Indian Pacing Electrophysiol. J. 2003;3(4):261-267
Selecting Dual Chamber or Single Chamber Implantable
Defibrillators: What is the Golden Rule?
Massimo Santini, M.D., F.E.S.C., F.A.C.C.
and Renato Ricci, M.D.,F.E.S.C.
Department of Cardiology, San Filippo
Neri Hospital, Rome, Italy.
Address for correspondence: Dr. Prof. Massimo Santini, Department
of Cardiology, San Filippo Neri Hospital,
via Martinotti, 20, 00135 Rome,
Italy. E-mail m.santini@rmnet.it,
renatopietroricci@tin.it
Keywords: defibrillator, inappropriate shock, atrial
fibrillation, heart failure, ventricular dysynchrony.
Introduction
During the last years, the implantation rate of dual chamber defibrillators
(ICD) significantly increased worldwide. In 1999, the proportion of dual
chamber ICD implants reached 30% in Europe and 50% in U.S.A.1. According to manufacturer data, in Italy, the ratio
between implanted single chamber and dual chamber units decreased from
1.97 in 1999 to 1.86 in 2000 and 1.50 in 2001. Technological progress,
demonstration of reliability and clinical efficacy of the new devices,
combined with their smaller size, contributed to their wide acceptance.
Nowadays, the matter to be debated is if all the patients in whom the atrium
can be sensed and paced should receive a dual chamber ICD or if device
selection should be individually evaluated according to different clinical
profiles. As a matter of fact, criteria to identify the patients who may
benefit more from dual chamber ICD have not been already defined. The theoretical
advantages of dual chamber ICD include: improved discrimination between
supraventricular and ventricular tachycardias, optimal treatment of symptomatic
bradycardias (pre-existing, drug-induced or late developing), hemodynamic
and antiarrhythmic benefits.
Discrimination between supra-ventricular and ventricular arrhythmias
Superiority of dual chamber detection algorithms versus single chamber
ICD in discriminating supraventricular from ventricular tachycardia has
been a matter of debate since their introduction for clinical implantation.
This issue is particularly challenging if we take into account that the
addition of enhanced criteria in the third generation single chamber
ICDs, such as tachycardia sudden onset and stability and ventricular electrogram
width and morphology, significantly increased single chamber ICD specificity
in tachycardia discrimination2,3,4,5. On the other hand, the weak point
of such enhanced criteria is represented by decreased sensitivity in ventricular
tachycardia detection5,6. Dual
chamber ICDs have the capability of detecting atrial activity and matching
atrial and ventricular patterns. Clinical studies using dual chamber ICDs
showed specificity values as high as 80-90% combined with 100% sensitivity7,8,9,10,11,12. Nevertheless, inappropriate
detection and therapy may still happen, mainly for “difficult arrhythmias”.
Hintringer et al13 performed a comparison of
the detection algorithms of four dual chamber ICD when dealing with a
wide spectrum of tachyarrhythmias. In spite of some differences due the
algorithms themselves, typical and atypical junctional tachycardia, orthodromic
atrio-ventricular tachycardia and 1:1 atrial flutter represented the most
challenging patterns. As a consequence, new more sophisticated algorithms
are being developed to deal with this task. Appropriate sensing of atrial
activity, either during sinus rhythm or during atrial tachyarrhythmias,
and appropriate rejection of ventricular activity by the atrial lead is
a critical issue to be dealt with. Deisenhofer et al14 undertook a prospective, randomized study to compare
the incidence of inappropriates therapies in patients treated with VVI-ICDs
and DDD-ICDs. They enrolled 92 patients and concluded that DDD-ICD and
VVI-ICD were equally safe and effective to treat life-threatening ventricular
arrhythmias. Although DDD-ICDs theoretically allow better rhythm classification,
the applied detection algorithms did not offer benefits in avoiding inappropriate
therapies during supraventricular tachyarrhythmias. As a matter of fact,
in the Deisenhofer series 75% of inappropriate therapies in the DDD-ICD
group were due to atrial sensing problems, either oversensing or undersensing.
