Implantable cardioverter defibrillators ICDs

In patients who have experienced VT and are at risk for sudden cardiac death, implantation of an implantable cardioverter-defibrillator (ICD) is the treatment of choice.44 An ICD is a device that provides internal electrical cardioversion of VT or defibril -lation of VF the ICD does not prevent the patient from developing the arrhythmia, but it reduces the risk that the patient will die of sudden cardiac death as a result of the arrhythmia. Whereas in the past ICD implantation required a thoracotomy, these devices now may be implanted transvenously, similarly to pacemakers, markedly reducing the complication rate. 

Implantable cardioverter-defibrillator (ICD) A device implanted into the heart transvenously with a generator implanted subcutaneously in the pectoral area that provides internal electrical cardioversion of ventricular tachycardia or defibriUation of ventricular fibrillation. 

The use of antiarrhythmic drugs in the United States is declining because of major trials that showed increased mortality with their use in several clinical situations, the realization of proarrhythmia as a significant side effect, and the advancing technology of nondrug therapies such as ablation and the implantable cardioverter-defibrillator (ICD). 

Abstract Two thirds of the nearly half a million deaths per year in the United States due to sudden cardiac death (SCD) is attributed to coronary artery disease (CAD) and most commonly results from untreated ventricular tachyarrhythmias. Patients with ischemic cardiomyopathy and left ventricular dysfunction are at highest risk for SCD, but this still defines only a small subset of patients who will suffer SCD. Multiple lines of evidence now support the superiority of implantable cardioverter defibrillator (ICD) therapy over antiarrhythmic therapy for both primary and secondary prevention of SCD in advanced ischemic heart disease. Optimization of ICD therapy in advanced ischemic cardiomyopathy includes preventing right ventricular pacing as well as the use of highly effective anti-tachycardia pacing to reduce the number of shocks. While expensive, ICD therapy has been shown to compare favorably to the accepted standard of hemodialysis in cost effectiveness analyses. 

As left ventricular dysfunction is a major predictor of sudden arrhythmic death, cardiac death and total mortality, it can be stated that in general sudden cardiac death prevention is achievable with the combination of an implantable cardioverter defibrillator (ICD) and medical therapy. 

The first implantable cardioverter-defibrillator (ICD) was placed in 1982. Since that time, their use has expanded exponentially. Several large clinical trials have demonstrated the superiority of ICDs compared with pharmacological therapy for the secondary prevention of arrhythmic death and possibly as primary therapy for patients at risk for ventricular arrhythmias. 

Low doses (100-200 mg/d) of amiodarone are effective in maintaining normal sinus rhythm in patients with atrial fibrillation. The drug is effective in the prevention of recurrent ventricular tachycardia. It is not associated with an increase in mortality in patients with coronary artery disease or heart failure. In many centers, the implanted cardioverter-defibrillator (ICD) has succeeded drug therapy as the primary treatment modality for ventricular tachycardia, but amiodarone may be used for ventricular tachycardia as adjuvant therapy to decrease the frequency of uncomfortable cardioverter-defibrillator discharges. The drug increases the pacing and defibrillation threshold and these devices require retesting after a maintenance dose has been achieved. 

Fig. 4.11 Cross-sectional view (from the top) of a prismatic high power lithium—silver vanadium oxide battery used to power an implantable cardioverter defibrillator (ICD). (By permission of Medtronic.)...

Recent studies demonstrate that cardiac resynchronization therapy (CRT) offers a promising approach to selected patients with chronic heart failure. Delayed electrical activation of the left ventricle, characterized on the ECG by a QRS duration that exceeds 120 ms, occurs in approximately one-third of patients with moderate to severe systolic heart failure. Since the left and right ventricles normally activate simultaneously, this delay results in asynchronous contraction of the left and right ventricles, which contributes to the hemodynamic abnormalities of this disorder. Implantation of a speciahzed biventricular pacemaker to restore synchronous activation of the ventricles can improve ventricular contraction and hemodynamics. Recent trials show improvements in exercise capacity, NYHA classification, quality of life, hemodynamic function, and hospitalizations. A device that combined CRT with an implantable cardioverter-defibrillator (ICD) improved survival in addition to functional status. CRT is currently indicated only in NYHA class ni-IV patients receiving optimal medical therapy (ACE inhibitors, diuretics, -blockers, and digoxin) and... 

