Search PubMed⌕ Search

Biomedical subjects

L N Benson

Publications and source records attributed to L N Benson.

At least 37 records · Page 2Linked to original sources
PubMed2001

The effect of implantation of aortic stents on compliance and blood flow. An experimental study in pigs.

Balloon dilation of coarctation of the aorta has been found to be an effective modality for treatment. Recently, in the older child and adult, implantation of endovascular stents has been considered a clinical alternative to dilation alone. Little is known, however, of the effect of implantation of stents on aortic compliance. To investigate this impact of implantation, we studied 18 piglets, divided into experimental and control groups. At median weight of 14 kg, 2 pairs of ultrasonic crystals were implanted on the aortic wall. After 1 week, all animals underwent catheterization. In the experimental group, a 3 cm long balloon expandable stent was implanted in the descending thoracic aorta between the pairs of crystals. Measurements of arterial pressure and dimensions were performed before implantation and immediately thereafter, and at follow-up catheterization. The index of stiffness, beta, and the the elastic modulus of aortic pressure-strain, were calculated as indexes of arterial compliance. The change in compliance during the period of study was not different between groups. At follow-up, no difference was observed between groups in the velocity of the aortic pulse wave, the augmentation index, or the maximum velocity of flow of blood. The stents remained patent and did not affect aortic growth or medial wall thickness. There was no difference between groups in levels of plasma renin activity and serum aldosterone. In this animal model studied over the short term, therefore, implantation of stents does not affect aortic compliance. Further studies are required to elucidate the long term effects of stents on the hemodynamics affecting the aortic wall and local flow dynamics.

Animals↗
PubMed2001

Safety and outcomes of thrombolysis with tissue plasminogen activator for treatment of intravascular thrombosis in children.

OBJECTIVES: In this study, we tried to determine the safety and outcomes of thrombolysis with tissue plasminogen activator of intravascular thrombus. STUDY DESIGN: Eighty consecutive children were treated between 1985 and 1999 in a tertiary care setting in a retrospective case series. There were 65 arterial thrombi (56 after cardiac catheterization) and 15 venous thrombi treated with tPA at an average dose of tPA of 0.5 mg/kg/hour for a median duration of 6 hours. RESULTS: Clot resolution was complete in 65% of children, partial in 20%, and there was no effect in 15%. There were major complications in 40%, minor complications in 30%, and no complications in 30%. Two patients had cerebral ischemia secondary to hypotension because of profound bleeding, with intracranial hemorrhage in 2 additional patients. Clot resolution was not related to patient age or weight, dose, and duration of tPA therapy and fibrinogen levels. However, complications were more likely in patients who weighed less, had a longer duration of therapy, a greater decrease in fibrinogen levels, and who failed to have resolution of their clot. CONCLUSIONS: tPA therapy can be effective in the thrombolysis of intravascular thrombus in children, but is associated with a low margin of safety and an unknown risk-benefit ratio.

Adolescent↗
PubMed2001

Extracardiac conduit versus lateral tunnel cavopulmonary connections at a single institution: impact on outcomes.

