Download PDF - Circulation: Arrhythmia and Electrophysiology

June 2012
Circulation: Arrhythmia and Electrophysiology
Topic Review
Circulation: Arrhythmia and Electrophysiology Editors’ Picks
Most Read Articles on Arrhythmia Devices (Defibrillation, Pacing,
Pacemakers, Heart Arrest, and Resuscitation)
The Editors
The following articles are being highlighted as part of Circulation: Arrhythmia and Electrophysiology’s Topic Review series. This series will
summarize the most important manuscripts, as selected by the editors, published in Circulation: Arrhythmia and Electrophysiology,
Circulation, and the other Circulation subspecialty journals. The studies included in this article represent the most read manuscripts ­published
on the topic of arrhythmia devices (defibrillation, pacing, pacemakers, heart arrest, and resuscitation) in 2010 and 2011. (Circ Arrhythm
Electrophysiol. 2012;5:e69-e77.)
Downloaded from http://circep.ahajournals.org/ by guest on May 12, 2017
Efficacy of Low Interatrial Septum and Right
Atrial Appendage Pacing for Prevention of
Permanent Atrial Fibrillation in Patients With
Sinus Node Disease: Results From the
Electrophysiology-Guided Pacing Site
Selection (EPASS) Study
failure (HF). The GREATER-EARTH trial tested the hypothesis
that left ventricular (LV) pacing alone is superior to biventricular (BiV) pacing with regard to exercise tolerance (primary outcome) and LV structural remodeling (secondary outcomes). This
multicenter, randomized, double-blind, crossover trial enrolled
patients with an LV ejection fraction ≤35%, QRS duration
≥120 ms, and severely impaired exercise tolerance (6-minute
walk distance ≤400 meters). A unique run-in period (with cardiac resynchronization therapy off) between implantation and the
baseline assessment allowed for maturation of the system, identification of disqualifying issues, and optimization of medical
therapy before randomization. The most marked clinical improvement occurred during this run-in phase and could be attributed, in
part, to uptitration of β-blockers. Overall, the 2 pacing strategies
resulted in similar improvements in exercise capacity and reverse
LV remodeling. The most effective mode varied between patients,
with some nonresponders to BiV pacing responding favorably to
LV pacing, and vice versa. In addition to providing a rationale
for a trial of crossover from 1 pacing mode to the other in initial
nonresponders, results may prove relevant to future innovations
in cardiac resynchronization therapy. Whereas, currently, there is
little reason not to place a right ventricular (RV) lead in a cardiac resynchronization therapy system, because it is essential for
defibrillation, the rationale for eliminating an RV lead will likely
become increasingly relevant with the development of new LV
leads (eg, multipolar or with defibrillation capacity) and novel
implantation techniques.
Roberto Verlato, MD; Giovanni Luca Botto, MD; Riccardo Massa, MD; Claudia
Amellone, MD; Antonello Perucca, MD; Maria Grazia Bongiorni, MD; Emanuele
Bertaglia, MD; Vigilio Ziacchi, MD; Marcello Piacenti, MD; Attilio Del Rosso, MD;
Giovanni Russo, MD; Maria Stella Baccillieri, MD; Pietro Turrini, MD; and Giorgio
Corbucci, PhD
Summary: Patients with sinus node dysfunction may develop atrial
fibrillation (AF). This study shows that pacing the interatrial septum
can play a role in the prevention of permanent/persistent AF in patients
with intra-atrial conduction delay to the posterior triangle of Koch.
These patients can be identified by a quick electrophysiological study
during the implanting procedure, as described in the report. The lead
technology to permanently pace specific atrial sites is available, and
the algorithms for continuous atrial pacing are also available. Finally,
the pacemakers automatically store data about AF burden, simplifying
the assessment of the development/progression of the disease.
Conclusions: In patients with sinus node dysfunction and intra-atrial
conduction delay, low interatrial septum pacing was superior to right
atrial appendage pacing in preventing progression to persistent or
permanent AF.1
Conclusions: LV pacing is not superior to BiV pacing; however, nonresponders to BiV pacing may respond favorably to LV pacing, suggesting a potential role as tiered therapy.2
Left Ventricular versus Simultaneous
Biventricular Pacing in Patients With Heart
Failure and a QRS Complex ≥120 Milliseconds
Effect of Right Ventricular versus Biventricular
Pacing on Electric Remodeling in the
Normal Heart
Bernard Thibault, MD; Anique Ducharme, MD, MSc; François Harel, MD, PhD;
Michel White, MD; Eileen O’Meara, MD; Marie-Claude Guertin, PhD; Joel Lavoie,
PhD; Nancy Frasure-Smith, PhD; Marc Dubuc, MD; Peter Guerra, MD; Laurent
Macle, MD; Léna Rivard, MD; Denis Roy, MD; Mario Talajic, MD; Paul Khairy, MD,
PhD; for the Evaluation of Resynchronization Therapy for Heart Failure
(GREATER-EARTH) Investigators
Samir Saba, MD; Haider Mehdi, PhD; Michael A. Mathier, MD; M. Zahadul Islam,
MBBS; Guy Salama, PhD; and Barry London, MD, PhD
Summary: Biventricular (BiV) pacing has been shown to have
beneficial effects in a subset of patients with systolic heart failure
(HF) and to prevent the deleterious effects of high-burden right
Summary: Cardiac resynchronization therapy is an important
adjunctive treatment modality for selected patients with heart
Correspondence to The Editors, Circulation: Arrhythmia and Electrophysiology Editorial Office, 560 Harrison Ave, Suite 502, Boston, MA 02118.
E-mail [email protected]
© 2012 American Heart Association, Inc.
Circ Arrhythm Electrophysiol is available at http://circep.ahajournals.org
e69
DOI: 10.1161/CIRCEP.112.973305
e70 Circ Arrhythm Electrophysiol June 2012
ventricular (RV) pacing in patients with preserved left ventricular (LV) function. The mechanisms of these salutary effects are
not fully elucidated. In this study, we examined the effect of
BiV versus RV pacing on the normal heart in a rabbit model
of epicardial pacing. After 4 weeks of pacing, the QT interval
was significantly shorter in the BiV group compared with the
RV or sham-operated (nonpaced) groups. Also, compared with
rabbits in the RV group, rabbits in the BiV group had shorter
RV-effective refractory period and shorter LV-paced QT interval during the drive train of stimuli and close to refractoriness.
