Sheldon M Singh

Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada

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Publications (40)192.35 Total impact

  • Yair Elitzur, Asaf Danon, Steve K. Singh, Sheldon M. Singh
    The Canadian journal of cardiology 01/2014; · 3.12 Impact Factor
  • [show abstract] [hide abstract]
    ABSTRACT: Atrioesophageal fistula (AEF) is an infrequent complication of radiofrequency (RF) ablation for atrial fibrillation (AF). The aim of this study was to determine the prevalence and operator-dependent factors associated with AEF using a nationwide survey of electrophysiologists (EP). Thirty-eight EPs performing AF ablation between 2008 and 2012 were invited to complete a web-based questionnaire assessing the prevalence and factors associated with AEF. Responses were obtained from 25 EPs (68 %) accounting for 7,016 AF ablations. Five cases of proven AEF (0.07 %) were reported. Operators who reported AEF [AEF (+)] more often used general anesthesia (GA) [90 % AEF (+) vs. 44 % AEF (-), p = 0.046]. AEF (+) operators were also more likely to be users of the non-brushing technique in the posterior wall of the LA [5 (100 %) AEF (+) vs. 5 (25 %) AEF (-), p = 0.005]. The combined usage of GA and non-brushing technique during LA posterior wall ablation had a strong association with AEF (+) operators [4 (80 %) AEF (+) vs. 2 (10 %) AEF (-), p = 0.002]. There was a trend towards higher maximal RF energy setting in the posterior wall [47.4 + 7.6 AEF (+) vs. 40.2 + 8 AEF (-), p = 0.09]. Other procedure parameters were similar. The reported prevalence of AEF among Canadian AF ablators is 0.07 %. AEF was associated with high mortality. The use of GA and non-brushing movements during posterior wall ablation were two factors associated with AEF.
    Journal of Interventional Cardiac Electrophysiology 12/2013; · 1.39 Impact Factor
  • Krishna Kumar Mohanan Nair, Sheldon M Singh
    Europace 10/2013; · 2.77 Impact Factor
  • Asaf Danon, Sheldon M Singh
    The Canadian journal of cardiology 08/2013; · 3.12 Impact Factor
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    ABSTRACT: The initial experience with left atrial esophageal fistula (LAEF) secondary to atrial fibrillation (AF) ablation procedures revealed a near universal mortality. A comprehensive description of the principles of LAEF repair in the modern era and its resulting impact on morbidity and mortality are lacking in the literature. To describe the presentation, surgical management and outcomes of patients with LAEF. A retrospective cohort analysis of 29 patients was performed, including previously unpublished cases of surgically repaired LAEF from 4 institutions (n=6), and all published cases of surgically repaired (n=16) or stented (n=7) LAEF. The average age was 55±13 years, 75% male, undergoing radiofrequency energy catheter ablation (n=26), cryoablation (n=1), high intensity focused ultrasound ablation (n=1) and surgical mini-MAZE (n=1), and presenting 30±12 days post ablation procedure. Overall 55% of patients receiving an intervention for LAEF died (41% surgical repair; 100% stent). Patients who did not receive primary esophageal repair were more likely to experience post-operative complications including mediastinitis, need for percutaneous endoscopic gastrostomy (PEG) feeds, esophageal stent or death (P=0.05). Additionally, interposing tissue between the repaired esophagus and LA resulted in fewer post-operative complications (P=0.02). While improved relative to initial reports, mortality associated with LAEF remains high after corrective intervention. Primary esophageal repair with the placement of tissue between the repaired esophagus and LA may result in lower morbidity and mortality.
    Heart rhythm: the official journal of the Heart Rhythm Society 08/2013; · 4.56 Impact Factor
  • Journal of Cardiovascular Electrophysiology 05/2013; · 3.48 Impact Factor
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    ABSTRACT: BACKGROUND: Percutaneous left atrial appendage (LAA) occlusion and novel pharmacological therapies are now available to manage stroke risk in patients with non-valvular atrial fibrillation (NVAF). However, the cost effectiveness of LAA occlusion compared to dabigatran and warfarin in patients with NVAF is unknown. METHODS AND RESULTS: Cost-utility analysis using a patient level Markov micro-simulation decision analytic model with a lifetime horizon was undertaken to determine the lifetime costs, quality-adjusted life years (QALY), and the incremental cost-effectiveness ratio (ICER) of LAA occlusion in relation to dabigatran and warfarin in patients with NVAF at risk for stroke without contraindications to oral anticoagulation (OAC). The analysis was performed from the perspective of the Ontario Ministry of Health and Long Term Care, the 3(rd) party payer for insured health services in Ontario, Canada. Effectiveness and utility data were obtained from the published literature. Cost data were obtained from the Ontario Drug Benefits Formulary and the Ontario Case Costing Initiative. Warfarin therapy had the lowest discounted QALY of 4.55 QALYs, followed by dabigatran at 4.64 QALYs, and LAA occlusion at 4.68 QALY. The average discounted lifetime cost for a patient on warfarin was $21 429, $25 760 for dabigatran and $27 003 for LAA occlusion. Compared with warfarin, the ICER for LAA occlusion was $41 565. Dabigatran was extendedly dominated. CONCLUSIONS: Percutaneous LAA occlusion represents a novel therapy for stroke reduction in patients at risk with NVAF that is cost-effective compared to warfarin.