The heart is an electromechanical system, in which mechanical pumping function is initiated and coordinated by automatic rhythmic cardiac electrical activity. Transient electrical disturbances m this activity (cardiac arrhythmias) can immediately cause death. The implantable cardioverter defibrillator (ICD) is a medical device that can be implanted in a human body and will automatically detect and treat cardiac arrhythmias. Mirowski et al. [1] first reported on a demonstration of a functioning ICD in 1970. In his demonstration, he induced a fatal ventricular tachyarrhythmia in a dog. The dog was then successfully and dramatically rescued by the automatic operation of a previously implanted ICD. The first report of successful ICD implantation in humans soon followed [2]. In subsequent decades, advances in ICD technology have reduced ICD size from more than 200 cm, originally, to as httle as 25 cm, while markedly improving functionality, reliability, and longevity. ICDs are now considered as standard of care for patients at risk for ventricular arrhythmia and are implanted in more than 150,000 patients per year in the United States alone [3]. 

Fig 1 19 Noncoated defibrillation electrodes (a) in this type of lead, coils are loose, and the extraction procedure can be more difficult. Histological cross-section of an implanted cardioverter-defibrillator (ICD) lead at the level of the bare shock coils in the heart (b). Fibrous tissue ingrowth in interstices between coils arrows), which fixes the ICD lead to the heart wall (from [13], and courtesy of St. Jude Medical)... 

Fig. 1.24 Guidant Reliance and Medtronic Quattro implantable cardioverter-defibrillator (ICD) leads have asymmetrical body designs, with the cables located on one side and the coiled conductor on the other. New models of St. Jude ICD leads have a concentric design (SJM Durata). In this case, the coil is in the body s central axis, equally surrounded by six protective cables (courtesy of St. Jude Medical, Boston Scientific, and Medtronic)...

FIQn 1 31 Comparison of a new implantable cardioverter-defibrillator (ICD) lead (top) with linear pins to previous ICD leads from the same and other companies (courtesy of St. Jude Medical, Boston Scientific and Medtronic)... 

Fig 2 3 Implantable cardioverter-defibrillator (ICD)-pocket erosion. Part of the ICD header and can are visible. There is evidence of drainage of purulent material and blood from the ulceration without cellulitis. There is a slight bluish discoloring of tissues immediately caudal to the exposed portion of the ICD. Also note multiple scars (five) due to previous attempts to cure pocket infection without extraction of all the hardware, ICD, and leads... 

Fig. 5.2 Low-profile knot performed with a nonabsorbable suture over the insulation of each conductor present in the lead (a) unipolar pacing lead (b) implantable cardioverter-defibrillator (ICD) integrated lead (c)bipolar pacing lead. The arrows show at which level the low-profile knot should be performed...

Fig 5 14 (a-d) Temporal-sequence fluoroscopic images (same patient as in Figure 5.8) after exposure of the atrial lead from the internal jugular vein showing introduction and sheath advancement over the lead, overcoming binding sites to the tip. (e-h) The same maneuver on an implantable cardioverter-defibrillator (ICD) ventricular lead... 

The use of implantable cardiac devices significantly increased over recent years. However, pacing and implantable cardioverter-defibrillator (ICD) lead-related complications are not rare in... 

Fig. 7.2 Serial anteroposterior fluoroscopic images taken during transvenous removal of a left-sided dual-chamber implantable cardioverter-defibrillator (ICD) system. After placement of a temporary right-ventricular (RV) pacing system

Fig 8 1 Nonpainful, considerable hematoma after elective implantable cardioverter-defibrillator (ICD) replacement in a patient with mechanical aortic valve prosthesis (a), ICD pocket of the same patient after 1 month without surgical intervention for hematoma drainage (b)... 

Table 10.1 Critical points during pacing and implantable cardioverter-defibrillator (iCD) transvenous lead removal... 

The outer insulation of pacing and implantable cardioverter-defibrillator (ICD) leads is relatively slippery in order to facilitate lead movement and implantation. This characteristic also plays a role in transvenous lead removal the presence of intact insulation makes sliding dilators over the lead easier. In the absence of insulation or when the insulation is damaged, removal may be challenging. 

There are three implantable devices used today to treat cardiac arrhythmias - the pacemaker, the implantable cardioverter defibrillator (ICD), and the cardiac resynchronization therapy (CRT) devices for heart failure patients. 

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