Alan Lumsden - Academia.edu (original) (raw)

Papers by Alan Lumsden

Journal of Vascular Surgery: Venous and Lymphatic Disorders, 2013

The standard initial noninvasive imaging modality for diagnosing May-Thurner syndrome is duplex u... more The standard initial noninvasive imaging modality for diagnosing May-Thurner syndrome is duplex ultrasound, but this modality provides only indirect measures and is frequently limited, necessitating further imaging to make the diagnosis. Other noninvasive imaging modalities (computed tomographic venography, time of flight, magnetic resonance venography) allow for direct visualization but lack hemodynamic and anatomic information about what is occurring throughout the cardiac cycle. Intravascular ultrasound is the invasive tool of choice in the setting of iliac vein compression syndrome, but quality, noninvasive imaging modalities have yet to be described. Contrast-enhanced, dynamic magnetic resonance venography allows for detailed imaging of the pelvis as well as dynamic vascular imaging, improving preoperative planning.

Journal of Vascular Surgery, 2011

Dm 0.885 to 0.962 (pϽ0.01) 0.910 to 0.981 (pϽ0.01) Cm 0.883 to 0.948 (pϽ0.01) 0.919 to 0.969 (pϽ0... more Dm 0.885 to 0.962 (pϽ0.01) 0.910 to 0.981 (pϽ0.01) Cm 0.883 to 0.948 (pϽ0.01) 0.919 to 0.969 (pϽ0.01) V 0.955 to 0.992 (pϽ0.01) 0.848 to 0.977 (pϽ0.01

Journal of Vascular Surgery, 2013

Objective: Current interventional techniques rely heavily on operator familiarity with catheters ... more Objective: Current interventional techniques rely heavily on operator familiarity with catheters and wires and on physician skills in effectively navigating through and managing target lesions. A novel robotic technology allows endovascular specialists to remotely control catheter tip deflection and advancement and to coordinate manipulation of currently available wires. The aim of this study was to successfully demonstrate feasibility and safety of navigation to and treatment of iliac and femoral artery lesions using Hansen Medical's vascular control catheter (VCC). Methods: A total of 20 limbs were included in this analysis for a first-in-man trial of the VCC and vascular catheter control system. The local Institutional Review Board approved the trial, and all patients included had symptomatic femoropopliteal occlusive disease. Preoperative imaging was available on all patients. Target lesions in the contralateral superficial femoral artery ranged from mild stenosis to chronic total occlusions (TransAtlantic Inter-Society A through D). Exclusion criteria included previously treated iliac and femoral lesions in the symptomatic leg and a body mass index >35. The operators comprised three experienced interventionalists (two vascular surgeons and an interventional radiologist) and a novice (cardiac surgeon). The primary end point of the study was to demonstrate successful cannulation of the target vessel (ie, navigation to the lesion with wire and catheter) with the Hansen VCC, with no device-related serious adverse events. Secondary end points were to assess the ability to treat lesions using the flexible catheter defined by successful insertion of a guidewire, angiography of the target vessel, delivery of balloon, and/or stent. Procedure times and radiation delivered were analyzed for the group and by operator, and t-test was performed to determine statistical significance. Complications were assessed by clinical examination and ultrasound. Results: Lesions were successfully and safely cannulated in all limbs treated. The VCC performed as designed in all cases. All interventionalists, regardless of experience, navigated the VCC with ease. However, statistically significant differences in navigation time and radiation per case were observed between the experienced and inexperienced interventionalists. There were no access site complications (hematoma, thrombosis, pseudoaneurysm) as evaluated by ultrasound. Conclusions: This initial experience in flexible robotics demonstrates that this technology is both efficacious and safe in the arterial tree. Although robotics provides superior maneuverability compared with current techniques, endovascular experience is crucial to taking full advantage of the extra capabilities. Valuable future considerations will include off-thewall (center lumen) navigation with three-dimensional imaging.

