Martin Borhani

Results of endoluminal grafting in an experimental aortic aneurysm model

We studied the impact of an endoluminally placed stented aortic graft on the geometry of a surgically created abdominal aortic dilation (AAD) in nonatherosclerotic mongrel dogs. Patulous iliac vein patch infrarenal aortoplasty produced a fusiform AAD, doubling the aorta diameter. Lumbar and mesenteric aortic tributaries were preserved and no mural thrombus formed. AADs created in 23 dogs were endoluminally excluded through transfemoral placement of a thin-wall Dacron graft 4 +/- 2 months later. Balloon-expandable stents were used to anchor each end of the graft to the aorta. The graft was crimped radially in its body and longitudinally at its ends to provide longitudinal and radial expandability in these respective zones. Serial color duplex, angiography, and direct caliper measurements were made. Before graft placement, a 19% +/- 11% diameter growth was observed. At graft placement, flow arrest immediately occurred in the space between the graft and the AAD intima in all cases. Although microscopic recanalization of the thrombus in this space was seen at sacrifice 6 and 12 months later, no macroscopic duplex flow was imaged. A 10% +/- 11% reduction in AAD diameter was measured at 6 months (p < 0.001), with no further reduction at 12 months. Graft dimensions remained stable. No anastomotic leaks developed. AAD growth stopped during the first year after effective endoluminal exclusion in normotensive dogs despite patent side branches (< 1.5 mm internal diameter) and no mural thrombus at the time of graft placement. Whether microscopic recanalization of the thrombus that forms outside the graft has an impact after 1 year remains to be seen.

Push–pull theory: Using mechanotransduction to achieve tissue perfusion and wound healing in complex cases

Wound healing has evolved from gauze therapy to the use of proteomics, gene therapy, and cellular-based therapies in the short time span of 45 years. Education for health care providers has not kept pace with the logarithmic acceleration in technology development and treatment options. A patient with a non-healing wound requires a comprehensive work-up, including a focus on six primary points of interest. These points include the status of tissue perfusion, role of bacterial contamination, pressure applied to the tissue, the immune status of the host, co-morbid medical conditions including the patients psychosocial status, and lastly, the status of the wound itself. Even after re-establishing macrovascular flow, many wounds either fail to improve or paradoxically worsen. Potential mechanisms for these unexpected findings include reperfusion injury, no-reflow, and the presence of stunned/hibernating tissue. Using the concept of mechanotransduction, the clinician can simulate normal pulsatile blood flow and re-establish adequate microvascular perfusion. Treatment regimens may include negative pressure therapy, electrical stimulation, ultrasound therapy, and other energy-based modalities.

Transesophageal Echocardiography–Guided Aortic Thrombectomy in a Patient With a Mobile Thoracic Aortic Thrombus

Thoracic aortic thrombi are a well-known cause of distal embolic phenomena. There is a paucity of case reports because of the rarity of this condition, and thus clear management guidelines are lacking. The authors present a case of a mobile thoracic aortic thrombus managed by a surgical approach. This report demonstrates how intraoperative transesophageal echocardiography (TEE) proved to be critical in guiding surgical management. The utility of TEE in the diagnosis and management of aortic thrombi is also discussed. In addition, currently reported management strategies for this complex condition are reviewed.

Cytotoxic Effect of Photodynamic Therapy With Photofrin II on Intimal Hyperplasia

This study evaluates the effect of photodynamic therapy using Photofrin II on prevention and treatment of initimal hyperplasia in a rabbit model of common carotid artery balloon injury. An established model was used. One week after injury (inhibition arm) or 6 weeks after injury (treatment arm), each common carotid artery was exposed to continuous external laser irradiation 48 hours after a 5 mg/kg intravenous dose of Photofrin II (fluency=7.6 joules/cm2, λ=630 nm). Histologic evaluation was performed 6 weeks following therapy in the inhibition arm and 1 day, 1 week, and 6 weeks following therapy in the treatment arm. Each arm included four subgroups (N=10/subgroup): control, drug only, laser only, and drug plus laser. The first two subgroups underwent sham reoperations without laser exposure. In the inhibition arm no effect was seen on intimal cell density or area stenosis 6 weeks after photodynamic therapy. In the treatment arm intimal cell density was markedly diminished in the drug plus laser subgroup sacrificed 1 day and 1 week (but not 6 weeks) after treatment as compared to the remaining subgroups. There was no significant impact on area of stenosis. A marked acute cytotoxic effect of photodynamic therapy on intimal hyperplasia was verified in vivo in the treatment arm. The extracellular matrix was not affected. Cellular repopulation of the treatment zone was observed. No sustained benefit was seen in either the inhibition or the treatment arm. Refinements in dosimetry will be necessary to achieve long-term benefits.

Inferior Vena Cava Stent-Graft Sepsis

We present the case of a patient with a complicated medical history, which included stent grafting as a life-saving measure for an iatrogenic inferior vena cava (IVC) injury. For persistent sepsis secondary to stent-graft infection, the patient underwent extraction of 2 IVC stent grafts, primary repair of a duodenal-caval fistula, and repair of the IVC with an allograft vein patch. Discussion of this case sought to shed light on the intricacies involved in medical decision making in an era of advanced medical technology.

Ischemia/Reperfusion: A Potential Cause for Tissue Necrosis

There are many clinical conditions which are either caused or exacerbated by ischemia/reperfusion injury (IRI). While the wound care community has expanded its understanding of the cellular and molecular mechanisms surrounding the healing process, research involving the microcirculation and its impact on healing has been limited. Reasons for this include but are not limited to an emphasis on the diagnosis and treatment of macrovascular disorders, the absence of surgical options directed at the microcirculation, and a limited number of pharmacologic and/or modality-based therapeutic options. There are also few well-accepted methods for the diagnosis of adequate tissue perfusion, and those that are available have not been transferred well from the lab to the bedside. Clinicians are therefore left with their experience and macro-level observations as a primary means for gauging successful outcomes. Once macro-level changes are apparent, however, it is often too late to intervene therapeutically thus limiting the potential efficacy of treatment options. In this chapter, we will describe the basic anatomy and physiology of the microcirculation and then focus on the consequences, both positive and negative, of the restoration of flow to ischemic tissue. New potentially useful diagnostic methods for assessing tissue perfusion and microcirculation will be presented along with a clinical case that will bring these didactic concepts into a real-world clinical setting. Finally, new treatment options that may mitigate the effects of ischemic reperfusion injury will be discussed.

Renofemoral shunt for protection of abdominal allografts during emergency abdominal aortic surgery

Emergency aortic surgery can be a daunting task in patients with functioning kidney and pancreas allografts because it poses the risk of allograft loss due to prolonged warm ischemia created by aortic cross-clamping. We present a case in which dual allografts, both originating from the right iliac arterial system, were protected from warm ischemia during aortic cross-clamping by creation of a temporary renofemoral shunt between the native left renal artery and right femoral artery. This simple technique maintained pulsatile allograft perfusion during aortic reconstruction for treatment of a ruptured mycotic aortic aneurysm complicated by an aortocolonic fistula.