(Circulation. 2000;102:736.)
© 2000 American Heart Association, Inc.
Clinical Investigation and Reports |
Randomized Crossover Comparison of DDDR Versus VDD Pacing After Atrioventricular Junction Ablation for Prevention of Atrial Fibrillation
From the Division of Cardiology, Foothills Hospital and the University of Calgary, Calgary, Alberta, Canada (A.M.G., M.S.R., D.G.W.); Hamilton General Hospital and McMaster University, Hamilton, Ontario, Canada (S.J.C.); Hôpital Notre Dame and the University of Montreal, Montreal, Quebec, Canada (P.L.); Hôpital Laval and Laval University, Quebec City, Canada (F.P.); Montreal Heart Institute and the University of Montreal, Montreal, Quebec, Canada (M.D.); St Paul’s Hospital and University of British Columbia, Canada (C.R.K.); University Hospital and the University of Western Ontario, London, Ontario, Canada (R.Y.); St Michael’s Hospital and the University of Toronto, Toronto, Ontario, Canada (D.N.); University Hospital and the University of Alberta, Edmonton, Alberta, Canada (K.M.K.); Queen Elizabeth II Medical Centre and Dalhousie University, Halifax, Nova Scotia, Canada (M.J.G.); and Hôpital du Sacre Coeur and the University of Montreal, Canada (T.K.).
Correspondence to Anne M. Gillis, MD, Division of Cardiology, The University of Calgary, 3330 Hospital Dr NW, Calgary, Alberta, Canada T2N 4N1. E-mail amgillis{at}ucalgary.ca
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Abstract |
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 Top Abstract IntroductionMethodsResultsDiscussionAppendix 1References |
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Background—Some clinical data suggest that atrial-based pacing prevents paroxysmal atrial fibrillation (AF). This study tested the hypothesis that DDDR pacing compared with VDD pacing prevents AF after atrioventricular (AV) junction ablation.
Methods and Results—Patients were randomized to DDDR pacing (n=33) or to VDD pacing (n=34) after AV junction ablation and followed every 2 months for 6 months. Patients then crossed over to the alternate pacing mode and were followed for an additional 6 months. Primary analysis included the time to first recurrence of sustained AF (duration >5 minutes), total AF burden, and the development of permanent AF. The time to first episode of AF was similar in the DDDR group (0.37 days, 95% CI 0.1 to 1.3 days) and the VDD pacing group (0.5 days, 95% CI 0.2 to 1.7 days, P=NS). AF burden increased over time in both groups (P<0.01). At the 6-month follow-up, AF burden was 6.93 h/d (95% CI 4.37 to 10.96 h/d) in the DDDR group and 6.30 h/d (95% CI 3.99 to 9.94 h/d) in the VDD group (P=NS). Twelve (35%) patients in the DDDR group and 11 (32%) patients in the VDD group had permanent AF within 6 months of ablation. Within 1 year of follow-up, 43% of patients had permanent AF.
Conclusions—DDDR pacing compared with VDD pacing does not prevent paroxysmal AF over the long term in patients in the absence of antiarrhythmic drug therapy after total AV junction ablation. Many patients have permanent AF within the first year after ablation.
Key Words: fibrillation • pacemakers • ablation • atrioventricular node
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Introduction |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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Atrioventricular (AV) junction ablation is a therapeutic option for the treatment of patients with paroxysmal atrial fibrillation (AF) who are unresponsive to or intolerant of antiarrhythmic therapy.1 2 3 4 Ventricular function and quality of life have been reported to be improved in patients after AV junction ablation.4 5 6 Recently, quality of life has been reported to improve in patients after AV junction ablation compared with patients treated with antiarrhythmic drug therapy.3 6 The appropriate choice of pacing mode after ablation is uncertain because many patients may progress to permanent AF, particularly if antiarrhythmic drug therapy is discontinued.3 7 8 Atrial-based pacing reduces the incidence of paroxysmal AF and chronic AF in the pacemaker population.9 10 It has been suggested that atrial-based pacing might prevent paroxysmal AF by eliminating bradycardia-induced dispersion of atrial repolarization that provides the substrate for AF and by overdrive suppression of supraventricular premature beats, which provide the trigger for AF.11 12 13 14 However, whether atrial pacing prevents paroxysmal AF or impedes the progress to permanent AF after ablation is unknown. Furthermore, it is unknown whether AV sequential pacing in the DDDR mode is superior to atrial-sensed ventricular synchronous pacing in the VDD mode after ablation. Although both are "physiological" pacing modalities and maintain AV synchrony, DDDR pacing provides the ability to pace the atrium and thus to isolate the potential benefits of atrial pacing from those of AV synchronization. We have previously reported that atrial pacing over a 3-month follow-up period did not prevent paroxysmal AF in patients without symptomatic bradycardia.14 The present study evaluates the effects of DDDR versus VDD pacing on AF recurrence over the long term in patients after AV junction ablation and cessation of antiarrhythmic drug therapy.
