Zachary K. Baldwin

Double-barrel technique for endovascular exclusion of an aortic arch aneurysm without sternotomy.

Purpose: To report the use of commercially available stents and a stent-graft in coaxial orientation to extend the proximal limits of endografting within the aortic arch. Case Report: A 70-year-old man was found to have an asymptomatic 7-cm saccular aortic arch aneurysm, extending distally from the origin of the left carotid artery and involving the left subclavian artery; there was only 11 mm between the innominate artery orifice and the aneurysm. The patient was deemed to be high risk for open surgical repair due to a history of 2 prior sternotomies and the requirement for hypothermic circulatory arrest. A “double-barrel” stent-graft strategy combining retrograde placement of an innominate stent with thoracic stent-graft implantation into zone 0 was successfully executed. The patient has continued to fare well after 10 months on close follow-up. Conclusion: The “double-barrel” stent technique may extend the limits of thoracic endografting by preserving the aortic arch branches while avoiding the need for sternotomy. Using this technique, proximal fixation can be obtained well into the ascending aorta using commercially available devices.

Double-Barrel Technique for Preservation of Aortic Arch Branches During Thoracic Endovascular Aortic Repair

Thoracic endovascular aortic repair (TEVAR) may involve either planned or inadvertent coverage of aortic branch vessels when stent grafts are implanted into the aortic arch. Vital branch vessels may be preserved by surgical debranching techniques or by placement of additional stents to maintain vessel patency. We report our experience with a double-barrel stent technique used to maintain aortic arch branch vessel patency during TEVAR. Seven patients underwent TEVAR using the double-barrel technique, with placement of branch stents into the innominate (n = 3), left common carotid (n = 3), and left subclavian (n = 1) arteries alongside an aortic stent graft. Gore TAG endografts were used in all cases, and either self-expanding stents (n = 6) or balloon-expandable (n = 1) stents were utilized to maintain patency of the arch branch vessels. In three cases the double-barrel stent technique was used to restore patency of an inadvertently covered left common carotid artery. Four planned cases involved endograft deployment proximally into the ascending aorta with placement of an innominate artery stent (n = 3) and coverage of the left subclavian artery with placement of a subclavian artery stent (n = 1). TEVAR using a double-barrel stent was technically successful with maintenance of branch vessel patency and absence of type I endoleak in all seven cases. One case of zone 0 endograft placement with an innominate stent was complicated by a left hemispheric stroke that was attributed to a technical problem with the carotid-carotid bypass. On follow-up of 2-18 months, all double-barrel branch stents and aortic endografts remained patent without endoleak, migration, or loss of device integrity. The double-barrel stent technique maintains aortic branch patency and provides additional stent-graft fixation length during TEVAR to treat aneurysms involving the aortic arch. Moreover, the technique uses commercially available devices and permits complete aortic arch coverage (zone 0) without a sternotomy. Although initial outcomes are encouraging, long-term durability remains unknown.

Catheter-Directed Thrombolysis for Deep Venous Thrombosis

Venous thromboembolism (VTE) represents a significant clinical problem, affecting patients of all age groups, nationalities, and socioeconomic strata. Despite its prevalence, the paradigms for care are largely centered around primary or secondary prophylaxis, with less emphasis on actual treatment of the thrombus. With the recent rapid development of advanced endovascular techniques, it is now feasible to dissolve many thrombi using catheter-directed thrombolysis (CDT), and favorable clinical experience has been reported in over 600 patients. If performed safely, the purported benefits of CDT for DVT include a decreased incidence of persistent phlebitic symptoms, improved quality of life and, possibly, a decreased incidence of recurrent thrombotic events.

Emergency procedures on the descending thoracic aorta in the endovascular era

BACKGROUND Thoracic endovascular aortic repair (TEVAR), initially developed for the treatment of degenerative aneurysms of the descending thoracic aorta, has been applied to the entire spectrum of descending thoracic aortic pathology in both the elective and emergent settings. This single center study evaluates the effectiveness of TEVAR for the treatment of acute surgical emergencies involving the descending thoracic aorta, including traumatic aortic disruption (TAD), ruptured descending thoracic aneurysm (RDTA), and acute complicated Type B dissection (cTBD). METHODS A retrospective review of the medical records of all patients undergoing emergent TEVAR at the University of Mississippi Medical Center between August 2007 and November 2010 was undertaken. Patients were studied for 30-day survival, complications, type of device used for the repair, and technical aspects of the procedure. RESULTS A total of 44 patients (59% male) with an average age of 49 years (range, 16-87 years) underwent emergent TEVAR during the study period. The technical success rate was 100%, with no patient requiring emergent open surgery for conditions involving the descending thoracic aorta at our institution during the study period. The majority (73%) of the repairs were accomplished using commercially available thoracic stent grafts. Abdominal endograft proximal extension cuffs were used in 12 (38%) of the 32 patients undergoing repair of TAD. Twenty-one patients (48%) required coverage of the left subclavian artery, two (10%) of whom subsequently required subclavian artery revascularization. Procedure-related complications included two strokes, one spinal cord ischemia, one unintentional coverage of the left carotid artery, one episode of acute renal failure, and three access site injuries. One patient undergoing repair of TAD had collapse of the stent graft in the early postoperative period. He was successfully treated by placement of an additional stent graft. Seven patients (16%) died within 30 days of surgery. Three of the deaths occurred in patients who had successfully undergone repair of a TAD and died of associated injuries. CONCLUSIONS Emergent TEVAR has become the treatment of choice for acute surgical emergencies involving the descending thoracic aorta. Short-term morbidity and mortality compare favorably with historic results for emergent open surgical procedures on the descending thoracic aorta. Survival is highest in patients undergoing repair of TAD. Using current endograft technology, nearly all emergent conditions of the descending thoracic aorta can be successfully treated with TEVAR.

