Practice Essentials
The implantable cardioverter-defibrillator (ICD) is first-line treatment and prophylaxis for patients who are at risk of sudden cardiac death (SCD). Multiple randomized trials have consistently demonstrated ICD implantation decreases mortality in patients who have suffered cardiac arrest, those with heart failure and reduced ejection fraction, and patients with specific structural heart diseases such as hypertrophic obstructive cardiomyopathy (HOCM), sarcoidosis, and others. [1, 2, 3]
Single-chamber, dual-chamber, and biventricular ICD/lead systems (cardiac resynchronization therapy [CRT]) are available for implantation to meet different patient population needs. CRT involves pacing of the left (LV) and right ventricle (RV) (biventricular pacing).
Current ICD/lead systems offer tiered therapy with programmable antitachycardia pacing (ATP) schemes, as well as low-energy and high-energy shocks in multiple tachycardia zones.
Advanced pacing modes and features include different activity sensor–driven rate response features. Sophisticated supraventricular tachycardia (SVT) versus ventricular tachycardia (VT) discrimination algorithms reduce the incidence of inappropriate shocks for atrial fibrillation and rapid ventricular response, sinus tachycardia, and other non–life-threatening SVTs. Diagnostic functions, including stored electrograms, allow for verification of shock appropriateness.
Technique
Incision
The skin incision is usually made in the right or left infraclavicular area, depending on the patient’s handedness. It is generally preferred that the ICD pulse generator (PG) be implanted on the opposite side of the patient’s dominant hand.
Creation of subcutaneous pocket
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An incision 5-7 cm in length is made and carried down to the subcutaneous tissue; the dissection is extended to the prepectoral fascia with electrocauterization, blunt dissection, or both.
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Once the incision is carried down to the prepectoral fascia, electrocautery is used to create a new plane in the inferior part of the incision with the help of an Army-Navy retractor.
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The pocket that will accommodate the ICD PG is then created with a combination of electrodissection and blunt dissection with the fingers.
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Once the pocket has been created and hemostasis achieved, attention is turned toward obtaining vascular access.
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The subclavian, axillary, or cephalic veins may all be used for access; generally, a modified Seldinger technique is used under fluoroscopic or ultrasonographic guidance.
Creation of subpectoral pocket
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For a subpectoral pocket, the author prefers, if possible, to use cephalic vein access for placement of the leads.
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The incision is carried down to the prepectoral fascia and down to the deltopectoral groove, usually first with cautery and subsequently with blunt dissection to avoid injury to the cephalic vein.
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The cephalic vein is then isolated and secured.
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The lateral edge of the deltopectoral muscle is subsequently lifted and gently separated from the pectoralis minor by using blunt dissection with Metzenbaum scissors; blunt dissection with fingers may also be used at this point.
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Once the subpectoral pocket has been created, attention is turned toward obtaining vascular access.
ICD and leads
For the majority of patients, a single-chamber ICD (with only a ventricular lead) is sufficient, especially in patients with chronic persistent atrial fibrillation. A dual-chamber ICD would be useful in patients who have indications for atrial sensing or pacing (those with sinus node disease) or to enhance the SVT versus VT discrimination enhancement by having an atrial electrogram during SVT or VT.
The high-voltage defibrillation ventricular leads may have two defibrillation coils, with the distal coil placed in the RV apex, and the more proximal coil typically extending from the junction of the high right atrium and the superior vena cava, or it may have only a single, distal defibrillation coil.
Insertion of the pulse generator
It is important to place the lead(s) in the bottom of the pocket and then to position the ICD PG in such a way that it covers the lead(s). This protects the lead(s) during any future PG change out.
In patients who require a subpectoral pocket (ie, very thin patients with minimal subcutaneous tissue), an experienced implanter should perform the operation using appropriate tools, as there is an increased risk of bleeding during the procedure.
See Technique for more detail.
Medication
Appropriate pain medication is necessary after the implantation procedure. Patients who undergo subpectoral ICD PG placement experience significantly more pain than do those who undergo subcutaneous device placement.
The evidence for postprocedural antibiotic administration is inconclusive and, for the most part, not based on randomized trials. Nevertheless, most practitioners prescribe oral antibiotics for a short period.
