Lee N Benson

SickKids, Toronto, Ontario, Canada

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Publications (207)774.41 Total impact

  • Catheterization and Cardiovascular Interventions 05/2014; · 2.51 Impact Factor
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    ABSTRACT: As increasing numbers of patients with congenital heart disease enter adulthood, there is a growing need for minimally invasive percutaneous interventions, primarily to minimize the number of repeated surgeries required by these patients. The use of percutaneous devices is commonplace for the treatment of simple lesions, such as atrial septal defect, patent foramen ovale, patent duct arteriosus, and abnormal vascular connections. There is also substantial experience with device closure of membranous and muscular ventricular septal defects, as well as more complex shunts such as baffle leaks after atrial switch repair and ventricular pseudoaneurysms. An increasing use of covered stents has improved the safety of aortic coarctation, conduit, and branch pulmonary stenosis interventions. Percutaneous pulmonary valve implantation now has an established role in the setting of dysfunctional right ventricle-pulmonary artery conduits or failing bioprosthetic pulmonary valves. Many patients remain unsuitable for percutaneous pulmonary valve implantation because of large diameter "native" outflow tracts, however, various techniques have emerged and multiple devices are in development to provide solutions for these unique anatomic challenges. Hybrid approaches involving use of surgical and transcatheter techniques are increasingly common, serving to optimize efficacy and safety of certain procedures; they depend on a collaborative and collegial relationship between cardiac surgeons and interventionalists that is primarily patient-centred.
    The Canadian journal of cardiology 01/2014; 30(1):75-86. · 3.12 Impact Factor
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    ABSTRACT: Hypertrophic cardiomyopathy (HCM) is the most common form of inherited cardiomyopathy. Echocardiography is the mainstay of screening and disease surveillance, and genetic testing has identified a carrier population without hypertrophy. The aim of this study was to investigate whether changes in left ventricular (LV) function are detectable before the advent of hypertrophy. Fourteen children with genotype-positive, phenotype-negative HCM were identified (12 male; median age, 9.14 years; range, 1.91-15.9 years; median weight, 34.6 kg; range, 15-92.1 kg) and compared with age-matched and sex-matched healthy controls. All children underwent full echocardiographic studies using an extensive functional protocol, including two-dimensional dimensions, Doppler tissue imaging, and two-dimensional speckle-tracking echocardiography. There were no differences in LV wall thickness, chamber dimensions, length, and shortening fraction between the groups. Doppler tissue imaging in children with HCM demonstrated mildly reduced septal velocities, notably A' (5.9 cm/sec [range, 4-8.9 cm/sec] vs 6.7 cm/sec [range, 5.2-9.5 cm/sec]; P = .009). Circumferential and longitudinal strain was similar between groups. Mean apical circumferential deformation was increased in the HCM group (-24.6 ± 3.8% vs -22.2 ± 2.5%, P = .04). There were significant increases in basal and apical rotation and LV twist in children with HCM, most marked at the apex (11.7 ± 4.4° vs 5.3 ± 2.5°, P = .0001). On receiver operating characteristic curve analysis, apical rotation > 7° conferred 83% sensitivity and 82% specificity for predicting HCM (area under the curve, 0.919; P = .0001). Increased LV rotation and twist are present in children with genotype-positive, phenotype-negative HCM. Apical rotation on speckle-tracking echocardiography provides good sensitivity and specificity for the prediction of gene-positive HCM and may be a clinically useful early marker of HCM before the onset of hypertrophy.
    Journal of the American Society of Echocardiography: official publication of the American Society of Echocardiography 12/2013; · 2.98 Impact Factor
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    ABSTRACT: Surgical and catheter-based interventions on pulmonary veins are associated with pulmonary vein stenosis (PVS), which can progress diffusely through the "upstream" pulmonary veins. The mechanism has been rarely studied. We used a porcine model of PVS to assess disease progression with emphasis on the potential role of endothelial-mesenchymal transition (EndMT). Neonatal piglets underwent bilateral pulmonary vein banding (banded, n = 6) or sham operations (sham, n = 6). Additional piglets underwent identical banding and stent implantation in a single-banded pulmonary vein 3 weeks postbanding (stented, n = 6). At 7 weeks postbanding, hemodynamics and upstream PV pathology were assessed. Banded piglets developed pulmonary hypertension. The upstream pulmonary veins exhibited intimal thickening associated with features of EndMT, including increased transforming growth factor (TGF)-β1 and Smad expression, loss of endothelial and gain of mesenchymal marker expression, and coexpression of endothelial and mesenchymal markers in banded pulmonary vein intimal cells. These immunopathologic changes and a prominent myofibroblast phenotype in the remodeled pulmonary veins were consistently identified in specimens from patients with PVS, in vitro TGF-β1-stimulated cells isolated from piglet and human pulmonary veins, and human umbilical vein endothelial cells. After stent implantation, decompression of a pulmonary vein was associated with reappearance of endothelial marker expression, suggesting the potential for plasticity in the observed pathologic changes, followed by rapid in-stent restenosis. Neonatal pulmonary vein banding in piglets recapitulates critical aspects of clinical PVS and highlights a pathologic profile consistent with EndMT, supporting the rationale for evaluating therapeutic strategies designed to exploit reversibility of upstream pulmonary vein pathology.
