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Europace Advance Access originally published online on October 24, 2007
Europace 2007 9(12):1119-1123; doi:10.1093/europace/eum226
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Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2007. For permissions please email: journals.permissions@oxfordjournals.org

PACING FOR ATRIAL FIBRILLATION

Evaluation of pacemaker dependence in patients on ablate and pace therapy for atrial fibrillation

Eraldo Occhetta1,*, Miriam Bortnik1, Gabriele Dell’Era1, Fabio Zardo2, Ermanno Dametto2, Biagio Sassone3, Luca Gabrieli3 and Paolo Marino1

1 Cardiology Division, Azienda Ospedaliera Maggiore della Carità, Corso Mazzini 18, 28100 Novara, Italy; 2 Cardiology Division, Azienda Ospedaliera S. Maria degli Angeli, Pordenone, Italy; 3 Cardiology Division, Ospedale di Bentivoglio, Bologna, Italy

Manuscript submitted 6 June 2007. Revision received 18 September 2007. * Corresponding author. Tel: +39 0321 3733413; fax: +39 0321 3733142. E-mail address: occhetta{at}r-j.it, eraldo.occhetta{at}maggioreosp.novara.it


   Abstract
Top
 Abstract
Introduction
 Methods
 Statistical analysis
 Results
 Discussion
 Conclusions
 Acknowledgements
 References
 
Aims: In patients with atrial fibrillation (AF) and uncontrolled ventricular rate, radiofrequency (RF) ablation of the atrioventricular (AV) node and pacemaker (PM) implantation (ablate and pace) is a valid therapeutic approach, especially in elderly patients. The aim of our study was to evaluate the PM dependence and the incidence of correlated clinical phenomena in a patients population with AV block induced by RF ablation of the AV junction.

Methods and results: One-hundred and sixty-three patients (71 men; mean age 71 ± 8 years) who had undergone ablate and pace therapy were evaluated. The patients underwent assessment of quality of life, impairment of consciousness, stroke/transient ischaemic attack (TIA), hospitalizations for heart failure, episodes of palpitations, and instrumental evaluation of PM dependence during PM inhibition (absence of escape rhythm; asystolic pause >5 s; escape rhythm <30 bpm after rhythm stabilization). Correlation between instrumentally evaluated PM dependence and clinical history was analysed. Hundred and thirty-two patients were evaluated after a mean follow-up period of 36 months [31 subjects (19%) died before the evaluation]; 55 patients (42%) were classified as PM-dependent: 38 (69%) complained of disturbances (19 dizziness, 15 pre-syncope, 4 syncope); 77 patients (58%) were considered non-PM-dependent: symptoms (dizziness, flush) were reported by only 3 (4%). No significant differences emerged between PM-dependent and non-PM-dependent patients with regard to episodes of pre-syncope, syncope, stroke/TIA, hospitalizations for heart failure, and quality of life.

Conclusion: This study confirms that ablate and pace is an effective and safe approach in subjects with chronic or recurrent AF and uncontrolled ventricular rate.

Key Words: Pacemaker dependence, Atrial fibrillation, Ablate and pace therapy


   Introduction
Top
 Abstract
 Introduction
Methods
 Statistical analysis
 Results
 Discussion
 Conclusions
 Acknowledgements
 References
 
Atrial fibrillation (AF) is currently the most common cardiac arrhythmia in the clinical setting, with a prevalence of 1–2% in the general population and up to 10% in elderly subjects.1Go In spite of the considerable progress in pharmacological and non-pharmacological therapy, this arrhythmia still constitutes a major clinical issue. Medical therapy alone is often unable to solve the problem and may cause serious side-effects; moreover, in the case of chronic AF, controlling AF paroxysms and mean ventricular rate may not be enough. In this context, transcatheter ablation of the atrioventricular junction followed by pacemaker (PM) implantation (the so-called ‘ablate and pace therapy’) may be a valid therapeutic tool to control symptoms, especially in older patients.

