Balloon-occlusion catheter rupture during balloon-occluded retrograde transvenous obliteration of gastric varices utilizing sodium tetradecyl sulfate: incidence and consequences

Balloon-occluded retrograde transvenous obliteration (BRTO) is an established procedure for the management of bleeding gastric varices in Asia. Invariably, the sclerosant utilized in Asia is ethanolamine oleate and the inventory used (vascular sheaths, balloon-occlusion catheters, and microcatheters) is not available outside Asia. A total of 41 BRTO procedures were performed with a technical and obliterative (gastric varix obliteration) success rate of 95% (n = 39 of 41) and 85% (n = 35 of 41), respectively. Complications were 4.9% (n = 2/41). A total of 6 balloon ruptures occurred (14.6%, n = 6 of 41). One rupture (16.7%, n = 1 of 6 of ruptures) lead to a technical failure and 2 ruptures (33.3%, n = 2 of 6 of ruptures) lead to an obliterative failure. Balloon rupture contributed to 50% of technical failures (n = 1/2, P = .274) and 33% of obliteration failures (n = 2/6, P = .148). In conclusion, the incidence of balloon-occlusion catheter rupture utilizing 3% sodium tetradecyl sulfate (STS) and inventory unique to the United States is significantly higher than in Asia (<8% rupture rate). However, these ruptures have no significant technical or clinical consequences.

Critical limb ischemia: advanced medical therapy

Systemic atherosclerosis and its risk factors are present in the majority of patients with critical limb ischemia. Aggressive medical therapy is an immediate and necessary part of the work-up and management of these patients and will involve a multidisciplinary approach. Risk stratification based on a patient's current clinical cardiovascular condition is important in determining the most appropriate and safe intervention and will allow both the patient and physician to make an informed decision regarding risk- and cost-benefits of treatment.

Criticial limb ischemia: epidemiology

Critical limb ischemia is found in 12% of the U.S. adult population. Its clinical presentation varies from no symptoms to intermittent claudication, atypical leg pain, rest pain, ischemic ulcers, or gangrene. Those with critical limb ischemia have a high incidence of cardiovascular comorbidities that reflect a significant systemic atherosclerotic burden; they have increased functional impairment and increased rates of functional decline compared with persons without critical limb ischemia. Interventions for critical limb ischemia and the impact of major amputation have a significant social and economic impact. At 1 year, 25% of patients will be dead, 30% will have undergone amputation, and only 45% will remain alive with both limbs. At 5 years, more than 60% of patients with critical limb ischemia will be dead.

Critical limb ischemia: cell and molecular therapies for limb salvage

There is a growing interest in developing new limb salvage therapies for patients with severe peripheral artery disease who have no alternative to amputation. Cell and gene therapy studies are showing promise in controlling pain and minor ulceration in patients with significant critical limb ischemia. Among cardiovascular cell and molecular therapy programs, The Methodist Hospital is one of the leading centers in both gene and cell therapy for critical limb ischemia. Randomized controlled trials continue to be performed, and these experimental therapies will move from research to pharmacy within the decade. In conjunction with aggressive medical and surgical management, these emergent therapies may help patients with critical limb ischemia avoid a major amputation and are one of the foundations of any advanced limb salvage program.

Skeletal muscle BOLD MRI: from underlying physiological concepts to its usefulness in clinical conditions

Blood oxygenation-level dependent (BOLD) MRI has gained particular attention in functional brain imaging studies, where it can be used to localize areas of brain activation with high temporal resolution. To a higher degree than in the brain, skeletal muscles show extensive but transient alterations of blood flow between resting and activation state. Thus, there has been interest in the application of the BOLD effect in studying the physiology of skeletal muscles (healthy and diseased) and its possible application to clinical practice. This review outlines the potential of skeletal muscle BOLD MRI as a diagnostic tool for the evaluation of physiological and pathological alterations in the peripheral limb perfusion, such as in peripheral arterial occlusive disease. Moreover, current knowledge is summarized regarding the complex mechanisms eliciting BOLD effect in skeletal muscle. We describe technical fundaments of the procedure that should be taken into account when performing skeletal muscle BOLD MRI, including the most often applied paradigms to provoke BOLD signal changes and key parameters of the resulting time courses. Possible confounding effects in muscle BOLD imaging studies, like age, muscle fiber type, training state, and drug effects are also reviewed in detail.