Also, protein expression of the KvLQT1 gene was significantly
increased in the BiV group compared with the RV and control
groups, whereas protein expression of SCN5A and connexin43
was significantly decreased in the RV compared with the other
study groups. ERG protein expression was significantly increased
in both pacing groups compared with the controls. These findings
underscore the effect of the sites of pacing on electric remodeling in the normal heart and may have implications as to the effect
of BiV pacing on arrhythmia incidence and burden.
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Conclusions: In this rabbit model, we demonstrate a direct effect of
BiV but not RV pacing on shortening the native QT interval as well as
the paced QT interval during burst pacing and close to the ventricular
effective refractory period. These findings underscore the fact that
the effect of BiV pacing is partially mediated through direct electric
remodeling and may have implications as to the effect of BIV pacing
on arrhythmia incidence and burden.3
Effect of Long-Term Right Ventricular Pacing
in Young Adults With Structurally
Normal Heart
Sandeep Sagar, MD, PhD; Win-Kuang Shen, MD; Samuel J. Asirvatham, MD;
Yong-Mei Cha, MD; Raul E. Espinosa, MD; Paul A. Friedman, MD; David O. Hodge,
MS; Thomas M. Munger, MD; Coburn J. Porter, MD; Robert F. Rea, MD; David L.
Hayes, MD; Arshad Jahangir, MD
Summary: This study elucidates the long-term effect of right
ventricular (RV) pacing on clinical outcomes in patients who
underwent pacemaker implantation for symptomatic isolated
congenital complete atrioventricular block (ICAVB). Over a
mean follow-up of 20 years (longest, 39 years), the observed
survival free of new heart failure (HF) after pacemaker implant
in the overall ICAVB group was significantly worse than that
of the age- and sex-specific Olmsted County, Minn, population
rates. This difference was, however, attributable to the development of HF and ventricular dysfunction in those who had tested
positive for antinuclear antibody (ANA) during adulthood, with
no difference between patients with antibody-negative ICAVB
and the Olmsted County population. The presence of a positive ANA was a strong predictor for the development of HF
and death. These results suggest that, in young patients without structural heart disease, pacing from the RV position does
not appear to have a detrimental effect on heart size or performance. The risk of HF after pacemaker implant is not solely the
result of abnormal ventricular activation but, instead, an interaction between pacing and abnormal myocardial substrate. In
patients with ICAVB, positive antibody status may predispose
to cardiomyopathy and worse clinical outcomes. ANA testing
should supplement the assessment of ventricular size and function by echocardiography to identify high-risk patients who
might progress to HF.
Conclusions: The natural history of patients with isolated congenital
atrioventricular block who require pacing depends on their antibody
status. ANA status was a predictor for the development of heart failure and death. Long-term RV pacing alone does not appear to be associated with development of heart failure, deterioration in ventricular
function, or reduced survival in patients with Ab(–) isolated congenital atrioventricular block.4
Induction of Therapeutic Hypothermia by
Paramedics After Resuscitation From
Out-of-Hospital Ventricular Fibrillation Cardiac
Arrest: A Randomized Controlled Trial
Stephen A. Bernard, MD; Karen Smith, BSc, PhD; Peter Cameron, MD; Kevin Masci;
David M. Taylor, MD; D. James Cooper, MD; Anne-Maree Kelly, MD; William
Silvester, MB, BS; for the Rapid Infusion of Cold Hartmanns (RICH) Investigators
Summary: The induction of therapeutic hypothermia after resuscitation from out-of-hospital ventricular fibrillation cardiac arrest
is recommended for the treatment of neurological injury by the
American Heart Association; however, the optimal timing of this
intervention is uncertain. Laboratory studies suggest that earlier
cooling may improve neurological outcomes. This study reports the
results of a randomized controlled trial in 234 patients comparing
paramedic cooling after return of a circulation by use of a rapid
infusion of large-volume, ice-cold intravenous fluid with cooling
after hospital arrival. Paramedic cooling decreased core temperature by 0.8°C compared with patients allocated to hospital cooling,
but the outcomes at hospital discharge were similar in both groups.
Further research into cooling during cardiopulmonary resuscitation
should be undertaken.
Conclusions: In adults who have been resuscitated from out-ofhospital cardiac arrest with an initial cardiac rhythm of ventricular
fibrillation, paramedic cooling with a rapid infusion of large-volume,
ice-cold intravenous fluid decreased core temperature at hospital
arrival but was not shown to improve outcome at hospital discharge
compared with cooling commenced in the hospital.5
Dispatcher-Assisted Cardiopulmonary
Resuscitation: Risks for Patients Not in
Cardiac Arrest
Lindsay White, MPH; Joseph Rogers, MS; Megan Bloomingdale; Carol Fahrenbruch,
MSPH; Linda Culley, BA; Cleo Subido, RPL; Mickey Eisenberg, MD, PhD; Thomas
Rea, MD, MPH
Summary: Cardiopulmonary resuscitation (CPR) instructions pro­
vided over the telephone by the 911 emergency dispatcher can
substantially increase bystander-initiated CPR and thereby
increase the chance for survival from out-of-hospital cardiac
arrest. Nevertheless, identification of cardiac arrest by dispatchers
and bystanders can sometimes be challenging. A number of conditions can resemble cardiac arrest; consequently, patients who are
not in cardiac arrest can receive CPR. The risk of bystander CPR
for patients not in arrest is uncertain and has implications for how
assertive dispatch is in instructing CPR. This article reports on
a 2.5-year prospective study of dispatcher-assisted CPR in King
County, Wash. Of the 1700 patients for whom dispatcher CPR
instructions were initiated during the study period, 55% (938 of
1700) were in arrest, 45% (762 of 1700) were not in arrest, and
18% (313 of 1700) were not in arrest and progressed to receive
bystander chest compressions. Of the patients not in arrest who
received chest compressions, 12% experienced discomfort, and
2% sustained injuries likely or possibly caused by bystander CPR.
The injuries were characterized most often by rib fracture, and no
patients suffered visceral organ injury. The results of the present
investigation indicate that the frequency of serious injury related
to dispatcher-assisted bystander CPR among nonarrest patients is
low. When coupled with the established benefits of bystander CPR
among those with arrest, the results support an assertive program
of dispatcher-assisted CPR.
