Experience with a third-generation implantable cardioverter-defibrillator

Area of Science:

• Cardiology
• Electrophysiology
• Medical Devices

Background:

• Patients with sustained ventricular tachycardia (VT) or ventricular fibrillation (VF) and organic heart disease often have reduced left ventricular ejection fraction.
• Implantable cardioverter-defibrillators (ICDs) are crucial for managing life-threatening arrhythmias.
• Evaluating the efficacy of different defibrillation strategies and pacing therapies is essential for optimizing patient outcomes.

Purpose of the Study:

• To assess the feasibility and efficacy of individualized electrical therapy using a Medtronic 7216A pacemaker cardioverter-defibrillator in patients with VT/VF.
• To evaluate defibrillation shock efficacy with various electrode configurations and shock patterns.
• To determine the effectiveness of pacing and shock therapies for terminating induced and spontaneous VT/VF episodes.

Main Methods:

• Implantation of a Medtronic 7216A pacemaker cardioverter-defibrillator in 16 patients with VT/VF and organic heart disease.
• Evaluation of endocardial and epicardial defibrillation shock efficacy using monophasic shocks (single, sequential, simultaneous) with dual and triple electrode configurations.
• Assessment of VT/VF detection rates and termination efficacy using pacing, shock therapy, or both.
• Noninvasive induction of VT/VF post-implant for testing therapeutic responses.

Main Results:

• Epicardial defibrillation thresholds ranged from 3 to 18 J, with no significant difference between sequential and simultaneous shocks.
• VT detection rates were 340–470 ms, and VF detection rates were 270–330 ms.
• All induced VF episodes were terminated by shocks; induced VT was terminated by pacing alone, low-energy shocks, high-energy shocks, or combined therapy.
• During follow-up, 78% of spontaneous VT episodes were terminated by pacing, and all VT/VF episodes were successfully terminated by electrical therapy.

Conclusions:

• Individualized electrical therapy using a programmable hybrid pacemaker cardioverter-defibrillator system is feasible and effective for patients with VT/VF.
• Pacing therapies demonstrate efficacy for both induced and spontaneous VT termination, potentially reducing patient exposure to shocks.
• The hybrid system offers nonthoracotomy implantation, effective arrhythmia termination, and versatile noninvasive troubleshooting capabilities.