Publications by authors named "Christopher C Cheung"

42 Publications

Outcomes of acute respiratory distress syndrome in COVID-19 patients compared to the general population: a systematic review and meta-analysis.

Expert Rev Respir Med 2021 May 5:1-8. Epub 2021 May 5.

Department of Internal Medicine, Kamineni Academy of Medical Sciences and Research Centre, Hyderabad, India.

Introduction: Acute respiratory distress syndrome (ARDS) due to coronavirus disease 2019 (COVID-19) often leads to mortality. Outcomes of patients with COVID-19-related ARDS compared to ARDS unrelated to COVID-19 is not well characterized.

Areas Covered: We performed a systematic review of PubMed, Scopus, and MedRxiv 11/1/2019 to 3/1/2021, including studies comparing outcomes in COVID-19-related ARDS (COVID-19 group) and ARDS unrelated to COVID-19 (ARDS group). Outcomes investigated were duration of mechanical ventilation-free days, intensive care unit (ICU) length-of-stay (LOS), hospital LOS, and mortality. Random effects models were fit for each outcome measure. Effect sizes were reported as pooled median differences of medians (MDMs), mean differences (MDs), or odds ratios (ORs).

Expert Opinion: Ten studies with 2,281 patients met inclusion criteria (COVID-19: 861 [37.7%], ARDS: 1420 [62.3%]). There were no significant differences between the COVID-19 and ARDS groups for median number of mechanical ventilator-free days (MDM: -7.0 [95% CI: -14.8; 0.7], p = 0.075), ICU LOS (MD: 3.1 [95% CI: -5.9; 12.1], p = 0.501), hospital LOS (MD: 2.5 [95% CI: -5.6; 10.7], p = 0.542), or all-cause mortality (OR: 1.25 [95% CI: 0.78; 1.99], p = 0.361). Compared to the general ARDS population, results did not suggest worse outcomes in COVID-19-related ARDS.
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http://dx.doi.org/10.1080/17476348.2021.1920927DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8108193PMC
May 2021

Patch monitors for arrhythmia monitoring in patients for suspected inherited arrhythmia syndrome.

J Cardiovasc Electrophysiol 2021 03 15;32(3):856-859. Epub 2021 Feb 15.

Heart Rhythm Services, Division of Cardiology, Center for Cardiovascular Innovation, University of British Columbia, Vancouver, British Columbia, Canada.

Introduction: Patients undergoing evaluation for an inherited arrhythmia syndrome undertake a series of ambulatory investigations including 24-h Holter monitor, exercise treadmill testing (ETT), and others. Patch monitors may simplify the evaluation, providing accurate arrhythmia evaluation and QT assessment.

Methods And Results: Patients referred for evaluation of an inherited arrhythmia syndrome underwent standard investigations, including 12-lead electrocardiography (ECG), 24-h Holter monitoring, ETT, along with supplemental monitoring using a 7-day ECG patch monitor. Heart rates (HR), corrected QT intervals (QTc), and ectopic burden were compared across monitoring modalities. Among 35 patients that wore the patch monitor, the median age was 39 years (54% male). There was intermediate correlation between resting HR across modalities (r = .58-.66) and poor correlation of peak HR (r = .27-.39). There was intermediate correlation between resting QTc intervals across modalities (r = .72-.77) but negligible correlation between QTc intervals at peak HR across modalities (r = -.01 to -.06). There was good correlation in PAC and PVC ectopic burden across the Holter and patch monitor.

Conclusion: Patch monitors may simplify the evaluation of patients for an inherited arrhythmia syndrome and provide resting QT assessment over time. However, QTc interval comparison at peak HRs remains variable, and may be limited by the single-lead ECG vector when using the patch monitor. Apart from QTc intervals at peak HR, patch monitors demonstrated good correlation with the ECG and Holter monitor for other parameters.
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http://dx.doi.org/10.1111/jce.14917DOI Listing
March 2021

Twirling around the block-A complex case of cardiac sarcoidosis.

Heart Rhythm 2021 Jan;18(1):151-153

Division of Cardiology, University of California, San Francisco, San Francisco, California. Electronic address:

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http://dx.doi.org/10.1016/j.hrthm.2020.08.012DOI Listing
January 2021

ECG quiz - Where is the block?

J Electrocardiol 2021 Jan-Feb;64:42-44. Epub 2020 Dec 6.

Division of Cardiology, University of California San Francisco, USA. Electronic address:

A 68 year-old man presented with palpitations. A standard 12‑lead ECG was performed and demonstrated significant conduction disease. Using findings on the index and prior ECGs, we review the differential diagnoses for his conduction abnormality. We discuss the possibility of phase III delay, phase IV delay, and "supernormal conduction" to explain the ECG findings. We explore each of these phenomena and review their relative likelihood as it applies to the case presented.
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http://dx.doi.org/10.1016/j.jelectrocard.2020.11.017DOI Listing
December 2020

The 2020 Canadian Cardiovascular Society/Canadian Heart Rhythm Society Comprehensive Guidelines for the Management of Atrial Fibrillation.

