Implantable Cardioverter-Defibrillator (ICD) Placement

Ventricular fibrillation (VF) is a common cause of sudden cardiac death (SCD) and is sometimes preceded by monomorphic or polymorphic ventricular tachycardia (VT). All sustained ventricular arrhythmias have the potential to be lethal arrhythmias. Although cardiopulmonary resuscitation, including chest compressions and assisted ventilation, can provide transient circulatory support for the patient with cardiac arrest, the only effective approach for terminating VF is electrical defibrillation. Implantable cardioverter-defibrillator (ICD) implantation is generally considered the first-line treatment option for the secondary prevention of SCD and for primary prevention in certain populations at high risk of SCD due to VT/VF.

This topic will review the general indications for ICD implantation as well as the components and functionalities of the ICD. The clinical trials documenting the efficacy of an ICD in different clinical settings (including both secondary and primary prevention), complications of ICD placement, optimal ICD programming, and follow-up care of patients with ICDs are discussed separately.

INDICATIONS The main indications for use of an ICD are as follows;

• Secondary prevention of sudden cardiac death (SCD) in patients with prior sustained ventricular tachycardia (VT), ventricular fibrillation (VF), or resuscitated SCD thought to be due to VT/VF.
• Primary prevention of SCD in patients at increased risk of life-threatening VT/VF.

Secondary prevention — Implantation of an ICD is recommended for the secondary prevention of SCD due to life-threatening VT/VF in the following settings:

• Patients with a prior episode of resuscitated VT/VF or sustained hemodynamically unstable VT in whom a completely reversible cause cannot be identified. This includes patients with a variety of underlying heart diseases and those with idiopathic VT/VF and congenital long QT syndrome, but not patients who have VT/VF limited to the first 48 hours after an acute myocardial infarction (MI).
• Patients with episodes of spontaneous sustained VT in the presence of heart disease (valvular, ischemic, hypertrophic, dilated, or infiltrative cardiomyopathies) and other settings (eg, channelopathies)
• Patients with unexplained syncope and high suspicion of VT/VF as the etiology.

A key issue is the prevention of total mortality (not arrhythmic or sudden death). Simply correcting VT/VF may not improve overall mortality. Therefore, patient selection for ICD implantation should take into account both the known risk of SCD due to VT/VF for a specific condition and the risk of total mortality from underlying medical conditions as well.

Primary prevention— Implantation of an ICD is recommended for the primary prevention of SCD due to life-threatening VT/VF in patients who have received optimal guideline-directed medical therapy. While guideline-directed medical therapy used to be relatively simple and included beta-blocker therapy and use of an angiotensin receptor blocker or ACE inhibitor, guideline-directed medical therapy now includes several other medications.

• Patients on guideline-directed medical therapy who have high risk of SCD include the following groups of patients Patients with a prior MI (at least 40 days ago) and left ventricular ejection fraction (LVEF) ≤30 percent.
• Patients with a cardiomyopathy, New York Heart Association (NYHA) functional class II to III, and LVEF ≤35 percent. Patients with a nonischemic cardiomyopathy generally require optimal medical therapy for three months with documentation of persistent LVEF ≤35 percent at that time. However, the DANISH trial calls into question the role of prophylactic ICDs in some patients with nonischemic cardiomyopathy. It is recommended that patients be evaluated at least three months after revascularization (coronary artery bypass graft surgery [CABG] or stent placement). Some patients with heart failure who are candidates for an ICD also have intraventricular conduction delay (≥120 milliseconds) and are candidates for cardiac resynchronization therapy (CRT) with a biventricular pacemaker. Such patients could be treated with a device with combined ICD and biventricular pacing functions (cardiac resynchronization therapy-defibrillator [CRT-D]).
• Patients with a prior MI, nonsustained VT, and LVEF ≤40 percent who have VF or sustained VT-induced during electrophysiology study.

ICD not recommended — ICD therapy is NOT recommended in the following settings

• Patients with ventricular tachyarrhythmias due to a completely reversible disorder in the absence of structural heart disease (eg, electrolyte imbalance, drugs, or trauma).
• Patients who do not have a reasonable expectation of survival with an acceptable functional status for at least one year, even if they otherwise meet ICD implantation criteria.
• Patients with incessant VT or VF in whom other therapies (eg, catheter ablation) should be considered first.
• Patients with severe psychiatric illnesses that may be aggravated by device implantation. In clinical practice, this situation is very rarely encountered and may apply more to primary prevention than secondary prevention settings. Patients with NYHA Class IV heart failure that is refractory to optimal medical treatment who are not candidates for cardiac transplantation or CRT.
• Patients with syncope without inducible ventricular tachyarrhythmias and without structural heart disease.
• Patients with VF or VT amenable to surgical or catheter ablation in whom the risk of sudden cardiac death is normalized after successful ablation (eg, pre-excited atrial fibrillation and subsequent ventricular arrhythmias associated with the Wolff-Parkinson-White syndrome, RV or LV outflow tract VT, idiopathic VT, or fascicular VT in the absence of structural heart disease)
• ICD implantation should be delayed in patients with active infections or other acute medical issues. If necessary, the patient can be bridged with a wearable cardioverter-defibrillator (WCD) until ICD implantation can be carried out.