    The Journal of thoracic and cardiovascular surgery 09/2013; · 3.41 Impact Factor
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    ABSTRACT: All 3 palliation strategies, Norwood, Sano, and Hybrid, currently used for hypoplastic left heart syndrome pose a risk of myocardial injury at different times and through different mechanisms. We sought to compare these strategies to understand longitudinal differences in interstage ventricular dysfunction and their subsequent impact on transplant-free survival and atrioventricular valve regurgitation (AVVR) as well as the relationship between adverse events and ventricular function. Serial echocardiographic reports and clinical data were reviewed for 138 children with hypoplastic left heart syndrome who underwent stage I surgical palliation (Sano: 11; Norwood: 73; Hybrid: 54) between 2004 and 2011. Stage II palliation was achieved in 92 (67%) patients (Sano: 7; Norwood: 51; Hybrid: 34). Interstage transplant-free survival, ventricular dysfunction, and AVVR were equivalent among palliation strategies. Patients with preserved ventricular function had a higher rate of transplant-free survival and freedom from AVVR, regardless of palliation strategy. Patients who had cardiac arrest, cardiopulmonary resuscitation, or extracorporeal membrane oxygenation (adverse events) experienced more transient and persistent ventricular dysfunction compared to those without adverse events. Surgical palliation strategies were not identified as risk factors for ventricular dysfunction or AVVR. Surgical palliation strategy does not affect mortality, interstage ventricular function, or interstage AVVR in children with hypoplastic left heart syndrome. Therefore, the different timing and mechanisms of myocardial injury among palliation strategies do not affect outcomes. Ventricular dysfunction adversely affects transplant-free survival and atrioventricular valve function. Adverse events are associated with the development of ventricular dysfunction. To improve outcomes, interstage treatment should focus on the preservation of ventricular function.
    Circulation 09/2013; 128(26 Suppl 1):S205-12. · 15.20 Impact Factor
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    ABSTRACT: Interventional cardiac catheterization has become an integral component of the management of adults with congenital heart disease. The origins of this approach come from the paediatric interventional experience, although techniques and indications for interventional cardiac catheterization in adults are now being developed for use in the burgeoning field of adult congenital heart disease. Progress in the application and acceptance of interventional cardiac catheterization in this setting has been swift, and the pace is quickening. This Review provides a broad overview of some of the most common procedures used in the treatment of adults with congenital heart lesions, with an emphasis on new tools that have revolutionized the field. Specifically, we discuss interventions that can be broadly classified into the following groups: techniques for closing shunt lesions, valvular interventions, methods for achieving patency of vascular obstructions, and selected additional interventions applicable to some complex lesions. We emphasize the need for a thorough understanding of the anatomy of the lesion, its natural or unnatural history, and indications for intervention before the procedure takes place. Such procedures must be performed in centres where the operators are knowledgeable of the lesions being addressed, with full surgical, anaesthetic, nursing and imaging support.
    Nature Reviews Cardiology 08/2013; · 10.40 Impact Factor
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    ABSTRACT: We sought to assess the efficacy, safety and clinical outcomes of the Advanta V12™ covered stent in management of coarctation of the aorta (CoA). Stent functionality was assessed by review of angiographic imaging, clinical data at admission, discharge and at the last clinic visit, stent configuration on chest roentgenogram, radiation exposure, and complications. Between October 2009 and February 2012, 17 patients underwent stent implantation. There were 9-12, 2-14, and 6-16 mm diameter stents deployed. Balloon angioplasty after implantation was required in 2 patients. Mean percent recoil in the middle of the stent for the 12, 14, and 16 mm implants was 14%, 24%, and 24%, respectively. There was improvement in CoA diameter from 6.6 ± 3.2 to 11.5 ± 1.7 mm (P < 0.0001) and a reduction in the peak pressure gradient from 23.1 ± 10.1 to 0.8 ± 3.3 mmHg (P < 0.0001). No patient had a symptomatic complication. Left arm cuff blood pressure fell 24 hours after implantation and left arm to leg blood pressure gradient fell to <20 mmHg in all (P < 0.0001). Follow-up was a median 242 days and at the last clinic visit there were no statistically different findings from discharge. Five children (33%) required antihypertensive medications but 3 were off medication at latest follow-up. Three patients (18%) required reintervention. The implantation of the Advanta™ V12 stent for the treatment of CoA is safe and effective in the early term. However, further study is required to determine longer-term stent efficacy.