See Medication for more detail.
Background
Cardiovascular diseases are responsible for approximately 17.7 million deaths in the world every year, [4] with 25% from sudden cardiac death (SCD). [5] The implantable cardioverter-defibrillator (ICD) is first-line treatment and prophylaxis for patients who are at risk of SCD. Multiple randomized trials have consistently demonstrated ICD implantation decreases mortality in patients who have suffered cardiac arrest, those with heart failure and reduced ejection fraction, and patients with specific structural heart diseases such as hypertrophic obstructive cardiomyopathy (HOCM), sarcoidosis, and others. [1, 2, 3]
Indications and techniques for ICD implantation have changed tremendously since the inception of this therapy in 1980. [6] Initially, most of the patients who received ICD therapy either showed evidence of sustained ventricular tachycardia (VT), ventricular fibrillation (VF), or they were survivors of SCD. [1, 7] At that time, thoracotomy was required for placement of epicardial defibrillation patches, and the large pulse generator (PG)/device size limited implantation sites to the upper abdomen.
The development of transvenous leads and the miniaturization of the PG allowed for pectoral placement of the defibrillator PG with a very low risk of complications. At present, most ICD placements now occur for primary prevention of SCD. [2, 3]
Indications
Indications for implantation of an implantable cardioverter-defibrillator (ICD) are established and classified on the basis of guidelines developed by the American College of Cardiology (ACC), the American Heart Association (AHA), and the Heart Rhythm Society (HRS). [8, 9, 10]
Class I indications
ICD therapy is indicated in the following:
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Patients who are survivors of cardiac arrest due to ventricular fibrillation (VF) or hemodynamically unstable sustained ventricular tachycardia (VT) after evaluation to define the cause of the event and to exclude any completely reversible causes
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Patients with structural heart disease and spontaneous sustained VT, whether hemodynamically stable or unstable
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Patients with syncope of undetermined origin with clinically relevant, hemodynamically significant sustained VT or VF induced at electrophysiologic study
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Patients with a left ventricular (LV) ejection fraction (EF) up to 35% due to prior myocardial infarction (MI) who are at least 40 days post-MI and are in New York Heart Association (NYHA) functional class II or III
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Patients with nonischemic dilated cardiomyopathy (DCM) with an LVEF up to 35% and who are in NYHA functional class II or III
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ICD therapy is indicated in patients with LV dysfunction due to prior MI who are at least 40 days post-MI, have an LVEF up to 30%, and are in NYHA functional class I
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Patients with nonsustained VT due to prior MI, an LVEF up to 40%, and inducible VF or sustained VT at electrophysiologic study
ICD implantation in pediatric patients and patients with congenital heart disease
ICD implantation is indicated in the following [9] :
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Survivors of cardiac arrest after evaluation to define the cause of the event and to exclude any reversible causes
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Patients with symptomatic sustained VT in association with congenital heart disease who have undergone hemodynamic and electrophysiologic evaluation; catheter ablation or surgical repair may offer possible alternatives in carefully selected patients
CRT
Cardiac resynchronization therapy (CRT) is indicated for the following:
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(With or without an ICD) Patients with sinus rhythm, an LVEF of 35% or less, a QRS duration of 120 ms or longer, and an NYHA functional class III or ambulatory IV heart failure symptoms despite optimal medical therapy [8]
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Patients with sinus rhythm, an LVEF of 35% or less, left bundle branch block (LBBB) with a QRS duration of at least 150 ms, and NYHA class II, III, or ambulatory IV symptoms despite optimal medical therapy [9]
Class IIa indications
ICD implantation is reasonable for patients with the following conditions [9] :
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Unexplained syncope, significant LV dysfunction, and nonischemic DCM
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Sustained VT and normal or near-normal ventricular function
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Hypertrophic cardiomyopathy (HCM) who have one or more major risk factors for sudden cardiac death (SCD)
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Prevention of SCD in patients with arrhythmogenic right ventricular dysplasia or cardiomyopathy (ARVD/C) who have one or more risk factors for SCD (sustained VT, unexplained syncope, frequent nonsustained VT [NSVT], family history of SCD, extensive right ventricular [RV] disease, marked QRS prolongation, late gadolinium enhancement on cardiovascular magnetic resonance imaging [CMRI], LV dysfunction and VT induction during electrophysiology study) [11, 12]
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To reduce SCD in patients with long-QT syndrome (LQTS) who are experiencing syncope or VT while receiving beta blockers
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Non-hospitalized patients awaiting transplantation