    Circulation 05/2013; · 15.20 Impact Factor
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    ABSTRACT: Abstract Objectives: Data regarding efficacy and safety of three-dimensional localisation systems (3D) are limited. We performed a meta-analysis of randomized trials comparing combined fluoroscopy and 3D guided to fluoroscopically-only guided procedures. Design: A systematic search was performed using multiple databases between 1990- 2010. Outcomes were acute and long-term success, ablation, procedure and fluoroscopic times, radiation dose (RD), and complications. Results: Thirteen studies involving 1292 patients were identified. 3D were tested against fluoroscopic guidance in 666 patients for supraventricular tachycardia (SVT), atrial flutter (AFL), atrial fibrillation (AF) and ventricular tachycardia (VT). Acute and long-term freedom from arrhythmia were not significantly different between 3D and control for AFL (acute success 97% vs. 93%, p=0.57; chronic success 93% vs. 96%, p=0.90) or SVT (acute success 94% vs. 100%, p=0.36; chronic success 88% vs. 88%, p=0.80). A shorter fluoroscopic time was achieved with 3D in AFL (p<0.001) and SVT (p=0.002). RD was significantly less for both AFL (p=0.002) and SVT (p=0.01). Ablation & procedure time and complications were not statistically different. Conclusions: Success, procedure time, and complications were similar between fluoroscopic and 3D-guided ablations. Fluoroscopic time and RD were significantly reduced for ablation of AFL and SVT with 3D.
    Scandinavian cardiovascular journal: SCJ 05/2013; · 1.07 Impact Factor
  • Sheldon M Singh, Isabelle Nault
    Canadian Medical Association Journal 04/2013; · 6.47 Impact Factor
  • Hatim Al Lawati, Sheldon M Singh
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    ABSTRACT: We describe a case of post-operative inferior myocardial infarction after abdominal aortic aneurysm repair due to compromise of a gastroepiploic coronary arterial graft.
    Indian heart journal 09/2012; 64(5):530-531.
  • Journal of Cardiovascular Electrophysiology 03/2012; 23(9):1033-4. · 3.48 Impact Factor
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    ABSTRACT: Angiotensin-converting enzyme (ACE) inhibitor use in patients at high risk of coronary artery disease has been associated with a decrease in the risk of myocardial infarction (MI) and death. However, it is unclear whether chronic use of these agents modifies the course and outcome of an acute coronary syndrome (ACS). This study assessed the association between chronic use of ACE inhibitors and clinical outcomes in patients with ACS. From 1999 through 2008, 13,632 Canadian patients with ACS were identified in the Global Registry of Acute Coronary Events (GRACE), the expanded GRACE (GRACE(2)), and the Canadian Registry of Acute Coronary Events (CANRACE). Patients were stratified by previous use of an ACE inhibitor. Clinical characteristics, in-hospital treatment, and outcomes were compared between the 2 groups. Multivariable logistic regression analysis adjusting for GRACE risk score and other clinical factors was performed. Patients receiving an ACE inhibitor before the ACS had a higher prevalence of diabetes (40.6% vs 21.2%, p <0.001), previous MI (51.8% vs 23.3%, p <0.001), heart failure (18.0% vs 6.9%), and higher GRACE scores at presentation (133 vs 124, p <0.001). Multivariable analysis demonstrated no significant association between previous ACE inhibitor use and death (adjusted odds ratio [OR] 1.15, confidence interval [CI] 0.90 to 1.49, p = 0.27), in-hospital re-MI (adjusted OR 0.99, CI 0.78 to 1.25, p = 0.91), or the composite end point of death/re-MI (adjusted OR 1.01, CI 0.84 to 1.20, p = 0.94). In conclusion, previous use of an ACE inhibitor is not independently associated with improved in-hospital outcomes after an ACS.
