Radiosurgical Ablation of the Renal Nerve in a Porcine Model: A Minimally Invasive Therapeutic Approach to Treat Refractory Hypertension.

BACKGROUND: Hypertension is strongly associated with cardiovascular diseases such as heart failure, stroke, kidney disease, and has been correlated with an increased risk for heart attack. Current treatment regimens for hypertension are highly inadequate, with reports indicating that only 50.1% of the clinical population with the disease has their blood pressure under control. OBJECTIVE: To study the feasibility of using minimally invasive radiosurgery to ablate the renal nerves as a novel treatment for refractory hypertension, and to assess the safety and efficacy of such an approach. METHODS: A Hanford porcine (miniswine) model (N = 6) was used to investigate the feasibility of using the CyberHeart radiosurgical platform (CyberHeart Inc., Mountain View, CA, USA) to create safe renal nerve ablations. Norepinephrine (NE) levels were measured pre and post treatment. Additionally, renal nerve and arterial histology were studied to examine effect. RESULTS: Plasma norepinephrine levels showed a decrease over the six-month time point. Urea, nitrogen, and creatinine levels showed no changes post procedure. Histology documented no significant arterial injury in targeted areas. Renal nerves documented histologic change consistent with nerve ablation. CONCLUSION: CyberHeart radiosurgery of the renal nerve is feasible and resulted in norepinephrine reduction and renal nerve injury consistent with radiosurgical targeted ablation.

Cost-Effectiveness of Cardiac Radiosurgery for Atrial Fibrillation: Implications for Reducing Health Care Morbidity, Utilization, and Costs.

In the United States (U.S.), atrial fibrillation (AF) is the second-most common cardiovascular condition after hypertension, affecting four million Americans each year. Individuals with AF are three times more likely to be hospitalized over the span of a year when compared to medically matched control groups. The considerably large clinical population of individuals with AF mandates that the cost-effectiveness and efficacy of current treatment regimens for AF have egregious implications for health care spending and public health. Unfortunately, catheter ablation for AF treatment has been shown to make only modest gains in quality-adjusted life years, has yet to demonstrate cost-utility advantages over conventional therapies for AF, and has a reported rate of recurrence for AF that is notably high. Thus, there is a major unmet clinical need for a therapeutic option to treat AF that produces more consistent and efficacious results that are cost-effective. Cardiac radiosurgery as a therapy for AF has the potential to be remarkably cost-effective and produce robust patient outcomes. CyberHeart Inc. has developed the world's first-ever cardiac radiosurgery (CRS) system designed to ablate the heart non-invasively. Procedures that ablate the heart utilizing the Cyberheart CRS system are anticipated to allow higher efficacy and more consistent results than current techniques such as catheter ablation. The aim of this study is to present the current healthcare utilization and expenditures in AF treatment, report the cost-effectiveness of catheter ablation for AF, and project the potential cost-effectiveness of cardiac radiosurgery for the treatment of AF.

Crux vena cava filter.

Inferior vena cava filters are widely accepted for pulmonary embolic prophylaxis in high-risk patients with contraindications to anticoagulation. While long-term complications have been associated with permanent filters, retrievable filters are now available and have resulted in the rapid expansion of this technology. Nonetheless, complications are still reported with optional filters. Furthermore, device tilting and thrombus load may prevent retrieval in up to 30% of patients, thereby eliminating the benefits of this technology. The Crux vena cava filter is a novel, self-centering, low-profile filter that is designed for ease of delivery, retrievability and improved efficacy while limiting fatigue-related device complications. This device has been proven safe and user-friendly in an ovine model and has recently been implanted in human subjects.

Volume associated dynamic geometry and spatial orientation of the inferior vena cava.

