Options in managing the patient with high defibrillation thresholds

Area of Science:

• Cardiology
• Biomedical Engineering
• Electrophysiology

Background:

• The desired defibrillation threshold (DFT) for implantable cardioverter defibrillators (ICDs) requires a 10 J safety margin below maximal generator energy.
• A small percentage of patients undergoing ICD implantation present with initial DFTs below this safety margin, posing a clinical challenge.

Purpose of the Study:

• To evaluate the effectiveness of various techniques in achieving adequate DFTs in patients with initially high thresholds.
• To identify patient characteristics associated with high DFTs and assess the safety of supplemental procedures.

Main Methods:

• Retrospective analysis of 206 patients undergoing ICD implantation.
• Application of multiple techniques to lower DFTs in 8 patients with initial thresholds below the 10 J safety margin.
• Techniques included adding a superior vena cava lead, converting to a biphasic-waveform generator, and adding a third epicardial lead.

Main Results:

• Eight patients (3.9%) had initial DFTs below the 10 J safety margin.
• High DFTs were more prevalent in patients with prior open-heart surgery and those on amiodarone therapy.
• Satisfactory DFTs were achieved in 7 of 8 patients (88%) after implementing supplemental techniques, with a significant reduction in mean DFT (41.4 J to 26.9 J).
• Addition of a superior vena cava lead and conversion to biphasic waveform were effective; a third epicardial lead was not.

Conclusions:

• Supplemental techniques, particularly adding a superior vena cava lead or using biphasic waveforms, are effective in achieving satisfactory DFTs in patients with initially high thresholds.
• These interventions can be safely implemented without major complications.
• Almost all patients can achieve adequate DFTs with these advanced strategies, enhancing ICD therapy safety and efficacy.