Publications by authors named "Christopher C Cheung"

52 Publications

Importance of genetic testing in unexplained cardiac arrest.

Eur Heart J 2022 Mar 30. Epub 2022 Mar 30.

Cardiovascular Genetics Center, Montreal Heart Institute, Department of Medicine, Université de Montréal, 5000 Belanger, Montreal, QC, Canada H1T 1C8.

Aims: Genetic testing is recommended in specific inherited heart diseases but its role remains unclear and it is not currently recommended in unexplained cardiac arrest (UCA). We sought to assess the yield and clinical utility of genetic testing in UCA using whole-exome sequencing (WES).

Methods And Results: Survivors of UCA requiring external defibrillation were included from the Cardiac Arrest Survivor with Preserved Ejection fraction Registry. Whole-exome sequencing was performed, followed by assessment of rare variants in previously reported cardiovascular disease genes. A total of 228 UCA survivors (mean age at arrest 39 ± 13 years) were included. The majority were males (66%) and of European ancestry (81%). Following advanced clinical testing at baseline, the likely aetiology of cardiac arrest was determined in 21/228 (9%) cases. Whole-exome sequencing identified a pathogenic or likely pathogenic (P/LP) variant in 23/228 (10%) of UCA survivors overall, increasing the proportion of 'explained' cases from 9% only following phenotyping to 18% when combining phenotyping with WES. Notably, 13 (57%) of the 23 P/LP variants identified were located in genes associated with cardiomyopathy, in the absence of a diagnosis of cardiomyopathy at the time of arrest.

Conclusions: Genetic testing identifies a disease-causing variant in 10% of apparent UCA survivors. The majority of disease-causing variants was located in cardiomyopathy-associated genes, highlighting the arrhythmogenic potential of such variants in the absence of an overt cardiomyopathy diagnosis. The present study supports the use of genetic testing including assessment of arrhythmia and cardiomyopathy genes in survivors of UCA.
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http://dx.doi.org/10.1093/eurheartj/ehac145DOI Listing
March 2022

A peculiar case of palpitations and syncope.

Heart Rhythm 2022 03;19(3):505-507

Section of Cardiac Electrophysiology, University of California San Francisco, San Francisco, California.

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http://dx.doi.org/10.1016/j.hrthm.2021.11.019DOI Listing
March 2022

Factors Affecting Yield of Genetic Testing of Sudden Deaths in Young Individuals.

JAMA Cardiol 2022 May;7(5):568

Section of Cardiac Electrophysiology, Division of Cardiology, University of California, San Francisco.

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http://dx.doi.org/10.1001/jamacardio.2021.6023DOI Listing
May 2022

From Improving Survival to Cost Savings for the Health System-Remote Monitoring for All?

Can J Cardiol 2022 Feb 9. Epub 2022 Feb 9.

Section of Cardiac Electrophysiology, University of California, San Francisco, California, USA.

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http://dx.doi.org/10.1016/j.cjca.2022.01.032DOI Listing
February 2022

Iatrogenic Atrioventricular Block.

Card Electrophysiol Clin 2021 12 25;13(4):711-720. Epub 2021 Sep 25.

Section of Cardiac Electrophysiology, Division of Cardiology, University of California San Francisco, MU-East 4th Floor, 500 Parnassus Avenue, San Francisco, CA 94143, USA. Electronic address:

Iatrogenic atrioventricular (AV) block can occur in the context of cardiac surgery, percutaneous transcatheter, or electrophysiologic procedures. In cardiac surgery, patients undergoing aortic and/or mitral valve surgery are at the highest risk for developing perioperative AV block requiring permanent pacemaker implantation. Similarly, patients undergoing transcatheter aortic valve replacement are also at increased risk for developing AV block. Electrophysiologic procedures, including catheter ablation of AV nodal re-entrant tachycardia, septal accessory pathways, para-Hisian atrial tachycardia, or premature ventricular complexes, are also associated with risk of AV conduction system injury. In this article, we summarize the common causes for iatrogenic AV block, predictors for AV block, and general management considerations.
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http://dx.doi.org/10.1016/j.ccep.2021.06.010DOI Listing
December 2021

Beware of the hazards: limitations of the proportional hazards assumption.

