Southlake Regional Health Center

Newmarket, Canada

Southlake Regional Health Center

Newmarket, Canada
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Mohareb M.M.,University of Toronto | Qiu F.,Institute for Clinical Evaluative science | Cantor W.J.,Southlake Regional Health Center | Kingsbury K.J.,Care Network | And 2 more authors.
Annals of Internal Medicine | Year: 2015

Background: The use of invasive coronary angiography in stable ischemic heart disease (IHD) varies widely. Objective: To validate the 2012 appropriate use criteria for diagnostic catheterization by examining the relationship between the appropriateness of cardiac catheterization in patients with suspected stable IHD and the proportion of patients with obstructive coronary artery disease (CAD) and subsequent revascularization. Design: Population-based, observational, multicenter cohort study. Setting: The Cardiac Care Network, a registry of all patients having elective angiography at 18 hospitals in Ontario, Canada, between 1 October 2008 and 30 September 2011. Patients: Persons without prior coronary revascularization or myocardial infarction who had angiography for suspected stable CAD. Measurements: Appropriateness scores were ascertained by using data collected at the time of the index angiography and were categorized as appropriate, inappropriate, or uncertain. Results: Among the final cohort of 48 336 patients, 58.2% of angiographic studies were classified as appropriate, 10.8% were classified as inappropriate, and 31.0% were classified as uncertain. Overall, 45.5% of patients had obstructive CAD. In patients with appropriate indications for angiography, 52.9% had obstructive CAD, with 40.0% undergoing revascularization. In those with inappropriate indications, 30.9% had obstructive CAD and 18.9% underwent revascularization; in those with uncertain indications, 36.7% had obstructive CAD and 25.9% had revascularization. Although more patients with appropriate indications had obstructive CAD and underwent revascularization (P < 0.001), a substantial proportion of those with inappropriate or uncertain indications had important coronary disease. Limitation: Data were not available on whether symptoms were atypical. Conclusion: Despite the association between appropriateness category and obstructive CAD, this study raises concerns about the ability of the appropriate use criteria to guide clinical decision making. Primary Funding Source: Canadian Institutes of Health © 2015 American College of Physicians.


Verma A.,Southlake Regional Health Center | Jiang C.-Y.,Zhejiang University | Betts T.R.,John Radcliffe Hospital | Chen J.,University of Bergen | And 11 more authors.
New England Journal of Medicine | Year: 2015

BACKGROUND: Catheter ablation is less successful for persistent atrial fibrillation than for paroxysmal atrial fibrillation. Guidelines suggest that adjuvant substrate modification in addition to pulmonary-vein isolation is required in persistent atrial fibrillation. METHODS: We randomly assigned 589 patients with persistent atrial fibrillation in a 1:4:4 ratio to ablation with pulmonary-vein isolation alone (67 patients), pulmonary-vein isolation plus ablation of electrograms showing complex fractionated activity (263 patients), or pulmonary-vein isolation plus additional linear ablation across the left atrial roof and mitral valve isthmus (259 patients). The duration of follow-up was 18 months. The primary end point was freedom from any documented recurrence of atrial fibrillation lasting longer than 30 seconds after a single ablation procedure. RESULTS: Procedure time was significantly shorter for pulmonary-vein isolation alone than for the other two procedures (P<0.001). After 18 months, 59% of patients assigned to pulmonary-vein isolation alone were free from recurrent atrial fibrillation, as compared with 49% of patients assigned to pulmonary-vein isolation plus complex electrogram ablation and 46% of patients assigned to pulmonary-vein isolation plus linear ablation (P = 0.15). There were also no significant differences among the three groups for the secondary end points, including freedom from atrial fibrillation after two ablation procedures and freedom from any atrial arrhythmia. Complications included tamponade (three patients), stroke or transient ischemic attack (three patients), and atrioesophageal fistula (one patient). CONCLUSIONS: Among patients with persistent atrial fibrillation, we found no reduction in the rate of recurrent atrial fibrillation when either linear ablation or ablation of complex fractionated electrograms was performed in addition to pulmonary-vein isolation. Copyright © 2015 Massachusetts Medical Society.


