Europace Advance Access originally published online on August 7, 2007
Europace 2007 9(10):857-861; doi:10.1093/europace/eum147
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CARDIAC RESYNCHRONISATION THERAPY
The BRIGHT study: bifocal right ventricular resynchronization therapy: a randomized study
1 Department of Cardiology, Ba 579, Erasmus Medical Centre Rotterdam, PO Box 2040, 3000 CA Rotterdam, The Netherlands; 2 Department of Cardiology, Waterland Hospital, Purmerend, The Netherlands; 3 Department of Cardiology, VU Medical Center, Amsterdam, The Netherlands; 4 Department of Cardiology, Ziekenhuis Gelderse Vallei, Ede, The Netherlands; 5 Department of Cardiology, Zaans Medisch Centrum, Zaandam, The Netherlands; 6 Department of Cardiology, Vlietland Ziekenhuis, Schiedam-Vlaardingen, The Netherlands
Manuscript submitted 5 February 2007. Accepted after revision 25 June 2007.
* Corresponding author. Tel: +31 10 4633991; fax: +31 10 4634420. E-mail address: j.res{at}erasmusmc.nl
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Abstract |
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Aims The BRIGHT study evaluated bifocal right ventricular (RV) (apex and outflow tract) pacing in a single, blind, randomized crossover study in patients eligible for cardiac resynchronization therapy (CRT). Forty-two patients were enrolled with the following characteristics: chronic drug refractory heart failure New York Heart Association (NYHA) class III–IV; ejection fraction (EF)<35%; QRS width
120 ms; and a left bundle branch block. The aim of the study was to assess an improvement in left ventricular (LV) EF, 6 min walk test, Minnesota quality-of-life score, and NYHA classification. Methods and result Patients were randomized to receive either bifocal pacing or the control mode, each for a period of 3 months. Parameters were measured prior to randomization and after 3 months of control or bifocal pacing. Eight patients failed to make the 7 month follow-up, three patients died (one prior to randomization at the first month), five patients dropped out, and three patients refused further participation. One patient had a persistent lead problem, which was subsequently replaced with an LV lead, and one patient suffered with persistent atrial fibrillation. Compared with baseline, bifocal pacing improved EF from 26 ± 12% to 36 ± 11% (P < 0.0008), NYHA classification decreased from 2.8 ± 0.4 to 2.3 ± 0.7 (P < 0.007). Furthermore, the 6 min walk test improved from 372 ± 129 m to 453 ± 122 m (P < 0.05), and the Minnesota Living with Heart Failure scores decreased from 33 ± 20 to 24 ± 21 (P < 0.006). In the control group, no significant changes in any parameters were observed. Eight patients did not tolerate reprogramming from DDD BRIGHT to control pacing, with symptoms disappearing in all patients after reprogramming to bifocal pacing.
Conclusion Bifocal RV pacing in patients with a classic indication for CRT shows improvement in all parameters.
Key Words: Bifocal pacing, Cardiac resynchronization therapy, Haemodynamics, Quality of life
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Introduction |
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Cardiac resynchronization therapy (CRT) has now emerged as a standard treatment in patients with advanced drug refractory heart failure, left bundle branch block, and systolic dysfunction.1
–6 However, large randomized trials have reported a substantial number of patients with failed implants or dysfunction of the left ventricular (LV) lead, with prevalence ranging from 6 to 14% with an average of 
10%.1–4,7,8 Moreover, the procedure is challenging and associated with major complications and, even, mortality.8
Bifocal pacing is defined as simultaneous pacing of the right ventricular (RV) outflow tract (RVOT) and the RV apex. One meta-analysis suggested that RVOT pacing may offer a modest but significant haemodynamic benefit over RV apex pacing in patients selected for pacemaker implantation for symptomatic brady-arrhythmias.9 Data on bifocal pacing as an alternative for CRT are limited to one small non-randomized study with 6 months follow-up in patients in whom a failure to implant an LV lead was reported.10 Since bifocal pacing is relatively easy,11,12 can be performed without additional costs or tools, and is associated with a low failure and complication rate, we investigated the haemodynamic and clinical outcome of this pacing configuration in patients eligible for CRT in a randomized crossover study.