BACKGROUND: The geometry and dynamics of the vena cava are poorly understood and current knowledge is largely based on qualitative data. The purpose of this study is to quantitate the dimensional changes that occur in the infrarenal inferior vena cava (IVC), in response to changes in intravascular volume. METHODS: IVC dimensions were measured at 1 cm and 5 cm below the renal veins, on serial contrasted computed tomographic (CT) scans, in 30 severely injured trauma patients during hypovolemic (admission) and fluid resuscitated (follow-up) states. Changes in volume of the infrarenal segment were calculated and correlated with changes in IVC diameter and orientation. The orientation of the infrarenal caval segment was quantified as the angulation of the major axis from the horizontal. A representation of the IVC diameter, as would be seen on standard anterior-posterior venographic imaging, was determined by projecting the CT image of the major axis onto a coronal plane. CT representations of venographic diameters were compared with measurements of the true major axis to assess accuracy of venograms for caval sizing and filter selection. RESULTS: All patients had evidence of a collapsed IVC (<15 mm minor axis dimension) on admission. Mean time between admission and follow-up CT was 49.5 (range: 1-202) days. The volume of the infrarenal segment increased more than twofold with resuscitation, increasing from 6.9 +/- 2.2 (range: 3.1-12.4) mL on admission, to 15.7 +/- 5.0 (range: 9.2-28.5) mL on follow-up (P < .01). At both 1 and 5 cm below the renal veins, the IVC expanded anisotropically such that the minor axis expanded up to five times its initial size accommodating 84% of the increased volume of the segment, while only small diameter changes were observed in the major axis accounting for less than 5% of the volume increase (P < .001). Further, the IVC was left-anterior-oblique in all patients, with the major axis 26 degrees off the horizontal on average. This orientation did not change significantly with volume resuscitation (P > 0.5). The obliquity of the IVC resulted in significant underestimation of caval size of up to 6.8 mm, when using the venographic representation for sizing instead of the true major axis (P < 0.001). CONCLUSIONS: In response to changes in intravascular volume, the IVC undergoes profound anisotropic dimensional changes, with greater displacement seen in the minor axis. In addition, the IVC is oriented left-anterior oblique and caval orientation is not altered by changes in volume status. IVC obliquity may result in underestimation of caval size by anterior-posterior venogram.

Evaluation of the Crux IVC Filter in an animal model.

PURPOSE: To determine the safety and performance of a new inferior vena cava (IVC) filter in an ovine model and evaluate the retrievability at 5 weeks. METHODS: The Crux Vena Cava Filter (VCF) is composed of 2 nitinol spiral supports with a polymeric filter suspended between them. Retrieval tails on each end facilitate retrieval. Twelve filters were placed in the infrarenal IVCs of 12 sheep. The vessels were imaged pre and post deployment to assess acute device performance. At 5 weeks, the vessels were re-imaged to evaluate continued device performance and vessel integrity. Nine of 12 filters were retrieved, and the animals were returned to their housing. The other 3 animals were sacrificed, and the filters and vessels were processed for gross and histological examination. At 9 weeks, 4 weeks after filter retrieval, vessel integrity of the remaining 9 animals was again assessed under fluoroscopy. The animals were sacrificed, and the IVCs were explanted for study. RESULTS: All 12 filters were implanted without complications at the intended deployment site and remained fixed over the implantation period. At 5 weeks, the filters intended for recovery were successfully retrieved, with a mean capture time of 9.6+/-13.7 minutes. There were no complications during the 4-week follow-up after filter retrieval. Post-retrieval imaging at 5 and 9 weeks showed no visible signs of vessel wall damage. Histological study of 3 explanted vessels and filters revealed slight neointima encapsulation of the filter elements and minimal incorporation. Gross examination of the post-retrieval vessel walls after the 4-week healing period showed minimal superficial vessel damage; histology showed minimal residual signs of hemorrhage, with little to no inflammatory reaction. CONCLUSION: The Crux VCF was deployed and safely retrieved without incident at 5 weeks in an animal model. There was no significant damage seen to the IVCs 1 month after filter retrieval.

"Over-the-wire" inversion saphenectomy: a simple, minimally invasive vein harvesting technique for arterial bypass.