Verma A.,Southlake Regional Health Center | Debruyne P.,Imelda Ziekenhuis | Nardi S.,Pineta Grande Hospital | Deneke T.,Herz und Gefass Klinik | And 4 more authors.
Circulation: Arrhythmia and Electrophysiology | Year: 2013

Background: This prospective, multicenter study sought to evaluate the incidence of asymptomatic cerebral emboli (ACE) during ablation of atrial fibrillation (AF) using a multielectrode radiofrequency (MER) system when specific procedural changes were applied. Methods and Results: Sixty subjects (age 60±10 years; 87% paroxysmal; CHADS2 score, 0.6±0.7) undergoing AF ablation with a circular MER catheter were studied. Three procedural changes were specified: (1) ablation was performed under therapeutic vitamin K antagonist and heparin to maintain activated clotting time >350 seconds; (2) submerged loading of the catheter into the introducer before sheath insertion to minimize air ingress; and (3) either the distal or proximal electrode of the circular MER catheter was deactivated to prevent inadvertent bipolar radiofrequency interaction. MRI was performed <7 days preablation and 2 days postablation. Subjects with new cerebral findings after ablation underwent repeat MRI after 1 month. An acute ACE lesion was defined by a new hyperintensity on diffusion-weighted and fluidattenuated inversion recovery cerebral MRI sequences. Neurological function was evaluated at baseline, postablation, and 1 month. All target pulmonary veins were isolated. In 60% (36/60) of patients, pre-existing cerebral lesions were seen on the preprocedure MRI (8 lesions per subject; interquartile range, 3-22). New postprocedural ACE occurred in only 1/60 patients (incidence, 1.7%; 95% confidence interval, 0.04-8.9), which was no longer visible on MRI after 1 month. Conclusions: Applying procedural changes to MER ablation significantly reduces the ACE incidence to 1.7%, which is on the low end of reported ACE rates of any technology. © 2013 American Heart Association, Inc.


Birnie D.H.,University of Ottawa | Healey J.S.,Population Health Research Institute | Wells G.A.,University of Ottawa | Verma A.,Southlake Regional Health Center | And 8 more authors.
New England Journal of Medicine | Year: 2013

BACKGROUND: Many patients requiring pacemaker or implantable cardioverter-defibrillator (ICD) surgery are taking warfarin. For patients at high risk for thromboembolic events, guidelines recommend bridging therapy with heparin; however, case series suggest that it may be safe to perform surgery without interrupting warfarin treatment. There have been few results from clinical trials to support the safety and efficacy of this approach. METHODS: We randomly assigned patients with an annual risk of thromboembolic events of 5% or more to continued warfarin treatment or to bridging therapy with heparin. The primary outcome was clinically significant device-pocket hematoma, which was defined as device-pocket hematoma that necessitated prolonged hospitalization, interruption of anticoagulation therapy, or further surgery (e.g., hematoma evacuation). RESULTS: The data and safety monitoring board recommended termination of the trial after the second prespecified interim analysis. Clinically significant device-pocket hematoma occurred in 12 of 343 patients (3.5%) in the continued-warfarin group, as compared with 54 of 338 (16.0%) in the heparin-bridging group (relative risk, 0.19; 95% confidence interval, 0.10 to 0.36; P<0.001). Major surgical and thromboembolic complications were rare and did not differ significantly between the study groups. They included one episode of cardiac tamponade and one myocardial infarction in the heparin-bridging group and one stroke and one transient ischemic attack in the continued-warfarin group. CONCLUSIONS: As compared with bridging therapy with heparin, a strategy of continued warfarin treatment at the time of pacemaker or ICD surgery markedly reduced the incidence of clinically significant device-pocket hematoma. (Funded by the Canadian Institutes of Health Research and the Ministry of Health and Long-Term Care of Ontario; BRUISE CONTROL ClinicalTrials.gov number, NCT00800137.) Copyright © 2013 Massachusetts Medical Society.


Verma A.,Southlake Regional Health Center | Champagne J.,University of Québec | Sapp J.,Queen Elizabeth II Hospital | Essebag V.,McGill University | And 5 more authors.
JAMA Internal Medicine | Year: 2013