Europace 2021 12;23(12):2048

Section of Cardiac Electrophysiology, Division of Cardiology, University of California San Francisco, 500 Parnassus Avenue, San Francisco, CA 94117, USA.

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http://dx.doi.org/10.1093/europace/euab137DOI Listing
December 2021

Effect of Continuous Electrocardiogram Monitoring on Detection of Undiagnosed Atrial Fibrillation After Hospitalization for Cardiac Surgery: A Randomized Clinical Trial.

JAMA Netw Open 2021 08 2;4(8):e2121867. Epub 2021 Aug 2.

Southlake Regional Health Center, University of Toronto, Newmarket, Ontario, Canada.

Importance: Postoperative atrial fibrillation (POAF) occurring after cardiac surgery is associated with adverse outcomes. Whether POAF persists beyond discharge is not well defined.

Objective: To determine whether continuous cardiac rhythm monitoring enhances detection of POAF among cardiac surgical patients during the first 30 days after hospital discharge compared with usual care.

Design, Setting, And Participants: This study is an investigator-initiated, open-label, multicenter, randomized clinical trial conducted at 10 Canadian centers. Enrollment spanned from March 2017 to March 2020, with follow-up through September 11, 2020. As a result of the COVID-19 pandemic, enrollment stopped on July 17, 2020, at which point 85% of the proposed sample size was enrolled. Cardiac surgical patients with CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes, prior stroke or transient ischemic attack, vascular disease, age 65-74 years, female sex) score greater than or equal to 4 or greater than or equal to 2 with risk factors for POAF, no history of preoperative AF, and POAF lasting less than 24 hours during hospitalization were enrolled.

Interventions: The intervention group underwent continuous cardiac rhythm monitoring with wearable, patch-based monitors for 30 days after randomization. Monitoring was not mandated in the usual care group within 30 days after randomization.

Main Outcomes And Measures: The primary outcome was cumulative AF and/or atrial flutter lasting 6 minutes or longer detected by continuous cardiac rhythm monitoring or by a 12-lead electrocardiogram within 30 days of randomization. Prespecified secondary outcomes included cumulative AF lasting 6 hours or longer and 24 hours or longer within 30 days of randomization, death, myocardial infarction, ischemic stroke, non-central nervous system thromboembolism, major bleeding, and oral anticoagulation prescription.

Results: Of the 336 patients randomized (163 patients in the intervention group and 173 patients in the usual care group; mean [SD] age, 67.4 [8.1] years; 73 women [21.7%]; median [interquartile range] CHA2DS2-VASc score, 4.0 [3.0-4.0] points), 307 (91.4%) completed the trial. In the intent-to-treat analysis, the primary end point occurred in 32 patients (19.6%) in the intervention group vs 3 patients (1.7%) in the usual care group (absolute difference, 17.9%; 95% CI, 11.5%-24.3%; P < .001). AF lasting 6 hours or longer was detected in 14 patients (8.6%) in the intervention group vs 0 patients in the usual care group (absolute difference, 8.6%; 95% CI, 4.3%-12.9%; P < .001).

Conclusions And Relevance: In post-cardiac surgical patients at high risk of stroke, no preoperative AF history, and AF lasting less than 24 hours during hospitalization, continuous monitoring revealed a significant increase in the rate of POAF after discharge that would otherwise not be detected by usual care. Studies are needed to examine whether these patients will benefit from oral anticoagulation therapy.

Trial Registration: ClinicalTrials.gov Identifier: NCT02793895.
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http://dx.doi.org/10.1001/jamanetworkopen.2021.21867DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8397929PMC
August 2021

Process of Care and a Practical Toolkit for Evaluating and Managing Arrhythmic Risk in the Cardiogenetic Pregnant Patient.