PURPOSE: To examine the feasibility and clinical outcome of a novel, minimally invasive technique for harvesting the great saphenous vein (GSV) for use in peripheral arterial bypass surgery. METHODS: Between May 2001 through March 2003, 27 patients (15 men; mean age 71+/-10 years) underwent extremity bypass procedures for limb salvage (88%) or disabling claudication (12%) using the inversion technique to harvest the GSV. The veins were turned "inside out" using a unique catheter and guidewire system. With the endothelial surface exposed, valve leaflets were excised, and adherent thrombus was washed away. Veins were inverted again to turn the endothelial surface back inside the lumen for use as a bypass conduit. RESULTS: Inversion vein harvesting and arterial bypass were completed in 24 (89%) of 27 patients; 2 patients were treated with synthetic grafts because of small GSVs. Another patient was found after vein harvesting to have inadequate arterial outflow despite a good quality conduit. The average vein length was 45+/-10 cm; a mean 4+/-1 incisions were made, including those for arterial exposure. Incisions made to divide vein tributaries averaged 2 cm in length. Duration of vein harvesting was 25 minutes (range 5-80). Wound complications were minor (2 hematomas, 2 cases of erythema, 2 seromas). Of 6 grafts that occluded after 30 days, 5 involved small-diameter vein grafts (< 3.5 mm). At a mean 12 months, primary and assisted primary graft patency rates were 88% (14/16) and 94% (15/ 16), respectively, for grafts with minimum diameters > or = 4 mm versus 38% (3/8) primary patency for veins < 4 mm (n = 8, p < 0.001). The limb salvage rate was 92% (22/24). CONCLUSIONS: Over-the-wire inversion saphenectomy is a simple and reliable minimally invasive technique for arterial bypass. Incisions are small and cosmetically superior to those of the traditional long incision method. One-year follow-up suggests that grafts harvested by inversion technique have excellent durability when the minimum vein diameter is > or = 4 mm, as determined by preoperative vein mapping.

Controlled localized thrombolysis with the "turbo" trellis to treat acute arterial occlusions following major surgery.

PURPOSE: To present the management of acute arterial ischemia following major abdominal and orthopedic surgery using a percutaneous thrombectomy device and a low dose of thrombolytic agent. CASE REPORT: A 38-year-old woman with T-8 paraplegia from a traumatic fall developed pelvic osteomyelitis, for which a left hemipelvectomy, hysterectomy, and partial vaginal resection were performed. Twelve hours after the procedure, the patient developed an ischemic left leg. Computed tomographic angiography demonstrated an occlusion of the left external iliac and common femoral arteries. A Turbo Trellis percutaneous thrombectomy device was used to lyse the left external iliac artery thrombosis using 1 mg of tissue plasminogen activator infused between the proximal and distal occluding balloons of the device. Total dispersion time was 5 minutes. There was complete thrombus removal without any significant bleeding complications. At 6 months, the artery remains widely patent. CONCLUSIONS: Combination therapy with mechanical thrombectomy devices and low dose thrombolytic agents can be used to treat acute arterial occlusions at a single setting. The increased speed of the Turbo Trellis may allow for smaller doses of thrombolytic agents and shorter treatment times.

Hypogastric artery bypass to preserve pelvic circulation: improved outcome after endovascular abdominal aortic aneurysm repair.