Conclusions: In this prospective study, the frequency of serious
injury related to dispatcher-assisted bystander CPR among nonarrest patients was low. When coupled with the established benefits
of bystander CPR among those with arrest, these results support an
assertive program of dispatcher-assisted CPR.6
The Editors Most Read on Arrhythmia Devices e71
Permanent Pacemaker Insertion After
CoreValve Transcatheter Aortic Valve
Implantation: Incidence and Contributing
Factors (the UK CoreValve Collaborative)
Muhammed Khawaja, MBBS; Ronak Rajani, MD; Andrew C. Cook, PhD; Ali
Khavandi, MD; Anouska Moynagh, MD; Saqib Chowdhary, MD; Mark S. Spence,
MD; Sue Brown, BSC; Sohail Q. Khan, MD; Nicola Walker, MBChB, PhD; Uday
Trivedi, MBBS; Nevil Hutchinson, MBBS; Adam J. De Belder, MD; Neil Moat,
MBBS; Daniel J. Blackman, MD; Richard D. Levy, MD; Ganesh Manoharan, MD;
David Roberts, MD; Saib S. Khogali, MD; Peter Crean, MD; Stephen J. Brecker, MD;
Andreas Baumbach, MD; Michael J. Mullen, MD; Jean-Claude Laborde, MD; and
David Hildick-Smith, MD
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Summary: Transcatheter aortic valve implantation has entered mainstream interventional cardiology as a treatment for aortic stenosis
in patients with prohibitively high operative risk. This is a growing
cohort of patients globally, given the increased longevity and prevalence of significant comorbidities. The CoreValve Revalving system
(CoreValve Medtronic) is 1 of the 2 prostheses currently in use, and
it has been noted to be associated with an increased need for permanent pacemaker implantation. This study represents the largest analysis of the rates of permanent pacemaker implantation in patients
receiving a CoreValve implant and uses clinical ECG data to create
an electroanatomic model to explain the phenomenon. Consideration
of these factors as addressed in this study has not only implications
for the future designs of transcatheter aortic valve implantation
devices but also immediate clinical impact on the standard of care of
this increasingly numerous patient group.
Conclusions: One third of patients undergoing a CoreValve transcatheter aortic valve implantation procedure require a permanent
pacemaker within 30 days. Periprocedural atrioventricular block,
balloon predilatation, use of the larger CoreValve prosthesis, increased
interventricular septum diameter, and prolonged QRS duration were
associated with the need for a permanent pacemaker.7
Inhaled Nitric Oxide Improves Outcomes
After Successful Cardiopulmonary
Resuscitation in Mice
Shizuka Minamishima, MD; Kotaro Kida, MD, PhD; Kentaro Tokuda, MD; Huifang
Wang, PhD; Patrick Y. Sips, PhD; Shizuko Kosugi, MD; Joseph B. Mandeville, PhD;
Emmanuel S. Buys, PhD; Peter Brouckaert, MD, PhD; Philip K. Liu, PhD; Christina
H. Liu, PhD; Kenneth D. Bloch, MD; and Fumito Ichinose, MD, PhD
Summary: Sudden cardiac arrest is one of the leading causes of
death worldwide. Despite advances in resuscitation techniques, <8%
of the 300 000 adults who experience cardiac arrest in the United
States each year survive to hospital discharge, and up to 60% of survivors have long-lasting neurological deficits. Although therapeutic
hypothermia has proven effective in clinical studies, no pharmacological agent is available to improve outcome from cardiac arrest.
Although originally developed as a selective pulmonary vasodilator,
inhaled nitric oxide (NO) has been shown to have systemic effects
in a variety of preclinical and clinical studies without causing systemic vasodilation. In the present study, we found that breathing a
low concentration of NO, starting 1 hour after successful cardiopulmonary resuscitation for 23 hours, markedly improves long-term
neurological and cardiac outcomes and survival in mice subjected to
cardiac arrest and cardiopulmonary resuscitation. The ability of NO
breathing to improve outcomes after cardiac arrest when begun after
cardiopulmonary resuscitation, if extrapolated to human beings,
makes inhaled NO a practical therapeutic approach that can be initiated after patients are transferred to a hospital. Furthermore, because
inhaled NO does not cause systemic hypotension, in contrast to systemic NO donors, it is uniquely suited for the treatment of patients
post cardiac arrest in whom blood pressure is often unstable. We
anticipate that the established safety profile of NO inhalation will
enable the rapid translation of findings in animal models to patients
experiencing postcardiac arrest syndrome.
Conclusions: These results suggest that NO inhalation after CA and
successful cardiopulmonary resuscitation improves outcome via soluble guanylate cyclase-dependent mechanisms.8
Outcomes After In-Hospital Cardiac Arrest in
Children With Cardiac Disease: A Report From
Get With the Guidelines – Resuscitation
Laura Ortmann, MD; Parthak Prodhan, MBBS; Jeffrey Gossett, MS; Stephen
Schexnayder, MD; Robert Berg, MD; Vinay Nadkarni, MD; Adnan Bhutta, MBBS; for
the American Heart Association’s Get With the Guidelines – Resuscitation (formerly
National Registry of Cardiopulmonary Resuscitation) Investigators
Summary: Survival after cardiac arrest is poor; however, small case
series have suggested that children with cardiac disease who experience a cardiac arrest have better outcomes. Our study of 3323 pediatric patients using Get With the Guidelines – Resuscitation found
that survival to hospital discharge was 37% in children with surgical
cardiac disease compared with 28% in children with medical cardiac disease and 23% in children without cardiac disease. Although
multiple previous studies have examined survival after cardiac
arrest in pediatric patients, children undergoing cardiac surgery
are a unique population, and their survival after arrest has not been
well-studied. Children after cardiac surgery have a much higher
risk of cardiac arrest compared with other pediatric populations, so
this improved survival is encouraging for the providers who care
for them. Notable is the higher odds of survival with the use of
extracorporeal cardiopulmonary resuscitation, and this report adds
to previous studies that have found extracorporeal cardiopulmonary
resuscitation to be an effective rescue therapy. This study will be
useful for medical providers when evaluating a patient’s prognosis and provides information for researchers wanting to study this
unique group of patients.
Conclusions: Children with surgical cardiac disease have significantly better survival to hospital discharge after an in-hospital cardiac
arrest compared with children with medical cardiac disease and noncardiac disease.9
DEFI 2005: A Randomized Controlled Trial of
the Effect of Automated External Defibrillator
Cardiopulmonary Resuscitation Protocol on
Outcome From Out-of-Hospital Cardiac Arrest
Daniel Jost, MD; Hervé Degrange, MD; Catherine Verret, MD, PhD; Olivier Hersan,
MD; Isabelle L. Banville, PhD; Fred W. Chapman, PhD; Paula Lank, RN, BSN; Jean
Luc Petit, MD; Claude Fuilla, MD; René Migliani, MD, PhD; Jean Pierre Carpentier,
MD, PhD; the DEFI 2005 Work Group
Summary: The American Heart Association Guidelines 2005 for
Emergency Cardiac Care made changes to the way that chest
compressions, ventilations, and defibrillation countershocks are
sequenced, in an effort to resuscitate more patients in cardiac arrest.
