Pacemakers and Implantable Cardioverter Defibrillators

Contents

Preface: Pacemakers and ICDs xi

Theofanie Mela

Erratum xiii

Newer Indications for ICD and CRT 181

James A. Merriam, Anil B. Rajendra, and Michael R. Gold

The first implantable pacemaker was developed about 50 years ago. Since that time,cardiac implantable electronic device therapy (CIED) has undergone dramaticchanges. Two of the most significant advances are the development of implantabledefibrillators (ICDs) to treat ventricular tachyarrhythmias and prevent sudden deathand left ventricular–based pacing to achieve cardiac resynchronization therapy(CRT). In this article, the authors review the current indications for ICD and CRT,with particular emphasis on recent updates in guidelines. Many countries andregions of the world now have guidelines for CIED use. In this article, the authorsonly focus on US guidelines.

Shock Avoidance and the Newer Tachycardia Therapy Algorithms 191

Kushwin Rajamani, Adam S. Goldberg, and Bruce L. Wilkoff

Sudden cardiac death is a leading cause of death in the United States and Europe.Implantable cardioverter defibrillators (ICDs) are a cornerstone of therapy for patientsat risk of first occurrence of ventricular arrhythmia, or secondary prevention in thosewho have previously suffered cardiac arrest or life-threatening arrhythmias. Despitetheir efficacy, ICD shocks are associated with significant physical and psychologicaladverse effects. As technology has progressed, newer device programing methodshave allowed for arrhythmia suppression and termination without the need for high-energy defibrillation, thus improving patient satisfaction, health, and outcomes.

Lead Extractions: Indications, Procedural Aspects, and Outcomes 201

Ulrika M. Birgersdotter-Green and Victor G. Pretorius

As a result of more cardiac implantable electronic devices being placed, a trendtoward increasing device infections, and concerns regarding lead malfunction, thereis an increased need for lead extraction skills and comprehensive lead managementprograms. This review discusses the current indications for lead extractions as wellas the training requirements and tools and technology needed to create the founda-tion for a successful lead management program.

Is Defibrillation Testing Necessary? 211

Andrea M. Russo and Mina K. Chung

With advancements in implantable cardioverter defibrillator (ICD) technology, thepractice of performing defibrillation threshold (DFT) testing at the time of implanta-tion has been questioned. With availability of biphasic waveforms, active cans,and high-output devices, opponents claim that DFT testing is no longer necessary.

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Clinical trials demonstrating the efficacy of ICDs in prevention of sudden cardiacdeath have, however, all used some form of defibrillation testing. This debate isfueled by the absence of data from randomized prospective trials evaluating therole of DFT testing in predicting clinical shock efficacy or survival. This review dis-cusses both sides of the argument.

The Totally Subcutaneous Implantable Defibrillator 225

John Rhyner and Bradley P. Knight

A video of the S-ICD implantation procedure accompanies this article

The subcutaneous implantable cardioverter-defibrillator (S-ICD) is a new therapeu-tic option for patients at risk of sudden cardiac arrest. The device uses a pulsegenerator implanted in the lateral thoracic region and a tunneled subcutaneouselectrode. Benefits of this configuration include the preservation of venous accessand reduction in the risk of systemic infection, vascular injury, and lead failure. Clin-ical trials suggest that the device effectively senses, discriminates, and convertsboth spontaneous and induced ventricular tachycardia and ventricular fibrillationepisodes with minimal complications. The S-ICD represents a novel implantablecardioverter-defibrillator configuration that may provide reliably effective therapyfor malignant tachyarrhythmias.

The Modern EP Practice: EHR and Remote Monitoring 239

Suneet Mittal, Colin Movsowitz, and Niraj Varma

Cardiac implantable electronic devices (CIEDs) store clinically valuable, time-sensi-tive information regarding system integrity, arrhythmias, and heart failure parameters.Remotemonitoring has impacted clinical practice by reducing scheduled office visits,providing protocols for device recalls and advisories, and facilitating themanagementof unscheduled encounters. The successful implementation of remote monitoringinto clinical practice requires a newwork flow and additional staff; the use of the elec-tronic medical record to manage the data emanating from CIEDs poses an additionalchallenge. Solutions to these issues are discussed, and projections aremade regard-ing the management of CIEDs in a modern electrophysiology practice.