    Journal of Interventional Cardiology 08/2013; 26(4):411-6. · 1.50 Impact Factor
  • Gareth J Morgan, Lee Benson
    The Journal of invasive cardiology 06/2013; 25(6):320. · 1.57 Impact Factor
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    Andrea W Wan, Kyong-Jin Lee, Lee N Benson
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    ABSTRACT: Covered stents have been used for the treatment of aortic coarctation to protect the arterial wall during dilation. Early results have shown them to be safe and effective. We report 2 cases of infolding of the proximal edge of a covered aortic coarctation stent. Management required implantation of a second stent. Poor stent apposition to the vessel wall and or recoil may allow conditions for these events to occur. © 2013 Wiley Periodicals, Inc.
    Catheterization and Cardiovascular Interventions 05/2013; · 2.51 Impact Factor
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    ABSTRACT: This review discusses the current safety issues related to U.S. Food and Drug Administration approved atrial septal defect devices and proposes a potential avenue to gather additional safety data including factors, which may be involved in device erosion.
    JACC Cardiovascular Interventions 05/2013; 6(5):433–442. · 7.42 Impact Factor
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    ABSTRACT: BACKGROUND: Ductal stenting plays a central role in hybrid palliation (with bilateral pulmonary artery [PA] banding) for hypoplastic left heart syndrome (HLHS). The "natural" history of ductal stent is relatively unknown. METHODS: We retrospectively reviewed 37 neonates with HLHS or its variants who underwent hybrid palliation between January 2004 and March 2010. RESULTS: Forty-nine ductal stents were deployed in 37 neonates. A single stent was implanted in 26, 2 in 10, and 3 in 1 neonate at the index procedure. There were 5 neonates (13.5%) who required reintervention on the stent with an additional implant; 4 stents were placed proximally (PA-end) and 1 on the aorta side. No infant required reintervention on the stent if the implant covered from the PA junction to beyond the aortic isthmus. There were 2 infants (5.4%) who developed retrograde arch obstruction. Of the cohort, 9 died before stage II, 1 had a bidirectional cavopulmonary shunt after conversion to a Norwood circulation, and 27 underwent comprehensive stage II. In 24 infants who did not require an additional stent, duct velocity increased during follow-up (p < 0.001). Stent position was altered distally in relation to the anterior border of the trachea with child growth. CONCLUSIONS: The stent should cover the full length of the duct from the PA junction to beyond the arch isthmus to reduce reintervention rates. Such stents tend to have progressive stenosis and move distally with child growth. However, lower body blood flow appears well maintained until the time of a comprehensive stage II repair.
    The Annals of thoracic surgery 03/2013; · 3.45 Impact Factor
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    ABSTRACT: OBJECTIVE: The management of patients with tetralogy of Fallot (ToF) and pulmonary atresia (PA) with major aortopulmonary collateral arteries (MAPCAs) is challenging. Frequently it is difficult to predict whether complete repair with closure of the ventricular septal defect (VSD) will be tolerated. The aim of this study was to investigate whether measurements of preoperative pulmonary blood flow are associated with early postoperative outcome after VSD closure. METHODS: In this retrospective study, the data from 10 patients who had undergone a cardiac magnetic resonance imaging study with flow measurements before attempted surgical complete repair were collected. Systemic blood flow (Qs) was calculated as the sum of descending aortic blood flow distal to the MAPCA origins and superior vena cava flow. Pulmonary blood flow (Qp) was measured either from the sum of the pulmonary flow (n = 7) or calculated as the difference between ascending aortic flow and Qs. RESULTS: Preoperative Qp/Qs averaged 1.71 ± 0.68 and correlated inversely with right ventricular systolic pressure (relative to systolic blood pressure, r = -0.75, P = .03) and positively with the total neopulmonary artery index (TNPAI, r = 0.66, P = .04), as measured by fluoroscopic angiography. Two children did not tolerate VSD closure. This was likely related to bronchial compression in 1 patient while the other had the lowest TNPAI and the lowest Qp/Qs of all patients. CONCLUSIONS: CMR provides not only anatomic but also functional information for surgical decision making in patients with ToF and PA with MAPCAs. Preoperative Qp/Qs is associated with postoperative right ventricular pressure and may be a marker of readiness for VSD closure.