These changes, which were based on theoretical considerations,
experimental studies, and few clinical studies, aimed to increase
cardiopulmonary resuscitation (CPR), in hopes of improving
patient outcomes. Although several published articles have reported
on the effect of increasing CPR in cohort studies, none has the
evidence level of a randomized controlled trial. The results of this
18-month, 845-patient, randomized controlled trial on out-of-hospital ventricular fibrillation cardiac arrest are of particular interest and
potential impact on the next cycle of the evidence review process
of the International Liaison Committee on Resuscitation, leading
to the American Heart Association 2010 guidelines. This randomized controlled trial demonstrated that, by following new automated
external defibrillator prompts, basic life support-trained firefighters
could shorten pauses in chest compressions and improve their overall CPR hands-on ratio from 48% to 61% during resuscitation of
patients with ventricular fibrillation out-of-hospital cardiac arrest;
however, this improvement in CPR metrics did not translate into
e72 Circ Arrhythm Electrophysiol June 2012
measurable differences in rates of return of spontaneous circulation before advanced cardiac life support arrival, survival to hospital
admission or discharge, or 1-year survival. The lack of benefit from
increased CPR in this trial, combined with experience from this and
other emergency medical systems, suggests that the survival rate
may be further improved by efforts focused on other changes to
community resuscitation such as increasing bystander CPR, shortening response times, or even providing more extensive and regular
CPR training to rescuers.
Conclusions: Following prompts from automated external defibrillators programmed with a protocol similar to AHA Guidelines 2005,
firefighters shortened pauses in CPR and improved overall hands-on
time, but survival to hospital admission of patients with ventricular
fibrillation out-of-hospital cardiac arrest did not improve.10
Relationship Between Supranormal Oxygen
Tension and Outcome After Resuscitation
From Cardiac Arrest
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J. Hope Kilgannon, MD; Alan E. Jones, MD; Joseph E. Parrillo, MD; R. Phillip
Dellinger, MD; Barry Milcarek, PhD; Krystal Hunter, MBA; Nathan I. Shapiro, MD;
Stephen Trzeciak, MD, MPH; on behalf of the Emergency Medicine Shock Research
Network (EMShockNet) Investigators
Summary: Historically, the administration of supplemental oxygen
has been considered a cornerstone of cardiopulmonary resuscitation
for victims of cardiac arrest; however, laboratory experiments and
recent clinical data suggest that, after a pulse is restored, excessive
supplemental oxygen could be harmful. Supranormal oxygen tension
can exacerbate oxygen-free radical formation and subsequent reperfusion injury; however, it is unclear if the risk of poor outcome is
a threshold effect at a specific supranormal oxygen tension or is a
dose-dependent association. The authors studied patients admitted to
an intensive care unit after resuscitation from cardiac arrest at 120
US hospitals. After excluding patients with hypoxia, there were 4459
patients in the sample. The authors tested the association between
postresuscitation arterial partial pressure of oxygen and in-hospital
mortality. The median postresuscitation arterial partial pressure of
oxygen was 231 (interquartile range 149 to 349) mm Hg. Fifty-four
percent of the patients died. Over ascending ranges of oxygen tension, the authors found significant linear trends of increasing in-hospital mortality and decreasing survival as functionally independent.
On multivariable analysis adjusted for patient-oriented covariates and
potential hospital effects, a 100-mmHg increase in postresuscitation
arterial partial pressure of oxygen was associated with a 24% increase
in relative risk of death. The authors observed no evidence supporting
a single threshold for harm from supranormal oxygen tension. In this
large sample of patients postresuscitation, the authors found that the
association between supranormal oxygen tension and risk of in-hospital death is a linear dose-dependent relationship. These data provide
further support that supranormal oxygen tension may be harmful in
patients resuscitated from cardiac arrest.
Conclusions: In this large sample of patients postresuscitation, we
found a dose-dependent association between supranormal oxygen
tension and risk of in-hospital death.11
J Wave, QRS Slurring, and ST Elevation in
Athletes With Cardiac Arrest in the Absence of
Heart Disease: Marker of Risk or
Innocent Bystander?
Riccardo Cappato, MD; Francesco Furlanello, MD; Valerio Giovinazzo, MD;
Tommaso Infusino, MD; Pierpaolo Lupo, MD; Mario Pittalis, MD; Sara Foresti, MD;
Guido De Ambroggi, MD; Hussam Ali, MD; Elisabetta Bianco, MD; Roberto
Riccamboni, MD; Gianfranco Butera, MD; Cristian Ricci, PhD; Marco Ranucci, MD;
Antonio Pelliccia, MD; and Luigi De Ambroggi, MD
Summary: The ECG pattern of early repolarization (ie, J wave, QRS
slurring, and/or ST elevation) in the inferior and lateral ECG leads
is a common finding in the general population and is even more
frequently observed in athletes. Recent studies have suggested a
potential proarrhythmic significance of these findings in the general
population, but data are lacking in athletes. We investigated whether
QRS-ST changes are markers of risk for cardiac arrest or sudden
death in athletes without underlying heart disease. In a selected
group of 21 young competitive athletes who had cardiac arrest in the
absence of heart disease, the prevalence of J wave and/or QRS slurring in the inferior (II, III, and aVF) and lateral leads (V4 to V6) was
significantly higher in cases than in control athletes. After sport discontinuation during 36-month follow-up, arrhythmia recurrences did
not differ between subgroups with and without J wave or QRS slurring. Because of discrepancy between the frequency of early repolarization pattern on 12-lead ECG and the rarity of cardiac arrest/sudden
death, the incidental finding of a J wave/QRS slurring in a healthy
athlete should be considered as a marker that minimally increases the
arrhythmic risk. The present findings provide novel insights on clinical profiles of athletes at possible risk of cardiac arrest.