Can J Cardiol 2020 12 22;36(12):1847-1948. Epub 2020 Oct 22.

Institut de Cardiologie de Montréal, Université de Montréal, Montréal, Québec, Canada.

The Canadian Cardiovascular Society (CCS) atrial fibrillation (AF) guidelines program was developed to aid clinicians in the management of these complex patients, as well as to provide direction to policy makers and health care systems regarding related issues. The most recent comprehensive CCS AF guidelines update was published in 2010. Since then, periodic updates were published dealing with rapidly changing areas. However, since 2010 a large number of developments had accumulated in a wide range of areas, motivating the committee to complete a thorough guideline review. The 2020 iteration of the CCS AF guidelines represents a comprehensive renewal that integrates, updates, and replaces the past decade of guidelines, recommendations, and practical tips. It is intended to be used by practicing clinicians across all disciplines who care for patients with AF. The Grading of Recommendations, Assessment, Development and Evaluations (GRADE) system was used to evaluate recommendation strength and the quality of evidence. Areas of focus include: AF classification and definitions, epidemiology, pathophysiology, clinical evaluation, screening and opportunistic AF detection, detection and management of modifiable risk factors, integrated approach to AF management, stroke prevention, arrhythmia management, sex differences, and AF in special populations. Extensive use is made of tables and figures to synthesize important material and present key concepts. This document should be an important aid for knowledge translation and a tool to help improve clinical management of this important and challenging arrhythmia.
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http://dx.doi.org/10.1016/j.cjca.2020.09.001DOI Listing
December 2020

Hemoptysis and Cryoballoon Ablation: Is it Crystal Clear?

JACC Clin Electrophysiol 2020 07;6(7):783-785

Heart Rhythm Services, Department of Medicine, University of British Columbia, Vancouver, British Columbia, Canada; Center for Cardiovascular Innovation, Vancouver, British Columbia, Canada.

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http://dx.doi.org/10.1016/j.jacep.2020.05.033DOI Listing
July 2020

Repeat Atrial Fibrillation Ablation Procedures in the CIRCA-DOSE Study.

Circ Arrhythm Electrophysiol 2020 09 23;13(9):e008480. Epub 2020 Jul 23.

Department of Medicine, University of British Columbia, Vancouver, Canada (C.C.C., M.W.D., J.G.A.).

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http://dx.doi.org/10.1161/CIRCEP.120.008480DOI Listing
September 2020

In-hospital and long-term outcomes among patients with spontaneous coronary artery dissection presenting with ventricular tachycardia/fibrillation.

Heart Rhythm 2020 11 24;17(11):1864-1869. Epub 2020 Jun 24.

Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Background: Spontaneous coronary artery dissection (SCAD) is an important cause of myocardial infarction (MI) in young to middle-age women. Ventricular tachycardia/ventricular fibrillation (VT/VF) may complicate acute SCAD presentations, and the long-term outcomes are unknown.

Objective: The purpose of this study was to report the outcomes of SCAD patients presenting with VT/VF.

Methods: We analyzed our prospective Canadian SCAD registries for patients presenting with VT/VF during index hospitalization. Long-term outcomes including VT/VF and cardiac arrest were collected. Univariate and multivariable analyses were performed to identify predictors of VT/VF at follow-up.

Results: Among 1056 consecutive SCAD patients, 84 (8.0%) presented with VT/VF, and 8 underwent implantable cardioverter-defibrillator (ICD) insertion. Patients with VT/VF during index hospitalization were younger (49.3 vs 52.0 years; P = .019) and were more likely to have ST-elevation MI, lower left ventricular ejection fraction (LVEF), and left main dissection (all P <.001). Initial VT/VF was associated with in-hospital events, including recurrent MI, unplanned revascularization, heart failure, ICD insertion, and in-hospital death (all P <.05). At mean follow-up of 4.8 ± 3.3 years, 8 patients suffered VT/VF (time to event 5.2 ± 6.2 years); 5 of 8 patients had VT/VF on initial SCAD presentation, and 1 of 8 had undergone ICD insertion. Predictors of VT/VF during follow-up included LVEF <50%, LVEF <35%, peripartum SCAD, unplanned revascularization, repeat MI, heart failure, and initial VT/VF. Multivariable analysis showed initial VT/VF (odds ratio [OR] 9.5; 95% confidence interval [CI] 2.0-44; P = .004) and LVEF <50% (OR 12.9; 95% CI 1.5-111; P = .019) were independent predictors of VT/VF at follow-up.

Conclusion: SCAD patients presenting with VT/VF were at greater risk for in-hospital events and recurrent VF/VT at follow-up. Both VT/VF and LVEF <50% were independent predictors of subsequent VT/VF.
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http://dx.doi.org/10.1016/j.hrthm.2020.06.019DOI Listing
November 2020

Changes to the electrocardiogram during exercise in anorexia nervosa.