OBJECTIVE: This study was carried out to compare the functional outcomes after hypogastric artery bypass and coil embolization for management of common iliac artery aneurysms in the endovascular repair of aortoiliac aneurysms (EVAR). METHODS: Between 1996 and 2002, 265 patients underwent elective or emergent EVAR. Data were retrospectively reviewed for 21 (8%) patients with iliac artery aneurysms 25 mm or larger that involved the iliac bifurcation. Patients underwent hypogastric artery bypass (n = 9) or coil embolization (n = 12). Interviews about past and current levels of activity were conducted. A disability score (DS) was quantitatively graded on a discrete scale ranging from 0 to 10, corresponding to "virtually bed-bound" to exercise tolerance "greater than a mile." Worsening or improvement of symptoms was expressed as a difference in DS between two time points (-, worsening; +, improvement). RESULTS: There was no difference in age (72.6 +/- 7.3 years vs 73.1 +/- 6.4 years), sex (male-female ratio, 8:1 vs 11:1), abdominal aortic aneurysm size (60.1 +/- 5.9 mm vs 59.3 +/- 7.0 mm), or number of preoperative comorbid conditions (1.9 +/- 0.8 vs 2.1 +/- 0.8) between hypogastric bypass and coil embolization groups, respectively. Mean follow-up was shorter after hypogastric bypass (14.8 vs 20.5 months; P <.05). There was no difference in the mean overall baseline DS between the bypass and the embolization groups (8.0 vs 7.8). Six (50%) of the 12 patients with coil embolization reported symptoms of buttock claudication ipsilateral to the occluded hypogastric artery. No symptoms of buttock claudication were reported after hypogastric bypass (P <.05). There was a decrease in the DS after both procedures; however, coil embolization was associated with a significantly worse DS compared with hypogastric artery bypass (4.5 vs 7.3; P <.001). In 4 (67%) of 6 patients with claudication after coil embolization symptoms improved, with a DS of 5.4 at last follow-up. This was significantly worse than in patients undergoing hypogastric artery bypass, with a DS of 7.8 at last follow-up (P <.001). There was no difference between the groups in duration of procedure, blood loss, length of hospital stay, morbidity, or mortality (0%). CONCLUSIONS: Hypogastric artery bypass to preserve pelvic circulation is safe, and significantly decreases the risk for buttock claudication. Preservation of pelvic circulation results in significant improvement in the ambulatory status of patients with common iliac artery aneurysms, compared with coil embolization.

Aneurysm enlargement following endovascular aneurysm repair: AneuRx clinical trial.

OBJECTIVE: The purpose of this study was to determine the incidence and significance of aneurysm enlargement, with or without treatment, in relation to the primary end points of rupture, surgical conversion, aneurysm-related death, and survival following endovascular repair. METHOD: Aneurysm (AAA) size changes and clinical outcome of all patients treated from 1997 through 1998 during the Phase II AneuRx multicenter clinical trial of endovascular AAA repair were reviewed. Aneurysm dimensions and the presence or absence of endoleak were determined by an independent core laboratory, with enlargement or shrinkage defined as a diameter change of 5 mm or more compared with baseline. RESULTS: Among 383 patients (89% men, 11% women, age 73 +/- 9 years), with a mean device implant time of 36 +/- 11 months (median = 39 months), aneurysm diameter decreased from 5.7 +/- 1.0 at baseline to 5.2 +/- 1.0 at 3 years (P =.0001). A total of 46 patients (12%) experienced AAA enlargement, 199 patients (52%) had no change in AAA diameter, and 138 patients (36%) had a decrease in AAA diameter of 5 mm or more. Significant risk factors for enlargement included age (enlargement patients were 4 years older on average than patients with aneurysms that decreased in size; P =.002) and the presence of an endoleak (P <.001). Among patients with endoleak at any time, 17% had aneurysm enlargement, whereas only 2% of patients without endoleak had aneurysm enlargement (P <.001). Patients with enlargement were more likely to undergo secondary endovascular procedures and surgical conversions (P <.001). Twenty patients (43%) with enlargement underwent treatment, and 26 patients were untreated. There were two deaths following elective surgical conversion and one death in a patient with untreated enlargement and a type I endoleak. Three aneurysms ruptured: one with enlargement, one with no change, and one with a decrease in aneurysm size; all three aneurysms were larger than 6.5 cm. Kaplan-Meier analysis showed that freedom from rupture at 3 years was 98% with enlargement, 99% with no change, and 99% with decrease in AAA size (log-rank test, not significant). Freedom from AAA death at 3 years was 93% in patients with enlargement, 99% in no increase, and 99% in decrease (P =.005). Survival at 3 years was 86% with increase, 82% with no change, and 93% with decrease (P =.02). CONCLUSIONS: Aneurysm enlargement following endovascular repair was not associated with an increased risk of aneurysm rupture or decrease in patient survival during a 3-year observation period. Aneurysm size rather than enlargement may be a more meaningful predictor of rupture. Close follow-up and a high re-intervention rate (43%) may account for the low risk of rupture in patients with enlargement. The long-term significance of aneurysm enlargement following endovascular repair remains to be determined.

Endograft technology: highlights of the past 10 years.