The Role of the Wearable Cardioverter Defibrillator in Clinical Practice 253

Mina K. Chung

The wearable cardioverter defibrillator (WCD) is an option for external monitoringand defibrillation in patients at risk for sudden cardiac arrest caused by ventriculartachycardia or ventricular fibrillation and who are not candidates for or who refusean implantable cardioverter defibrillator (ICD). WCDs provide monitoring withbackup defibrillation protection. WCDs have been used when a patient’s conditiondelays or prohibits ICD implantation, or as a bridge when an indicated ICD mustbe explanted. WCDs are used for primary prevention of sudden cardiac death duringhigh-risk gap periods early after myocardial infarction, coronary revascularization, ornew diagnosis of heart failure.

Does Atrial Fibrillation Detected by Cardiac Implantable Electronic Devices HaveClinical Relevance? 271

Taya V. Glotzer and Paul D. Ziegler

The precise role atrial fibrillation (AF) plays in increasing the risk of stroke is not wellunderstood; this is especially true for the implanted device population. Currentcardiac implanted electronic devices have a very high sensitivity and specificity

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for true AF detection. It does not seem to matter if the AF episode is proximal to thestroke event, and risk seems to be increased by relatively brief AF episodes. Theappearance of new atrial high-rate episodes increases thromboembolic event rates.Until larger trials or registries are conducted, it is important to follow establishedguidelines regarding anticoagulation.

Newer Algorithms in Bradycardia Management 283

Daniel Sohinki and Owen A. Obel

Permanent cardiac pacemakers (PPM) are effective in the treatment of bradycardiain a growing number of clinical scenarios. An appreciation of the capacity of PPMs toresult in negative hemodynamic and proarrhythmic effects has grown alongside clin-ical experience with permanent pacing. Such experience has necessitated thedevelopment of algorithms aimed at optimizing device functionality across a broadspectrum of physiologic and pathologic conditions. This review highlights recentdevice-based algorithms used in automated threshold testing, reduction of rightventricular pacing, prevention and treatment of pacemaker-mediated tachycardia,mode switching for atrial tachyarrhythmias, rate-modulated pacing, and advancesin arrhythmia storage and remote monitoring.

Indications for Cardiac Resynchronization Therapy 293

Thomas M. O’Brien, Edward J. Schloss, and Eugene S. Chung

Initial studies established patient selection criteria for cardiac resynchronization ther-apy (CRT) as left ventricular ejection fraction less than or equal to 35%, QRS greaterthan or equal to 120 ms, and New York Heart Association 3–4. Based on newer data,post hoc analyses, and meta-analyses, these criteria have been refined and guide-lines updated, highlighting left bundle branch morphology and QRS greater than150 ms in selecting patients with a likelihood of favorable outcomes. Guidelines willchange as more data become available; the decision to apply CRT should be basedon patient clinical profile and the balance of risk tolerance and likelihood of benefit.

MRI for Patients with Cardiac Implantable Electrical Devices 299

Grant V. Chow and Saman Nazarian

MRI has become an invaluable tool in the evaluation of soft tissue and bony abnor-malities. The presence of a cardiac implantable electrical device (CIED) may compli-cate matters, however, because these devices are considered a contraindication toMRI scanning. When MRI is performed in patients with a CIED, risks include reedswitch activation in older devices, lead heating, system malfunction, and significantradiofrequency noise resulting in inappropriate inhibition of demand pacing, tachy-cardia therapies, or programming changes. This report reviews indications and risk-benefit evaluation of MRI in patients with CIED and provides a clinical algorithm forperforming MRI in patients with implanted devices.

Implantable Defibrillators in Long QT Syndrome, Brugada Syndrome, HypertrophicCardiomyopathy, and Arrhythmogenic Right Ventricular Cardiomyopathy 305

Mustafa Dohadwala and Mark S. Link

Sudden death is often the first manifestation in inherited cardiac arrhythmia syn-dromes. Patients with long QT syndrome who have an episode of syncope whileon beta-blockade should be offered an implantable cardioverter-defibrillator (ICD).

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In Brugada syndrome and hypertrophic cardiomyopathy, ICDs are often the mosteffective treatment of primary and secondary prevention of cardiac arrest. Risk strat-ification is crucial in identifying those at greatest risk to provide lifesaving therapywith an ICD while avoiding complications in those unlikely to receive benefit.

Index 319