The present study tested the hypotheses that (1) DDDR pacing would reduce the time to first recurrence of paroxysmal AF compared with VDD pacing in patients after AV junction ablation and (2) that DDDR pacing would reduce the recurrence of paroxysmal AF and total burden of AF over time compared with VDD pacing in patients after AV junction ablation.
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Methods |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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Study Population
The study population consisted of patients with a history of paroxysmal AF who had
3 episodes of paroxysmal AF within the year
before pacemaker implantation. Patients also had to be refractory to or
intolerant of medical therapy because of significant adverse effects
and hence had undergone a total AV junction ablation. Patients enrolled
in this study had participated in the initial phase of the Atrial
Pacing Peri-Ablation for Prevention of Atrial Fibrillation
(PA3) Trial.14 Those proceeding to
AV junction ablation participated in this second phase of the
PA3 Trial. The study was approved by all the
medical ethics review boards of the participating institutions (see
Appendix).
Study Protocol
The study design is outlined in Figure 1
. Consenting patients received a
Medtronic Thera DR pacemaker before AV junction ablation. The Thera DR
device can store information on the time, date, and duration of up to
15 consecutive episodes of an atrial tachyarrhythmia in
the device memory. This information was retrieved with the use of the
pacemaker programmer during follow-up visits. After pacemaker
implantation, antiarrhythmic drugs were usually discontinued and
patients were randomly assigned to pacing in the DDDR or VDD modes. The
programmed parameters for the 2 modes used in this study
are shown in Table 1. Patients
randomized to the DDDR mode were programmed to a lower rate of 70 bpm
to ensure that the atrium would be paced most of the time. Patients
randomized to the VDD mode were programmed to a lower rate of 60 bpm.
This rate was chosen to preserve AV synchrony most of the time. If the
sinus rate fell below 60 bpm, then asynchronous ventricular
pacing would result.
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All patients completed a 2-week stabilization phase to allow antiarrhythmic drugs to wash out. The high-rate atrial episode diagnostic data were retrieved and the counters were cleared at the 2-week follow-up visit. Patients were then assessed at subsequent follow-up visits scheduled 2, 4, and 6 months after ablation. At each visit, the high-rate atrial episode data were retrieved. These data were used to determine the primary outcome event of the study. At the 6-month follow-up visit, patients were crossed over to the alternate pacing mode and followed every 2 months for an additional 6 months. Ambulatory ECGs were obtained at each follow-up visit.
Study Outcome Events
The primary study outcome event was time to first
recurrence of sustained AF lasting at least 5 minutes and
occurring 2 weeks after randomization. Since the time course of
recurrence may not be completely random, the intervals between
first and second episodes and between second and third episodes of
paroxysmal AF were also determined.15 Other outcome
measures included AF burden, which was defined as hours of AF per day
and the proportion of patients in whom permanent AF (which was defined
as an AF burden of 24 h/d) would develop. AF burden was calculated as
the total duration of AF detected during the follow-up period. In the
case when the event counters were filled before completion of the total
follow-up duration, AF burden was calculated as the total duration of
AF during the time to detection of the first 15 episodes of sustained
AF.