Following this procedure, patients are constantly stimulated by the PM. However, the clinical relevance of PM-dependence has not yet been clearly established; indeed, the literature data are often discordant.2Go–5Go Moreover, it may be difficult to correlate instrumentally documented PM dependence with possible clinical implications.

The aim of this multicentric study conducted in a population of patients who had undergone ablate and pace therapy was to discern the percentage of PM-dependent subjects and the incidence of major clinical events (syncope, episodes of heart failure, cerebral ischaemia, and mortality) and to assess quality of life during long-term follow-up.


   Methods
Top
 Abstract
 Introduction
 Methods
Statistical analysis
 Results
 Discussion
 Conclusions
 Acknowledgements
 References
 
The study involved 163 patients (71 male, 92 female; mean age 71 ± 8 years) who had successfully undergone ablation of the AV junction followed by PM implantation at the Italian Cardiology Centers of Novara (n = 119), Pordenone (n = 30), and Bologna (n = 14) from February 1995 to November 2005. All the enrolled patients were affected by AF (chronic 88%, paroxysmal 12%) and where severely symptomatic in spite of pharmacological therapy.

Transcatheter ablation was performed in accordance with the standard technique;6Go particular care was taken to create the lesion at the level of the AV node in order to obtain an escape rhythm with a narrow QRS. A rate-responsive PM (single-chamber in the case of chronic AF or dual-chamber in the case of paroxysmal AF) was implanted during the same session.

Apart from the routinary follow-up examinations, the study design included a ‘one-off’ evaluation of patients through the acquisition of any adverse events that might have occurred in the post-ablation period (syncope or pre-syncope, episodes of heart failure, cerebral ischaemia, and mortality) and through compilation of the Minnesota Living with Heart Failure Questionnaire7Go to assess post-procedure quality of life.

All subjects gave a written informed consent prior to inclusion in the study.

During extemporary examination of the PM, PM dependence was ascertained by means of:

  1. three sudden inhibitions of ventricular stimulation until the appearance of an escape rhythm, and in any case for a maximum period of asystole of 10 s;
  2. if no spontaneous escape rhythm emerged, another two inhibitions of ventricular stimulation after the PM had been reprogrammed to VVI 30 bpm for 2 min.

The inhibition protocol was interrupted when a spontaneous escape rhythm emerged or when major symptoms occurred.

Patients were deemed to be PM-dependent if one of the following conditions was observed:

  1. complete absence of escape rhythm during the protocol;2Go
  2. asystolic pause >5 s before any emergence of the escape rhythm3Go (Figure 1);
  3. escape rhythm rate <30 bpm after an adequate stabilization period;2Go
  4. syncope during PM inhibition.


Figure 1
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  		Figure 1 Pacemaker-dependent patient. On pacemaker inhibition (arrow), an asystolic pause of 7.5 s occurs before the emergence of an escape rhythm with a low rate and narrow QRS.

 
Patients were deemed to be non-PM-dependent if the escape rhythm during PM inhibition emerged after a pause <5 s. (Figure 2).


Figure 2
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  		Figure 2 Non-pacemaker-dependent patient. Pacemaker inhibition is followed by an asystolic pause of 1.2 s and subsequent onset of a good escape rhythm with a rate of 40 bpm and narrow QRS.

 

   Statistical analysis
Top
 Abstract
 Introduction
 Methods
 Statistical analysis
Results
 Discussion
 Conclusions
 Acknowledgements
 References
 
Comparison between groups was performed by means of non-parametric Mann–Whitney, Fisher and Chi-square tests.8Go


   Results
Top
 Abstract
 Introduction
 Methods
 Statistical analysis
 Results
Discussion
 Conclusions
 Acknowledgements
 References
 
During a mean follow-up of 36 months (range 1–120 months), 31 patients (19%) died; the causes of death are reported in Table 1. One patient died suddenly, whereas in 12 patients the cause of death could not be established. The Kaplan–Meier mortality curve is displayed in Figure 3.