J Electrocardiol 2020 Jul - Aug;61:99-105. Epub 2020 Jun 10.

Hearts in Rhythm Organization, Division of Cardiology, Department of Medicine, University of British Columbia, 220-1033 Davie St., Vancouver V6E 1M7, B.C., Canada. Electronic address:

Background: Anorexia Nervosa (AN) is an eating disorder characterized by low body weight, distorted body image, and an intense fear of gaining weight. Electrocardiogram (ECG) changes, particularly in the QT interval, have been implicated in AN-associated sudden death but not well defined.

Objectives: To characterize QT interval changes during exercise in anorexia nervosa.

Methods: The QT interval was evaluated in a prospective cohort undergoing structured exercise. Patients from the St. Paul's Hospital Provincial Adult Tertiary Eating Disorders Program underwent a 6-minute modified exercise test protocol. A single lead ECG patch recording device was used to record a Lead I equivalent, due to challenges applying standard ECG monitoring in subjects with low body mass. Heart rate (HR) and QT interval were assessed.

Results: Eighteen eating disorder patients (16 female) completed testing (age 31 ± 12 years, BMI 16.5 ± 3.8 kg/m). Patients were compared to age- and sex-matched healthy controls. HR was similar between patients and controls (baseline: 65 (55-70)bpm vs. 69 (53-73)bpm, p = 0.83; maximum: 110 (94-139) bpm vs. 108 (93-141) bpm, p = 0.96; end recovery: 62 (54-68) bpm vs. 66 (55-75) bpm, p = 0.39). QTc intervals were similar between groups at baseline (381 ± 17 ms vs. 381 ± 46 ms, p = 0.93) and end recovery (397 ± 42 ms vs 398 ± 42 ms, p = 0.91). However, AN patients demonstrated QTc prolongation while controls showed QTc shortening at maximum HR (426 ± 70 ms vs. 345 ± 59 ms, p = 0.001).

Conclusion: Low level exercise HR increases are similar between AN patients and controls, but the QTc interval fails to shorten, which may explain the increased arrhythmic risk in AN.
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http://dx.doi.org/10.1016/j.jelectrocard.2020.06.012DOI Listing
June 2020

Driving Restrictions and Early Arrhythmias in Patients Receiving a Primary-Prevention Implantable Cardioverter-Defibrillator (DREAM-ICD) Study.

Can J Cardiol 2020 08 28;36(8):1269-1277. Epub 2020 May 28.

Heart Rhythm Services, Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Background: Current guidelines recommend 4 weeks of private driving restriction after implantation of a primary-prevention implantable cardioverter-defibrillator (ICD). These driving restrictions result in significant inconvenience and social implications. Advances in medical treatment and ICD programming have lowered the overall rate of device therapies. The objective of this study was to assess the incidence of ICD therapies at 30, 60, and 180 days after implantation.

Methods: Driving Restrictions and Early Arrhythmias in Patients Receiving a Primary-Prevention Implantable Cardioverter-Defibrillator (DREAM-ICD) was a retrospective cohort study conducted at 2 Canadian university centres enrolling patients with new implantation of a primary-prevention ICD. Device programming was standardised according to current guidelines. A total of 803 patients were enrolled.

Results: The cumulative rates of appropriate ICD therapies at 30, 60, and 180 days were 0.12%, 0.50%, and 0.75%, respectively. There was no syncope during the first 6 months. The median duration to the first appropriate ICD therapy was 208 (range 23-1109) days after implantation. The rate of inappropriate ICD therapies at 30 days was only 0.2%. Overall, < 13.6% of all appropriate ICD therapies occurred within the first 6 months after implantation.

Conclusions: The rate of appropriate ICD therapies within the first 30 days after device insertion is extremely low in contemporary primary prevention cohorts with guideline-concordant device programming. There was no increased risk for ventricular arrhythmia early after ICD insertion. The results of DREAM-ICD suggest the need for a revision of the existing driving restrictions for primary-prevention ICD recipients.
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http://dx.doi.org/10.1016/j.cjca.2020.05.029DOI Listing
August 2020

Wearable cardioverter-defibrillators: A review of evidence and indications.

Trends Cardiovasc Med 2021 Apr 12;31(3):196-201. Epub 2020 Mar 12.