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Brugada syndrome who have had syncope
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Brugada syndrome who have documented VT that has not resulted in cardiac arrest
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Catecholaminergic polymorphic VT who have syncope and/or documented sustained VT while receiving beta blockers
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Cardiac sarcoidosis, giant cell myocarditis, or Chagas disease
ICD implantation in pediatric patients and patients with congenital heart disease
ICD implantation is reasonable for patients with congenital heart disease with recurrent syncope of undetermined origin in the presence of either ventricular dysfunction or inducible ventricular arrhythmias at electrophysiologic study. [9]
CRT
CRT can be useful for patients who have the following conditions [9] :
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An LVEF up to 35%, sinus rhythm, LBBB with a QRS duration of 120-149 ms, and NYHA class II, III, or ambulatory IV symptoms on guideline-directed medical therapy (GDMT)
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An LVEF up to 35%, sinus rhythm, a non-LBBB pattern with a QRS duration of at least 150 ms, and NYHA class III/ambulatory class IV symptoms on GDMT
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Atrial fibrillation and an LVEF up to 35% on GDMT if a) the patient requires ventricular pacing or otherwise meets CRT criteria and b) atrioventricular (AV) nodal ablation or pharmacologic rate control will allow near 100% ventricular pacing with CRT
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On GDMT, with an LVEF up to 35% and undergoing new or replacement device placement with anticipated requirement for significant (>40%) ventricular pacing
Class IIb indications
ICD therapy may be considered in patients with the following [9]
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Nonischemic heart disease who are in NYHA functional class I with a persistent LVEF up to 35%
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LQTS and risk factors for SCD
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Syncope and advanced structural heart disease in whom a thorough invasive and noninvasive investigations have failed to define a cause
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A familial cardiomyopathy associated with sudden death
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LV noncompaction
ICD implantation in pediatric patients and patients with congenital heart disease
ICD therapy may be considered for patients with recurrent syncope associated with complex congenital heart disease and advanced systemic ventricular dysfunction when thorough invasive and noninvasive investigations have failed to define a cause. [9]
CRT
CRT may be considered for patients who have the following [9] :
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An LVEF up to 30%, an ischemic heart failure etiology, sinus rhythm, LBBB with a QRS duration of at least 150 ms, and an NYHA class I symptoms on GDMT
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An LVEF up to 35%, sinus rhythm, a non-LBBB pattern with a QRS duration of 120-149 ms, and an NYHA class III/ambulatory class IV on GDMT
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An LVEF up to 35%, sinus rhythm, a non-LBBB pattern with a QRS duration of at least 150 ms, and NYHA class II symptoms on GDMT
Class III indications
The following class III ICD indications apply to adults as well as pediatric patients and those with congenital heart diseases; ICD implantation is not indicated in these groups.
ICD therapy is not indicated for patients with the following [9] :
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No reasonable expectation of survival with an acceptable functional status for at least 1 year, even if they meet ICD implantation criteria specified in the class I, IIa, and IIb recommendations above
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Incessant VT or VF
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Significant psychiatric illnesses that may be aggravated by device implantation or that may preclude systematic follow-up
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NYHA class IV status with drug-refractory congestive heart failure (CHF) who are not candidates for cardiac transplantation or implantation of a CRT device that incorporates both pacing and defibrillation capabilities
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Syncope of undetermined cause in the setting of absence of inducible ventricular tachyarrhythmias and without structural heart disease
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VF or VT that is amenable to surgical or catheter ablation (eg, atrial arrhythmias associated with Wolff-Parkinson-White [WPW] syndrome, RV or LV outflow tract VT, idiopathic VT, or fascicular VT in the absence of structural heart disease)
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Ventricular tachyarrhythmias due to a completely reversible disorder in the absence of structural heart disease (eg, electrolyte imbalance, drugs, or trauma)
Available evidence suggests that ICD implantation can be safely accomplished in patients who are anticoagulated with warfarin with a therapeutic international normalized ratio (INR) in the range of 2 to 3. [13]
CRT
The following are class III indications ("no benefit") for CRT [9] :
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CRT is not recommended for patients with NYHA class I or II symptoms and non-LBBB pattern with a QRS duration less than 150 ms.