AF Detection
The high-rate atrial tachycardia detection feature
of the Thera DR was used for AF detection in this study. This feature
has been reported to have a high sensitivity and specificity for the
detection of atrial
tachyarrhythmias,14 16 17 and we have
validated this detection algorithm previously.14 In the
present study, validation of appropriate detection of AF was
carried out with the use of an enhanced Marker channel feature of the
device to download to one channel of the ambulatory ECG, with marker
signals representing what the device interpreted as atrial
and ventricular electrograms. Appropriate detection of
episodes of AF was observed in all 35 patients who had AF during
ambulatory ECG monitoring during follow-up visits.
All episodes of AF detected by the pulse generator were reviewed by 2 observers who were blinded to the programmed pacing modality. Specific rules had been developed previously to diagnose oversensing of near-field P waves or far-field R waves or competitive atrial pacing based on characteristic beat-to-beat intervals during an episode.14 17 Of 3061 episodes of AF detected in the study population, only 4 episodes caused by oversensing (0.1%) were inappropriately detected as AF. These episodes were excluded in the final data analysis.
Data Analysis
Analysis was performed according to the
intention-to-treat principle. The time to occurrence of the first
episode of sustained AF and the second episode of sustained AF were
determined by means of the Kaplan-Meier method.18
Differences in the survival curves were compared by means of the
log-rank test.19 Geometric mean data were calculated
following a log transformation, and these differences were compared by
means of a 2-way ANOVA or ANOVA for repeated measures where
appropriate. Differences in proportions were compared by means of
2 analysis. Data are presented
as mean±1 SD or geometric mean and 95% CI when log transformation was
used. A value of P<0.05 for 2-sided comparisons was
considered significant.
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Results |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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Study Population
Thirty-three patients were randomized to the DDDR group and 34 patients were randomized to the VDD group. The clinical characteristics of the 2 groups were similar (Table 2
).
Interrogation of the pacemaker at the 2-month follow-up visit revealed
that the atrium was paced 41±29% of the time and the ventricle was
paced 99.7±0.3% of the time in patients randomized to the DDDR group
and that the ventricle was paced 99.8±0.2% of the time in the
patients randomized to the VDD group. The low proportion of atrial
pacing in the DDDR group reflects the high AF burden observed.
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Early Crossovers to DDDR From VDD Mode
Five patients randomized to the VDD group were crossed over to
DDDR pacing before completion of the 6-month follow-up period because
of hemodynamic symptoms or feeling unwell. These
patients were included in the VDD group for the intention-to-treat
analysis.
Time to First and Second AF
Survival free of recurrent sustained AF after the 2-week
stabilization period based on intention-to-treat analysis is
shown in Figure 2. There was no
significant difference between the 2 groups (P>0.3). Since
the time to first event assumes that AF occurs randomly, which may not
be the case,15 event-free survival of the interval
between the first and second episodes of sustained AF were also
compared on the basis of intention-to-treat analysis. These
data were censored to adjust for those who remained in AF and hence
were not at risk to have a second episode. No differences were observed
between the 2 groups (Figure 3).
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AF Recurrence Characteristics
The characteristics of recurrences of AF are shown in
Table 3. The majority of patients (94%)
had sustained AF during the initial 6-month follow-up period, and most
patients had multiple episodes of AF. There were no significant
differences in the time to first episode of AF, the interval between
first and second episodes of AF, and the burden of AF
(P=NS). The AF burden increased significantly over time in
both groups (P<0.01, Figure 4). Twelve (35%) patients in the DDDR
group and 11 (32%) patients in the VDD group had permanent AF at the
completion the 6-month follow-up period.
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) and VDD groups
(
). Data are geometric mean with 95% CIs. AF burden increased
significantly over initial 6-month follow-up in both groups
(P<0.01) and continued to increase during next 6 months
(P<0.01) after crossover to alternate pacing strategy
at 6-month follow-up visit. AF burden 12 months after ablation was
similar in both groups. PAF indicates paroxysmal AF.
Six-Month Crossover
Patients crossed over to the alternate pacing modality after 6
months of follow-up. However, because of the high proportion of
patients who had permanent AF before the 6-month follow-up visit, the
number of patients actually being paced in the DDDR or VDD pacing modes
during the last 6 months of follow-up was small. The AF burden
continued to increase during the last 6 months after crossover to the
alternate pacing modality (Figure 4
). AF burden was similar in
both groups 1 year after ablation.