Division of Cardiology, Electrophysiology and Arrhythmia Service, University of California, San Francisco. 500 Parnassus Avenue, Box 1354, MU 429, San Francisco, CA 94143-1354, United States. Electronic address:

The wearable cardioverter-defibrillator (WCD) was first approved for clinical use in 2002, and is routinely used in select populations at high risk for sudden cardiac death. WCDs are frequently considered as a bridge to definitive therapy or in circumstances where insertion of conventional implantable cardioverter-defibrillators (ICD) is temporarily contraindicated. In this review, we summarize the literature on WCDs. From prospective trials to the first randomized controlled trial with WCD, there is a growing body of evidence that suggests that the WCD is safe and effective. In the first randomized controlled trial of the WCD (VEST Trial), there was no reduction in arrhythmia death but there was a reduction in all-cause mortality. We discuss the mortality impact, rate of inappropriate shocks, compliance, and potential quality of life implications with the WCD. Finally, we present the evidence for WCD use in select populations (e.g., post-myocardial infarction, device extraction), and the current guideline recommendations for WCD use.
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http://dx.doi.org/10.1016/j.tcm.2020.03.002DOI Listing
April 2021

A Case of Adult-Onset Kawasaki Disease Shock Syndrome Complicated by Coronary Aneurysms.

CJC Open 2019 Jul 10;1(4):206-208. Epub 2019 Apr 10.

Division of General Internal Medicine, University of British Columbia, Vancouver, British Columbia, Canada.

We present a case of adult-onset Kawasaki disease shock syndrome complicated by coronary aneurysms, in which profound hypotension and reduced left ventricular ejection fraction were treated successfully with intravenous immunoglobulin. The diagnosis of Kawasaki disease shock syndrome should be considered in cases of rapidly developing shock, particularly in young adults with an infectious prodrome, in whom it may be under-recognized. We advocate for early identification to minimize delays in treatment with intravenous immunoglobulin, which reverses left ventricular dysfunction and decreases risk of long-term sequelae such as coronary artery aneurysms.
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http://dx.doi.org/10.1016/j.cjco.2019.04.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7063621PMC
July 2019

Arrhythmias in Cardiac Amyloidosis: Challenges in Risk Stratification and Treatment.

Can J Cardiol 2020 03 12;36(3):416-423. Epub 2019 Dec 12.

Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Cardiac amyloidosis occurs secondarily to the deposition of insoluble protein fibrils in cardiac tissue leading to progressive myocardial dysfunction, clinical heart failure, and arrhythmia. In recent years, increasing awareness and improved screening have resulted in an increased prevalence of cardiac amyloidosis, with contemporary estimates reporting a prevalence of 18-55 cases per 100,000 person-years, accounting for > 13% of heart failure hospitalizations. The arrhythmic manifestations of cardiac amyloidosis can range from conduction-system disease and bradyarrhythmias to atrial fibrillation and sudden cardiac death. Bradyarrhythmias and conduction system disease may occur secondarily to amyloid infiltration, but the timing of pacemaker implantation remains unclear. When available, biventricular pacing should be considered in symptomatic patients, particularly in those expected to receive a high burden of ventricular pacing (> 40%). The management of atrial fibrillation can be challenging, because contemporary agents for rate and rhythm control may be poorly tolerated in patients with cardiac amyloidosis. Patients with cardiac amyloidosis also have a high rate of intracardiac thrombus and should be anticoagulated in the presence of atrial fibrillation (regardless of CHADS score). We generally consider transesophageal echocardiography before cardioversion regardless of anticoagulation status or duration of arrhythmia. Ventricular arrhythmias may also occur in patients with cardiac amyloidosis, and decisions surrounding implantable cardioverter-defibrillator implantation should balance the risks of ventricular arrhythmia and sudden cardiac death with the competing risks of worsening heart failure and noncardiac death. In this review, we cover the primary arrhythmic manifestations of cardiac amyloidosis and discuss their management considerations.
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http://dx.doi.org/10.1016/j.cjca.2019.11.039DOI Listing
March 2020

Genetic Testing in Inherited Arrhythmias: Approach, Limitations, and Challenges.

Can J Cardiol 2020 04 10;36(4):584-587. Epub 2019 Sep 10.

Heart Rhythm Services, Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Genetic testing is playing an ever-expanding role in cardiovascular care and is becoming part of the "toolkit" for the cardiovascular clinician. In patients with inherited arrhythmias, genetic testing can confirm a suspected diagnosis, establish a diagnosis in unexplained cases, and help facilitate cascade family screening. Many inherited arrhythmia syndromes are monogenic diseases arising from a single pathogenic variant involved in the structure and function of cardiac ion channels or structural proteins. As such, "arrhythmia gene panels" will often cast a wide net for such heritable diseases. However, challenges may arise when genetic testing results are ambiguous, or when genetic testing results (genotype) and clinical phenotypes do not match. In cases of "genotype-phenotype matching," genetic results complement the clinical phenotype and genetic testing can be used in diagnosis, family screening, and occasionally prognostication. It becomes more challenging when genetic results are negative or noncontributory and "contradict" the clinical phenotype. "Genotype mismatches" can also occur when genotype-positive patients have no clinical phenotype, or when genetic testing results point towards a completely different disease than the clinical phenotype. We discuss an approach to genetic testing and review the challenges that may arise when interpreting genetic testing results. Genetic testing has opened a wealth of opportunities in the diagnosis, management, and cascade screening of inherited arrhythmia syndromes, but has also opened a "Pandora's box" of challenges. Genetic results should be interpreted with caution and in a multidisciplinary clinic, with support from genetic counsellors and an expert with a focused interest in cardiovascular genetics.
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http://dx.doi.org/10.1016/j.cjca.2019.08.041DOI Listing
April 2020

The Potential Impact of Intrathoracic Impedance on Defibrillation Threshold Testing in S-ICDs.