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CRT is not indicated for patients whose comorbidities and/or frailty limit survival with good functional capacity to less than 1 year.
Contraindications
Implantable cardioverter-defibrillator (ICDs) are contraindicated in patients experiencing tachyarrhythmias with reversible or transient causes including, but not limited to, the following:
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Acute myocardial infarction
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Drug intoxication
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Drowning
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Electric shock
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Electrolyte imbalance
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Hypoxia, or sepsis
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Patients who have a unipolar pacemaker implanted
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Patients with incessant ventricular tachycardia (VT) or ventricular fibrillation (VF)
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Patients whose primary disorder is chronic atrial tachyarrhythmia with no concomitant VT or VF
Technical Considerations
Implantation of an implantable cardioverter-defibrillator (ICD) within 40 days of an acute myocardial infarction (MI)
The results from the Defibrillators in Acute Myocardial Infarction Trial (DINAMIT) and the subsequent Immediate Risk-Stratification Improves Survival (IRIS) trial which enrolled patients with left ventricular (LV) ejection fractions (EFs) of up to 35% and 40%, respectively after an MI without revascularization have shed light on this entity. [14, 15] Although there was a significant reduction in arrhythmic death, there was an increase in nonarrhythmic death, which resulted in no overall benefit. The high-risk profile of the patients or device-related risks such as inappropriate pacing may have influenced the outcomes. [16, 17] Due to the high risk of sudden cardiac death (SCD) in the first 30 days of acute MI, a wearable external defibrillator with reevaluation of cardiac function after 40 days is a reasonable option. [18, 19, 20]
Implantation within 3 months of coronary artery bypass graft (CABG) surgery or percutaneous coronary intervention (PCI)
The MADIT II (Multicenter Automatic Defibrillator Implantation Trial with Cardiac Resynchronization Therapy) trial and SCD-HeFT (Sudden Cardiac Death in Heart Failure Trial) enrolled patients with prior CABG or PCI. The enrollment criteria relative to time from CABG or PCI was different between the studies (MADIT II required 3 months, and SCD-HeFT required 1 month from procedure to enrollment). In a MADIT II post hoc analysis, there was a reduced benefit of ICD therapy in patients who received an ICD between 3 months and 6 months after CABG or PCI as compared to patients who received an ICD 6 months or longer after CABG or PCI. [21] However, for patients in SCD-HeFT group, ICD therapy benefit was similar regardless of the time from CABG or PCI to ICD implantation. [22]
New York Heart Association (NYHA) class IV heart failure
The potential benefit of primary prevention in NYHA class IV patients is not defined. However, in the Cardiac-Resynchronization Therapy With or Without an Implantable Defibrillator in Advanced Chronic Heart Failure (COMPANION) trial, investigators randomized NYHA class III and IV heart failure patients with an LVEF up to 35%, and a QRS duration of 120 ms or longer to optimal medical therapy, CRT, or CRT with an ICD (CRT-D). [23] The data indicated that CRT and CRT-D significantly reduced death or hospitalization for any cause, but only CRT-D reduced all-cause mortality.