The Journal of Thoracic and Cardiovascular Surgery, 2014

Increased use of continuous-flow left ventricular assist devices for long-term mechanical support... more Increased use of continuous-flow left ventricular assist devices for long-term mechanical support necessitates a better understanding of hemodynamic changes in the native heart and the ascending aorta. By using patient-specific computational models, correlations of potentially adverse hemodynamic conditions with the orientation of the left ventricular assist device outflow graft and their relationship with aortic insufficiency and ischemic events were investigated. Methods: Computed hemodynamic parameters, including wall shear stress, pressure in the ascending aorta, and dissipation of turbulent energy, were correlated with the orientation of the left ventricular assist device graft outflow in 5 patients (4 with the HeartMate II device [Thoratec Corp, Pleasanton, Calif] and 1 with the Heart-Ware Ventricular Assist Device [HeartWare Inc, Framingham, Mass]; 3 patients experienced moderate aortic insufficiency, and 2 patients experienced ischemic events). Hemodynamic conditions for aortic insufficiency and ischemic events were differentiated by linear discriminant analysis.

Journal of Magnetic Resonance Imaging, 2011

Purpose-To image the femoral arteries in peripheral arterial disease (PAD) patients using a bilat... more Purpose-To image the femoral arteries in peripheral arterial disease (PAD) patients using a bilateral receive coil. Materials and Methods-An eight-channel surface coil array for bilateral MRI of the femoral arteries at 3T was constructed and evaluated. Results-The bilateral array enabled imaging of a 25-cm segment of the superficial femoral arteries (SFA) from the profunda to the popliteal. The array provided improved the signal-to-noise ratio (SNR) at the periphery and similar SNR in the middle of a phantom compared to three other commercially available coils (4-channel torso, quadrature head, whole body). Multicontrast bilateral images of the in vivo SFA with 1 mm inplane resolution made it possible to directly compare lesions in the index SFA to the corresponding anatomical site in the contralateral vessel without repositioning the patient or coil. A set of bilateral time-of-flight, T1-weighted, T2weighted, and proton density-weighted images was acquired in a clinically acceptable exam time of ≈45 minutes. Conclusion-The developed bilateral coil is well suited for monitoring dimensional changes in atherosclerotic lesions of the SFA.

Circulation, 2014

The first description of FMD is attributed to Leadbetter and Burkland 7 in a 5½-year-old boy with... more The first description of FMD is attributed to Leadbetter and Burkland 7 in a 5½-year-old boy with severe hypertension and a renal artery partially occluded by an intra-arterial mass of smooth muscle. He underwent a unilateral nephrectomy of an ectopic pelvic kidney, and his hypertension was cured. The authors stated, "It seems quite obvious that by chance we have stumbled on a peculiar anomaly of development affecting a renal artery." 7 The term fibromuscular hyperplasia was introduced in 1958 by McCormack and associates 8 after their observation of 3 patients with arterial hypertension and renal artery

Artificial Organs, 2013

This study aims to investigate differences in hemodynamic conditions in the thoracic aorta for pu... more This study aims to investigate differences in hemodynamic conditions in the thoracic aorta for pulsatile and continuous-flow left ventricular assist devices (LVADs) using computational fluid dynamics (CFD). Patient-specific models were reconstructed from three patients with continuous-flow LVAD (HeartMate II, Thoratec Corporation) and three patients with biventricular assist devices (Excor, Berlin Heart) where only the aortic part was included in the simulations. CFD simulations were performed with constant inflow for the continuous-flow LVADs and time-varying inflow for the pulsatile devices. Differences in flow patterns, wall shear stress (WSS), and dynamic pressure in the ascending aorta were compared for both cases. Retrograde flow patterns were observed in all cases proximal to the location of the outflow cannula anastomosis site. On average, dynamic pressures derived from the retrograde flow velocities were higher in the continuous-flow group with large variations dependent on the angle of the cannula anastomosis relative to the ascending aorta (continuous group: 0.14 ± 0.2 mm Hg, pulsatile group: 0.013 ± 0.008 mm Hg). Elevated WSS contralaterally to the anastomosis site was observed in three of the six models with higher values for the continuous cases. Lower WSS and reduced pressure in the ascending aorta, both favorable hemodynamic conditions, were found in pulsatile versus continuous-flow LVADs by means of CFD. These findings indicate, along with clinical observations reported by others, the superior performance of pulsatile LVADs.