The proportion of patients who were in AF at each follow-up visit and
the proportion of patients in whom permanent AF developed increased
significantly after AV node ablation in all patients (Figure 5, P<0.001). Within 1 year of
AV node ablation, 43% of the study population had permanent AF.
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Discussion |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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Present therapeutic strategies for the management of AF, which include pharmacological maintenance of sinus rhythm or heart rate control of AF, are unsatisfactory for many patients.20 AV junction ablation with implantation of a VVIR or DDDR pacemaker alleviates symptoms of uncontrolled or irregular heart rates and may result in improved hemodynamic function.1 2 3 4 5 6 At present, it is uncertain whether the DDDR pacing modality is indicated after AV junction ablation, particularly if antiarrhythmic drug therapy is discontinued. Some studies have reported a high progression to permanent/chronic AF after total AV junction ablation in patients with AF.3 7 8 The present study is the first to assess whether atrial-based pacing might prevent the development of chronic AF over the long term after total AV junction ablation and to isolate the potential benefits of atrial pacing over preservation of AV synchrony.
The rationale that AV sequential pacing might be indicated in such patients is based on clinical and experimental data, suggesting that physiological pacing prevents the development of AF.9 10 11 12 13 14 It has been suggested that atrial pacing might prevent AF by eliminating bradycardia-induced dispersion of atrial repolarization, which is believed to provide the electrophysiological substrate for AF, and by overdrive suppression of supraventricular premature beats, which provide the trigger for AF. In our previous study, we have shown that over the short term, atrial pacing did not prevent AF.14 In the present study, atrial-based pacing did not prevent AF over the long term in this highly symptomatic patient population. Nor did we observe a benefit of DDDR pacing over VDD pacing on AF recurrence. This suggests that prevention of relative bradycardia in the atrium is not an important approach for the prevention of AF. This is in keeping with observations that bradycardia immediately preceding the onset of AF is observed in only 8% to 10% of episodes.13 21 The minimal atrial pacing rate evaluated in the present study was 70 bpm and thus it is possible that atrial pacing at higher baseline rates might have been beneficial. It is also possible that pacing algorithms designed to ensure atrial pacing the majority of the time might have been beneficial. The present study is the first to assess the impact of atrial pacing for prevention of AF over the long term. Since patients had frequent AF, the electrophysiological substrate predisposing to recurrent AF probably persisted over time and contributed to the development of permanent AF in some.22 It is thus possible that atrial pacing might allow recovery of the electrophysiological substrate for AF over time in patients with fewer episodes of AF.
No attempt was made to maintain antiarrhythmic drug therapy, therefore the present study must be considered a trial of atrial pacing in the absence of adjunctive antiarrhythmic drug therapy. The results of this study may not apply to the situation in which antiarrhythmic drug therapy is continued after AV junction ablation. It is possible, as suggested by other investigators, that combined pacing and pharmacological therapy might have been beneficial in this group.12
The choice of pacing mode after AV junction ablation remains controversial. Some investigators have elected to use the simple, less costly VVIR pacing system. Others have suggested implantation of a dual-chamber, rate-responsive system with mode switching capabilities, based on the assumption that atrial pacing and/or maintenance of AV synchrony would prevent the progression to chronic AF. Mitchell et al23 retrospectively studied the atrial rhythm in 49 patients after AV junction ablation for paroxysmal AF. At a mean follow-up of 18.6 months, 67% were in sinus or atrial paced rhythm. Brignole et al3 reported that 24% of 21 patients had permanent AF 6 months after AV junction ablation, whereas none of the 18 patients randomized to antiarrhythmic therapy had permanent AF. Gianfranchi et al8 followed 63 patients with paroxysmal AF for 23±16 months after AV junction ablation and reported that permanent AF developed in 35%. The actuarial rate of progression to permanent AF was 22%, 40%, and 56% at 1, 2, and 3 years, respectively, after ablation. Gribbin et al7 reported that 42% of 62 patients had permanent AF over a mean follow-up of 30 months after AV junction ablation. Marshall et al6 reported that 12 of 37 patients receiving DDDR pacemakers had permanent AF within 6 weeks of AV junction ablation compared with none of 19 patients treated with antiarrhythmic drug therapy. Buys et al24 suggested that VDD pacing is an acceptable modality after AV junction ablation because only 4 of 17 patients had permanent AF during a mean follow-up of 18 months. In the present study, the time course of development of permanent AF was independent of the pacing modality DDDR versus VDD. The rate of progression to permanent AF in the present study was more rapid than reported by most investigators. This may reflect a patient population with a higher disease burden of AF compared with other studies.