Figure 3
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  		Figure 3 (A) Kaplan–Meier mortality curve. Left vertical axis shows per cent of subjects dead at follow-up; right vertical axis number of patients entering each observation time interval; horizontal axis months of follow-up. (B) Kaplan–Meier mortality curve. Left vertical axis shows per cent of subjects dead at follow-up; horizontal axis months of follow-up. Number of patients entering each observation time interval is given in the table below.

 


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  		Table 1 Cause of death in the 31 patients who died during follow-up

 
PM-dependence was therefore evaluated in 132 patients. At the time of the procedure, 20 subjects were in sinus rhythm and 112 in AF; 27 patients (20%) were on antiarrhythmic therapy (amiodarone: 10 patients, propafenone: 2, flecainide: 2, sotalol: 3, other beta-blockers: 9, combination of amiodarone + flecainide: 1). The majority of the patients (89%) had a concomitant heart disease (36% hypertensive, 19% ischaemic, 21% valvular, 7% dilated cardiomyopathy, 6% hypertrophic cardiomyopathy). Mean left ventricular (LV) ejection fraction (LVEF) was 49 ± 11.6%. Patients who died before the evaluation showed a significant lower LVEF (mean 43 ± 13.2% vs. 50.7 ± 10.5% of the patients in which the planned evaluation was possible; P = 0.004).

According to the criteria outlined in Methods, 55 patients (42%) were classified as PM-dependent and 77 (58%) as non-PM-dependent (Table 2).


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  		Table 2 Rate and morphology of escape rhythms during pacemaker inhibition in pacemaker-dependent and non-pacemaker-dependent patients

 
During the PM inhibition protocol:
  1. in 29% of the PM-dependent patients (16/55) no escape rhythm emerged, either on sudden inhibition or on inhibition after prolonged PM stimulation at 30 bpm;
  2. in 71% of the patients deemed PM-dependent (39/55) an asystolic pause >5 s was recorded, followed by a slow escape rhythm, with a mean rate of 28 bpm (range 10–41 bpm); the QRS was narrow in 47% of these patients (Table 2);
  3. in the group of non-PM-dependent patients, the post-inhibition pause was <5 s and the mean escape rhythm rate was 42 bpm (range 30–90 bpm); three patients displayed partial recovery of AV conduction (‘modulation’ effect of the ablative procedure), with mean ventricular rates of 70, 80 and 90 bpm; in non-PM-dependent patients, QRS duration was short in 62% of cases (Table 2).

On PM inhibition, markedly different percentages of symptomatic patients were observed in the PM-dependent (69%) and non-PM-dependent (4%) groups: P < 0.0001. In the PM-dependent group, although 31% of the patients were asymptomatic, the symptoms complained by the symptomatic patients were characterized by minor impairments of consciousness (dizziness in 35% and pre-syncope in 27%); only 7% (four patients) presented a syncopal event (Table 3). The small percentage of symptomatic non-PM-dependent patients complained only of dizziness (2%) and flush (1%) (Table 3).


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  		Table 3 Symptoms reported during pacemaker inhibition in pacemaker-dependent and non-pacemaker-dependent patients

 
With regard to the presence of anamnestic complaints during the follow-up of both groups, no statistically significant differences were observed in the incidence of major or minor impairments of consciousness, palpitations, neurological ischaemic events, and/or hospitalization for heart failure (Table 4). Similarly, quality of life in the months prior to the evaluation showed no significant difference between PM-dependent and non-PM-dependent patients, mean Minnesota questionnaire scores being 28 ± 21 and 25 ± 18, respectively (P = 0.67).


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  		Table 4 Anamnestic disturbances reported during follow-up in pacemaker-dependent and non-pacemaker-dependent patients

 

   Discussion
Top
 Abstract
 Introduction
 Methods
 Statistical analysis
 Results
 Discussion
Conclusions
 Acknowledgements
 References
 
Several observational studies9Go–11Go and randomized trials12Go,13Go have demonstrated the efficacy of ablate and pace therapy in controlling mean ventricular rate and in improving both quality of life and exercise tolerance in subjects with AF refractory to pharmacological therapy. Compared with other methods of ablation, which are being used increasingly frequently in the treatment of AF, ablation of the atrioventricular junction is a fairly simple procedure. Moreover, it has a high success rate and, in most cases, enables daily drug administration to be reduced. It is, however, a palliative procedure and gives rise to several problems, a major one being the induction of PM dependence.