Conclusions: J wave and/or QRS slurring was found more frequently
among athletes with cardiac arrest/sudden death than in control athletes. Nevertheless, the presence of this ECG pattern appears not to
confer a higher risk for recurrent malignant ventricular arrhythmias.12
Mechanisms Underlying the Lack of Effect of
Implantable Cardioverter-Defibrillator Therapy
on Mortality in High-Risk Patients With Recent
Myocardial Infarction: Insights from the
Defibrillation in Acute Myocardial Infarction
Trial (DINAMIT)
Paul Dorian, MD, MSc; Stefan H. Hohnloser, MD; Kevin E. Thorpe, MMath;
Robin S. Roberts, MTech; Karl-Heinz Kuck, MD; Michael Gent, DSc; and
Stuart J. Connolly, MD
Summary: In the Defibrillation in Acute Myocardial Infarction Trial
(DINAMIT) study, implanted defibrillators did not reduce mortality
in high-risk patients if implanted early after myocardial infarction.
In patients randomized to an implantable cardioverter-defibrillator
(ICD), sudden deaths were reduced, but nonarrhythmic mortality
was increased. In an analysis of the potential causes of this finding,
patients who are destined to receive therapy from their ICD (compared with those destined not to receive therapy) have clinical features that also increase their risk of nonsudden death, including risks
related to heart failure and recurrent ischemic events. During followup, patients who receive therapy from their ICD are more likely to
have intercurrent cardiac clinical adverse events both before and after
ICD therapy compared with patients who receive no therapy or do not
have an ICD. In an early postmyocardial infarction setting, the same
clinical circumstances that increase the risk of ventricular arrhythmias
also increase the risk of nonsudden death; in addition, ICD therapies
themselves may increase the risk of subsequent death. These findings
underscore the limitations of a strategy of ICD implantation in certain
high-risk groups, especially early after acute myocardial infarction.
Conclusions: In patients receiving ICDs early after myocardial
infarction, those factors that are associated with arrhythmia requiring
ICD therapy are also associated with a high risk of nonsudden death,
negating the benefit of ICDs in this setting.13
Low-Energy Multistage Atrial Defibrillation
Therapy Terminates Atrial Fibrillation With
Less Energy Than a Single Shock
Wenwen Li, PhD; Ajit H. Janardhan, MD, PhD; Vadim V. Fedorov, PhD; Qun Sha,
MD; Richard B. Schuessler, PhD; and Igor R. Efimov, PhD
Summary: Atrial fibrillation (AF) is the most common
tachyarrhythmia worldwide, and the number of Americans with this
condition is expected to grow as the population ages. Patients with
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AF experience increased rates of thromboembolic stroke, congestive heart failure, cognitive dysfunction, and mortality. For symptomatic patients, cardioversion of AF to sinus rhythm using a single
high-voltage external shock remains a mainstay of therapy. External
cardioversion is painful, necessitating costly anesthesia and careful periprocedural patient monitoring. Previous attempts to design
an implantable device that converts AF to sinus rhythm safely have
been hampered primarily because of the discomfort associated
with shocks. Defibrillating AF with a conventional, single biphasic
shock remains significantly above the human pain threshold; however, prior studies in rabbits and dogs showed that atrial defibrillation could be achieved with significantly lower energy if multiple
shocks are used rather than a single biphasic shock. The goal of
this study was to further reduce the atrial defibrillation threshold
in vivo, using a more clinically relevant canine model of AF. Here
we introduce a novel multiple-shock, multistage electrotherapy that
significantly reduces the atrial defibrillation threshold below single
biphasic and multiple-shock therapies. Importantly, the novel electrotherapy tested here cardioverts AF at an energy that is likely at
or below the human pain threshold (0.19±0.12 J). The findings give
clinicians hope that multiple-stage electrotherapy may eventually
allow pain-free cardioversion of AF and opens (or reopens) the door
to the possibility of an implantable device that achieves pain-free
defibrillation of AF in humans.
Conclusions: Three-stage electrotherapy significantly reduces the AF
defibrillation threshold and opens the door to low-energy atrial defibrillation at or below the pain threshold.14
Differences Between Out-of-Hospital Cardiac
Arrest in Residential and Public Locations and
Implications for Public-Access Defibrillation
Fredrik Folke, MD; Gunnar H. Gislason, MD, PhD; Freddy K. Lippert, MD; Søren L.
Nielsen, MD; Peter Weeke, MD; Morten L. Hansen, MD, PhD; Emil L. Fosbøl, MD,
PhD; Søren S. Andersen, MD; Søren Rasmussen, MSc, PhD; Tina K. Schramm, MD;
Lars Køber, MD, DMSc; and Christian Torp-Pedersen, MD, DMSc
Summary: Whereas a tremendous amount of resources has focused
on deployment of automated external defibrillators (AEDs) in public
locations, the majority of out-of-hospital cardiac arrests (OHCAs)
take place in residential areas and remain not covered by publicly
placed AEDs. Furthermore, little is known about how to identify
residential areas with the highest risk of OHCA, let alone the possible cost of public-access defibrillation in such areas. We therefore
performed a systematic analysis of OHCAs in residential areas of
Copenhagen to examine whether high-risk areas of OHCA suitable
for AED placement could be identified. Using simple demographic
characteristics of a city center, we were able to identify residential areas characterized by having at least 1 OHCA every 4.3 to 5.6
years within a 100 ×100-m area. These areas comprised <3% of all
residential quarters but included up to 9% of all residential cardiac
arrests. The estimated cost of AED deployment in selected residential
areas was below $100 000 per quality-adjusted life-year but likely to
exceed the corresponding cost for AED deployment in public locations. Furthermore, individuals with OHCAs in residential locations were more likely to have characteristics associated with a poor
outcome compared with public ones in that the patients were older
and more often male, the ambulance response interval was longer,
arrests occurred more often at night, and the patients had ventricular
fibrillation less often. Therefore, if future public-access defibrillation programs in residential areas are to succeed without excessive
costs, strategic placement of AEDs in selected residential areas is a
necessity.