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Patients |
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Forty-two patients eligible for CRT were enrolled in the BRIGHT study, in nine participating centres from the end 2002 until mid-2005 (see Appendix). All patients had advanced chronic heart failure class III–IV according to the New York Heart Association (NYHA) despite optimal pharmacological therapy. In addition, patients had the following characteristics: ejection fraction (EF)<35%, QRS duration
120 ms, and a left bundle branch block on the ECG. Patient characteristics were as follows: age 69 ± 9 years, 11 females/31 males, NYHA class 3.0 ± 0.2; LV EF 26 ± 8%; QRS width 180 ± 19 ms, and PR interval 203 ± 39 ms. Coronary artery disease was present in 22 patients (52%), and 8 patients (19%) had prior coronary artery bypass grafting. Patients were on the following medications: beta-blockade 32 (76%), ACE-inhibitors 38 (90%), diuretics 33 (79%), aldosterone antagonists 13 (31%), coumarine therapy 34 (81%), statins 17 (40%), amiodarone 17 (40%), anti-arrhythmic drugs 1 (2%), and digoxine 12 (22%). |
Methods |
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Patients were enrolled in the study prior to the implantation of the pacemaker. The Human Institutional Review Board approved the study in all the participating centres. The positioning of the RVOT lead was aimed in the high septal region according to the classification of Lieberman et al.13
After pacemaker implantation, the pacemaker was programmed to an inactive mode, and a run in a period of 4 weeks was planned. The study included a 6 month randomized crossover phase, during which atrioventricular (AV) bifocal RV pacing was compared with ventricular inhibited (inactive) pacing at a basic rate of 40 bpm, each for a period of 3 months in a random order (Figure 1). Left ventricular ejection fraction was calculated using the Simpson biplane formula according to the recommendations of the American Society of Echocardiography.14 Mitral regurgitation (MR) was classified as mild=1+(jet area/left atrial area < 10%), moderate=2+(jet area/left atrial area 10–20%), moderate to severe=3+(jet area/left atrial area 20–45%), and severe=4+(jet area/left atrial area>45%).15 The 6 min walk test was carried out according to the recommendations of Guyatt et al.16 and Lipkin et al.17 The Minnesota questionnaire contains 21 questions regarding patients’ perception of the effects of heart failure on their daily lives. Each question is rated on a scale of 0–5, producing a total score of 0–105, with the higher the score, the worse the quality of life.
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All measurements were performed before randomization and at 3 and 6 months follow-up visits after randomization. Thirty-four patients were evaluated at 6 month follow-up, and eight patients did not meet the 6 month follow-up for various reasons. In total, three patients died after pacemaker implantation: one before randomization, and two patients after randomization, one in the control period, and the other in the bifocal pacing mode. Cause of death was progressive heart failure in all patients. Five patients were considered dropouts during the follow-up, three patients refused further participation, one patient with a presumed persistent lead problem was referred to another hospital and his RVOT lead was replaced by an LV lead. Lead failure was not clearly demonstrated. Another patient developed persistent atrial fibrillation and successfully underwent external cardioversion, with subsequent improvement beyond the time schedule of the study. Analysis of all parameters was performed according to the attention-to-treat principle. Average values ± SD were given for continuous parameters, and paired Student’s t-test was performed for statistical analysis. A P-value of < 0.05 was considered as significant.
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Results |
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Lead implantation was performed without technical difficulties in all patients, with the exception of one patient with advanced AV block associated with active fixation of the lead in the RVOT, as defined by Lieberman et al.13
Analysis of the X-ray showed that the position of the lead tip was below the RVOT and close to the His-bundle. In 6 patients, the lead tip was positioned below the RVOT, in 36 patients in the RVOT, in 26 patients in the high septal region, and in a further 10 patients in the low septal region of the RVOT. In one patient, the introduction of the RV apex lead induced ventricular fibrillation. No other arrhythmias were reported during implantation. Total procedure time (skin–skin) was 102 ± 32 min (median 90, range 52–210) for all implanting physicians including also those who had to pass the learning curve for this procedure. For the most experienced implanter, the median implant time was 77 min. Lead measurements and data on lead handling on 34 patients (and 6 pilot patients) were reported earlier.18 An average of 2.7 ± 2.4 (range 1–10) positions were attempted for the RVOT implantation, in most cases due to high thresholds. Two leads positioned in the RVOT showed intra-operative dislocation and were repositioned successfully. One RVOT lead and one RVA lead were repositioned due to high pacing thresholds in a second procedure, but within the period of 1 month. Atrioventricular optimization was performed at 1 month prior to randomization; an average AV delay of 120 ± 10 ms was found to be optimal. The VV interval was set at zero. Results are shown in Table 1. During the active phase, the mean distance walked in 6 min was 22% longer (P < 0.05) than during the inactive phase. The Minnesota score decreased by a mean of 18% (P < 0.007) with active pacing, whereas LV EF increased by 20% (P < 0.008) compared with inactive pacing. In comparison with baseline, the QRS complex showed a small but significant decrease in duration: 182 ± 20 ms to 171 ± 8 ms (P < 0.04). Subgroup analysis of the patients with short and long PR intervals showed no differences.