Acute Aortic Treatment Center

Acute aortic syndromes are a life-threatening set of conditions that require rapid triage and intervention to obtain satisfactory outcomes. The Methodist Hospital is the first institution to establish an Acute Aortic Treatment Center (AATC) based on a clinical care pathway that expedites the care of acute aortic syndromes. This pathway has resulted in a 64% reduction in time to definitive therapy and a reduction in intensive care unit (ICU) length of stay. Establishment of a multidisciplinary pathway to treat acute aortic syndromes improves efficiency and enhances outcomes.

Correlation between hemodynamic parameters and intra-arterial septum motion in DeBakey Type III aortic dissections using 2D pcMRI and 4D MRA

Outcome prediction in DeBakey Type III aortic dissections (AD) remains challenging. Large variations in AD morphology, physiology and treatment exist. A patient-specific approach towards a detailed understanding of the distinct features of each single case might be needed to account for this variation. In particular, an improved characterization of hemodynamic parameters in addition to geometrical quantities may yield deeper insight into this complex disease. Advances in cardiovascular magnetic resonance imaging (CMR) have resulted in pulse sequences that provide time-resolved information of blood velocities, aortic wall motion and, with the administration of exogenous intravenous contrast bolus, contrast passage timings. Here we provide a combined approach in a group of 10 AD patients using 2D phase contrast magnetic resonance imaging (2D pcMRI) and Time-resolved Angiography With Interleaved Stochastic Trajectories (TWIST) to quantify blood velocities, flow rates, maximum signal enhancement from exogenous contrast and time to maximum signal enhancement in the true lumen (TL) and false lumen (FL). The FL-TL dynamic pressure gradient was derived from 2D pcMRI velocity measurements. These hemodynamic parameters were correlated with dynamic parameters for the intra-arterial septum (IS) wall motion derived from 2D pcMRI. A strong positive correlation was found between the TL-FL dynamic pressure gradient and maximum IS extension (R=0.76) as well as with maximum IS contraction (R=-0.51) Taking the ratio of maximum extension to maximum contraction, the correlation increased to R= 0.81. The ratio of TL to FL volumetric flow rate showed a high correlation with the difference in FL-TL times to maximum enhancement (R=0.87) illustrating that higher flow in the TL will result in delayed contrast arrival in the FL and vice versa. Analogous, the TL to FL ratio of maximum enhancement correlated with the TL to FL ratio of the maximum volumetric flow rate (R=0.85). 2D pcMRI and 4D MRA in combination with exogenous intravenous contrast bolus allows characterization of hemodynamics in DeBakey type III AD. High correlations between IS wall motion, TL and FL pressure differences, flows and times to maximum enhancement were found. An extension of our analysis to follow-up imaging examinations are warranted to establish the potential for hemodynamic parameters determined with CMR as a marker for clinical outcome in longitudinal studies.

Biology of metabolic syndrome in a vascular patient

Metabolic syndrome is highly prevalent in vascular patients and has a significant impact on the outcomes of vascular interventions. It comprises of a set of metabolically driven risk factors, including truncal obesity, dyslipidemia, elevated blood pressure and elevated fasting blood glucose. Increased insulin resistance within the context of obesity and hypertension contributes to atherogenic dyslipidemia, hyperglycemia, and prothrombotic and proinflammatory states which lead to the adverse impact of metabolic syndrome on the response to injury and on atherosclerotic disease progression. This review focuses on the complex biology of metabolic syndrome and its relevance to management of vascular patients, including outcomes and implications for the coronary, cerebrovascular and lower-extremity vascular beds.