This finding stresses the need of careful positioning of the atrial lead
during implantation in order to combine optimal atrial electrogram amplitude
with far field rejection. It has been suggested that positioning the atrial
lead in the lateral atrial wall and selecting bipolar leads with short
tip-to-ring distance may reduce far field incidence15,16. In spite of that, atrial sensing problems may
intermittently appear during the follow-up, also when they were not present
at implant or during post-implant testing. A possible explanation for
frequent intermittent atrial sensing problems may be the special filter
settings in the atrial sensing channels of DDD-ICD, which differs substantially
from those of DDD pacemakers. In fact, most detection algorithms in DDD-ICDs
need correct and continuous atrial sensing with only short or even no
blanking times. This may be difficult when taking into account low voltage
atrial electrogram during atrial fibrillation and large ventricular far
fields during paced ventricular beats.
Hemodynamic issues
A emerging key point in debating optimal device selection is represented
by the impact of single chamber and dual chamber ICD implantation on
hemodynamics.
It has been demonstrated that, in patients with sinus bradycardia and/or
atrio-ventricular conduction disturbances, physiologic pacing by sequential
dual chamber stimulation and optimized, individually programmed, atrio-ventricular
delay may offer major improvement in hemodynamics and clinical outcome,
mainly when heart failure coexists17,18,19. On the other hand, during the
last years it has been demonstrated that asynchronous ventricular activation
induced by apical right ventricular pacing may induce major interventricular
and/or intraventricular dysynchrony, which may deteriorate hemodynamics
and impair myocardial metabolism20,21.
Isovolumic contraction time and isovolumic relaxation time lenghtening
may critically shorten diastolic filling, impairing cardiac output. Furthermore,
delayed activation of the left ventricular lateral wall may lead to late
contraction which happens after aortic valve closure, so that not only it
does not contribute to stroke volume, but also impair diastolic filling22.
Concern about the potential deleterious effect of unnecessary right ventricular
pacing in ICD population is even greater than in pacemaker patients,
when considering the higher prevalence of heart failure and left ventricular
dysfunction in patients who need ICD implantation23,24. The recently published DAVID25 (Dual Chamber and VVI Implantable Defibrillator)
Trial dealt with this issue. Objective of the study was to determine
the efficacy of dual chamber pacing compared with backup ventricular
pacing in patients with standard indications for ICD implantation but
without indications for antibradycardia pacing. The design of the study
was a single-blind, parallel group, randomized, multicenter clinical trial.
Five hundred and six patients candidates for ICD with left ventricular
ejection fraction of 40% or less, no indications for antibradycardia pacing
and no persistent atrial tachyarrhythmias, received a dual chamber ICD
and were randomly assigned to have the ICD programmed to ventricular back-up
pacing at 40/min or to dual chamber rate responsive pacing at 70/min. Main
outcome measurement was the combined end point of time to death or first
hospitalization for congestive heart failure. The study was early stopped
by the Data and Safety Monitoring Board because the conditional power for
the original alternative (DDDR-70 being better than VVI-40) was less than
10%. The VVI-40 group had fewer occurrences of the composite end point
than DDD-70 group: one-year survival free was 83.9% versus 73.3% (relative
hazard 1.61; 95% confidence interval 1.06-2.44, p< 0.03). Although the
VVI-40 patients had fewer events, the component end points, either death
or heart failure hospitalizations, did not individually reach statistical
significance.
Some criticisms have been pointed out about the DAVID Trial. The study
definitely demonstrated that right ventricular pacing is deleterious in
patients with left ventricular dysfunction, but it cannot be concluded
that single chamber ICD with back-up ventricular pacing is the most useful
device for patients with heart failure. In spite of a large enrolled
population, the follow-up was very short because of early stopping of
the study. Only a minority of patients completed one year follow-up. Programming
dual chamber rate responsive pacing at 70/min without long AV delay
does not seem the best choice for patients without any indication for
antibradycardia pacing. Unnecessary apical right ventricular pacing is
probably the key to explain the higher event rates in DDD-70 arm. The
Authors stressed that dual chamber pacing could be beneficial in heart
failure patients since it may allow a wider use of drugs such as beta blockers
which depress sinus and AV node function. As a matter of fact, there were
no differences in drug regimen between the VVI and DDD arms after randomization
as well as after 6-month follow-up. Finally, patients with atrial tachyarrhythmias
were excluded from the study, so introducing a limitation in the clinical
value of the study.