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Owing to the crossover design, of the patients programmed to the bifocal pacing mode first, eight patients did not tolerate reprogramming from DDD bifocal pacing mode to control back-up pacing at the 3 month interval. After measurements were taken for the study, they were reprogrammed to the bifocal pacing mode, and symptoms disappeared within a few days. Total hospital admission days were 20 in the bifocal group vs. 31 in the control group (NS). Symptomatic arrhythmias during the follow-up were noticed in one single patient, who developed persistent atrial fibrillation and recovered well after external cardioversion.
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Discussion |
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The present study demonstrates a significant haemodynamic and clinically beneficial effect of bifocal pacing in patients with an indication for CRT according to the guidelines of the American Heart Association.19
Comparison with any other study is difficult because no other randomized study in heart failure patients with similar design and long-term follow-up has been performed. Recently, two studies reported on the acute effects of bifocal RV pacing in patients with severe heart failure and poor LV function. van Campen et al.20 compared the acute haemodynamic effects of different LV pacing sites and also included bifocal RV pacing. Although the RV apex and LV posterolateral configuration resulted in the highest increase in cardiac index (10.8±9.3%), bifocal RV pacing was associated with a significant increase in cardiac index (8.9 ± 5.8%) compared with baseline. Moreover, in 21% of all patients, bifocal RV pacing resulted in the highest increase in cardiac index compared with LV pacing configurations. Lane et al.21 compared temporary bifocal RV pacing and biventricular LV pacing using tissue Doppler imaging. They reported a significant reduction in intra LV, inter LV–RV, and global mechanical dyssynchrony during bifocal pacing compared with baseline in patients with drug refractory heart failure and systolic LV dysfunction. Since LV biventricular pacing resulted in a significantly higher reduction of all tissue Doppler-derived variables compared with bifocal pacing, these authors conclude that bifocal pacing can be used when LV lead placement is not possible.
Several case reports and studies have been published with long-term follow-up (>3 months). Wojciuk et al.22 report an impressive improvement in LV EF from 23 to 43% in 4 months. Similar improvements have been described by Vlay23 in three patients who improved in functional class from IV to II. An indirect comparison of biventricular pacing vs. bifocal pacing can be observed in the case report of Satish et al.24 A patient who was paced at the RV apex for bradycardia reasons for a long time was upgraded to a biventricular pacing device. The clinical condition improved and LV EF increased from 27 to 39%. After early battery depletion, the biventricular pacing system has to be abandoned because of the very high threshold of the LV lead. A pacing lead was implanted in the RVOT, and the patient remained stable on bifocal pacing. The LV EF was determined at 40%.
The effects of bifocal pacing have also been described in a small non-randomized series of bifocal pacing in heart failure patients presented by O’Donnell et al.10 They reported on six patients with the CRT indications and in whom the LV lead implantation in the coronary sinus had failed. Left ventricular ejection fraction in the bifocal group increased from 15 to 26% over an observation period of 6 months. A similar difference is found between the bifocal and control groups in the present study: 36 ± 11% in the bifocal group vs. 26 ± 12% in the control group.