Integration of the computational fluid dynamics technique with MRI in aortic dissections

Short-term and long-term prognosis and their determining factors of Type III/Stanford B aortic dissections (TB-AD), which separate the aorta distal at the origin of the subclavian artery into a true lumen and false lumen, have been elusive: One quarter of patients thought to be treated successfully, either by medical or by surgical means, do not survive 3 years. Unfavorable hemodynamic conditions are believed to lead to false lumen pressure increases and complications. A better characterization of TB-AD hemodynamics may therefore impact therapeutic decision making and improve outcome. The large variations in TB-AD morphology and hemodynamics favor a patient-specific approach. Magnetic resonance imaging with its capability to provide high-resolution structural images of the lumen and aortic wall and also to quantify aortic flow and kinetics of an exogenous tracer is a promising clinical modality for developing a deeper understanding of TB-AD hemodynamics in an individual patient. With the information obtained with magnetic resonance imaging, computational fluid dynamics simulations can be performed to augment the image information. Here, an overview of the interplay of magnetic resonance imaging and computational fluid dynamics techniques is given illustrating the synergy of these two approaches toward a comprehensive morphological and hemodynamic characterization of TB-AD.

Longitudinal computational fluid dynamics study of aneurysmal dilatation in a chronic DeBakey type III aortic dissection

Computational fluid dynamics, which uses numeric methods and algorithms for the simulation of blood flow by solving the Navier-Stokes equations on computational meshes, is enhancing the understanding of disease progression in type III aortic dissections. To illustrate this, we examined the changes in patient-derived geometries of aortic dissections, which showed progressive false lumen aneurysmal dilatation (26% diameter increase) during follow-up. Total pressure was decreased by 29% during systole and by 34% during retrograde flow. At the site of the highest false lumen dilatation, the temporal average of total pressure decreased from 45 to 22 Pa, and maximal average wall shear stress decreased from 0.9 to 0.4 Pa. These first results in the study of disease progression of type III DeBakey aortic dissection with computational fluid dynamics are encouraging.

Hybrid approach for removal of an errant intra-vascular pedicle spinal fixation screw in the thoracic aorta

Late presentation of aortic injuries secondary to internal fixation hardware is uncommon and generally associated with pseudoaneurysm formation. We herein present a case of transmural migration of a pedicle screw into the descending thoracic aorta, which was revealed incidentally by computed tomography scan after almost 4 years of hardware implantation. Approximately 75% of the pedicle screw was exposed to the bloodstream, and was successfully removed using endovascular segmental exclusion to avoid aortic cross-clamping and an open approach via left thoracotomy. This case illustrates the successful repair of an iatrogenic aortic injury using a hybrid technique.

Technological devices in peripheral percutaneous interventions

New innovations and novel approaches to peripheral arterial occlusive disease have brought enormous benefits to the vascular patient. Diseases that were once manageable only by surgical intervention are now easily and successfully treated by minimally invasive procedures. While the early days of percutaneous intervention were filled with inventions of new devices, today the focus centers on using modern technology and manufacturing to further improve upon these devices. Advances in guidewires and catheters have allowed us to visualize and treat lesions in nearly any vessel, and technology is guiding us towards specialized applications for specific lesions in specific vessels. However, one of the big hurdles remaining in treating arterial occlusive diseases is the rate of restenosis and the need for reinterventions. The location and architecture of these vessels make them uniquely difficult to treat, and call for new technology to address these challenges. Current developments of drug-eluting and bioabsorbable stents are at the forefront of new advancements specifically directed at improving current patency and restenosis rates; perhaps the next step in percutaneous intervention will rely on nanotechnology and the molecular surface engineering that may achieve a new era of devices that are able to target specific cell ligands or proteins to prevent the inflammatory and proliferative response from vessels. The present review will focus on the current literature regarding technological devices in peripheral percutaneous interventions and clinical applications. Future advancements in materials engineering and biotechnology will continue to improve the current standard of percutaneous intervention for peripheral arterial occlusive diseases.