Atrial fibrillation in ICD patients
Atrial fibrillation prevention and early treatment by dual chamber devices,
mainly if equipped with atrial antitachycardia functions, may represent
a major benefit in patients with heart failure. ICD patients actually
show a high incidence of atrial tachyarrhythmias. It has been reported
that 20% of them had atrial fibrillation before implantation and that during
the life-span of the defibrillator more than 50% may develop atrial fibrillation26. Atrial fibrillation may lead to inappropriate
ventricular shocks27, ventricular arrhythmia
induction28, may impair hemodynamics and induce
thromboembolic events or acute myocardial infarction, and has been identified
as an individual predictor of poor prognosis29,30. Atrial antitachycardia functions available in
some last generation dual chamber ICDs (pacing prevention algorithms and
antitachycardia pacing) have been demonstrated to be effective in preventing
and early treating atrial tachyarrhythmias. In our own experience31, related to 112 patients receiving an ICD because
of life threatening ventricular arrhythmias, followed on average for
1 year, anti-tachy-pacing efficacy was as high as 71% on atrial tachycardia
and as 36% on atrial fibrillation. Shock success rate was 92% when delivered
energy was adequately programmed, which means at least twice the atrial
defibrillation threshold at implant. Similar results have been reported
by others32. The impact of atrial prevention
algorithms and atrial therapies on atrial fibrillation burden has been investigated
by Friedman and coworkers33. They designed
a study in which atrial fibrillation prevention and termination therapies
were randomly programmed “on” or “off” for three months and then crossed
over to the opposite arm for an additional 3 months. Fifty-two patients
were studied. During the “on” period the arrhythmia burden (hours/month)
significantly decreased: the mean burden from 58.5 to 7.8 and the median
burden from 2.82 to 0.63. The mean burden reduction was 87%. The reduction
in arrhythmia burden during the “on” period could be demonstrated also in
the subgroup of patients (forty-one) in whom no shocks were delivered and
only antitachy pacing therapies were applied.
Considering the major clinical impact of symptomatic atrial fibrillation
in patients who are candidate for defibrillator implantation, a device
equipped with atrial antitachycardia facilities may improve clinical
outcome, by preventing acute heart failure, by decreasing inappropriate
shocks, by reducing hospitalizations and by improving quality of life.
Perspectives
The key point for single chamber or dual chamber ICD selection has been
progressively switching from optimal tachycardia discrimination to the
impact on hemodynamics and on atrial arrhythmia control. To this regard,
few controlled data are available and perspectives randomized trials
are strongly needed. The impact of device selection on the overall clinical
outcome is the target of an ongoing trial [Dual Chamber & Atrial Tachyarrhythmias
Adverse Events Study (DATAS), protocol in press34]
aimed at comparing clinical benefits of dual chamber ICD with atrial
antitachycardia functions with single chamber ICD. The primary end point
will be the composite end-point resulting from all-causes mortality,
invasive intervention, hospitalizations due to cardiovascular cause, inappropriate
shocks and sustained symptomatic atrial tachyarrhythmias. The enrollment
is going to be completed soon and the results will be available within
the next two years.
On the other hand, new indications for ICD implantation in primary prevention
of sudden death and introduction of triple chamber ICDs capable of
delivering cardiac resynchronization therapy are going to change very
soon the whole approach to ICD selection. The MADIT-2 trial35 demonstrated that in patients with prior myocardial
infarction and left ventricular ejection fraction < 30%, ICD implantion
was able to reduce 2-year mortality by 31%. Rules for ICD selection in
MADIT-2 patients are probably quite different from those applied for
patients receiving an ICD in sudden death secondary prevention. A wider
use of single chamber ICDs should be expected. First, accurate discrimination
between supraventricular and ventricular tachycardia should be less meaningful
in patients for whom therapy programming is focused mainly on treating
fast ventricular tachycardia and ventricular fibrillation. Secondly, considering
the large number of new potential candidates for ICD implantation, selecting
a simpler and less costly device may improve the cost-effectiveness of
ICD in primary prevention. Development of new low-cost single chamber
devices, just capable of detecting ventricular fibrillation and delivering
a limited number of shocks is expected for the next years. Such strategy
will allow a wider protection of high risk population without an unacceptable
increasing of the costs.
Cardiac resynchronization has been demonstrated to improve functional
class, exercise tolerance and quality of life as well as to reduce hospitalisations
due to worsening of heart failure36,37 in patients with drug refractory heart failure
with atrio-ventricular, inter-ventricular and intra-ventricular dysynchrony.
Cardiac resynchronization may be combined with ICD. Considering the large
number of ICD candidates with heart failure, drawing guidelines aimed to
make the right choice for individual patients will be a major challenge
for the next few years.
References
1.
Jung W and Luderitz B: Should all candidates for ICD
therapy receive a dual chamber system? J Int Card Electrophysiol 1999;3:203-206.