Conclusions: On the basis of simple demographic characteristics of a
city center, we could identify residential areas suitable for automated
external defibrillator placement. Individuals with OHCA in residential locations were more likely to have characteristics associated with
poor outcome compared with public cardiac arrests.15
Chest Compressions Cause Recurrence
of Ventricular Fibrillation After the First
Successful Conversion by Defibrillation in
Out-of-Hospital Cardiac Arrest
Jocelyn Berdowski, MSc, MSE; Jan G.P. Tijssen, PhD; and Rudolph W. Koster, MD,
PhD
Summary: The current guidelines (GL) for cardiopulmonary resuscitation issued in 2005 advise to immediately resume cardiopulmonary resuscitation (CPR) after a defibrillation shock by abandoning
postshock rhythm analysis and checking for signs of life to minimize CPR interruption. This shortens the delay to CPR resumption
by about half a minute. At the same time, the CPR cycle is extended
from 1 to 2 minutes. This study analyzed the relation among CPR
resumption, ventricular fibrillation (VF) recurrence, and VF duration after a first successful shock during randomized treatment with
resuscitation GL2000 or GL2005. Our study demonstrated a close
relation between initiation of chest compressions and recurrence
of VF. In the first 2 seconds of CPR resumption, the hazard of VF
recurrence was 15 times larger than before the start of CPR, regardless of the preceding rhythm or guideline used. The hazard remained
increased during the first 8 seconds of CPR. VF recurred in 72%
of cases in both groups. Because of earlier resumption and longer
duration of CPR, the patient treated with GL2005 had VF recurrence significantly sooner and stayed in VF longer as well: a median
of 40 seconds in the first CPR cycle. From a metabolic point of
view, prolonged VF is more energy-consuming than asystole. This
could possibly explain why the application of GL2005 did not show
improved survival in all published literature. Further research is
needed to determine whether prolonged VF recurrence during CPR
influences survival.
Conclusions: Early CPR resumption after defibrillation causes early
VF recurrence.16
Modulation of Calcium-Activated Potassium
Channels Induces Cardiogenesis of
Pluripotent Stem Cells and Enrichment of
Pacemaker-Like Cells
Alexander Kleger, MD, PhD; Thomas Seufferlein, MD; Daniela Malan, PhD; Michael
Tischendorf; Alexander Storch, MD; Anne Wolheim; Stephan Latz; Stephanie Protze;
Marc Porzner, MD; Christian Proepper, PhD; Cornelia Brunner, PhD; Sarah-Fee Katz;
Ganesh Varma Pusapati, PhD; Lars Bullinger, MD; Wolfgang-Michael Franz, MD;
Ralf Koehntop; Klaudia Giehl, PhD; Andreas Spyrantis, PhD; Oliver Wittekindt, PhD;
Quiong Lin; Martin Zenke, PhD; Bernd K. Fleischmann, MD; Maria Wartenberg, PhD;
Anna M. Wobus, PhD; Tobias M. Boeckers, MD; and Stefan Liebau, MD
Summary: It is well-accepted that embryonic stem cells represent
a particularly attractive source for ex vivo generation of cardiomyocytes. Considering the feasibility of in vitro model systems
for pharmacological screenings, toxicological, or even potential
cell therapeutic applications, major obstacles need to be overcome.
Pharmaceutical model systems require a (1) high purity of the
cell system; (2) specifically, differentiated cell subtypes, such as
cardiac pacemaker-like cells; and (3) absence of unphysiological
alterations due to genetically engineered cell genomes. Relative to
the future potential for cell therapeutic applications, furthermore,
in vivo improvement of (1) contractile heart function; (2) prevention of arrhythmias caused by insufficient graft guidance; (3) potential teratoma formation; and (4) immunotolerance are the crucial
premises. The differentiation system presented here provides an
interesting tool for applications in biomedical engineering, pathophysiological, and toxicological studies and even potential therapeutic applications. Here we provide a new cardiac differentiation
system exclusive of genetic manipulation and lineage selection and
thus fulfilling most of these criteria.
Conclusions: SKCa activation drives the fate of pluripotent cells
toward mesoderm commitment and cardiomyocyte specification,
e74 Circ Arrhythm Electrophysiol June 2012
preferentially into nodal-like cardiomyocytes. This provides a novel
strategy for the enrichment of cardiomyocytes and, in particular, the
generation of a specific subtype of cardiomyocytes, pacemaker-like
cells, without genetic modification.17
Safety of Pacemaker Reuse: A Meta-Analysis
With Implications for Underserved Nations
Timir S. Baman, MD; Pascal Meier, MD; Joshua Romero, BA; Lindsey Gakenheimer;
James N. Kirkpatrick, MD; Patricia Sovitch, NP; Hakan Oral, MD; and Kim A. Eagle,
MD
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Summary: A great disparity in medical health care is clearly evident
in the field of cardiac electrophysiology (specifically, pacemaker
implantation) in which the specialty is either severely underdeveloped or entirely nonexistent in many low- and middle-income
countries. In an effort to promote cost savings, as well as to provide
care to those with no other means of acquiring a device, a number of articles in a wide variety of international settings have been
published describing the safety and efficacy of pacemaker reuse.
The aim of this meta-analysis is to assess the safety of pacemaker
reuse. Pooled individual patient data (n=2270) from 18 trials were
included in the analysis. The results demonstrate that there is no
significant difference in infection rate between pacemaker reuse
and new device implantation (P=0.58); however, there was an
increased risk for malfunction in the reuse group (P=0.002). This
difference was mainly driven by abnormalities in set screws, which
possibly occurred during device extraction as well as nonspecific
device “technical errors.” Overall, pacemaker reuse was associated
with an overall low rate of infection (<2%) and device malfunction (<1%) and may represent a viable option for patients in underserved nations with symptomatic bradycardia and no other means of
obtaining a device. We believe that postmortem pacemaker reuse is
a safe, feasible, and ethically responsible means of delivering electrophysiological health care to those in great need.
Conclusions: This study suggests that pacemaker reuse has an
overall low rate of infection and device malfunction and may be
a safe and efficacious means of treating patients in underserved
nations with symptomatic bradyarrhythmias and no other method
of obtaining a device; however, the results also denote a higher rate
of device malfunction as compared with new device implantation.
Patients with highly symptomatic conduction disease may benefit
from pacemaker reuse; however, they should be closely monitored
for device malfunction, especially during implantation.18
Extraction of Old Pacemaker or
Cardioverter-Defibrillator Leads by Laser
Sheath versus Femoral Approach
Pierre Bordachar, MD; Pascal Defaye, MD; Eric Peyrouse, MD; Serge Boveda,
MD; Bilel Mokrani, MD; Christelle Marquié, MD; Laurent Barandon, MD, PhD;
Emilie Marcant Fossaert, MD; Stephane Garrigue, MD; Sylvain Reuter, MD; Julien
Laborderie, MD; Eloi Marijon, MD; Jean-Claude Deharo, MD; Peggy Jacon, MD;
Salem Kacet, MD; Sylvain Ploux, MD; Antoine Deplagne, MD; Michel Haissaguerre,
MD; Jacques Clementy, MD; Philippe Ritter, MD; and Didier Klug, MD
Summary: Some operators routinely extract chronically implanted
transvenous leads using a femoral approach, whereas others prefer
a superior approach. This prospective study compared the safety
and effectiveness of laser sheaths versus femoral snare extractions.