Can J Cardiol 2019 Nov 25;35(11):1604.e13-1604.e16. Epub 2019 Jul 25.

Heart Rhythm Services, St Paul's Hospital, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

A man with an ischemic cardiomyopathy and chronic obstructive pulmonary disease underwent subcutaneous implantable cardioverter-defibrillator (S-ICD) placement under general anesthesia. Following induction of ventricular fibrillation (VF), defibrillation testing (65J) failed, requiring external rescue. Repeat shock testing with reversed polarity (65J) failed. A third shock and external defibrillation failed (80J and 200J), followed by a second external defibrillation (200J), which did not immediately terminate VF, and a device shock 2 seconds later (80J, successful). Repeat shock testing (80J) under conscious sedation without mechanical ventilation was successful. We discuss this case of failed defibrillation testing during S-ICD placement, potentially due to lung hyperinflation, requiring double sequential defibrillation.
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http://dx.doi.org/10.1016/j.cjca.2019.07.624DOI Listing
November 2019

Caring for the pregnant woman with an inherited arrhythmia syndrome.

Heart Rhythm 2020 02 7;17(2):341-348. Epub 2019 Aug 7.

Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Pregnancy is a period of increased cardiovascular risk in a woman's life. In the setting of an inherited arrhythmia syndrome (IAS), cardiologists and obstetricians may be unfamiliar with cardiovascular optimization and risk stratification in pregnancy. Historically, there were little data addressing the safety of pregnancy in these rare disorders. Recent advances suggest that no type of IAS represents an absolute contraindication to pregnancy. However, it is imperative that obstetric and cardiovascular clinicians understand the major forms of IAS and how they affect the risks and course of pregnancy. This includes any disease-specific proarrhythmic triggers unique to pregnancy, such as the postpartum period in long QT syndrome (especially type 2), which poses the greatest risk of arrhythmias, and the adrenergic nature of labor and delivery, which is relevant to catecholaminergic polymorphic ventricular tachycardia. Fortunately, several effective antiarrhythmic options exist that pose little fetal risk. IAS-specific optimization of implantable cardioverter-defibrillator algorithms, drug therapy, and a maternal cardiac plan addressing the antepartum, labor, and delivery and postpartum periods reduces the risk. Where evidence does not exist, there are plausible mechanistic considerations to guide clinicians. To achieve optimal outcomes, early involvement of an expert pregnancy heart team comprising obstetrics, genetics, cardiology, and anesthesiology team members and a shared decision-making approach to IAS issues in pregnancy are needed.
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http://dx.doi.org/10.1016/j.hrthm.2019.08.004DOI Listing
February 2020

Changes on the electrocardiogram in anorexia nervosa: A case control study.

J Electrocardiol 2019 Sep - Oct;56:64-69. Epub 2019 Jul 8.

Heart Rhythm Services, Division of Cardiology, Department of Medicine, University of British Columbia, 220-1033 Davie St, Vancouver, British Columbia V6E 1M5, Canada. Electronic address:

Purpose: Anorexia nervosa is a complex psychiatric condition with increased mortality. The electrocardiogram (ECG) may show repolarization changes which may associate with an increased risk of sudden death. Up to 80% of patients may be prescribed psychopharmacotherapies which alter the ECG, potentially compounding arrhythmic risk. This study aimed to describe and improve understanding of ECG changes in eating disorders and assess the effect of psychopharmacotherapies.

Methods: Adolescent patients diagnosed with anorexia nervosa were reviewed. ECGs were reviewed by blinded expert reviewers, and repolarization parameters were compared to healthy controls. Patients on and off psychopharmacotherapies were compared.

Results: Thirty-eight anorexia nervosa patients off psychopharmacotherapies were age matched to 53 healthy controls. Heart rate was lower in anorexia nervosa patients (56 vs. 74 bpm, p < 0.001). The absolute QT interval was longer in patients compared to controls (408 vs. 383 ms, p < 0.001), but the QTc by Hodges' formula was similar between groups (401 vs. 408 ms, p = 0.16). The prevalence of T-wave flattening and inversion was also similar between groups (13% vs. 4%, p = 0.12) and T-peak to T-end interval (Tpe) was shorter in patients compared to controls (p < 0.01). ECG parameters were similar between patients on and off psychopharmacotherapies aside from off-drug patients showing lower HR (56 vs. 65, p = 0.04).