2. Barold HS, Newby KH, Tomassoni G,
Kearney M, Brandon J, Natale A: Prospective evaluation of new and old criteria
to discriminate between supraventricular and ventricular tachycardia
in implantable defibrillators. Pacing Clin Electrophysiol 1998;21:1347-55.
3.
Swerdlow CD, Chen PS, Kass RM, Allard JR, Peter CT:
Discrimination of ventricular tachycardia from sinus tachycardia and
atrial fibrillation in a tiered-therapy cardioverter defibrillator.
J Am Coll Cardiol 1994;23:1342-55.
4.
Schaumann A, von zur Muhlen F, Gonska BD, Kreuzer
H: Enhanced detection criteria in implantable cardioverter-defibrillators
to avoid inappropriate therapy. Am J Cardiol 1996;78(5A):42-50.
5.
Brugada J: Is inappropriate therapy a resolved issue
with current implantable cardioverter defibrillators? Am J Cardiol 1999;83:40D-44D.
6.
Neuzner J, Pitschner HF, Schlepper:
Programmable VT detection enhancements in implantable cardioverter defibrillator
therapy. Pacing Clin Electrophysiol 1995;18:539-47.
7.
Sinha AM, Stellbrink C, Karla D, Hahn A, Hanrath
P: Discrimination of ventricular and supraventricular tachycardias with
a new detection algorithm in a dual chamber ICD. MZV Verlag 2000;20;201-7.
8.
Sadoul N, Jung W, Jordaens L, et al: Diagnostic
performance of a dual-chamber cardioverter defibrillator programmed with
nominal settings: a European prospective study. J Cardiovasc Electrophysiol.
2002;13:25-32.
9.
Wilkoff
BL, Kuhlkamp V, Volosin K, et al: Critical analysis of dual chamber implantable
cardioverter defibrillator arrhyhtmia detection. Results and technical
considerations. Circulation 2001;103:381-386.
10.
Korte
T, Jung W, Wolpert C, et al: A new classification algorithm for discrimination
of ventricular from supraventricular tachycardia in a dual chamber implantable
cardioverter defibrillator. J Cardiovasc Electrophysiol 1998;9:70-3.
11. Osswald
S, Cron TA, Sterns L, Alt E, Stotts L, Coenen M: New ICD technologies:
first clinical experience with dual chamber sensing for differentiation
of supraventricular tachyarrhythmias. Pacing Clin Electrophysiol 1998;21:292-5.
12.
Boriani
G, Biffi M, Dall’Acqua A, et al: Rhythm discrimination based on rate branch
and morphology discrimination algorithm to improve the diagnostic performance
in a dual chamber implantable cardioverter defibrillator. Eur Heart
J 2001;22 (Abstract Suppl.):178.
13.
Hintringer
F, Schwarzacher S, Eibl G, Pachinger O: Inappropriate detection of supraventricular
arrhythmias by implantable dual chamber defibrillators: a comparison
of four different algorithms. Pacing Clin Electrophysiol 2001;24:835-841.
14.
Deisenhofer
I, Kolb C, Ndrepepa G, et al: Do current dual chamber cardioverter defibrillators
have advantages over conventional sigle chamber cardioverter defibrillator
in reducing inappropriate therapies? A randomized, prospective study.
J Cardiovasc Electrophysiol 2001;12:134-42.
15.
Frohlig G, Helwani Z, Kusch O, Berg M, Schieffer H:
Bipolar ventricular far-field signals in the atrium. Pacing Clin Electrophysiol
1999;22:1604-13.
16.
Weretka
S, Becker R, Hilbel T, et al: Far-field R wave oversensing in a dual chamber
arrhythmia management device: predisposing factors and practical implications.
Pacing Clin Electrophysiol 2001;24:1240-6.
17. Hesselson AB, Parsonnet
V, Bernstein AD, Bonavita GJ: Deleterious effect of long-term single-chamber
ventricular pacing in patients with sick sinus syndrome: The hidden
benefits of dual-chamber pacing. J Am Coll Cardiol 1992;19:1542-1549.
18. Frielingsdorf J, Gerber
AE, Dur P, Vuilliomenet A, Bertel O: Importance of an individually programmed
atrioventricular delay at rest and on work capacity in patients with
dual chamber pacemakers. Pacing Clin Electrophysiol 1994;17:37-45.