Contemporary standards for the diagnosis and treatment of heparin-induced thrombocytopenia (HIT)

BACKGROUND Heparin binding to platelet factor 4 (PF4) generates a new antigenic epitope. In an unpredictable fashion, as many as approximately 17% of patients treated with unfractionated heparin (UFH) and approximately 8% treated with low-molecular-weight heparin (LMWH) subsequently develop the anti-heparin-PF4 antibodies that mediate heparin-induced thrombocytopenia and thrombosis (HIT). Very few of those patients with circulating anti-heparin-PF4 antibodies, however, progress to develop clinical HIT (referred to previously as Type II HIT). Only 20% of those who harbor antibodies ( approximately 3% of those exposed to heparin) will manifest the thrombocytopenia subsequently. Even fewer patients (0.03% to 0.09% of those exposed to heparin) experience the marked platelet activation and morbid thromboses characteristic of the HIT syndrome. The pathogenesis of heparin-induced thrombocytopenia (HIT) remains elusive. The pathophysiologic understanding to date has revolved around pathogenic anti-heparin-PF4 antibodies that trigger platelet activation, release of platelet procoagulant microparticles, and resultant thrombosis. The clinical diagnosis of HIT is confusing because current assays to detect anti-heparin-PF4 antibodies do not correlate well with the disease. Currently available assays lack either adequate sensitivity and interlaboratory reproducibility (ie, functional serotonin release assays) or specificity (ie, enzyme-linked immunosorbent assays or ELISAs). CONCLUSIONS Fortunately, the treatment for HIT is not confusing. The purposes of this review are as follows: (1) to examine the relevant clinical definition of HIT, (2) to explore our current understanding as to the pathogenesis of HIT, and (3) to present an algorithm for the identification and treatment of the HIT syndrome.

Endovascular solutions to complications of open aortic repair.

Open repair of abdominal aortic aneurysms (AAAs) or occlusive disease can be complicated by pseudoaneurysm formation and aneurysmal dilatation of native vessels. Reports of reoperation for these new lesions have a mortality rate of 5–17% electively, and 24–88% if ruptured. These complications are commonly several years after initial repair, and progression of other comorbidities can further complicate a repeat exploration. The authors reviewed 5 cases of late complications of open aortic bypass surgery treated with endovascular stent grafting as an alternative to reexploration in patients with increased risk for morbidity and mortality. Over a 6-year experience, 5 patients underwent endovascular stent grafting to repair paraanastomotic aneurysms. Patient records were reviewed and clinical cardiac risk evaluation was performed. Follow-up clinic notes and computed tomography (CT) scans were evaluated. Between October 1996 and February 2002, 5 patients underwent 6 endovascular procedures to repair paraanastomotic aneurysms. Mean period between interventions was 16.6 ±6.27 years (range 10–25); mean age at endovascular procedure 74.2 ±6.37 years (range 67–84). Cardiac clinical risk index increased in 80% of patients by Goldman Risk Index and in 40% by the Modified Cardiac Risk Index. On completion angiography, there was complete exclusion of the paraanastomotic aneurysms in all cases (100%). Length of postoperative stay was 1.5 ±0.547 days. Mean estimated blood loss at conclusion of endovascular procedure was 577 ±546.504 cc (range, 60 cc–1,500 cc). Mean follow-up was 24.4 ±24.593 months (range, 5–67 months). On repeat imaging, all stent grafts remain patent without rupture or endoleak. Endovascular stent grafting to repair late complications of open AAA repair is a viable alternative to reexploration in patients with significant comorbidities. These procedures can be performed without violating the previous surgical planes of sites. The operations can be performed under local anesthesia and with reduced hospitalizations. In patients with increased risk factors, endovascular stent grafting is a less morbid alternative to open surgical techniques.