    The Journal of thoracic and cardiovascular surgery 02/2013; · 3.41 Impact Factor
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    ABSTRACT: The goal of this study was to prospectively assess blood pressure (BP) and echocardiographic parameters to delineate the incidence and nature of the hypertension burden in this cohort. Few data are available on the long-term outcomes of aortic stenting. Thirty-one patients with successfully stented coarctation during childhood (mean age 12.4 years) underwent 24-h ambulatory BP monitoring (ABPM), exercise BP measurement, and echocardiographic assessment. Mean time after stent implantation was 5.3 ± 4 years. Hypertension was noted on one-off right-arm BP assessment in 3 patients (10%), but on the basis of the 24-h ABPM assessment in 14 patients (45%). Twenty-four of 31 patients (80%) had an abnormally elevated exercise BP response. Peak exercise BP correlated with left ventricular mass index (r = 0.51; p < 0.05), which was also significantly increased in the entire cohort (mean = 91.3 g/m(2); p < 0.05). In patients with significant somatic growth since implantation, the indexed diameter of the stent (to aortic diameter) had significantly decreased from the 48th percentile at the implantation to the 4th percentile during the study (p < 0.05). There was no difference in any parameter between patients with native or those with recurrent coarctation. Hypertension is endemic in patients with stented coarctation, irrespective of the absence of residual obstruction. Due to abnormal BP homeostasis, hypertension should be aggressively pursued by ABPM assessment and exercise stress testing in this population. Relative hypoplasia of the stented arch after somatic growth may contribute to this tendency and should provoke consideration of elective serial redilation of coarctation stents.
    JACC. Cardiovascular Interventions 02/2013; 6(2):192-201. · 1.07 Impact Factor
  • Andrea Wan, Lee Benson
    Interventional Cardiology Clinics. 01/2013; 2(1):11–22.
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    Journal of Cardiovascular Magnetic Resonance 01/2013; 15(1). · 4.44 Impact Factor
  • Interventional Cardiology Clinics. 01/2013; 2(1):153–172.
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    ABSTRACT: OBJECTIVE: Retrograde aortic arch malperfusion after ductal stenting can be life-threatening after univentricular hybrid palliation. Arch perfusion can be maintained with a main pulmonary artery to innominate artery shunt placed during the stage I procedure: a "reverse Blalock-Taussig shunt." METHODS: A retrospective review of 37 infants who underwent hybrid palliation from January 2004 to March 2010 was performed. The infants were divided into 2 groups, those with (group I, n = 16) and those without (group II, n = 21) a reverse Blalock-Taussig shunt. RESULTS: At the initial palliation, no differences were found in the demographics, systolic or diastolic pressures, or ventricular or atrioventricular valve function between the 2 groups. Group I had more infants with aortic atresia (P < .01) and smaller ascending aortas (P < .01). Before stage II, the retrograde aortic Doppler flow velocity increased in group I (P < .01) and was unchanged in group II. The reintervention rates before stage II were similar between the 2 groups. Before stage II, the ventricular end-diastolic pressure, left and right pulmonary artery pressures and diameters, and mixed venous and arterial saturations were similar between the 2 groups. The complication rates between the 2 groups were not significantly different, although a nonsignificant trend toward more neurologic complications was noted in group I. The Kaplan-Meier survival estimate at 1 year was similar between the 2 groups (63% for group I vs 71% for group II). CONCLUSIONS: The presence of a reverse Blalock-Taussig shunt was not associated with more adverse events than those without. Gradual retrograde arch obstruction occurs commonly in palliated infants with aortic atresia. A reverse Blalock-Taussig shunt might play an important role to address the potential of retrograde obstruction, augmenting arch blood flow.