19. Frielingsdorf J, Deseo T, Gerber
AE, Bertel O: A comparison of quality-of-life in patients with dual chamber
pacemakers and individually programmed atrio-ventricular delays. Pacing
Clin Electrophysiol 1996;19:1147-1154.
20. Harper GR, Pina
IL, Kutalek SP: Intrinsic conduction maximizes cardiopulmonary performance
in patients with dual chamber pacemakers. Pacing Clin Electrophysiol
1991;14:1787-1791.
21. Ansalone G, Trambaiolo P, Giorda
G, Giannantoni P, Ricci R, Santini M: Multisite stimulation in refractory
heart failure. G Ital Cardiol 1999;29:451-459.
22.
Ansalone G,
Giannantoni P, Ricci R, et al: Doppler myocardial imaging in patients
with heart failure receiving biventricular pacing treatment. Am Heart
J 2001;142:881-896.
23. Moss
AJ, Hall WJ, Cannom DS, et al: Improved survival with an implanted
defibrillator in patients with prior myocardial infarction, low ejection
fraction and asymptomatic non-sustained ventricular tachycardia. N Engl
J Med 1996;335:1933-40.
24.
The AVID investigators.
A comparison of antiarrhythmic drug therapy with implantable defibrillators
in patients resuscitated from near fatal ventricular arrhythmias. N
Engl J Med 1997;337:1576-1583.
25. Wilkoff
BL, Cook JR, Epstein AE, et al. The DAVID Trial Investigators: Dual
chamber pacing or ventricular bacup pacing in patients with an implantable
defibrillator. The Dual Chamber and VVI Implantable Defibrillator (DAVID)
Trial. JAMA 2002;288:3115-23.
26. Schmitt C, Montero M, Melichercik J: Significance
of supraventricular tachyarrhythmias in patients with implanted pacing
cardioverter defibrillators. Pacing Clin Electrophysiol 1998;17:295-302.
27.
Grimm W, Flores
BF, Marchlinski FE. Electrocardiographically documented unnecessary,
spontaneous shocks in 241 patients with implantable cardioverter defibrillators.
Pacing Clin Electrophysiol. 1992;15:1667-73.
28.
Marchlinski
FE, Callans DJ, Gottlieb CD, Schwartzman D, Preminger M: Benefits and
lessons learned from stored electrogram information in implantable defibrillators.
J Cardiovasc Electrophysiol. 1995;6:832-51.
29.
Pinski SL, Yao Q, Epstein AE, et al: Determinants
of outcome in patients with sustained ventricular tachyarrhythmias:
the antiarrhythmic versus implantable defibrillators (AVID) study registry.
Am Heart J 2000;139:804-813.
30. Wolf PA, Mitchell JB, Baker CS, Kannel WB, D’Agostino
RB: Impact of atrial fibrillation on mortality, stroke and medical
costs. Arch Intern Med 1998;158:229-234.
31. Ricci R, Pignalberi C, Disertori M, et al: Efficacy
of a dual chamber defibrillator with atrial antitachycardia functions
in treating spontaneous atrial tachyarrhythmias in patients with life-threatening
ventricular tachyarrhythmias. Eur Heart J 2002;23:1471-1479.
32. Schoels W, Swerdlow CD, Jung W, Stein KM, Seidl
KH, Haffajee CJ, for the Worldwide Jewel AF Investigators: Worldwide
clinical experience with a new dual chamber implantable cardioverter
defibrillator system. J Cardiovasc Electrophysiol 2001;12:521-528.
33. Friedman PA, Dijkman B, Warman EN, et al, for the
Worldwide Jewel AF Investigators: Atrial therapies reduce atrial arrhythmia
burden in defibrillator patients. Circulation. 2001;104:1023-1028.
34. Quesada A, Almendral J, Arribas F, et al on behalf
of DATAS investigators. The DATAS rationale and design: A controlled,
randomized trial assessing the clinical benefit of the dual chamber
(DDED) defibrillator (in press).
35. Moss AJ, Zareba W, Jackson Hall W, et al: Prophylactic
implantation of a defibrillator in patients with myocardial infarction
and reduced ejection fraction. N Engl J Med 2002;346:877-83.
36. Cazeau S, Leclerq C, Lavergne T, et al: Effects
of multisite biventricular pacing in patients with heart failure and
intraventricular conduction delay. N Engl J Med 2001:344:873-880.
37. Abraham WT, Fisher WG, Smith AL, et al: Cardiac
resynchronization in chronic heart failure. N Engl J Med 2002;346:1845-53.
