Implantable Cardioverter-Defibrillator (ICD) Insertion

An implantable cardioverter-defibrillator (ICD) protects patients at risk of sudden cardiac death from ventricular tachycardia (VT) or ventricular fibrillation (VF), such as survivors of cardiac arrest and patients with severe cardiomyopathy. A pacemaker treats a heart that beats too slowly; an ICD also watches for dangerously fast rhythms and treats them with tiered therapy of increasing strength, up to a shock. To do this the generator holds a high-energy battery and a capacitor that charges to about 600 to 800 volts (35 to 40 joules), and the right ventricular lead carries one or two shocking coils; the generator case itself often acts as part of the shock pathway ('active can'). An atrial lead may be added, and a left ventricular lead in the coronary sinus for cardiac resynchronization (a biventricular ICD). The operation is done much like a transvenous pacemaker insertion, in the OR or the electrophysiology lab, under local anesthesia with sedation (general anesthesia when needed). What makes it different is the testing: VF may be started on purpose and the device must stop it, the defibrillation threshold (DFT) test. This is the point of greatest risk, so external defibrillator pads are placed on the patient beforehand, a charged external defibrillator is ready, and the team watches the blood pressure. The leads are thicker and stiffer than pacing leads, and a larger introducer is used. Most patients who need an ICD have weak hearts and other illnesses. Risks include bleeding, infection of the pocket or leads, lead displacement, collapsed lung or bleeding from a subclavian puncture, heart failure after testing, and shocks given for fast normal rhythms. A manufacturer's representative usually brings the device and runs the testing equipment.