OBJECTIVE: To compare outcomes of extracardiac conduit and lateral tunnel Fontan connections in a single institution over a concurrent time period. METHODS: Between January 1994 and September 1998, 60 extracardiac conduit and 47 lateral tunnel total cavopulmonary connections were performed. Age, sex, and weight did not differ between the 2 groups. Compared with the lateral tunnel group (LT group), patients undergoing the extracardiac conduit procedure (EC group) had a trend to a higher incidence of morphologically right ventricle (EC group 48% vs LT group 32%; P <.09), a higher incidence of isomerism/heterotaxy syndrome (EC 22% vs LT 0%; P <.001), worse atrioventricular valve regurgitation (EC 11% moderate-plus vs LT 0%; P <.06), and lower McGoon indices (EC 1.8 +/- 0.5 vs LT 2.1 +/- 0.5; P <.03). Preoperative arrhythmias, transpulmonary gradients, room air oxygen saturations, ejection fractions, ventricular end-diastolic pressure, and pulmonary artery distortion did not differ between groups. Cardiopulmonary bypass times and fenestration usage were similar in both groups. RESULTS: Overall operative mortality was 5.6% and did not differ between groups. The LT group had a significantly higher incidence of postoperative sinoatrial node dysfunction (45% vs EC group 15%; P <.007), supraventricular tachycardia (33% vs EC group 8%; P <.0009), and need for temporary postoperative pacing (32% vs 12%; P <.01). Median duration of intensive care unit stay (EC 2 days, range 1-10 days, vs LT 2.8 days, range 1-103 days; P <.07) and ventilatory support (EC 1 day, range 0.25-10 days, vs LT 1 day, range 0.25-99 days; P <.03) were all longer in the LT group. Median chest tube drainage (EC 8 days, LT 9 days) was similar in both groups. Follow-up averaged 2.5 +/- 1.4 years in the EC group and 2.8 +/- 1.9 years in the LT group. There were 2 late deaths. Overall survival is 94% at 1 month, 92% at 1 year, and 92% at 5 years. Late ejection fraction or atrioventricular valve function did not differ between groups. Intermediate follow-up Holter analysis showed a higher incidence of atrial arrhythmias in the LT group (23% vs 7%; P <.02). Multivariable analysis showed that (1) prolonged cardiopulmonary bypass time was the only independent predictor for perioperative mortality, prolonged ventilation and intensive care unit length of stay, and increased time to final removal of chest tube drains and (2) lateral tunnel Fontan connection is an independent predictor of early postoperative and intermediate atrial arrhythmias. CONCLUSIONS: Although patients in the EC group were at higher preoperative risk, their outcomes were comparable with those of the LT group. Use of the extracardiac conduit technique for the modified Fontan operation reduces the risk of early and midterm atrial arrhythmia.

Arrhythmias, Cardiac↗
PubMed2001

Intravascular and intracardiac stents used in congenital heart disease.

Intravascular or intracardiac stenoses occur in many forms of congenital heart disease or after attempted surgical repair. Although balloon dilation is one option for management, restenosis can occur due to elastic recoil immediately after the procedure. To address to such stenotic lesions, many reports support implanting endovascular stents to provide a framework for vessel expansion. Both balloon-expandable fixed tubular mesh stainless steel devices, and self-expandable stents have had an extensive clinical application. In pediatric patients, stents are used for a variety of stenoses, such as systemic venous obstruction pathways (eg, Mustard, Fontan baffle, or bidirectional cavopulmonary connections), pulmonary artery, right ventricular to pulmonary conduits, aortic coarctation, the arterial duct, aorticopulmonary collaterals, or postoperative systemic to pulmonary shunts. Because of improvements in device profile, implantation rates have increased. Complications such as stent fracture, migration, aneurysm formation, and in-stent restenosis occur but only rarely. This latter event may be because of intimal hyperplasia and/or continued vessel (and patient) growth related to the stent diameter. As such, some instances require redilation to manage the acquired lesion. Stent application has importantly altered management algorithms in congenital heart disease.

Adolescent↗
PubMed2001

Endovascular stents in the management of coarctation of the aorta in the adolescent and adult: one year follow up.

OBJECTIVES: To test the hypothesis that endovascular stents used with dilation of coarctation of the aorta (CoA) improve late outcomes. Balloon dilation for CoA has been limited by concerns over the risk for acute dissection, late restenosis, or aneurysm formation. DESIGN: All patients seen with CoA between November 1994 and September 1997 underwent attempted stent implantation. Follow up was obtained for all patients and a subgroup (n = 18) had repeat catheterisation at a mean (SD) of 1.3 (0.5) years to assess residual gradient and stent-CoA morphology. RESULTS: Stents were placed in 27 patients (15 male and 12 female patients, mean age 30.1 (13.1) years), of whom seven had prior surgical coarctectomy and one had a prior balloon dilation. Hypertension was present in 26 patients (mean pressure 164 (26)/86 (13) mm Hg), of whom 16 were on antihypertension drugs. CoA gradients were 46 (20) mm Hg (range 18-106 mm Hg) at baseline and 3 (5) mm Hg after the procedure. One patient had a stroke following the procedure; another patient had incomplete dilation and underwent a second procedure. At 1.8 (1) years after the procedure the mean pressure was 130 (14)/74 (11) mm Hg with seven patients on antihypertension treatment. The clinical gradient was 4 (8) mm Hg (range 0-32 mm Hg). At follow up angiography, the mean gradient was 4(6) mm Hg, and two patients had a gradient over 10 mm Hg. Aneurysms formed in three patients at the dilation site; one patient was referred for surgery. CONCLUSION: In this age group stent management for CoA appears to be an effective technique and results in sustained reduction in CoA gradients at early term follow up, but aortic aneurysm was detected in 17% of patients who had repeat angiography.