We undertook a (1) prospective single-center randomized study to
compare the safety and effectiveness of laser sheath versus femoral
snare extractions and the radiation exposure associated with each;
and (2) nonrandomized comparison of registries from several French
centers specializing in lead extractions from the femoral or superior
approach. Regardless of the technique implemented, complete or
partial extractions were achieved in >95% of procedures. The rates
of mortality and of major complications, although low, were not negligible and indicate that these procedures must be performed by a
trained team working in an environment equipped with immediate
surgical backup. We found no significant difference between the
proximal approach, using laser, and the femoral approach, using
snares, with respect to procedural success and complication rates;
however, procedures performed using the femoral approach were
longer and were associated with a longer exposure of the operators
and patients to fluoroscopy.
Conclusions: Old transvenous leads were extracted with similar success and complication rates by the femoral and laser approaches;
however, the femoral approach was associated with longer procedures and a longer duration of fluoroscopic exposure.19
Complication Rates Associated With
Pacemaker or Implantable
Cardioverter-Defibrillator Generator
Replacements and Upgrade Procedures:
Results From the REPLACE Registry
Jeanne E. Poole, MD; Marye J. Gleva, MD; Theofanie Mela, MD; Mina K. Chung,
MD; Daniel Z. Uslan, MD; Richard Borge, MD; Venkateshwar Gottipaty, MD, PhD;
Timothy Shinn, MD; Dan Dan, MD; Leon A. Feldman, MD; Hanscy Seide, MD;
Stuart A. Winston, DO; John J. Gallagher, MD; Jonathan J. Langberg, MD; Kevin
Mitchell, RN, BS; Richard Holcomb, PhD; for the REPLACE Registry Investigators
Summary: Cardiac implantable electronic device use is increasing
worldwide. Improvements in medical therapy will result in many
patients requiring subsequent procedures for generator replacement
or “upgrades” to multilead systems. Although data from retrospective
series have been available, REPLACE is the first prospective multicenter trial to examine complications related to generator replacement.
The 2 patient populations studied included patients who needed only a
generator replacement and those who required a lead addition or revision for advanced therapy. This study examined a broad range of major
and minor complications. Major complications with planned generator
replacements alone were modest; however, when a transvenous lead
addition or revision was combined with a generator replacement, the
risk was markedly higher, especially for left ventricular leads. Our
results support the use and development of devices with long battery
life to minimize the lifetime surgical risk for a patient. The choice of
device for each patient must be carefully considered. Mitigation of leadrelated risks is also important. Using the fewest leads necessary for the
clinical need of the patient is critical. The risk associated with upgrade
procedures is concerning and favors performing indicated complex
procedures before the development of advanced end-stage medical and
cardiac disease, situations in which the risk may be prohibitive. Finally,
our results provide insight into procedural outcomes for the next phase
of life for patients who receive cardiac implantable electronic devices
and a more robust analysis that can be used to establish a benchmark
for comparative performance in this time of healthcare reform.
Conclusions: Pacemaker and implantable cardioverter-defibrillator
generator replacements are associated with a notable complication
risk, particularly those with lead additions. These data support careful decision-making before device replacement, when managing
device advisories and when considering upgrades to more complex
systems.20
cAMP Sensitivity of HCN Pacemaker Channels
Determines Basal Heart Rate but Is Not
Critical for Autonomic Rate Control
Patrick A. Schweizer, MD, MSc; Nana Duhme, MSc; Dierk Thomas, MD; Rüdiger
Becker, MD; Jörg Zehelein, MD; Andreas Draguhn, MD; Claus Bruehl, PhD; Hugo A.
Katus, MD; and Michael Koenen, PhD
Summary: Pharmacological If inhibition is clinically used to treat
patients with stable angina and sinus tachycardia; however, the role
of If in sinus node function and, particularly, mechanisms underlying autonomic heart rate regulation are incompletely understood.
According to the BEAUTIFUL study, blockage of If current in patients
The Editors Most Read on Arrhythmia Devices e75
with stable coronary artery disease and left ventricular systolic
dysfunction reduced resting heart rate by 6 bpm (8%), a minor effect
related to the reduction of 21 bpm (31%) observed in HCN4-695X
carriers. Our results suggest that mutant carriers might tolerate sinus
bradycardia owing to their preserved ability to accelerate heart rate
according to physical requirements. Thus, cardiac-specific blockage
of If may allow for significant reduction of basal heart rate without
adversely affecting chronotropic competence. This suggestion has
important clinical implications. Improvements in drug selectivity
will reduce extracardiac side effects, as well as nonspecific channel
inhibition, and may offer a more effective blockage of If pacemaker
currents in the future. On the other hand, as shown in the present
study, functional inactivation of If might unmask arrhythmogenic
potential during adrenergic stimulation. These considerations are
­
relevant to safety concerns other than bradycardia associated with
­
­high-dose If-blockage.
Conclusions: In humans, cAMP responsiveness of If determines basal
heart rate but is not critical for maximum heart rate, heart rate variability, or chronotropic competence. Furthermore, cAMP-activated If
may stabilize heart rhythm during chronotropic response.21
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Utility of the Ventricular Fibrillation Waveform
to Predict a Return of Spontaneous Circulation
and Distinguish Acute From Post Myocardial
Infarction or Normal Swine in Ventricular
Fibrillation Cardiac Arrest
Julia H. Indik, MD, PhD; Daniel Allen, BS; Michael Gura, MS; Christian Dameff,
MS; Ronald W. Hilwig, DVM, MS, PhD; and Karl B. Kern, MD
Summary: Ventricular fibrillation (VF) and pulseless ventricular
tachycardia are the initial rhythm in about one quarter of cardiac
arrests. Although the performance of effective chest compressions
with minimal to no interruptions is well-known to be a critical component in resuscitation, the optimal duration of chest compressions
before defibrillation shocks is unclear. It is unknown if the timing of
shocks and chest compressions should be the same for patients with
acute myocardial infarction (MI) as those with a history of MI or
even those without any cardiovascular disease. Furthermore, it is recognized that patients with acute MI resuscitated from cardiac arrest
caused by VF may not show ST-segment elevation, complicating
decisions of whether to send patients for emergent cardiac catheterization once a perfusing rhythm has been restored. This investigation
explores the evolution of the VF waveform parameters of amplitude
spectral area and slope in acute MI, post MI, and control swine. We
find that amplitude spectral area and slope predict the restoration of a
perfusing rhythm after a shock, independent of the underlying myocardium, and, furthermore, with well-performed chest compressions,
amplitude spectral area at a threshold of 33.5 mV-Hz showed a sensitivity of 83% to distinguish an acute from a nonacute MI state.