Earlier studies14Go–16Go downplayed this problem, demonstrating the presence of a valid escape rhythm in the vast majority of patients who had undergone AV node ablation. More recently, however, the ample case records collected by Curtis et al.2Go revealed that an escape rhythm was present in only 67% of the 156 patients included in the register of the Ablate and Pace Trial and that an escape rhythm with a rate >40 bpm was observed in only 31%. Moreover, their study did not report the prevalence of disturbances linked to possible malfunctioning of the system (four deaths due to unspecified causes were recorded during follow-up).

In our population, 58% of patients resulted to be non-PM-dependent. Even among those classified as PM-dependent, the presence of an escape rhythm (with narrow QRS in 47% of cases) was documented in 71% of patients; in only 29% of patients, asystole occurred without the emergence of any escape rhythm on PM inhibition. These results might be explained by the particular care taken during the procedure to precisely ablate the atrioventricular node while preserving sub-nodal conduction as far as possible. In this regard, however, there is no consensus that AV node ablation induces less PM dependence than ablation of the His bundle.3Go

Although the percentage of PM-dependent patients who reported symptoms during the PM inhibition protocol was high (69%), no significant incidence of anamnestic disturbances during follow-up was observed. Likewise, quality of life assessment during follow-up revealed no significant difference between PM-dependent and non-dependent patients. A relatively high percentage of patients, including PM-dependent patients, complained of palpitations during follow-up; this may be linked to difficulties in correctly programming the rate-responsive function of the PM.17Go

The use of ablate and pace therapy has, in the past, been limited by concerns about its potential deleterious effects on overall mortality. However, a study by Ozcan et al.4Go showed that, in the absence of concomitant organic heart disease, the survival of patients undergoing ablate and pace therapy was substantially the same as the one expected in the general population and similar to that reported in patients treated pharmacologically. The literature also reports cases of sudden death following the ablate and pace procedure. According to Geelen et al.,5Go this type of mortality is around 6%; in most cases, however, the ventricular arrhythmias reported were linked to bradycardia-dependent mechanisms. In our population, only one case (0.6%) of sudden death occurred, the pathogenesis of which could not be determined. Nevertheless, a high number of deaths occurred (12 patients) which could not be explained, owing to the difficulty of obtaining reliable information from the patients’ relatives after the event. In any case, however, following the ablate and pace procedure, it seems advisable to programme a fairly high PM stimulation rate, at least initially.5Go

In patients with LV dysfunction, ablate and pace therapy is more problematic. In two studies involving patients suffering from congestive heart failure, Vanderheyden et al.18Go and Twidale et al.19Go reported a worsening of the haemodynamic status following ablation of the AV junction in 7 and 9% of their patients, respectively. The benefits yielded by regularization of the heart rate may therefore be offset by the well-known negative haemodynamic effects of long-term permanent right ventricular apical pacing.20Go In this regard, at least in patients with compromised LV function, it is currently preferable to utilize alternative pacing sites.21Go,22Go Moreover, in patients with spontaneous or ablation-induced intraventricular conduction delay, biventricular pacing can yield significant benefits with regard to symptoms and functional capacity. Indeed, the recently published PAVE study,23Go involving a group of patients with chronic AF who underwent ablation of the AV junction, documented a greater improvement in patients during biventricular pacing than in those with conventional right apical pacing, both in LVEF and in exercise tolerance on a 6-min walking test. Besides, the benefit was found to be greater in the subgroup of patients with compromised systolic function or symptomatic heart failure.