The past decade has seen the evolution of an exciting technology that has changed forever the treatment of aortic aneurysmal disease. From rather crude homemade stent-grafts constructed in the surgical suite to elegant commercially manufactured devices in a variety of configurations and sizes, the aortic endograft has experienced a meteoric rise in popularity to become a beneficial, minimally invasive therapy that can obviate the risk of rupture and death. There are now 3 approved endovascular devices on the market for infrarenal abdominal aortic aneurysm repair, and it is likely that additional and improved devices will become available in the future. This review revisits the developmental history of the aortic endograft, noting the ongoing refinements that have arisen from our experiences with the growing population of stent-graft patients. Although research continues to search for solutions to the problems of endoleak and migration, long-term results even with the earlier second and third-generation devices are better than has been achieved with open surgical repair.

CaRESS: carotid revascularization using endarterectomy or stenting systems.

The primary objective of the CaRESS Phase I trial is to determine the sample size needed to reliably test the hypothesis that carotid stenting systems with distal embolic protection (CAS) is equivalent to carotid endarterectomy (CEA) in the treatment of symptomatic and asymptomatic carotid artery disease in a broad-risk population. A total of 397 patients were treated at 14 clinical centers. The primary endpoint results of combined all-cause mortality and stroke at 30-days and 1-year are presented. The CaRESS Phase I study was able to closely resemble clinical practice and results suggest equivalence between treatment groups.

Stent graft migration after endovascular aneurysm repair: importance of proximal fixation.

OBJECTIVE: We reviewed the incidence of stent-graft migration after endovascular aneurysm repair in a prospective multicenter trial and identified factors that may predispose to such migration. METHODS: All patients who received treatment during the course of the multicenter AneuRx clinical trial were reviewed for evidence of stent-graft migration over 5 years, from 1996 to 2001. Post-deployment distance from the renal arteries to the proximal end of the stent graft and the proximal fixation length (length of the infrarenal neck covered by the stent graft) were determined in patients for whom pre-procedure and post-procedure computed tomography scans were measured in an independent core laboratory. RESULTS: Stent-graft migration was reported in 94 of 1119 patients, with mean time after device implantation of 30 +/- 11 months. Freedom from migration was 98.6% at 1 year, 93.4% at 2 years, and 81.2% at 3 years (Kaplan-Meier method). Subset (n = 387) analysis revealed that initial device deployment was lower in 47 patients with migration, as evidenced by a greater renal artery to stent-graft distance (1.1 +/- 0.7 cm), compared with 340 patients without migration (0.8 +/- 0.6 cm; P =.006) on post-implantation computed tomography scan. Proximal fixation length was shorter in patients with migration (1.6 +/- 1.4 cm) compared with patients without migration (2.3 +/- 1.4 cm; P =.005). There was significant variation in migration rate among clinical sites (P <.001), ranging from 0% to 30% (median, 8%), with a greater than twofold difference in migration rate between the lowest quartile (6%) and the highest quartile (15%) clinical sites. Univariate and multivariate analysis revealed that renal artery to stent-graft distance (P =.001) and proximal fixation length (P =.005) were significant predictors of migration, and that each millimeter increase in distance below the renal arteries increased risk for subsequent migration by 5.8% and each millimeter increase in proximal fixation length decreased risk for migration by 2.5%. Pre-implantation aortic neck length, neck diameter, degree of device oversizing, correct versus incorrect oversizing, device type (stiff vs flexible), placement of proximal extender cuffs at the original procedure, and post-procedure endoleak were not significant predictors of migration. Migration was treated with placement of extender modules in 23 patients and surgical conversion in 7 patients; 64 patients (68%) with migration have required no treatment. CONCLUSIONS: Stent-graft migration among patients treated in the AneuRx clinical trial appears to be largely related to low initial deployment of the device, below the renal arteries, and short proximal fixation length. Significant variation in migration rate among clinical sites highlights the importance of the technical aspects of stent-graft deployment. Advances in intraoperative imaging and deployment techniques that have been made since completion of the clinical trial facilitate precision of device placement below the renal arteries and should increase proximal fixation length. Whether this, together with increased iliac fixation length, will result in lower risk for migration remains to be determined in long-term follow-up studies.