Conclusions: Autonomic and repolarization changes are evident on the ECG of anorexia nervosa patients, though the QTc interval was in fact similar between groups. Changes in T-wave morphology and duration may be promising metrics of repolarization effects of anorexia nervosa.
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http://dx.doi.org/10.1016/j.jelectrocard.2019.07.006DOI Listing
July 2019

The wearable cardioverter-defibrillator vest: Indications and ongoing questions.

Prog Cardiovasc Dis 2019 May - Jun;62(3):256-264. Epub 2019 May 9.

Division of Cardiology, Electrophysiology and Arrhythmia Service, University of California, San Francisco. Electronic address:

Multiple clinical trials have demonstrated the efficacy of implantable cardioverter-defibrillators (ICDs) for the prevention of sudden cardiac death (SCD) among specific high-risk populations. However, it remains unclear how to optimally treat those patients who are at elevated risk of cardiac arrest but are not among the presently identified groups proven to benefit from an ICD, are unable to tolerate surgical device implantation, or refuse invasive therapies. The wearable cardioverter-defibrillator (WCD) is an alternative antiarrhythmic device that provides continuous cardiac monitoring and defibrillation capabilities through a noninvasive, electrode-based system. The WCD has been shown to be highly effective at restoration of sinus rhythm in patients with a ventricular tachyarrhythmia, and one randomized trial using the WCD in patients with recent myocardial infarction at elevated risk for arrhythmic death reported a decrease in overall mortality despite no SCD mortality benefit. The current clinical indications for WCD use are varied and continue to evolve as experience with this technology increases.
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http://dx.doi.org/10.1016/j.pcad.2019.05.005DOI Listing
October 2019

Comparison of Ajmaline and Procainamide Provocation Tests in the Diagnosis of Brugada Syndrome.

JACC Clin Electrophysiol 2019 04 27;5(4):504-512. Epub 2019 Mar 27.

Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Objectives: The authors studied the response rates and relative sensitivity of the most common agents used in the sodium-channel blocker (SCB) challenge.

Background: A type 1 Brugada electrocardiographic pattern precipitated by an SCB challenge confers a diagnosis of Brugada syndrome.

Methods: Patients undergoing an SCB challenge were prospectively enrolled across Canada and the United Kingdom. Patients with no prior cardiac arrest and family histories of sudden cardiac death or Brugada syndrome were included.

Results: Four hundred twenty-five subjects underwent SCB challenge (ajmaline, n = 331 [78%]; procainamide, n = 94 [22%]), with a mean age of 39 ± 15 years (54% men). Baseline non-type 1 Brugada ST-segment elevation was present in 10%. A total of 154 patients (36%) underwent signal-averaged electrocardiography, with 41% having late potentials. Positive results were seen more often with ajmaline than procainamide infusion (26% vs. 4%, p < 0.001). On multivariate analysis, baseline non-type 1 Brugada ST-segment elevation (odds ratio [OR]: 6.92; 95% confidence interval [CI]: 3.15 to 15.2; p < 0.001) and ajmaline use (OR: 8.76; 95% CI: 2.62 to 29.2; p < 0.001) were independent predictors of positive results to SCB challenge. In the subgroup undergoing signal-averaged electrocardiography, non-type 1 Brugada ST-segment elevation (OR: 9.28; 95% CI: 2.22 to 38.8; p = 0.002), late potentials on signal-averaged electrocardiography (OR: 4.32; 95% CI: 1.50 to 12.5; p = 0.007), and ajmaline use (OR: 12.0; 95% CI: 2.45 to 59.1; p = 0.002) were strong predictors of SCB outcome.

Conclusions: The outcome of SCB challenge was significantly affected by the drug used, with ajmaline more likely to provoke a type 1 Brugada electrocardiographic pattern compared with procainamide. Patients undergoing SCB challenge may have contrasting results depending on the drug used, with potential clinical, psychosocial, and socioeconomic implications.
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http://dx.doi.org/10.1016/j.jacep.2019.01.026DOI Listing
April 2019

Letter by Cheung et al Regarding Article, "Concealed Arrhythmogenic Right Ventricular Cardiomyopathy in Sudden Unexplained Cardiac Death Events".

Circ Genom Precis Med 2019 03;12(3):e002447

Heart Rhythm Services, Division of Cardiology, University of British Columbia, Vancouver, Canada.

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http://dx.doi.org/10.1161/CIRCGEN.118.002447DOI Listing
March 2019

Pregnancy in Catecholaminergic Polymorphic Ventricular Tachycardia.

JACC Clin Electrophysiol 2019 03 26;5(3):387-394. Epub 2018 Dec 26.

Heart Rhythm Services, Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Objectives: This investigation was a retrospective study of catecholaminergic polymorphic ventricular tachycardia (CPVT) patients in Canada and the Netherlands to compare pregnancy, postpartum, and nonpregnant event rates.