Role of S-1-P receptors and human vascular smooth muscle cell migration in diabetes and metabolic syndrome

BACKGROUND

Sphingosine-1-phosphate (S-1-P) is a bioactive sphingolipid released from activated platelets that stimulates migration of vascular smooth muscle cells (VSMC) in vitro. S-1-P is associated with oxidized low-density lipoprotein (oxLDL) and is important in vessel remodeling. S-1-P will activate multiple G protein-coupled receptors (S-1-PR 1 to 5), which can regulate multiple cellular functions, including cell migration. The aim of this study is to examine the role of S-1-PR signaling during smooth muscle cell migration in response to S-1-P.

METHODS

Human VSMCs were cultured in vitro. Expression of S-1-PR 1 to 5 was determined in conditions mirroring diabetes (40 mM glucose) and metabolic syndrome (25 mM glucose with 20 μM linoleic acid and 20 μM oleic acid). Linear wound and Boyden microchemotaxis assays of migration were performed in the presence of S-1-P with and without siRNA against S-1-PR 1 to 5. Assays were performed for activation of ERK1/2, p38(MAPK) and JNK.

RESULTS

Human VSMCs express S-1-PR1, S-1-PR2, and S-1-PR3. There was no significant expression of S-1-PR4 and S-1-PR5. The expression of S-1-PR1 and S-1-PR3 is enhanced under high glucose conditions and metabolic syndrome conditions. Migration of VSMC in response to S-1-P is enhanced 2-fold by diabetes and 4-fold by metabolic syndrome. In diabetes, S-1-PR1 expression is enhanced, while S-1-PR2 and S-1-PR3 expression are both maintained. In metabolic syndrome, S-1-PR1 and 3 expressions are enhanced and that of S-1-PR2 is reduced. siRNA to S-1-PR1 results in a 2-fold reduction in S-1-P-mediated cell migration under all conditions. siRNA to S-1-PR2 enhanced cell migration only under normal conditions, while siRNA S-1-PR3 decreased migration in metabolic syndrome only. Down-regulation of S-1-PR1 reduced ERK1/2 activation in response to S-1-P, while that of S-1-PR2 had no effect under normal conditions. In diabetes, down-regulation of S-1-PR1 reduced activation of all three MAPKs. In metabolic syndrome, down-regulation of S-1-PR1 and S-1-PR3 reduced activation of all three MAPKs.

CONCLUSION

S-1-PR 1, 2, and 3 regulate human VSMC migration and their expression level and function are modulated by conditions simulating diabetes and metabolic syndrome.

Preliminary findings in quantification of changes in septal motion during follow-up of type B aortic dissections

OBJECTIVE

To quantify longitudinal changes in intra-arterial septum (IS) motion with two-dimensional (2D) phase-contrast magnetic resonance imaging (2D pcMRI) in type B aortic dissections (AD) to improve the understanding of AD and its midterm development.

METHODS

From a database of 42 patients who underwent a dynamic magnetic resonance imaging (MRI) examination at the Acute Aortic Treatment Center of The Methodist DeBakey Heart & Vascular Center, 2D pcMRI image data was available from 10 patients with type B AD for both short-term (mean, 6.6 days; range, 1-10 days; n = 7) and midterm follow-up (mean, 155 days; range, 60-324; n = 5). IS motion was quantified as motion of IS boundary points averaged over the cardiac cycle. Relative change in IS motion was expressed as percent change compared with initial presentation. Maximum IS extension (true lumen [TL] expansion) and contraction (TL compression), IS fraction in phase with aortic flow and correlation of IS motion with aortic flow (IS compliance) were quantified.