   Conclusions
Top
 Abstract
 Introduction
 Methods
 Statistical analysis
 Results
 Discussion
 Conclusions
Acknowledgements
 References
 
Instrumental evaluation revealed that 58% of our patients were non-PM-dependent and that as many as 42% were PM-dependent. Although these latter patients risked encountering serious clinical problems in the event of malfunction of the pacing system, no significant differences between the two groups emerged with regard to the occurrence of adverse events or to quality of life during a prolonged period of follow-up.

The results of our study seems to confirm that ablate and pace therapy is a safe and effective method of controlling heart rate in patients with chronic or recurrent AF. The pacing site must, however, be carefully chosen according to the type of patient, in order to avoid the adverse effects of the desynchronization induced by conventional pacing.24Go


   Acknowledgements
Top
 Abstract
 Introduction
 Methods
 Statistical analysis
 Results
 Discussion
 Conclusions
 Acknowledgements
References
 
We wish to acknowledge Diego Venturini, Ph.D. and Elena Turri, Ph.D. (from Medtronic Italia, Inc.) for the data collection and assistance with data analysis; they did not participate to the data interpretation and discussion considerations.

Conflict of interest: none declared.


   References
Top
 Abstract
 Introduction
 Methods
 Statistical analysis
 Results
 Discussion
 Conclusions
 Acknowledgements
 References
 
[1] Kannel WB, Abbott RD, Savage DD, McNamara PM. Epidemiologic features of atrial fibrillation: the Framingham study. N Engl J Med (1982) 306:1018–22.[Abstract]

[2] Curtis AB, Kutalek SP, Prior M, Newhouse TT, for the Ablate and Pace Trial Investigators. Prevalence and characteristics of escape rhythms after radiofrequency ablation of the atrioventricular junction: results from the registry for AV junction ablation and pacing in atrial fibrillation. Am Heart J (2000) 139:122–5.[Web of Science][Medline]

[3] Deharo JC, Mansourati J, Graux P, Gallay P, Thirion X, Macaluso G, et al. Long-term pacemaker dependency after radiofrequency ablation of the atrioventricular junction. Am Heart J (1997) 133:580–4.[CrossRef][Web of Science][Medline]

[4] Ozcan C, Jahangir A, Friedman PA, Patel PJ, Munger TM, Rea RF, et al. Long-term survival after ablation of the atrioventricular node and implantation of a permanent pacemaker in patients with atrial fibrillation. N Engl J Med (2001) 344:1043–51.[Abstract/Free Full Text]

[5] Geelen P, Brugada J, Andries E, Brugada P. Ventricular fibrillation and sudden death after radiofrequency catheter ablation of the atrioventricular junction. Pacing Clin Electrophysiol (1997) 20:343–8.[CrossRef][Medline]

[6] Trohman RG, Simmons TW, Moore SL, Firstenberg MS, Williams D, Maloney JD. Catheter ablation of the atrioventricular junction using radiofrequency energy and a bilateral cardiac approach. Am J Cardiol (1992) 70:1438–43.[CrossRef][Web of Science][Medline]

[7] Rector TS, Kubo SH, Cohn JH. Patients’ self-assessment of their heart failure: content, reliability, and validity of a new measure, the Minnesota Living with Heart Failure questionnaire. Heart Fail (1987) 3:198–209.

[8] Glanz Stanton A. Primer of Biostatistics. (2005) McGraw-Hill Medical Publishing.

[9] Twidale N, Sutton K, Barlett L, Dooley A, Winstanley S, Heddle W, et al. Effects on cardiac performance of atrioventricular node catheter ablation using radiofrequency current for drug-refractory atrial arrhythmias. Pacing Clin Electrophysiol (1993) 16:1275–84.[CrossRef][Medline]

[10] Marshall HJ, Harris ZI, Griffith MJ, Gammage MD. Atrioventricular nodal ablation and implantation of mode switching dual chamber pacemakers: effective treatment for drug refractory paroxysmal atrial fibrillation. Heart (1998) 79:543–7.[Abstract/Free Full Text]