Background: CPVT is characterized by life-threatening arrhythmias during exertion or emotional stress. The arrhythmic risk in CPVT patients during pregnancy is unknown.

Methods: Baseline demographics, genetics, treatment, and pregnancy complications were reviewed. Event rate calculations assumed a 40-week pregnancy and 24-week postpartum period.

Results: Ninety-six CPVT patients had 228 pregnancies (median 2 pregnancies per patient; range: 1 to 10; total: 175.4 pregnant patient-years). The median age of CPVT diagnosis was 40.7 years (range: 12 to 84 years), with a median follow-up of 2.9 years (range: 0 to 20 years; total 448.1 patient-years). Most patients had pregnancies before CPVT diagnosis (82%). Pregnancy and postpartum cardiac events included syncope (5%) and an aborted cardiac arrest (1%), which occurred in patients who were not taking beta-blockers. Other complications included miscarriages (13%) and intrauterine growth restriction (1 case). There were 6 cardiac events (6%) during the nonpregnant period. The pregnancy and postpartum event rates were 1.71 and 2.85 events per 100 patient-years, respectively, and the combined event rate during the pregnancy and postpartum period was 2.14 events per 100 patient-years. These rates were not different from the nonpregnant event rate (1.46 events per 100 patient-years).

Conclusions: The combined pregnancy and postpartum arrhythmic risk in CPVT patients was not elevated compared with the nonpregnant period. Most patients had pregnancies before diagnosis, and all patients with events were not taking beta-blockers at the time of the event.
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http://dx.doi.org/10.1016/j.jacep.2018.10.019DOI Listing
March 2019

Challenge and Impact of Quinidine Access in Sudden Death Syndromes: A National Experience.

JACC Clin Electrophysiol 2019 03 28;5(3):376-382. Epub 2018 Nov 28.

University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Objectives: This study sought to determine the nature of quinidine use and accessibility in a national network of inherited arrhythmia clinics.

Background: Quinidine is an antiarrhythmic medication that has been shown to be beneficial in select patients with Brugada syndrome, early repolarization syndrome, and idiopathic ventricular fibrillation. Because of the low prevalence of these conditions and restricted access to quinidine through a single regulatory process, quinidine use is rare in Canada.

Methods: Subjects prescribed quinidine were identified through the Hearts in Rhythm Organization that connects the network of inherited arrhythmia clinics across Canada. Cases were retrospectively reviewed for patient characteristics, indications for quinidine use, rate of recurrent ventricular arrhythmia, and issues with quinidine accessibility.

Results: In a population of 36 million, 46 patients are currently prescribed quinidine (0.0000013%, age 48.1 ± 16.1 years, 25 are male). Brugada syndrome, early repolarization syndrome, and idiopathic ventricular fibrillation constituted a diagnosis in 13 subjects (28%), 6 (13%), and 21 (46%), respectively. Overall, 37 subjects (81%) had cardiac arrest as an index event. After initial presentation, subjects experienced 7.47 ± 12.3 implantable cardioverter-defibrillator shocks prior to quinidine use over 34.3 ± 45.9 months, versus 0.86 ± 1.69 implantable cardioverter-defibrillator shocks in 43.8 ± 41.8 months while on quinidine (risk ratio: 8.7, p < 0.001). Twenty-two patients access quinidine through routes external to Health Canada's Special Access Program.

Conclusions: Quinidine use is rare in Canada, but it is associated with a reduction in recurrent ventricular arrhythmias in patients with Brugada syndrome, early repolarization syndrome, and idiopathic ventricular fibrillation, with minimal toxicity necessitating discontinuation. Drug interruption is associated with frequent breakthrough events. Access to quinidine is important to deliver this potentially lifesaving therapy.
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http://dx.doi.org/10.1016/j.jacep.2018.10.007DOI Listing
March 2019

Early Repolarization Pattern Inheritance in the Cardiac Arrest Survivors With Preserved Ejection Fraction Registry (CASPER).

JACC Clin Electrophysiol 2018 11 29;4(11):1473-1479. Epub 2018 Aug 29.

University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Objectives: This study explored early repolarization (ER) pattern inheritance between survivors of unexplained cardiac arrest (UCA) and their first-degree relatives.

Background: ER is considered a factor that confers an increased risk of sudden death. A monogenic explanation for ER is seldom evident after cascade screening.

Methods: UCA survivors and their first-degree relatives enrolled in the CASPER (Cardiac Arrest Survivors With Preserved Ejection Fraction Registry) were included in the study. ER was defined and characterized according to accepted criteria. Logistic regression was performed to explore the association between ER status in the UCA survivor and first-degree relative groups based on the presence of an ER pattern in their related family members after adjusting for age, sex, and ethnicity.

