Implantable Cardiac Monitors for the Detection of Atrial Fibrillation - How Far Have We Come?

Abstract

Abstract
Symptoms are insensitive and non-specific for the diagnosis of atrial fibrillation (AF). Extensive Holter monitor recordings are essential to correctly diagnose AF and, subsequently, to inform therapeutic decisions for its management. Pacemakers and implantable cardioverter defibrillators that detect atrial arrhythmias are a valuable resource for the investigation and quantification of AF. The application of these monitoring systems, however, is limited to a relatively small number of patients. Additional monitoring technologies are therefore necessary to detect the large number of asymptomatic AF episodes, as well as their resulting morbidities (including stroke and heart failure) and mortality. New, non-invasive systems could allow outsourcing of long-term Holter monitoring from the hospital, with attendant improvements in the extent of Holter monitoring and the quality of recording results. Subcutaneous implantable systems, with automated detection algorithms for atrial arrhythmias, represent a new opportunity for long-term rhythm monitoring. In summary, improving implantable cardiac monitors for AF detection could allow us not only to objectively evaluate the efficacy of different therapies but also to refine the future therapeutic management of AF.

Keywords
Atrial fibrillation (AF), Holter monitor, implantable cardiac monitor (ICM), pacemaker, implantable cardioverter defibrillator (ICD), cardiac resynchronisation therapy defibrillator (CRT-D), catheter ablation

Disclosure: Helmut P─é─¢rerfellner is a consultant for Medtronic. The authors have no other relevant affiliations or financial involvement with any organisation or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.
Received: 29 September 2010 Accepted: 16 December 2010 Citation: European Cardiology, 2011;7(1):34├óÔé¼ÔÇ£6
Correspondence: Christian Meyer, University of D─é─¢sseldorf, Medical Faculty, Division of Cardiology, Pneumology and Angiology, Moorenstr. 5, 40225 D─é─¢sseldorf, Germany. E: Christian.Meyer@med.uni-duesseldorf.de or Helmut P─é─¢rerfellner, Department of Cardiology, Public Hospital Elisabethinen, Academic Teaching Hospital of the Universities of Innsbruck and Graz, Fadingerstrasse 1, A-4010 Linz, Austria. E: helmut.puererfellner@elisabethinen.or.at

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Atrial fibrillation (AF) is a major cause of hospitalisation, morbidity and mortality. It is associated with an almost two-fold risk of death and an almost five-fold increase in the risk of stroke. Moreover, AF aggravates heart failure and, in turn, heart failure promotes AF. The burden of AF is projected to increase in the future as a result of demographic changes, improved survival following adverse cardiovascular events and associated comorbidities. However, the true epidemiology and impact of the rising incidence of AF on healthcare systems have not been determined so far, since the use of monitoring systems currently available for the detection of AF is limited in most patient groups and especially in the general population.

Symptoms are insensitive and non-specific for the identification of AF. Studies1 on antiarrhythmic drugs showed that 70% of AF episodes are not noticed by patients. Studies using the Holter monitor (Mortara Instrument, Inc., Wisconsin, US) demonstrated that asymptomatic episodes are 10├óÔé¼ÔÇ£12 times more frequent than symptomatic events, yet patients who are asymptomatic may still be at increased risk of stroke and mortality and may also suffer from comorbidities, such as heart failure, hypertension and diabetes. Acute stroke is a common first presentation of patients with AF, given that arrhythmia often develops asymptomatically. Significantly, the available data indicate that paroxysmal AF carries the same risk of stroke as persistent or permanent AF. Therefore, improved technologies for the early detection of this growing epidemic are imperative.

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