[11] Kay GN, Ellenbogen KA, Giudici M, Redfield MM, Jenkins LS, Mianulli M, et al. The Ablate and Pace Trial: a prospective study of catheter ablation of the AV conduction system and permanent pacemaker implantation for treatment of atrial fibrillation. J Interv Card Electrophysiol (1998) 2:121–35.[CrossRef][Web of Science][Medline]

[12] Brignole M, Menozzi C, Gianfranchi L, Musso G, Mureddu R, Bottoni N, et al. Assessment of atrioventricular junction ablation and VVIR pacemaker versus pharmacological treatment in patients with heart failure and chronic atrial fibrillation. A randomized controlled study. Circulation (1998) 98:953–60.[Abstract/Free Full Text]

[13] Brignole M, Gianfranchi L, Menozzi C, Alboni P, Musso G, Bongiorni MG, et al. Assessment of atrioventricular junction ablation and DDDR mode-switching pacemaker versus pharmacological treatment in patients with severely symptomatic paroxysmal atrial fibrillation. A randomized controlled study. Circulation (1997) 96:2617–24.[Abstract/Free Full Text]

[14] Schmidinger H, Probst P, Schneider B, Weber H, Kaliman J. Subsidiary pacemaker function in complete heart block after His-bundle ablation. Circulation (1988) 78:893–8.[Abstract/Free Full Text]

[15] Langberg JJ, Chin MC, Rosenqvist M, Cockrell J, Dullet N, Van Hare G, et al. Catheter ablation of the atrioventricular junction with radiofrequency energy. Circulation (1989) 80:1527–35.[Abstract/Free Full Text]

[16] Alison JF, Yeung-Lai-Wah JA, Schulzer M, Kerr CR. Characterization of junctional rhythm after atrioventricular node ablation. Circulation (1995) 91:84–90.[Abstract/Free Full Text]

[17] Bortnik M, Francalacci G, Occhetta E, Vassanelli C. Problematiche gestionali nel follow-up di un paziente sottoposto ad ‘ablate and pace therapy. G Ital Aritmol Cardiostim (2003) 1:17–22.

[18] Vanderheyden M, Goethals M, Anguera I, Nellens P, Andries E, Brugada J, et al. Hemodynamic deterioration following radiofrequency ablation of the atrioventricular conduction system. Pacing Clin Electrophysiol (1997) 20:2422–38.[CrossRef][Medline]

[19] Twidale N, Manda V, Nave K, Seal A. Predictors of outcome after radiofrequency ablation of the atrioventricular node for atrial fibrillation and congestive heart failure. Am Heart J (1998) 136:647–57.[CrossRef][Web of Science][Medline]

[20] Szili-Torok T, Kimman GP, Theuns D, Poldermans D, Roelandt JRTC, Jordaens LJ. Deterioration of left ventricular function following atrio-ventricular node ablation and right ventricular apical pacing in patients with permanent atrial fibrillation. Europace (2002) 4:61–5.[Free Full Text]

[21] Barold SS. Adverse effects of ventricular desynchronization induced by long-term right ventricular pacing. J Am Coll Cardiol (2003) 42:624–6.[Free Full Text]

[22] Occhetta E, Bortnik M, Magnani A, Francalacci G, Piccinino C, Plebani, et al. Prevention of ventricular desynchronization by permanent para-Hisian pacing after atrioventricular node ablation in chronic atrial fibrillation. A crossover, blinded, randomized study versus apical right ventricular pacing. J Am Coll Cardiol (2006) 47:1938–45.[Abstract/Free Full Text]

[23] Doshi RN, Daoud EG, Fellows C, Turk K, Duran A, Hamdan MH, et al. Left ventricular-based cardiac stimulation post AV nodal ablation evaluation (the PAVE Study). J Cardiovasc Electrophysiol (2005) 16:1160–5.[CrossRef][Web of Science][Medline]

[24] Manolis AS. The deleterious consequences of right ventricular apical pacing: time to seek alternate site pacing. Pacing Clin Elecrophysiol (2006) 29:298–315.[CrossRef]


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