Sustained inhibition of experimental neointimal hyperplasia with a genetically modified herpes simplex virus

OBJECTIVE Reported herein is a potential strategy for sustained smooth muscle cell (SMC) inhibition with a virulence-attenuated herpes simplex virus (HSV). Experiments were conducted in vitro to demonstrate selective SMC cytotoxicity and in vivo to demonstrate reduced neointimal hyperplasia (NIH) in a clinically relevant animal model. METHODS In vitro: Cultured human umbilical artery smooth muscle cells (UASMC) and venous endothelial cells (HUVEC) were exposed to varying multiplicities of infection (MOI) of a gamma(1)34.5-deleted HSV-1 virus (R849). Cell survival was assessed at 48 and 72 hours with a colorimetric MTT viability assay. In vivo: New Zealand White rabbit external jugular veins (n = 21) were exposed to R849 (2.5 x 10(6) pfu/mL) or culture medium at 110 to 120 mm Hg for 10 minutes, then fashioned as vein patches on carotid arteries. Carotid arteries were ligated distally to decrease blood flow and stimulate a hyperplastic response (ultra-low shear stress model). After 2, 4, 12, and 24 weeks, patched segments were perfusion-fixed with glutaraldehyde and morphometrically examined for NIH formation. RESULTS In vitro: At 48 hours, R849 exhibited preferential cytotoxicity to UASMC compared with HUVEC, with 11% +/- 10% of UASMCs and 49% +/- 8% of HUVECs surviving after infection with MOI = 25 (P <.05). Higher MOI resulted in poor survival of both cell lines. In vivo: Blood flow was similarly reduced in all animals both at surgery (0.9 +/- 0.1 mL/min vs 1.6 +/- 0.3 mL/min) and at harvest (2.7 +/- 0.4 mL/min vs 2.5 +/- 0.5 mL/min). R849-infected patches exhibited markedly less NIH than control patches did at 2 weeks (162 +/- 14 microm vs 49 +/- 6 microm; P <.05), 4 weeks (190 +/- 27 microm vs 67 +/- 8 microm; P <.05), and 12 weeks (233 +/- 18 microm vs 113 +/- 2 microm; P <.05). CONCLUSION The virulence-attenuated HSV strain R849 demonstrates selective cytotoxicity for SMC and is capable of sustained inhibition of NIH in an experimental model of vein graft failure.

Gene Therapy for the Extension of Vein Graft Patency: A Review

The mainstay of treatment for long-segment small-vessel chronic occlusive disease not amenable to endovascular intervention remains surgical bypass grafting using autologous vein. The procedure is largely successful and the immediate operative results almost always favorable. However, the lifespan of a given vein graft is highly variable, and less than 50% will remain primarily patent after 5 years. The slow process of graft malfunction is a result of the veins chronic maladaptive response to the systemic arterial environment, its primary component being the uncontrolled proliferation of vascular smooth muscle cells (SMCs). It has recently been suggested that this response might be attenuated through pre-implantation genetic modification of the vein, so-called gene therapy for the extension of vein graft patency. Gene therapy seems particularly well suited for the prevention or postponement of vein graft failure since: (1) the stimulation of SMC proliferation appears to largely be an early and transient process, matching the kinetics of current gene transfer technology; (2) most veins are relatively normal and free of disease at the time of bypass allowing for effective gene transfer using a variety of systems; and (3) the target tissue is directly accessible during operation because manipulation and irrigation of the vein is part of the normal workflow of the surgical procedure. This review briefly summarizes the current knowledge of the incidence and basic mechanisms of vein graft failure, the vector systems and molecular targets that have been proposed as possible pre-treatments, the results of experimental genetic modification of vein grafts, and the few available clinical studies of gene therapy for vascular proliferative disorders.

Endovascular Stent Graft Repair of a Thoracic Aortic Gunshot Injury

Endovascular treatment approaches offer minimally invasive alternative strategies for the management of vascular injuries. While endovascular stent graft repair of blunt injury to the thoracic aorta is well described, there are few reports of its application for treatment of penetrating injuries of the thoracic aorta. We report the successful treatment of a through-and-through gunshot injury of the thoracic aorta and review how this technology may be applied for the treatment of penetrating thoracic aortic injury.

Ureteroarterial fistula with ruptured anastomotic pseudoaneurysm: Successful management with vascular exclusion, extra-anatomic bypass and nephrectomy: A case report

Ureteroarterial fistula is a rare but life-threatening condition most often arising as a consequence of combined vascular and urologic pathology. Only about 70 cases are reported in the English literature. Principles of repair include complete vascular isolation, extra-anatomic bypass, and urinary stream diversion away from major vascular conduits. The case presented herein is only the second reported instance of fistulization to an anastomotic pseudoaneurysm of an iliopopliteal bypass.