Undersensing by an ICD due to alternans of the ventricular electrogram.

Area of Science:

• Electrophysiology
• Cardiology
• Medical Devices

Background:

• Ventricular electrogram (VEGM) alternans during ventricular tachycardia (VT) is a rare cause of implantable cardioverter-defibrillator (ICD) undersensing.
• This phenomenon can lead to inappropriate failure to deliver life-saving therapy.

Purpose of the Study:

• To describe a case of VEGM alternans causing ICD undersensing during VT.
• To present a simple, noninvasive method for correcting this undersensing issue.

Main Methods:

• Case report of a patient with a St. Jude ICD experiencing sustained monomorphic VT.
• Analysis of surface QRS alternans, alternating cycle lengths, and VEGM alternans.
• Noninvasive reprogramming of ICD sensitivity threshold.

Main Results:

• The patient exhibited VEGM alternans leading to intermittent undersensing of the VT.
• Programming the ICD sensitivity threshold from 62.5% to 50% successfully corrected the undersensing.
• This adjustment did not compromise the defibrillation threshold.

Conclusions:

• VEGM alternans is a critical consideration in ICD performance during VT.
• Simple adjustments in ICD programming can effectively manage VEGM alternans-induced undersensing.
• Noninvasive troubleshooting is a viable first-line approach for such device-related issues.