Can J Cardiol 2021 12 17;37(12):2001-2013. Epub 2021 Aug 17.

Centre for Cardiovascular Innovation, Division of Cardiology, University of British Columbia, Vancouver, British Columbia, Canada. Electronic address:

Patients with inherited arrhythmia syndromes (IASs) and inherited cardiomyopathies (ICs) are periodically encountered in both general and specialist practices. These syndromes include long QT syndrome, catecholaminergic polymorphic ventricular tachycardia, Brugada syndrome, early repolarisation syndrome, and hypertrophic and arrhythmogenic cardiomyopathies. In general, the presence of an IAS or IC is not a contraindication to pregnancy, but does require additional expertise and patient engagement. In this review, we summarise the various pregnancy-related considerations in patients with IAS and IC, including the impact of physiologic/hemodynamic changes on heart failure progression or arrhythmia propensity, maternal and fetal pregnancy risk stratification, prenatal genetic testing, and the specialised care and monitoring required through pregnancy, labour, and delivery and into the postpartum period. Management of patients with IASs and IC during pregnancy and the postpartum period requires collaboration between patient and provider, with a shared understanding of the general safety and potential risks during the pregnancy and postpartum periods. Patients should be aware of the safety of various medications throughout pregnancy, and those with implantable cardioverter-defibrillators should be managed according to device guidelines. A peripartum care and delivery plan should be established, with multidisciplinary input from various specialists including obstetrics, cardiac obstetrics, and inherited arrhythmia specialists wherever appropriate.
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http://dx.doi.org/10.1016/j.cjca.2021.08.004DOI Listing
December 2021

Atrial Tachycardia Ablation at the Pulmonic Valve in a Patient With Congenitally Corrected Transposition of Great Arteries.

JACC Clin Electrophysiol 2021 11 27;7(11):1473-1481. Epub 2021 Jul 27.

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

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http://dx.doi.org/10.1016/j.jacep.2021.06.017DOI Listing
November 2021

Management of Atrial Fibrillation in 2021: An Updated Comparison of the Current CCS/CHRS, ESC, and AHA/ACC/HRS Guidelines.

Can J Cardiol 2021 10 26;37(10):1607-1618. Epub 2021 Jun 26.

University of British Columbia, Vancouver, British Columbia, Canada; Montréal Heart Institute, Université de Montréal, Montréal, Québec, Canada; Center for Cardiovascular Innovation, Vancouver, British Columbia, Canada. Electronic address:

Given its complexity, the management of atrial fibrillation (AF) has relied increasingly on expert guideline recommendations; however, discrepancies between these professional societies can lead to confusion among practicing clinicians. This article compares the recommendations in the 2019 American Heart Association (AHA)/American College of Cardiology (ACC)/Heart Rhythm Society (HRS), the 2020 European Society of Cardiology (ESC), and the 2020 Canadian Cardiovascular Society/Canadian Heart Rhythm Society (CCS/CHRS) AF guidelines. Although many of the recommendations are fundamentally similar, there are important differences among guidelines; specifically, key differences are present in (1) definitions and classification of AF; (2) the role of opportunistic AF detection; (3) symptom and quality-of-life evaluation; (4) stroke-risk stratification and the indication for oral anticoagulation (OAC) therapy; (5) the role of aspirin in prevention of stroke for patients with AF; (6) the antithrombotic regimens employed in the context of coronary artery disease; (7) the role of OAC, and specifically non-vitamin K direct-acting oral anticoagulants (DOACs), in patients with chronic and end-stage renal disease; (8) the target heart rate for patients treated with a rate-control strategy, along with the medications recommended to achieve the heart-rate target; and (9) the role of catheter ablation as first-line therapy or in patients with heart failure. These differences highlight areas of continuing clinical uncertainty in which there are important needs and opportunities for future investigative work.
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http://dx.doi.org/10.1016/j.cjca.2021.06.011DOI Listing
October 2021

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 10 5;15(10):1347-1354. 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
October 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 01;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
June 2021

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 2021

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 04 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
June 2021
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