    The Journal of thoracic and cardiovascular surgery 12/2012; · 3.41 Impact Factor
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    ABSTRACT: Hybrid and Norwood strategies differ substantially in terms of stage II palliative procedures. We sought to compare these strategies with an emphasis on survival and reintervention after stage II and subsequent Fontan completion. Of 110 neonates with functionally single-ventricle physiology who underwent stage I palliation between 2004 and 2010, 75 (69%) infants (Norwood, n=43; hybrid, n=32) who subsequently underwent stage II palliation were studied. Survival and reintervention rates after stage II palliation, anatomic and physiologic variables at pre-Fontan assessment, and Fontan outcomes were compared between the groups. Predictors for reintervention were analyzed. Freedom from death/transplant after stage II palliation was equivalent between the groups (Norwood, 80.4% versus hybrid, 85.6% at 3 years, P=0.66). Hybrid patients had a higher pulmonary artery (PA) reintervention rate (P=0.003) and lower Nakata index at pre-Fontan evaluation (P=0.015). Aortic arch and atrioventricular valve reinterventions were not different between the groups. Ventricular end-diastolic pressure, mean PA pressure, and ventricular function were equivalent at pre-Fontan assessment. There were no deaths after Fontan completion in either group (Norwood, n=25, hybrid, n=14). Survival after stage II palliation and subsequent Fontan completion is equivalent between the groups. The hybrid group had a higher PA reintervention rate and smaller PA size. Both strategies achieved adequate physiology for Fontan completion. Evolution of the hybrid strategy requires refinement to provide optimal PA growth.
    Circulation 09/2012; 126(11 Suppl 1):S123-31. · 15.20 Impact Factor
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    ABSTRACT: We report 4 cases of left main coronary artery (LMCA) compression after remote repair of conotruncal lesions and their successful surgical management.
    The Annals of thoracic surgery 05/2012; 94(1):283-5. · 3.45 Impact Factor
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    ABSTRACT: We investigated the natural history, outcomes of myectomy, and impact on survival of obstructive hypertrophic cardiomyopathy (HCM) in childhood. All 120 children diagnosed with HCM between 1971 and 2006 were studied. Available echocardiograms (n=685) were incorporated in regression analyses adjusted for repeated measures. Multiphase parametric models and competing risks methodology were used to define outcomes. Left ventricular outflow tract (LVOT) obstruction (peak gradient>30 mm Hg) developed in 61 (50%) of the cohort. Onset of obstructive features occurred during 2 discrete periods of risk; either during infancy (within 3 years of age), or otherwise later during early adolescence and beyond. Among children with obstructive HCM, the following 2 distinct groups were apparent: (1) those with peak LVOT gradients less than 65 mm Hg showed hemodynamic improvement (p<0.001) with medical strategies; and (2) those with peak gradients greater than 65 mm Hg instead had accelerated septal hypertrophy (p<0.001) with progression of peak gradients (p<0.01), and therefore underwent myectomy. Myectomy restored the gradient (mean 57 mm Hg reduction, 95% confidence interval 25 to 88, p<0.01) to nonobstructive levels. Furthermore, peak gradients and septal hypertrophy did not progress thereafter; they instead mirrored the natural history of nonobstructive HCM. Overall, in our experience, obstructive disease (or need for myectomy) did not influence late risk of death compared with children with nonobstructive HCM. Obstructive HCM is phenotypically heterogeneous in childhood. Peak gradients less than 65 mm Hg respond well to nonsurgical management. The patient subset with higher gradients (>65 mm Hg) instead responds poorly and early myectomy should be pursued. Reassuringly, late survival in this cohort was not compromised by development of obstructive symptoms.
    The Annals of thoracic surgery 03/2012; 93(3):840-8. · 3.45 Impact Factor

Publication Stats

3k Citations
774.41 Total Impact Points


  • 1984–2014
    • SickKids
      • • Division of Cardiology
      • • Division of Cardiovascular Surgery
      • • Division of Paediatric Emergency Medicine
      • • Labatt Family Heart Centre
      • • Division of Clinical Biochemistry
      • • Department of Paediatrics
      Toronto, Ontario, Canada
  • 2013
    • Weill Cornell Medical College
      • Division of Cardiology
      New York City, New York, United States
    • Nottinghamshire Healthcare NHS Trust
      Nottigham, England, United Kingdom
  • 1994–2013
    • University of Toronto
      • • Division of Cardiology
      • • Department of Paediatrics
      • • Labatt Family Heart Centre
      • • Hospital for Sick Children
      • • Faculty of Medicine
      • • Department of Biochemistry
      Toronto, Ontario, Canada
  • 2011
    • Hunter New England Health
      New Lambton, New South Wales, Australia
  • 2007
    • University Health Network
      • Department of Cardiology
      Toronto, Ontario, Canada
  • 2006
    • Peterborough Regional Health Centre
      Peterborough, Ontario, Canada
  • 2002–2006
    • UHN: Toronto General Hospital
      Toronto, Ontario, Canada
  • 2005
    • University Hospital Southampton NHS Foundation Trust
      Southampton, England, United Kingdom
    • University of Iowa
      • Department of Cardiothoracic Surgery
      Iowa City, IA, United States
  • 2004
    • Universitair Ziekenhuis Leuven
      Louvain, Flanders, Belgium