbance observer is used to estimate the output currents of the LC filter which are normally not measured. The proposed principle can be easily extended to flying capacitor converters with more than three voltage levels.

Predictive control for a series stacked flying-capacitor active rectifier

The use of power electronics in power systems have increased in recent years. Because of limitations in the power switches available new converter topologies have been developed to achieve higher voltage ratings. One such topology is a series stack of converters where the input voltage is divided between multiple converters. This paper evaluates three finite-state modelbased predictive control algorithms for the control of such a topology. The algorithms are applied to a series stack of two three-level, flying-capacitor converters. The converters operate as active rectifiers with the possibility of being implemented as a solid state transformer. The different algorithms are compared by means of simulation results.