Cardiac Electronic Implantable Device Therapy

Cardiac Electronic Implantable Device Therapy

Yang Yang

Irakli Giorgberidze

Lorraine Cornwell


The first case of successful defibrillation in a human was performed in 1947 by Dr Claude Beck, a cardiothoracic surgeon, on a 14-year-old boy whose rhythm had degenerated into ventricular fibrillation (VF) during surgery for pectus excavatum.1 Based on the contemporary studies of Carl Wiggers, who showed that timely defibrillation restored sinus rhythm in animals with VF,2 Beck applied a direct shock to the heart cardioverting it back to sinus rhythm.

With time, both open- and closed-chest defibrillation became the mainstay of resuscitation from cardiac arrest. Michel Mirowski and Morton Mower invented and built the first implantable cardioverter-defibrillator (ICD)3 that was implanted in February 1980.4 The first ICD weighed over 200 g and used large epicardial patches for defibrillation while requiring a thoracotomy for implantation.

Over time the ICD attained indications for sudden death prevention in patients who survived ventricular tachycardia (VT) or cardiac arrest (secondary prevention) and those with left ventricular (LV) systolic dysfunction at risk of sudden death (primary prevention).5 Subsequently, studies demonstrated that simultaneously pacing both right and left ventricle (ie, biventricular pacing) in electrically dyssynchronous ventricles could improve mechanical synchrony, LV systolic function, and the functional status of patients6 and decrease mortality.7 With those findings, biventricular pacing or cardiac resynchronization therapy (CRT) has become the standard of care for heart failure patients with a wide QRS complex on the electrocardiogram. Thus, the benefits of ICD therapy in sudden death prevention and the benefits of CRT in the improvement of heart failure led to the combination of biventricular pacing with defibrillation (ie, implantable CRT-defibrillators [CRT-D] device).

Due to the initial limitations of both generator size and need for epicardial patches, the earliest ICDs required cardiothoracic and abdominal wall surgery. With advances in technology, the device (ie, generator) is now a fifth its original size and implanted via minimally invasive surgery via the creation of small subcutaneous pocket in a pectoral region. Epicardial patches have been replaced by intracardiac leads (wire electrodes) that use sheath-based introducer techniques for transvenous implantation under fluoroscopic guidance.

ICDs consist of a pulse generator and up to three intracardiac leads for CRT-D systems. The pulse generator—also known as “the can”—contains the high-voltage capacitor, battery, and sensing circuitry for the device. Contemporary ICDs function as a defibrillator and also incorporate all functions of a pacemaker. The defibrillator lead, which consists of a pace/sensing electrode and one or two coils for defibrillation, is usually implanted into the right ventricle. In dual-chamber ICDs, a regular pacing lead is also implanted into the right atrium. With CRT devices, LV pacing is accomplished by a lead that is advanced into one of the epicardial LV veins via the coronary sinus (CS).

Contemporary techniques for ICD and CRT-D implantation are minimally invasive procedures that use local anesthesia and conscious sedation, percutaneous venous access through the Seldinger technique and only one incision for the creation of the generator pocket. The right ventricular and right atrial leads are then guided into the appropriate location under fluoroscopic guidance. Specially designed guiding sheaths are used for delivery of the LV lead to the selected branch of the CS. The generator is secured in either a subcutaneous or submuscular pocket. The whole procedure can be done on a same-day basis requiring minimal hospitalization.

May 8, 2022 | Posted by in CARDIOLOGY | Comments Off on Cardiac Electronic Implantable Device Therapy

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