Adolescent↗
PubMed2001

Contemporary management of children with atrial septal defects: a focus on transcatheter closure.

Atrial septal defects that result in right atrial and ventricular volume overload should be closed if diagnosed in children and adolescents. With closure of the atrial septal defect, the left-to-right shunt is eliminated e.g. the volume loading of the right heart, the excessive pulmonary blood flow and the total cardiac work load are reduced. The possibility of future arrhythmic events is lessened and paradoxical emboli across the septum eliminated. The first intracardiac surgical repair of a congenital lesion was a defect in the atrial septum nearly 50 years ago. Surgical closure remains a valuable, although viable technique. Recently percutaneous transcatheter techniques are now available. The conventional approach is via a median sternotomy incision but is associated with pain, risk of wound infection, postoperative immobilization and a permanent scar. It has been suggested that alternative approaches such as surgical repair using mini-sternotomy or lateral thoracotomy incisions yield similar results to the conventional surgical technique and are associated with fewer adverse effects. Transcatheter closure has developed over the last two decades and has evolved into a well tolerated, efficient and cost effective method with minimal discomfort for the patients. Complete closure rates are high and this approach has become a viable option for ASD management.

Cardiac Catheterization↗
PubMed2001

Collaborative interventional and surgical strategies in the management of congenital heart lesions.

In the last 15 years the development of catheter-directed percutaneous therapies have improved the delivery of care to children with congenital heart lesions. Paralleling these advances, enhanced surgical techniques are now applied to complex cardiac lesions previously thought to be inoperable. This chapter outlines several treatment strategies which utilize surgical and catheter-based algorithms to address congenital heart disorders.

Algorithms↗
PubMed2000

Balloon angioplasty of native coarctation: clinical outcomes and predictors of success.

OBJECTIVES: We sought to investigate the clinical impact of balloon angioplasty for native coarctation of the aorta (CoA) and determine predictors of outcome. BACKGROUND: Balloon dilation of native CoA remains controversial and more information on its long-term impact is required. METHODS: Hemodynamic, angiographic and follow-up data on 69 children who underwent balloon angioplasty of native CoA between 1988 and 1996 were reviewed. Stretch, recoil and gain of CoA circumference and area were calculated and related to outcomes. RESULTS: Initial systolic gradients (mean +/- SD, 31+/-12 mm Hg) fell by -74+/-27% (p < 0.001), with an increase in mean CoA diameters of 128+/-128% in the left anterior oblique and 124+/-87% in the lateral views (p < 0.001). Two deaths occurred, one at the time of the procedure and one 23 months later, both as a result of an associated cardiomyopathy. Seven patients had residual gradients of >20 mm Hg. One patient developed an aneurysm, stable in follow-up, and four patients had mild dilation at the site of the angioplasty. Freedom from reintervention was 90% at one year and 87% at five years with follow-up ranging to 8.5 years. Factors significantly associated with decreased time to reintervention included: a higher gradient before dilation, a smaller percentage change in gradient after dilation, a small transverse arch and a greater stretch and gain, but not recoil. CONCLUSION: Balloon dilation is a safe and efficient treatment of native CoA in children. Greater stretch and gain are factors significantly associated with reintervention, possibly related to altered elastic properties and vessel scarring.

Angioplasty, Balloon↗
PubMed2000

Implantation of endovascular stents for hypoplasia of the transverse aortic arch.

