European trial shows greater efficacy of dual chamber over single
chamber ICDs
20 June 2006 Nice, France. Dual chamber implantable
cardioverter-defibrillators (DC ICDs) showed greater efficacy in reducing
clinically significant adverse events compared to single chamber (SC) ICDs
for patients with a standard ICD indication, according to data presented at
Cardiostim 2006, the 15th World Congress in Cardiac Electrophysiology and
Cardiac Techniques.
The results of the Dual Chamber & Atrial Tachyarrhythmias Adverse Events
Study (DATAS), presented at Cardiostim 2006, showed that clinically
significant adverse events can be reduced by one-third with dual chamber
ICDs compared to single chamber ICDs in patients at risk of sudden cardiac
death.(1) ICDs represent an appropriate therapy option for the hundreds of
thousands of patients at risk of sudden cardiac death worldwide every
year.(1)(2)(3)
Sudden cardiac death is the single most frequent cause of death due to
coronary disease in the industrialised world.(3) In 75 to 80 percent of
cases, it is caused by ventricular fibrillation, the fast and irregular
quivering of the lower chambers of the heart called ventricles.(3) "The
immediate treatment of ventricular fibrillation with a defibrillator is
crucial to save people's lives," said Dr. Jesus Almendral from the
Department of Cardiology at Hospital General Universitario Gregorio Maranon
in Madrid, Spain, and member of the steering committee of the DATAS study.
"However, it is really important to use technically advanced ICDs that can
adjust therapy when appropriate to reduce clinical adverse events," he
added. The DATAS trial The DATAS (Dual Chamber & Atrial
Tachyarrhythmias Adverse Events Study) trial showed that the rate of
clinically significant adverse events was lower with DC ICDs compared to SC
ICDs in patients at risk of sudden cardiac death and indicated for ICD
therapy.(1) A statistically and clinically significant 33 percent (p=0.003)
reduction in the rate of adverse events was documented in the DC ICD group
by the clinically significant adverse events (CSAE) score. Over a follow-up
of 17 months, annual mortality was 2.7 percent in the DC ICD group and 6.8
percent in patients treated with a single chamber ICD. Inappropriate shocks
were registered in 1.3 percent of patients per year of follow-up with DC
ICDs versus 6.8 percent of those with SC ICDs. Overall, patients with DC
ICDs had a lower or similar incidence of each kind of clinically significant
adverse events compared to those with SC ICDs. The randomised, multicentre
DATAS trial, supported by Medtronic, analysed 334 patients at risk of sudden
cardiac death and rated their risk of adverse events. Participating centres
included consecutive patients with a standard ICD indication, who were
randomly assigned to DC ICDs or SC ICDs and followed for 17 months. In both
arms, the CSAE score was calculated by combining reported clinically
significant adverse events including death, invasive interventions,
hospitalisations, inappropriate shocks and sustained long duration of atrial
tachyarrhythmias, adjusted according to their clinical severity. "By
monitoring both the atrium and ventricle in the heart, DC ICDs can diagnose
the nature of the arrhythmia and distinguish atrial from ventricular
tachyarrhythmias, or the loss of synchrony between the two chambers," said
Dr. Almendral. "This is very important to administer the most suitable
therapy to reset the heart rhythm." Single chamber ICDs Single
chamber ICDs sense bradycardia (abnormally slow heart rhythm) and detect
arrhythmias in the right ventricle only; provide therapy; and pace only the
ventricle at a fixed rate. This may result in incomplete sensing and therapy
in some patients, which may fail to accommodate the physiologic conduction
(natural rhythm) pathways of the heart. Because SC ICDs do not monitor both
chambers, they are more likely to deliver inadequate therapy.
This possible situation is directly referred to in the DATAS study design
paper by Dr. Aurelio Quesada, member of the steering committee from the
Cardiology Department at Hospital General Universitario in Valencia, Spain.
The most frequent inappropriate shocks in patients with SC ICDs are
administered for fast ventricular rhythm caused by atrial fibrillation.(4)
Avoiding inappropriate shocks is important because they may hamper quality
of life for patients, cause arrhythmia, hospitalisation and even death.(4)
Dual chamber ICDs In contrast, dual chamber ICDs have two leads
that monitor the right atrium and the right ventricle, can defibrillate the
ventricle, and pace both the atrium and the ventricle in atrio-ventricular
synchrony. For patients with bradycardia pacing needs — either at time of
implant or that which develops in the future — features like MVP (Managed
Ventricular Pacing), found only in certain Medtronic dual chamber devices,
reduce unnecessary right ventricular pacing by 99 percent (median value). In
addition, dual chamber ICDs provide superior SVT discrimination to further
reduce inappropriate shocks (as compared to SC ICDs), as well as diagnostics
to better monitor atrial fibrillation or heart failure disease progression.
"The results of the DATAS trial support the superiority of sophisticated DC
ICDs in distinguishing and treating atrial and ventricular tachyarrhythmias
to save people's lives," said Steve Mahle, president of the Cardiac Rhythm
Disease Management business at Medtronic. "The trial also validates the need
for dual chamber devices for patients with standard ICD indication, and
further illustrates the importance of finding better, safer and more
patient-friendly therapies for those at risk of sudden cardiac death." The
latest and technically most advanced DC ICD manufactured by Medtronic, the
Virtuoso(TM) ICD, recently received United States Food and Drug
Administration approval and CE Mark and is now available in Europe and the
U.S. for patients at risk of sudden cardiac death.
References 1. J Almenadral, F Arribas, A Quesada et al. Are dual
chamber ICDs beneficial? The DATAS trial: a randomised trial focussed on
clinically significant adverse events. Presented at 15th Cardiostim, Nice,
16 June 2006 2. D P Zipes. Epidemiology and mechanism of sudden cardiac
death. Can J Cardiol. Vol 21, Suppl. A, May 15 2005. 3. S G Priori, E
Aliot, c Blomstrom-Lundqvist et al. Task force of sudden cardiac death,
European Society of Cardiology, Summary of recommendations. Europace,
2002;4:3-18 4. A Quesada, J Almendral, F Arribas et al. The DATAS
rationale and design: a controlled, randomized trial to assess the clinical
benefit of dual chamber (DDED) defibrillator. Europace, 2004;6:142-150
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