Background: The DISCERN AF study (Discerning Symptomatic and Asymptomatic Episodes Pre and Post Radiofrequency Ablation of Atrial Fibrillation) monitored atrial fibrillation (AF) using an implantable cardiac monitor (ICM) to assess the incidence and predictors of asymptomatic AF before and after catheter ablation. Methods: Patients with symptomatic AF underwent implantation of an ICM with an automated AF detection algorithm 3 months before and 18 months after ablation. Patients kept a standardized diary to record symptoms of arrhythmia, and ICM data were downloaded every 3 months. All episodes were blindly adjudicated and correlated with the diary. Asymptomatic recurrences were ICM episodes of 2 minutes or longer with no associated diary symptoms. Results: Fifty patients had 2355 ICM episodes. Of these, 69.0% were true AF/atrial flutter (AFL)/atrial tachycardia (AT);16.0%, sinus with extrasystoles;11.0%, artifact; and 4.0%, sinus arrhythmia. Total AF/AFL/AT burden was reduced by 86% from a mean (SD) of 2.0 (0.5) h/d per patient before to 0.3 (0.2) h/d per patient after ablation (P<.001), and 56.0% of all episodes were asymptomatic. The ratio of asymptomatic to symptomatic AF episodes increased after ablation from 1.1 to 3.7 (P=.002). By symptoms alone, 29 of 50 patients (58%) were free of AF/AFL/AT after ablation compared with 23 of 50 (46%) using ICM-detected AF/AFL/AT recurrence. Asymptomatic episodes were more likely AFL/AT and were significantly shorter and slower, with lower heart rate variability. However, the postablation state was the strongest independent predictor of asymptomatic AF. Conclusions: The ratio of asymptomatic to symptomatic AF episodes increased from 1.1 before to 3.7 after ablation. Postablation state is the strongest predictor of asymptomatic AF. Symptoms alone underestimate post-ablation AF burden, with 12% of patients having asymptomatic recurrences only. © 2013 American Medical Association.


Singh J.P.,Massachusetts General Hospital | Ptaszek L.M.,Massachusetts General Hospital | Verma A.,Southlake Regional Health Center
Heart Rhythm | Year: 2010

Most practitioners of atrial fibrillation (AF) ablation have attempted to move beyond pulmonary vein isolation into the realm of physiology-driven ablation for patients with persistent AF. This new strategy involves a combination of a common anatomic approach (with isolation of the pulmonary veins) and an individualized strategy tailored to the electrophysiologic characteristics of the atrial substrate present in each patient. In this review, we summarize the current reasoning and controversies related to this new approach. In addition, we attempt to unravel some of the complexities of targeting these patient-specific atrial electrical signals. © 2010 Heart Rhythm Society.


Ziegler P.D.,Medtronic Inc. | Koehler J.L.,Medtronic Inc. | Verma A.,Southlake Regional Health Center
PACE - Pacing and Clinical Electrophysiology | Year: 2012

Background: Ventricular rate control (VRC) is an important treatment strategy for patients with permanent atrial fibrillation (AF). We assessed the prevalence of poor VRC and the adequacy of various intermittent monitoring regimens to accurately characterize VRC during permanent AF. Methods: We retrospectively analyzed data from dual chamber implantable cardioverter defibrillator (ICD) and cardiac resynchronization therapy defibrillator (CRT-D) patients in the Medtronic Discovery™ Link having permanent AF (AF burden >23 hours/day) and ≤365 consecutive days of device data. Poor VRC was defined as a day with the mean ventricular rate during AF >100 beats/minute (bpm) for ICD patients and >90 bpm for CRT-D patients. Intermittent monitoring regimens were simulated from continuous device data by randomly selecting subsets of days in which data were available for analysis. Assessments of poor VRC were computed after replicating 1,000 simulations. Results: ICD (n = 1,902, age = 71 ± 10) and CRT-D (n = 3,397, age = 72 ± 9) patients were included and followed for 365 days. The prevalence of poor VRC was 24.8% among ICD patients and 28.6% among CRT-D patients. Significantly more patients were identified as having poor VRC with continuous monitoring compared to all intermittent monitoring regimens (sensitivity range = 8%-31%). Furthermore, 11.6% of ICD patients and 17.9% of CRT-D patients experienced ≤7 days with poor VRC, to which the sensitivities of annual 7- and 21-day recordings were <7% and <20%, respectively. Conclusions: A significant proportion of permanent AF patients experience poor VRC that would be missed with random intermittent monitoring. Whether improved knowledge of VRC with continuous monitoring will lead to improved outcomes compared to intermittent monitoring requires further study. (PACE 2012;1-7) © 2012 Wiley Periodicals, Inc.