Hypoplasia of the transverse aortic arch is commonly associated with aortic coarctation. Persistent or recurrent obstruction can occur at this level after successful repair of the native coarcted segment. The purpose of this report is to present a new technique to treat such lesions, namely with implantation of a balloon-expandable stent. This approach was used successfully in 4 children with such hypoplasia occurring after repair of coarctation. Implantation led to both anatomical and physiological relief of obstruction in all. The patients tolerated the procedure, and there were no major adverse events.

Adolescent↗
PubMed2000

Non-invasive determination of the systolic peak-to-peak gradient in children with aortic stenosis: validation of a mathematical model.

Doppler derived systolic pressure gradients have become widely applied as noninvasively obtained estimates of the severity of aortic valvar stenosis. There is little correlation, however, between the Doppler derived peak instantaneous gradient and the peak-to-peak gradient obtained at catheterisation, the latter being the most applied variable to determine severity in children. The purpose of this study was to validate a mathematical model based on data from catheterisation which estimates the peak-to-peak gradient from variables which can be obtained by noninvasive means (Doppler derived mean gradient and pulse pressure), according to the formula: peak-to-peak systolic gradient = 6.02+/-1.49*(mean gradient)-0.44*(pulse pressure). Simultaneous cardiac catheterization and Doppler studies were performed on 10 patients with congenital aortic valvar stenosis. Correlations between the gradients measured at catheter measured, and those derived by Doppler, were performed using linear regression analysis. The mean gradients correlated well (y = 0.67 x +11.11, r = 0.87, SEE = 6 mm Hg, p = 0.001). The gradients predicted by the formula also correlated well with the peak-to-peak gradients measured at catheter (y = 0.66 x +14.44, r = 0.84, SEE = 9 mm Hg, p = 0.002). The data support the application of the model, allowing noninvasive prediction of the peak-to-peak gradient across the aortic valvar stenosis.

Adolescent↗
PubMed2000

Outcomes for children with cardiomyopathy awaiting transplantation.

OBJECTIVE: To determine factors associated with outcomes after listing for transplantation in children with cardiomyopathies. BACKGROUND: Childhood cardiomyopathies form a heterogeneous group of diseases, and in many, the prognosis is poor, irrespective of the etiology. When profound heart failure develops, cardiac transplantation can be the only viable option for survival. METHODS: We included all children with cardiomyopathy listed for transplantation between 12/89 and 4/98 in this historical cohort study. RESULTS: We listed 31 patients, 15 male and 16 female, 27 with dilated and 4 with restrictive cardiomyopathy, for transplantation. The median age at listing was 5.7 years, with a range from fetal life to 17.8 years. Transplantation was achieved in 23 (74%), with a median interval from listing of 54 days, and a range from zero to 11.4 years. Of the patients, 14 were transplanted within 30 days of listing. Five patients (16%) died before transplantation. Within the Canadian algorithm, one of these was in the third state, and four in the fourth state. One patient was removed from the list after 12 days, having recovered from myocarditis, and two remain waiting transplantation after intervals of 121 and 476 days, respectively. Patients who died were more likely to be female (5/5 vs. 11/26; p=0.04) and to have been in the third or fourth states at listing (5/5 vs. 15/26; p=0.04). The use of mechanical ventricular assistance, in 10 patients, was not a predictor of an adverse outcome. While not statistically significant, survival to transplantation was associated with treatment using inhibitors of angiotensin converting enzyme, less mitral regurgitation, a higher mean ejection fraction and cardiac index, and lower right ventricular systolic pressure. CONCLUSIONS: Children with cardiomyopathy awaiting transplantation have a mortality of 16% related to their clinical state at the time of listing.

Adolescent↗
PubMed2000

Dynamic morphology of the secundum atrial septal defect evaluated by three dimensional transoesophageal echocardiography.