RESULTS

IS motion at initial presentation was 0.68 ± 0.2 mm and was reduced at short-term (0.48 ± 0.3 mm; P = .07) and midterm (0.5 ± 0.2 mm; P = .1) follow-up. Trend in relative change of IS motion was variable during short-term follow-up: reduced in three subjects (-75% ± 6%) and elevated in four subjects (48% ± 23%). During midterm follow-up, relative change in IS motion was reduced in four subjects (28% ± 19%) and slightly elevated in one (6.2%). IS contraction decreased with follow-up while IS extension slightly increased. Fraction of IS moving in phase with aortic flow increased but IS compliance decreased, suggesting increasing IS stiffness.

CONCLUSIONS

Reduction of IS motion in AD is seen with short-term and midterm follow-up. Intersubject variability of this trend is high at short-term follow-up but low at midterm follow-up. Detailed analysis of IS motion parameters indicate reduction of IS contraction and IS compliance with time. This has potential implications for endovascular management of type B aortic dissections, as expansion of aortic stent grafts can be limited by a stiff IS.

Percutaneous mechanical thrombectomy for extensive acute lower-extremity deep venous thrombosis in a patient after double-lung transplantation

Venous thromboembolism, which includes deep venous thrombosis (DVT) and pulmonary embolism (PE), has been estimated to affect 25% of patients after major surgery; however, the literature on venous thromboembolism after thoracic transplantation and optimal approach remains limited. We report the status of a 67-year-old female who developed massive right lower-extremity DVT after double-lung transplantation. Because her surgery had taken place a week before this event, it was decided that pharmaco-thrombolysis was contraindicated due to the high risk of bleeding complications in a fresh double-lung transplant recipient. The patient was taken emergently to the operating room for percutaneous mechanical thrombectomy, which provided grade III (complete lysis) and restored venous patency in the affected extremity. This report highlights the successful use of purely percutaneous mechanical thrombectomy for acute DVT in a double-lung recipient, and also advocates inferior vena cava filter placement to prevent embolic events during the mechanical thrombectomy.

Blood oxygenation level-dependent (BOLD) MRI of human skeletal muscle at 1.5 and 3 T

PURPOSE

To evaluate the dependence of skeletal muscle blood oxygenation level-dependent (BOLD) effect and time course characteristics on magnetic field strength in healthy volunteers using an ischemia/reactive hyperemia paradigm.

MATERIALS AND METHODS

Two consecutive skeletal muscle BOLD magnetic resonance imaging (MRI) measurements in eight healthy volunteers were performed on 1.5 T and 3.0 T whole-body MRI scanners. For both measurements a fat-saturated multi-shot multiecho gradient-echo EPI sequence was applied. Temporary vascular occlusion was induced by suprasystolic cuff compression of the thigh. T2 time courses were obtained from two different calf muscles and characterized by typical curve parameters. Ischemia- and hyperemia-induced changes in R2 (ΔR2) were calculated for both muscles in each volunteer at the two field strengths.

RESULTS

Skeletal muscle BOLD changes are dependent on magnetic field strength as the ratio ΔR2(3.0 T)/ΔR2(1.5 T) was found to range between 1.6 and 2.2. Regarding time course characteristics, significantly higher relative T2 changes were found in both muscles at 3.0 T.

CONCLUSION

The present study shows an approximately linear field strength dependence of ΔR2 in the skeletal muscle in response to ischemia and reactive hyperemia. Using higher magnetic fields is advisable for future BOLD imaging studies of peripheral limb pathologies.

Delayed aortic rupture after aortic endograft placement in patient with spinal hardware

Aortic injuries presenting in a delayed fashion after attempted repair of an acute injury are uncommon. We report a case of a patient presenting with an initial aortic injury associated with thoracic spinal hardware placement, which was repaired with an open and endovascular approach, and 5 months later presented with hemoptysis. The cause of hemoptysis was erosion of the descending thoracic aorta between the spinal hardware and the thoracic endograft. The patient underwent descending aorta replacement with a Dacron tube graft, removal of the hardware, and coverage with a pedicled omental flap. This is a unique presentation of erosion of the aorta between the spinal hardware and the earlier placed endovascular stent-graft.