Results: A total of 289 patients from 14 Canadian sites were studied (age: 43.0 ± 15.9 years; 148 women), and 945 electrocardiograms were analyzed. Seventy-five patients had the ER pattern. There was a significantly higher prevalence of the ER pattern in UCA survivors who had first-degree relatives with the ER pattern (adjusted odds ratio: 5.79; 95% confidence intervals [CIs]: 1.79 to 18.7). There was also a nonsignificant higher prevalence of the ER pattern in first-degree relatives of UCA survivors with the ER pattern (OR: 2.43; 95% CI: 0.70 to 8.43). The highest prevalence of the ER pattern was seen in first-degree relatives of UCA survivors with ER syndrome (29%).

Conclusions: The ER pattern appeared to be more common among UCA survivors and first-degree relatives whose related family members had similar changes on electrocardiography, which suggested that genetically complex factors contribute to electrocardiographic patterns that predispose to cardiac arrest.
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http://dx.doi.org/10.1016/j.jacep.2018.07.001DOI Listing
November 2018

Atrial fibrillation detected initially during acute medical illness: A systematic review.

Eur Heart J Acute Cardiovasc Care 2019 Mar 7;8(2):130-141. Epub 2018 Nov 7.

1 Population Health Research Institute, McMaster University, Canada.

Objective:: There is uncertainty about the incidence of and prognosis associated with atrial fibrillation that is documented for the first time in the setting of an acute stressor, such as surgery or medical illness. Our objective was to perform a systematic review of the incidence and long-term recurrence rates for atrial fibrillation occurring transiently with stress in the setting of acute medical illness.

Data Sources:: Medline, Embase and Cochrane Central to September 2017.

Study Selection:: We included retrospective and prospective observational studies, and randomised controlled trials. The population of interest included patients hospitalised for medical (i.e. non-surgical) illness who developed newly diagnosed atrial fibrillation. Studies were included if they included data on either the incidence of atrial fibrillation or the rate of atrial fibrillation recurrence in atrial fibrillation occurring transiently with stress patients following hospital discharge.

Data Extraction:: Two reviewers collected data independently and in duplicate. We characterised each study's methodology for ascertainment of prior atrial fibrillation history, atrial fibrillation during hospitalisation and atrial fibrillation recurrence after hospital discharge.

Data Synthesis:: Thirty-six studies reported the incidence of atrial fibrillation. Ten used a prospective design and included a period of continuous electrocardiographic (ECG) monitoring. Atrial fibrillation incidence ranged from 1% to 44%, which was too heterogeneous to justify meta-analysis ( I=99%). In post-hoc meta-regression models, the use of continuous ECG monitoring explained 13% of the variance in atrial fibrillation incidence, while care in an intensive care unit explained none. Two studies reported the long-term rate of atrial fibrillation recurrence following atrial fibrillation occurring transiently with stress. Neither of these studies used prospective, systematic monitoring. Recurrence rates at 5 years ranged from 42% to 68%.

Conclusions:: The incidence of atrial fibrillation with medical illness may be as high as 44%, with higher estimates in reports using continuous ECG monitoring. Within 5 years following hospital discharge, atrial fibrillation recurrence is documented in approximately half of patients; however, the true rate may be higher.

Protocol Registration: PROSPERO CRD42016043240.
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http://dx.doi.org/10.1177/2048872618799748DOI Listing
March 2019

The Emerging Role of Wearable Technologies in Detection of Arrhythmia.

Can J Cardiol 2018 08 9;34(8):1083-1087. Epub 2018 May 9.

Heart Rhythm Services, Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Over the past decade, there has been an explosion of consumer devices for the purposes of health and fitness tracking. The wearable technology market, composed of devices that monitor physiological parameters, such as heart rate and sleep pattern, is anticipated to grow to 929 million connected devices in 2021. These devices encompass wristbands, glasses, in-ear monitors, or electronic shirts, with varying capacity to monitor heart rate, heart rhythm, blood pressure, physical activity, respiratory rate, blood glucose, and sleep patterns. For heart-rate monitoring, most wearable devices use photoplethysmography (PPG) technology, meaning they are inherently less accurate than conventional electrocardiography monitoring techniques (reference standard). However, a growing body of evidence suggests that these technologies can be harnessed to facilitate arrhythmia detection in the appropriate context. Studies evaluating PPG-based wearables in conjunction with machine-learning algorithms have shown promise in detection of such arrhythmias, as atrial fibrillation. Limitations of wearable technologies include their accuracy and accessibility and the clinical implications of wearable-detected arrhythmias. Despite this, wearable technologies represent an important frontier in health evaluation. Future wearables will benefit from improved reliability and accuracy, collect additional health and fitness parameters, support management of chronic disease, and provide real-time connectivity and feedback that may supplant conventional medical monitoring. Wearables have the potential to become truly disruptive in our health care sector, with large segments of the population soon to have readily available health data that the physician must interpret.
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http://dx.doi.org/10.1016/j.cjca.2018.05.003DOI Listing
August 2018