OBJECTIVE: To define by three dimensional echocardiography the pattern and potential determinants of contraction of a secundum atrial septal defect through the cardiac cycle, and to evaluate the possibility of using cross sectional transthoracic and transoesophageal imaging to assess the dynamic nature of the defect. DESIGN: Three dimensional echocardiography was performed using a multiplane transoesophageal probe on 50 patients with a secundum atrial septal defect (median age 9.8 years). Nine patients were excluded because of poor images or morphological features that precluded defect measurement. In 41 cases, defect area, long and short axis length, and distance of the attenuated anterior rim were measured in their largest and smallest dimensions. RESULTS: Defect area changed significantly through the cardiac cycle (mean change 61%, p < 0.0001; range 17% to 86%). The defect contracted symmetrically and was not related to patient age, defect size, heart rate, Qp/Qs ratio, the presence of an aneurysmal atrial septum, or attenuated anterior rim. In all cases with an attenuated anterior rim (n = 13), the length of the rim significantly decreased (p = 0. 001) during atrial systole. Dynamic changes measured by either transthoracic or transoesophageal cross sectional images did not correlate with those obtained by three dimensional imaging. CONCLUSIONS: Three dimensional echocardiography shows dynamic features of defects in the atrial septum. This information may lead to an improved understanding of the pathophysiology of atrial shunting.

Adolescent↗
PubMed1999

Stenting of coronary artery stenosis in Kawasaki disease.

Coronary artery lesions can develop in Kawaski disease as a major complication, and result in aneurysm formation and stenosis. Reported is the evolution of important coronary artery stenosis in a pediatric patient managed with an endovascular stent.

Child↗
PubMed1999

Endovascular stent implantation to relieve extrinsic right pulmonary artery compression due to an enlarged neoaorta.

This case report describes extrinsic compression of the right pulmonary artery, following aortic reconstructive surgery, to create a neo-ascending aorta in a 5-year-old boy with aortic atresia, coarctation of the aorta, and a ventricular septal defect, in an effort to achieve a biventricular circulation (Yasui operation). The obstruction was successfully relieved by transcatheter implantation of a balloon-expandable stent.

Aorta↗
PubMed1999

Stent implantation to create interatrial communications in patients with complex congenital heart disease.

A restrictive interatrial communication can complicate the management of complex congenital heart disease. The purpose of this report is to present a new technique to achieve a patent and reliable interatrial communication by using an endovascular stent. A stent was successfully implanted across a fenestrated extracardiac conduit in two patients with low cardiac output after Fontan operations and across the interatrial septum in a patient with double inlet left ventricle and severe left atrioventricular stenosis. The procedures were uncomplicated and all patients showed immediate hemodynamic improvement. Cathet. Cardiovasc. Intervent. 47:310-313, 1999.

Child, Preschool↗
PubMed1999

Endovascular stent implantation for the management of postoperative right ventricular outflow tract obstruction: clinical efficacy.

OBJECTIVE: Extracardiac conduits between the right ventricle and pulmonary arteries commit patients to multiple reoperations. We reviewed our experience with stent implantation in obstructed conduits. METHODS: Between 1990 and 1997, stents were implanted across 43 conduits. The median age at procedure was 6 years (0.5-17 years), and the median interval between conduit insertion and stent implantation was 2.4 years (0.3-14 years). RESULTS: Mean systolic right ventricular pressures and gradients, respectively, decreased from 71 +/- 18 mm Hg and 48 +/- 19 mm Hg before to 48 +/- 15 mm Hg and 19 +/- 13 mm Hg after stent placement. Mean percentage of predicted valve area for body surface area increased from 26% +/- 12% to 48% +/- 17% after stent placement. Fifteen patients underwent a second transcatheter intervention (dilation or additional stent), and 2 patients, a third, allowing further postponement of surgery in 8 patients. One sudden death occurred 2.8 years after stent placement. Surgical conduit replacement has occurred in 20 patients. Body growth was maintained during follow-up. Freedom from surgical reintervention was 86% at 1 year, 72% at 2 years, and 47% at 4 years. Higher right ventricular pressure and gradient before and after stent placement and lower percentage of predicted valve area for body surface area after stent placement were associated with shorter palliation. CONCLUSION: Endovascular stent placement across obstructed conduits is a safe and effective palliation that allows for normal body growth.

Cardiac Catheterization↗