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European Trial Shows Greater Efficacy of Dual Chamber Implantable Cardioverter-Defibrillators as Compared to Single Chamber ICDs in Patients at Risk of Sudden Cardiac Death


DATAS results at Cardiostim show reduction of clinically significant adverse events by one-third with DC ICDs

NICE, France, 16 June 2006 – 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 today. 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 The results of the DATAS clinical trial, presented at Cardiostim 2006, the 15th World Congress in Cardiac Electrophysiology and Cardiac Techniques, showed that clinically significant adverse events can be reduced by one-third with DC ICDs compared to SC ICDs in patients at risk of sudden cardiac death.1

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. Jesús Almendral from the Department of Cardiology at Hospital General Universitario Gregorio Marañon 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 centers 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™ 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.

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About Medtronic
Medtronic, Inc. ( - NYSE: MDT), headquartered in Minneapolis, is the global leader in medical technology – alleviating pain, restoring health, and extending life for millions of people around the world.

Any forward-looking statements are subject to risks and uncertainties such as those described in Medtronic’s Quarterly Report on Form 10-Q for the quarter ended January 27, 2006. Actual results may differ materially from anticipated results.

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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