Study Limitations
The diagnostic data counters were used for detection
of AF in the present study. It is possible that some episodes were
not detected because of undersensing. However, ambulatory ECG
monitoring validated detection of AF by the pacemaker in the study
population. The low proportion of atrial pacing documented during
follow-up in the DDDR group probably reflects the fact that many
patients had persistent AF and that the AF burden was high in the
remaining patients. It is also possible that the baseline sinus rate
increased after ablation, after cessation of antiarrhythmic drugs.
However, we cannot exclude the possibility that a higher programmed
atrial pacing rate or other pacing algorithms designed to promote
atrial pacing might have reduced the AF burden.
Conclusions
DDDR pacing compared with VDD pacing does not prevent
recurrence of paroxysmal AF, nor does it delay the development
of permanent AF in patients with frequent paroxysmal AF after total AV
junction ablation. Given the high proportion of patients who have
permanent AF within 12 months of ablation, a VVIR pacing system may be
satisfactory for many patients.
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Acknowledgments |
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This study was supported by a grant-in-aid from Medtronic, Inc, Minneapolis, Minn. Dr Gillis is a Senior Scholar of the Alberta Heritage Foundation for Medical Research. The authors thank Ken Riff, MD, and Nick Jensen, DVM, Medtronic, Inc, for their advice on study design; Rahul Mehra, PhD, Michael Hill, PhD, and Stephanie Fitts, PhD, Medtronic, Inc, for help with validating the high-rate atrial episodes; Margot McDonald, Karen Hillier, Andrew Mah, and Catherine St George, study coordinators, and Ronda Ross for help with manuscript preparation.
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Footnotes |
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Dr Gillis is a consultant to Medtronic, Inc; she is also a stockholder of that firm. Dr Yee is a member of an advisory committee for Medtronic, Inc.
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Appendix 1 |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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The following participated in this study (listed in descending order of number of patients randomized): Hamilton General Hospital, Hamilton, Ontario, Canada: Stuart J. Connolly, Wesley James, Catherine LeFeuvre, Maryann Menard. Foothills Medical Center, Calgary, Alberta, Canada: Anne M. Gillis, D. George Wyse, John M. Rothschild, L. Brent Mitchell, Henry J. Duff, Karen Hillier, Charlotte Hale. Hôpital Notre Dame, Montreal, Quebec, Canada: Pierre Lacombe, Diane Therrin, Claude Provencal, Louise Patry. Institut de Cardiologie, Hôpital Laval, Quebec City, Quebec, Canada: François Philippon, Marcel Gilbert, Gilles O’Hara, Johanne Rompré. Institut de Cardiologie, Montreal, Quebec, Canada: Marc Dubuc, Mario Talajic, Dennis Roy, Eric Lavallee. St Paul’s Hospital Vancouver, British Columbia, Canada: Charles R. Kerr, John Boone, John Yeung-Wai-Lah, Sheila Flavelle, Susan Mooney. St Michael’s Hospital, Toronto, Ontario, Canada: David Newman, Paul Dorian, Jane Laslop, Linda DeBelias. University Hospital, London, Ontario, Canada: Raymond Yee, George Klein, Caro Norris. University Hospital, Edmonton, Alberta, Canada: Katherine M. Kavanagh, Shane Kimber, Ingrid Scott. Queen Elizabeth II Health Sciences Center, Victoria General Hospital, Halifax, Nova Scotia, Canada: Martin J. Gardner, Laurence Sterns, Marcia Shields. Hôpital du Sacre-Coeur, Montreal, Quebec, Canada: Teresa Kus, Franck Molin, Ginette Gaudette.
Received December 6, 1999; revision received March 4, 2000; accepted March 10, 2000.
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References |
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TopAbstractIntroductionMethodsResultsDiscussionAppendix 1References |
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