Journal of Vascular Surgery, 2006

Introduction: Extracranial carotid artery aneurysm (CCA), although uncommon, represents a challen... more Introduction: Extracranial carotid artery aneurysm (CCA), although uncommon, represents a challenge to treatment strategy. The purpose of this study was to analyze the treatment evolution and clinical outcome of all patients with CCA over a two decade period. Methods: Clinical data of all patients diagnosed with CCA who underwent interventions from 1984 to 2004 were reviewed. Patients were divided into two groups. Group I (1985-1994) and group II (1995-2004) were compared with regards to clinical presentation, treatment modality, and clinical outcome. Results: A total of 42 cases of CCA were found during the study period (group I, n‫;22؍‬ group II, n‫.)02؍‬ Pulsatile neck mass was the most common presenting symptom (n‫,93؍‬ 93%), followed by neurological symptoms (n‫,6؍‬ 14%). Twenty two (52%) were atherosclerotic aneurysms, fifteen (36%) false aneurysms, and five (12%) posttraumatic aneurysms. Both groups shared similar comorbidities and demographic profiles. All patients in group I underwent operative interventions, which included 12 resection with interposition bypass grafting (55%), six resection with patch angioplasty (27%), and four carotid ligation (18%). In group II, five patients underwent resection with interposition placement (25%) and one carotid ligation (5%). The remaining 14 patients underwent endovascular interventions (70%) which included seven stent-graft exclusions, six carotid stenting with coil exclusions, and one endovascular occlusion. Hospital length of stay was significantly shorter in group II than group I (3.5 vs. 9.4 days, p<0.01). The incidence of cranial nerve injury in group I and II were 14% vs. 5% (p<0.04), respectively. The 30-day mortality/major stroke rates in group I and II were 14% vs. 5% (p< 0.04), respectively. During the follow-up period (0.8 months-20 years; mean, 4.6 years), 16 patients died, largely due to cardiac etiologies (n‫,11؍‬ 69%). Conclusions: Treatment modality of CCA has largely evolved from operative to endovascular intervention at our institution. Treatment benefits of endovascular modality include shorter convalescent and less procedural-related complications. This evolution reflects the improvement of endovascular devices and increased utility of endovascular applications.

The Journal of Trauma: Injury, Infection, and Critical Care, 2004

To quantify longitudinal changes in intra-arterial septum (IS) motion with two-dimensional (2D) p... more To quantify longitudinal changes in intra-arterial septum (IS) motion with two-dimensional (2D) phasecontrast 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.

Annals of vascular surgery, 2014

The success of remotely steerable catheters designed for cardiac ablation procedures in the perip... more The success of remotely steerable catheters designed for cardiac ablation procedures in the peripheral vasculature (in the laboratory and in highly select live cases) has led to the development of a vascular robotic system designed specifically for use in the arterial and venous systems. Limited bench-top and animal testing has been successful, but no randomized, controlled study of the system's safety has been performed. In a 3-phase study, we performed a randomized, controlled trial comparing standard manual catheterization and balloon angioplasty of visceral, renal, and contralateral lower extremity vessels in a porcine model. We also demonstrated feasibility of standard device deployment through the system. There was 100% technical success in test (robotic) and control (manual) arm cannulation and balloon angioplasty of all target vessels, without complications. Pathologic analysis at 7 days revealed significantly fewer traumatic lesions in the test animal arm as compared wi...