Outcomes
Primary prevention implantable cardioverter-defibrillator (ICD) therapy
In the Multicenter Automatic Defibrillator Implantation Trial II (MADIT II) study, ICD reduced all cause mortality by 31% in 1232 patients with myocardial infarction (MI) at least 30 days or longer before enrollment and an a left ventricular (LV) ejection fraction (EF) of 30%. [2] Later, a post-hoc subset analysis demonstrated a survival benefit for ICD in patients with a QRS duration of at least 120 ms. [24]
A 2018 substudy report of the MADIT-Cardiac Resynchronization Therapy (MADIT-CRT) trial indicated that in CRT-treated heart failure patients, left atrial abnormality on electrocardiography (ECG) appeared to be an ECG indicator of poor long-term outcome in those with left bundle branch block (LBBB). [25] The investigators suggested that the P-wave terminal force in lead V1 (PTF-V1) (in which a PTF-V1 of 0.04 mm/s or longer was considered abnormal) provided additional prognostic information in the context of CRT, thereby potentiating the role of ECG in stratifying risk in heart failure patients. [25]
The Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) found ICD benefit to be similar across multiple QRS width cut-off points. [3, 26] The study included patients with ischemic or nonischemic New York Heart Association (NYHA) class II or III heart failure and an LVEF up to 35%, and patients were randomized to ICD therapy, or amiodarone, or placebo. ICD therapy significantly reduced all-cause mortality, whereas amiodarone did not compared to placebo. The benefit was found to be similar between nonischemic and ischemic cardiomyopathy. However, although mortality reduction was associated with with NYHA class II, no benefit of ICD therapy was observed in the remaining NYHA class III patients.
A post-hoc analysis of SCD-HeFT assessed the ICD benefit across five risk groups. [27] In the NYHA class III group, some were at high risk and might have influenced the observed lack of ICD benefit. Note that mortality benefit from ICD therapy is highest in the lower and intermediate group rather than the highest risk group. In 2006, the American College of Cardiology, American Heart Association, and European Society of Cardiology (ACC/AHA/ESC) guidelines for management of patients with ventricular arrhythmias and prevention of sudden cardiac death (SCD) assigned a class I recommendation for primary prevention ICD therapy to NYHA class II and III patients with an LVEF up to 30%-40% with coronary artery disease (CAD) and prior MI. These guidelines also assigned a class I recommendation for patients with nonischemic cardiomyopathy, NYHA class II and III, and an LVEF up to 30%-35%). [28]
In the 2008 ACC/AHA/Heart Rhythm Society (HRS) guidelines, the ranges of LVEF were streamlined to LVEF up to 35% except for NYHA class I coronary artery disease patients with an LVEF up to 30% who are not cardiac resynchronization therapy (CRT) candidates but who are awaiting cardiac transplantation can be considered for a primary prevention ICD implantation (class IIa). [8]
Preliminary data indicate that not only do elderly patients (≥75 years) undergo CRT with ICD less often than younger patients, [29] but the elderly do not appear to derive a survival benefit with the addition of an ICD. [30]
In a study that evaluated the role of ICD implantation for primary prevention of SCD in 212 high-risk patients with long QT syndrome (LQTS), investigators identified clinical and genetic variables associated with appropriate shock risk, which have the potential for use in risk stratification in this patient population. [31] For example, factors associated with an increased risk of appropriate shock included a corrected QT interval (QTc) of 550 ms or longer and previous syncope while on beta-blockers. LQT2 and multiple mutations were associated with a greater risk for recurrent shocks relative to LQT1. [31]
Wearable cardioverter-defibrillators appear to be a safe and effective alternative for pediatric patients with ventricular arrhythmias at high risk for SCD but who are not ideal candidates for placement of ICDs. [32]
Secondary prevention ICD therapy
The results of the National Institutes of Health-funded Amiodarone Versus Implantable Defibrillator study (AVID) [1] (which enrolled survivors of cardiac arrest, patients with syncopal ventricular tachycardia [VT], and patients with symptomatic VT with an LVEF up to 40%) showed a significant reduction in all-cause mortality for patients treated with an ICD compared to those who received antiarrhythmic medication. [1]
The Canadian Implantable Defibrillator Study (CIDS) and the Cardiac Arrest Study Hamburg (CASH) trial both demonstrated a trend toward mortality reduction with ICD therapy. [33, 34] Therefore, secondary prevention ICD therapy is a class I recommendation for patients meeting AVID criteria in ACC/AHA guidelines. [8, 28, 35] In a meta-analysis of AVID, CASH, and CIDS, the ICD therapy benefit was found to be limited to patients with LVEF of 35% or below. [36]