Conclusions: In a swine model of VF cardiac arrest, amplitude spectral area, and slope predict return of spontaneous circulation independent of myocardial substrate. Furthermore, with chest compressions,
the VF waveform evolves differently and may offer a means to distinguish an acute MI.22
Amiodarone Versus Procainamide for the
Acute Treatment of Recurrent Supraventricular
Tachycardia in Pediatric Patients
Philip M. Chang, MD; Michael J. Silka, MD; David Y. Moromisato, MD; and
Yaniv Bar-Cohen, MD
Summary: Relative efficacy of different pharmacological approaches
to the management of recurrent supraventricular arrhythmias in
pediatric patients is largely unknown because systematic comparisons between the various antiarrhythmic agents are limited,
the number of patient cohorts available for study is small, and the
end points for treatment are variable. This retrospective singleinstitution study included 37 patients (median age, 34 days; the
majority with congenital heart disease) with recurrent supraventricular tachycardia. The majority had atrial arrhythmias, and a quarter
had reentry using an accessory pathway. Intravenous administration of procainamide was more effective than intravenous amiodarone, without substantial differences in the incidence of adverse
events, a somewhat surprising finding given the general perception
of amiodarone therapy. The findings suggest that intravenous procainamide warrants an important role in the management of pediatric patients with recurrent supraventricular arrhythmias.
Conclusions: In this cohort, procainamide achieved greater success
compared with amiodarone in the management of recurrent supraventricular tachycardia without statistically significant differences in
adverse event frequency.23
Determination of Inadvertent Atrial Capture
During Para-Hisian Pacing
Manoj Obeyesekere, MBBS; Peter Leong-Sit, MD; Allan Skanes, MD; Andrew Krahn,
MD; Raymond Yee, MD; Lorne J. Gula, MD; Matthew Bennett, MD; and George J.
Klein, MD
Summary: The para-Hisian pacing maneuver is very useful in clinical
electrophysiology, but care must be taken to avoid technical and interpretative pitfalls. Inadvertent atrial capture during the maneuver may
give the erroneous impression of retrograde conduction over a septal
accessory pathway in the absence of an accessory pathway or retrograde conduction over the atrioventricular (AV) node in the presence
of an accessory pathway. Intuitively, direct atrial capture should give
a very short stimulus-to-atrial interval. A stimulus-to–atrial interval
at the proximal coronary sinus (stim-PCS) of <60 ms (or <70 ms at
the high right atrium [stim-HRA]) is observed only with direct atrial
capture. A stim-PCS of >90 ms (or stim-HRA >100 ms) is observed
only in the absence of atrial capture. An overlap zone between these
values exists where atrial capture cannot be excluded or confirmed.
A change of stimulus-to-atrial interval of 20 ms using a small catheter adjustment to lose or obtain atrial capture deliberately reliably
ensures that inadvertent atrial capture has not occurred.
Conclusions: Stim-PCS and stim-HRA can be used to monitor for
inadvertent atrial capture during para-Hisian pacing. A stim-PCS <60
ms (or stim-HRA <70 ms) and stim-PCS >90 ms (or stim-HRA >100
ms) were observed only with and without atrial capture, respectively,
but there was significant overlap between these values. Deliberate
atrial capture and loss of capture reliably identifies atrial capture
regardless of intervals.24
Comparison of a Novel, Single-Lead Atrial
Sensing System With a Dual-Chamber
Implantable Cardioverter-Defibrillator System
in Patients Without Antibradycardia Pacing
Indications: Results of a Randomized Study
Christian Sticherling, MD; Markus Zabel, MD; Sebastian Spencker, MD;
Udo Meyerfeldt, MD; Lars Eckardt, MD; Steffen Behrens, MD; Michael Niehaus, MD;
for the ADRIA Investigators
Summary: Supraventricular tachyarrhythmias are a frequent cause
for inappropriate therapy in patients with implantable cardioverterdefibrillators (ICDs). Atrial sensing and electrogram recordings are
potentially helpful to discriminate supraventricular from ­ventricular
tachycardias. The present study compared a novel, ICD system that
incorporates an atrial sensing bipole in the single ICD lead (A+ICD, 124 patients) with a conventional, dual-chamber ICD system with a separate atrial lead (125 patients) in patients without
bradycardia pacing indications. Both systems correctly identified
all ventricular tachycardia episodes, and supraventricular
e76 Circ Arrhythm Electrophysiol June 2012
tachyarrhythmia discrimination with the A+ system was not i­ nferior
to that of the conventional system. The A+ system was faster to
implant. This single-lead system offers potentially useful atrial
sensing without the need to implant an additional atrial lead.
Conclusions: The novel A+-ICD system can be implanted faster and
is equivalent to a standard DR-ICD with regard to the detection of
ventricular tachyarrhythmias and supraventricular tachyarrhythmias.
It represents a useful alternative to obtain atrial sensing.25
New Criteria During Right Ventricular Pacing
to Determine the Mechanism of
Supraventricular Tachycardia
Soufian T. AlMahameed, MD; Alfred E. Buxton, MD; and Gregory F. Michaud, MD
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Summary: Rapid accurate distinction of atrioventricular nodal reentry from orthodromic atrioventricular reentry tachycardia is critical to
successful catheter ablation for these supraventricular tachycardias
(SVT). Right ventricular pacing that entrains SVT is often used to
make this distinction but is not helpful when pacing fails to entrain
or terminates SVT. We developed and tested 2 new criteria for distinguishing these SVTs using right ventricular pacing trains that do
not require entrainment. From right ventricular pacing trains, the
transition zone is defined from the first QRS complex that is fusion
between SVT and pacing to the first paced complex that has a stable
QRS morphology (either completely paced or constantly fused).
During the transition zone, advance of the stimulus-atrial interval or
a fixed stimulus-atrial indicates orthodromic atrioventricular reentry
tachycardia. In 92 patients with SVT of various mechanisms, these
criteria showed excellent diagnostic accuracy and could be applied
regardless of whether pacing terminated SVT.
Conclusions: During right ventricular pacing, within 40 milliseconds
of the tachycardia cycle length, orthodromic atrioventricular reentry
tachycardia is the likely mechanism when atrial timing is perturbed
or a fixed stimulus-atrial interval is established within the transition
zone.26
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Circ Arrhythm Electrophysiol. 2012;5:e69-e77
doi: 10.1161/CIRCEP.112.973305
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