Morillo C.A.,Hamilton Health Sciences | Verma A.,Southlake Regional Health Center | Connolly S.J.,Hamilton Health Sciences | Kuck K.H.,Asklepios Klinik St Georg | And 6 more authors.
JAMA - Journal of the American Medical Association | Year: 2014

IMPORTANCE: Atrial fibrillation (AF) is the most common rhythm disorder seen in clinical practice. Antiarrhythmic drugs are effective for reduction of recurrence in patients with symptomatic paroxysmal AF. Radiofrequency ablation is an accepted therapy in patients for whom antiarrhythmic drugs have failed; however, its role as a first-line therapy needs further investigation. OBJECTIVE: To compare radiofrequency ablation with antiarrhythmic drugs (standard therapy) in treating patients with paroxysmal AF as a first-line therapy. DESIGN, SETTING, AND PATIENTS: A randomized clinical trial involving 127 treatment-naive patients with paroxysmal AF were randomized at 16 centers in Europe and North America to received either antiarrhythmic therapy or ablation. The first patient was enrolled July 27, 2006; the last patient, January 29, 2010. The last follow-up was February 16, 2012. INTERVENTIONS: Sixty-one patients in the antiarrhythmic drug group and 66 in the radiofrequency ablation group were followed up for 24 months. MAIN OUTCOMES AND MEASURES: The time to the first documented atrial tachyarrhythmia of more than 30 seconds (symptomatic or asymptomatic AF, atrial flutter, or atrial tachycardia), detected by either scheduled or unscheduled electrocardiogram, Holter, transtelephonic monitor, or rhythm strip, was the primary outcome. Secondary outcomes included symptomatic recurrences of atrial tachyarrhythmias and quality of life measures assessed by the EQ-5D tool. RESULTS: Forty-four patients (72.1%) in the antiarrhythmic group and in 36 patients (54.5%) in the ablation group experienced the primary efficacy outcome (hazard ratio [HR], 0.56 [95% CI, 0.35-0.90]; P = .02). For the secondary outcomes, 59% in the drug group and 47% in the ablation group experienced the first recurrence of symptomatic AF, atrial flutter, atrial tachycardia (HR, 0.56 [95% CI, 0.33-0.95]; P = .03). No deaths or strokes were reported in either group; 4 cases of cardiac tamponade were reported in the ablation group. In the standard treatment group, 26 patients (43%) underwent ablation after 1-year. Quality of life was moderately impaired at baseline in both groups and improved at the 1 year follow-up. However, improvement was not significantly different among groups. CONCLUSIONS AND RELEVANCE: Among patients with paroxysmal AF without previous antiarrhythmic drug treatment, radiofrequency ablation compared with antiarrhythmic drugs resulted in a lower rate of recurrent atrial tachyarrhythmias at 2 years. However, recurrence was frequent in both groups. TRIAL REGISTRATION: clinicaltrials.gov Identifier: NCT00392054 Copyright 2014 American Medical Association. All rights reserved.


Alsahli M.,Southlake Regional Health Center | Alsahli M.,King's College | Gerich J.E.,University of Rochester
Endocrinology and Metabolism Clinics of North America | Year: 2013

Hypoglycemia remains a common problem for patients with diabetes and is associated with substantial morbidity and mortality. This article summarizes our current knowledge of the epidemiology, pathogenesis, risk factors, and complications of hypoglycemia in patients with diabetes and discusses prevention and treatment strategies. © 2013 Elsevier Inc.


Verma A.,Southlake Regional Health Center | Macle L.,Montreal Heart Institute | Cox J.,Queen Elizabeth Health science Center | Skanes A.C.,London Health Sciences Center
Canadian Journal of Cardiology | Year: 2011

Catheter ablation of atrial fibrillation (AF) offers a promising treatment for the maintenance of sinus rhythm in patients for whom a rhythm control strategy is desired. While the precise mechanisms of AF are incompletely understood, there is substantial evidence that in many cases (particularly for paroxysmal AF), ectopic activity most commonly located in and around the pulmonary veins of the left atrium plays a central role in triggering and/or maintaining arrhythmic episodes. Catheter ablation involves electrically disconnecting the pulmonary veins from the rest of the left atrium to prevent AF from being triggered. Further substrate modification may be required in patients with more persistent AF. Successful ablation of AF has never been shown to alter mortality or obviate the need for oral anticoagulation; thus, the primary indication for this procedure should be improvement of symptoms caused by AF. The success rate of catheter ablation for AF is superior to the efficacy of antiarrhythmic drugs, but success is still in the range of 75%-90% after 2 procedures. Ablation is also associated with a complication rate of 2%-3%. Thus, ablation should primarily be used as a second-line therapy after failure of antiarrhythmic drugs. In contrast to AF, catheter ablation of atrial flutter has a higher success rate with a smaller incidence of complications. Thus, catheter ablation for atrial flutter may be considered a first-line alternative to antiarrhythmic drugs. © 2011 Canadian Cardiovascular Society.

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