Annals of vascular surgery, 2010

Thoracic endovascular aortic repair (TEVAR) has emerged as an acceptable off-label treatment moda... more Thoracic endovascular aortic repair (TEVAR) has emerged as an acceptable off-label treatment modality for aortic dissection. We report our experience in endovascular treatment of this disease with an emphasis on defining the patterns of morbidity. We retrospectively reviewed all (n = 90) patients with thoracic aortic disease who received a TEVAR between February 2005 and December 2007. Aortic dissection was the indication in 23 (26%) patients (48% acute, 52% chronic; Stanford A 17%, Stanford B 83%). For the purposes of this report, we concentrated on the type B dissection (17 patients). Eighty-two percent of the patients were symptomatic on presentation, and 56% of cases were performed either urgently or emergently. Technical success was achieved in 100% of cases, with an average operative time of 178 + or - 119 min. Forty-seven percent required a left subclavian bypass. Thirty-day mortality was 5.5% and morbidity was 12%. Postoperative complications included respiratory failure in ...

Vascular and endovascular surgery

Aortic graft infections, albeit rare, pose a significant treatment challenge. Aortic stump disrup... more Aortic graft infections, albeit rare, pose a significant treatment challenge. Aortic stump disruption, in particular, is a potentially devastating complication. We describe a novel technique of using the parietal peritoneum to bolster a friable aortic stump in a 56-year-old man after an infected aortobifemoral graft was removed. The parietal peritoneal pedicle, in our experience, provides an effective alternative to reinforce an aortic stump when conventional coverage options have been exhausted.

Annales de Chirurgie Vasculaire, 2010

ABSTRACT

Journal of Vascular Surgery, 2001

Sloughing of the scrotal skin is an extremely rare event due to pelvic ischemia. We report herein... more Sloughing of the scrotal skin is an extremely rare event due to pelvic ischemia. We report herein one case of scrotal skin sloughing and impotence after bilateral hypogastric artery embolization for endoluminal aortoiliac aneurysm repair. Postoperative penile plethysmography demonstrated a 75% reduction in the penile brachial index, suggesting that pelvic ischemia is the main culprit for this complication. The devastating

Journal of Surgical Research, 2009

Vascular medicine (London, England), 2014

Calcification in atherosclerotic plaques has been viewed as a marker of plaque stability, but whe... more Calcification in atherosclerotic plaques has been viewed as a marker of plaque stability, but whether calcification accumulates in specific anatomic sites in the carotid artery is unknown. We determined the burden and distribution of calcified plaque in carotid endarterectomy (CEA) tissues. A total of 22 CEA tissues were imaged with high-resolution micro-computed tomography (micro-CT). Total plaque burden and total calcium score using the Agatston method were quantified. The Agatston score (AS) was also normalized for tissue size. Plaque and calcium distribution were analyzed separately for three CEA regions: common segment (CS), bulb segment (BS), and internal/external segments (IES). The average CEA tissue length was 40.83 (interquartile range [IQR] 33.31-42.41) mm with total plaque burden of 103.45 (IQR: 78.84-156.81) mm(3) and total AS of 38.58 (IQR 11.59-89.97). Total plaque volume was 21.02 (IQR: 14.47-25.42) mm(3) in the CS, 37.89 (22.59-48.32) mm(3) in the BS, and 54.05 (36....

Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 2009

Currently, there is no method to predict outcome of endovascular treatment (EVAR) of type III B a... more Currently, there is no method to predict outcome of endovascular treatment (EVAR) of type III B aortic dissections (TB-AD). A new image processing algorithm is presented for quantifying IS displacement from cine 2D phase contrast magnetic resonance images (2D pcMRI) towards a new classification of TB-AD based on IS mobility. Bulk motion of the true aortic lumen (tAB) center (ALC),

Conference proceedings : ... Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual Conference, 2011

Outcome prediction in DeBakey Type III aortic dissections (AD) remains challenging. Large variati... more 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 en...