    The American journal of cardiology 11/2011; 109(3):332-6. · 3.58 Impact Factor
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    ABSTRACT: Beyond pulmonary vein isolation (PVI), adjuvant ablation at the sites of complex fractionated atrial electrograms (CFAE) has been shown to improve the long-term success of catheter ablation of persistent atrial fibrillation (AF). However, this approach often requires extensive ablation due to the widespread distribution of CFAE within the left atrium. An optimal strategy would identify areas of CFAE which, when selectively targeted with ablation, result in AF termination with an acceptable long-term freedom from AF. It is possible that the intraprocedural administration of an antiarrhythmic drug may help accomplish this. The Modified Ablation Guided by Ibutilide Use in Chronic AF (MAGIC-AF) Study is an international multicenter prospective randomized double-blinded clinical trial assessing the utility of the intraprocedural administration of 0.25 mg of intravenous ibutilide before performing CFAE ablation. The primary efficacy endpoint of this study will be the freedom from AF at 1 year after a single procedure off antiarrhythmic agents. Safety endpoints will include procedural and radiofrequency ablation time as well as overall procedural complication rate. Patients undergoing a first ever catheter ablation procedure for persistent AF will be included. Individuals with hypertrophic cardiomyopathy, complex congenital heart disease including atrial septal defects, and ejection fraction <35% will be excluded from the study. All patients will first undergo PVI. Those patients who remain in AF will then be randomized in a 1:1 fashion to receive either 0.25 mg intravenous ibutilide or saline placebo followed by a CFAE based ablation strategy. Two hundred randomized patients will be enrolled in this study-100 in each study arm. The MAGIC-AF study will assess the utility of a combined pharmaco-ablative strategy in patients with persistent AF undergoing a CFAE based ablation strategy.
    Journal of Cardiovascular Electrophysiology 10/2011; 23(4):352-8. · 3.48 Impact Factor
  • Heart rhythm: the official journal of the Heart Rhythm Society 09/2011; 9(10):1650-1. · 4.56 Impact Factor
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    ABSTRACT: Luminal esophageal temperature (LET) monitoring is one strategy to minimize esophageal injury during atrial fibrillation ablation procedures. However, esophageal ulceration and fistulas have been reported despite adequate LET monitoring. The objective of this study was to assess a novel approach to LET monitoring with a deflectable LET probe on the rate of esophageal injury in patients undergoing atrial fibrillation ablation. Forty-five consecutive patients undergoing an atrial fibrillation ablation procedure followed by esophageal endoscopy were included in this prospective observational pilot study. LET monitoring was performed with a 7F deflectable ablation catheter that was positioned as close as possible to the site of left atrial ablation using the deflectable component of the catheter guided by visualization of its position on intracardiac echocardiography. Ablation in the posterior left atrial was limited to 25 W and terminated when the LET increased 2°C from baseline. Endoscopy was performed 1 to 2 days after the procedure. All patients had at least 1 LET elevation >2°C necessitating cessation of ablation. Deflection of the LET probe was needed to accurately measure LET in 5% of patients when ablating near the left pulmonary veins, whereas deflection of the LET probe was necessary in 88% of patients when ablating near the right pulmonary veins. The average maximum increase in LET was 2.5±1.5°C. No patients had esophageal thermal injury on follow-up endoscopy. A strategy of optimal LET probe placement using a deflectable LET probe and intracardiac echocardiography guidance, combined with cessation of radiofrequency ablation with a 2°C rise in LET, may reduce esophageal thermal injury during left atrial ablation procedures.
    Circulation Arrhythmia and Electrophysiology 02/2011; 4(2):149-56. · 5.95 Impact Factor
  • Sheldon M Singh, Pamela S Douglas, Vivek Y Reddy
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    ABSTRACT: Studies assessing the presence of a residual iatrogenic atrial septal defect (iASD) after transseptal catheterization with 8F transseptal sheaths have suggested that the majority of these iASDs close within 6 months. However, these studies have been limited by small patient numbers and short follow-up. Additionally, there are a number of novel catheter procedures in interventional cardiology and electrophysiology that use larger transseptal sheaths. The objective of this study was to assess the incidence of and complications associated with iASDs in a large cohort of patients undergoing transseptal catheterization with a 12F transseptal sheath. Patients (n=253) without a preexisting interatrial shunt undergoing WATCHMAN implantation as part of the PROTECT AF study were included in this current study. Patients underwent transesophageal echocardiography with echo-contrast immediately after the procedure and at 45 days and 6 months and 12 months. Eighty-seven percent of patients had an iASD immediately after the procedure, the majority of which sealed by 6 months (incidence of iASD, 34% at 45 days, 11% at 6 months, 7% at 12 months). Whereas the majority of iASDs were >3 mm in diameter immediately after the procedure, the minority of iASD were >3 mm during the follow-up period. Additionally, interatrial shunting was predominantly left-to-right when an iASD was present. There was no significant difference in the rate of stroke and/or systemic embolism during the follow-up period in patients with or without iASD. Transseptal catheterization procedures with a large-diameter transseptal sheath have a high spontaneous closure rate of iASDs that is not associated with an increased rate of stroke/systemic embolization during long-term follow-up.