A few studies also evaluated the effects of bifocal pacing in a group of patients with severely impaired LV function due to Chagas disease.25,26 However, all the patients or at least a large majority in these studies has permanent atrial fibrillation and/or a complete AV block and/or Chagas cardiomyopathy. da Silva Menezes25 reported an initial improvement in the LV EF after 3 months of bifocal pacing from 24 ± 6% to 38 ± 10%. However, these favourable effects could not be maintained beyond the first 6 months, and the total mortality was high with 43% in the first year. This negative clinical course may be related to the progression of the Chagas disease. Pachon et al.26 studied 39 patients with dilated cardiomyopathy and an indication for pacing because of brady-arrhythmia and reported a significant 12% increase in LV EF during bifocal stimulation compared with RV apical stimulation together with a 50.4% reduction in the quality-of-life score. Total follow-up period was only 30 days.
The mechanism of the observed benefits of bifocal pacing was not evaluated in this study, but several factors may be involved, such as AV optimization, reduction of MR, and correction of inter- and intraventricular dyssynchrony. With respect to the MR, the present study demonstrated a reduction in MR by bifocal pacing compared with the pre-randomization period. Atrioventricular optimization was performed in all patients in a similar manner as in patients selected for CRT.27 Lane et al.21 describe a similar improvement in LV EF and systolic blood pressure with biventricular pacing compared with bifocal RV pacing. They reported that the mechanisms involved in biventricular pacing and bifocal pacing were similar, expressed by the improvements in intraventricular dyssynchrony, inter LV–RV dyssynchrony, and global dyssynchrony.
Left ventricular-based CRT is now established as a treatment for patients with advanced congestive heart failure and intraventricular conduction delay in the absence of an indication for pacing for brady-arrythmias.1–6,20,21 Although substantial haemodynamic effect is evident from many studies, the technique used for LV lead implantation is associated with major limitations, including a definite learning curve, failure to implant, a relatively high dislocation rate, and additional complications such as phrenic nerve stimulation. This is in contrast to the experience with placing an RVOT lead, where a short learning curve is needed, no special delivery tools are involved, and the technical success rate is very high after an initial but short learning curve.11,12 Nevertheless, the implantation of the RVOT lead is not totally without complications as mentioned in this study. Special attention should be paid to the precise implantation site. Mond et al.28 describe the technique in detail, where the importance of standard radiographic views is underlined and the use of the 12-lead electrocardiogram may help in appropriate lead placement. They also advocate the use of a novel (Amplatz shape-like) stylet curve. This is in accordance with our later experience, where a modified atrial J-shaped stylet was used.
Limitations of the study
The main limitation of this pilot study is the short follow-up period and the relative small number of patients. In addition, there was a relatively high dropout rate in this study. However, patients with an incomplete follow-up did not alter the results of our analysis. Despite these limitations, the difference in the study parameters such as NYHA class, LV EF, 6 min walking distance, and quality-of-life score is substantial compared with the control group.
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Conclusion |
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Clear benefits are present with bifocal RV pacing in patients with a classic indication for CRT. Bifocal pacing may be considered in patients with technical failures of CRT implantation and in whom epicardial lead implantation is associated with a relatively high morbidity. More studies, for example, those dealing with a direct comparison of bifocal right vs. biventricular pacing or addressing mortality, are strongly warranted.
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Appendix |
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List of participants and participating centres
- M. Bokern, M. Mihciokur, D. Kok, Waterland Ziekenhuis, Purmerend
- J. Res, P. Bronzwaer, C. van Engelen, Zaans Medisch Centrum, Zaandam
- P. Westendorp, P. van Rossum, R. Ziegler, Beatrix Ziekenhuis, Gorinchem
- T. van Loenhout, P. van Kalmthout, Ziekenhuis de Gelderse Vallei, Bennekom
- H. Spierenburg, R. van der Heijden, Vlietland Ziekenhuis, Schiedam-Vlaardingen
- H. Olthof, L. Verdegen, Elkerliek Ziekenhuis, Helmond
- C. Janssen, R. Taverne, Ziekenhuis Zorgzaam, Terneuzen
- C. Fauser, P. Zwart, P. Kuipers, Bernhoven Ziekenhuis, Oss
- C. de Cock, H.S.Vos, VU Medisch Centrum, Amsterdam
- J. Res, P. Bronzwaer, C. van Engelen, Zaans Medisch Centrum, Zaandam
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Acknowledgements |
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The authors wish to acknowledge the unrestricted support from Biotronik Netherlands and the clinical and technical work of the BRIGHT investigators in the participating clinics (see Appendix).
Conflict of interest: none declared.
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References |
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