    Circulation Arrhythmia and Electrophysiology 01/2011; 4(2):166-71. · 5.95 Impact Factor
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    ABSTRACT: Catheter ablation of left-sided atrial arrhythmias generally is performed using a transfemoral venous approach through the inferior vena cava (IVC). In this report, we assessed the feasibility of a percutaneous transhepatic approach to ablation of left-sided atrial arrhythmias in 2 patients with interruption of the IVC. Patient 1 had atrial flutter in the setting of complex congenital heart disease and prior Fontan for univentricular physiology and a single atrium. Patient 2 had atrial fibrillation. Percutaneous hepatic vein access was obtained with ultrasound and fluoroscopic guidance. Transseptal catheterization was performed in patient 2. After the procedure, the hepatic tract in patient 1 was cauterized using a bipolar radiofrequency catheter, and an Amplatzer vascular plug was used in patient 2 to obtain hemostasis. Percutaneous hepatic vein access was achieved without complications. After electroanatomical mapping, a linear lesion was placed between the single atrioventricular valve and the confluence of the hepatic veins in patient 1; this terminated the flutter, and bidirectional block was achieved. In patient 2, the pulmonary veins were electrically isolated using an extraostial approach, isolating the ipsilateral veins in pairs. Additionally, ablation of right-side atrial flutter was achieved by obtaining bidirectional block across a linear lesion between the tricuspid valve and confluence of the hepatic veins. Hemostasis of the transhepatic tract was attained in both patients. In patients with interrupted IVCs, a percutaneous transhepatic approach is a feasible alternative for performing catheter ablation of complex left-sided arrhythmias.
    Circulation Arrhythmia and Electrophysiology 01/2011; 4(2):235-41. · 5.95 Impact Factor
  • Circulation Arrhythmia and Electrophysiology 12/2010; 3(6):668-70. · 5.95 Impact Factor
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    ABSTRACT: While able to achieve clinical success, the current step-wise approach to persistent atrial fibrillation (AF) ablation requires considerable "substrate" ablation and frequently mandates multiple procedures to address consequent atrial tachycardias (ATs). An alternative strategy minimizing the amount of ablation while maintaining clinical success would be desirable. We hypothesize that intraprocedural administration of a low-dose antiarrhythmic drug (AAD) during AF will organize areas of passive activation and not affect areas critical to AF maintenance, thereby potentially minimizing the ablation lesion set. Eleven patients (age = 55 +/- 6 years; LA = 48 +/- 15 mm; median AF duration = 3 years) with persistent AF undergoing catheter ablation were enrolled in this exploratory prospective observational study. After pulmonary vein (PV) isolation, a mean cycle length (mCL) map was created and areas with mCL <120 ms were considered to represent complex fractionated atrial electrograms (CFAE). Ibutilide (0.25-1.0 mg) was then administered and a second mCL map created. Ablation lesions were placed at CAFE sites identified after ibutilide administration. Activation and/or entrainment mapping was employed to address ATs. The endpoint of ablation was achieving sinus rhythm. The average LA mCL increased (146 vs 165 ms, P = 0.01) and the LA CFAE surface area decreased after ibutilide administration. Additional ablation organized AF to either sinus rhythm or AT in 10/11 (91%) patients. After a median follow up of 455 days, 8 of 11 (72%) patients were free from AF. Three patients underwent a repeat ablation procedure (average 1.27 ablations/patient). Ibutilide administration may organize atrial activity and facilitate AF termination during ablation while minimizing the ablation lesion set.
    Journal of Cardiovascular Electrophysiology 06/2010; 21(6):608-16. · 3.48 Impact Factor
  • Sheldon M Singh, Avi Fischer, Vivek Y Reddy
    Heart rhythm: the official journal of the Heart Rhythm Society 03/2010; 8(7):1111. · 4.56 Impact Factor

Publication Stats

221 Citations
192.35 Total Impact Points


  • 2011–2013
    • Sunnybrook Health Sciences Centre
      • Division of Cardiology
      Toronto, Ontario, Canada
  • 2003–2013
    • University of Toronto
      • • Sunnybrook Health Sciences Centre
      • • Department of Medicine
      Toronto, Ontario, Canada
  • 2010–2011
    • Mount Sinai School of Medicine
      Manhattan, New York, United States
  • 2008
    • Massachusetts General Hospital
      • Division of Cardiology
      Boston, MA, United States