What is the cause of symptoms in a patient with a single chamber ICD?
Trainee Cardiac Physiologist, Nottingham University Hospital NHS Trust
Disclosure: The author has no conflict of interests to declare.
A 42-year old male implanted with a secondary prevention single chamber implantable cardiac defibrillator (ICD), (Medtronic Visia SR) attended for an in person ICD check to investigate symptoms described as palpitations and pulsating in the neck. Relevant device related history includes a recent admission involving multiple appropriate high voltage (HV) shocks for polymorphic ventricular tachycardia (PVT) degenerating to ventricular fibrillation (VF). Episodes of PVT were initiated by ventricular ectopy. Management at the time included the introduction of antiarrhythmic medication and programming of the lower rate limit (LRL) to 80 bpm to suppress ectopic activity which was reduced to 60 bpm pre discharge. Prior to device interrogation a 12-lead electrocardiogram (ECG) was recorded, displayed in figure 1. Device settings are detailed below.
Lower rate: 60 bpm.
ICD therapies: Single VF therapy zone 200 bpm (30/40 beat initial detection interval with 12/16 redetection interval), ATP during charging 35J x 6.
Figure 1. ECG recorded prior to device interrogation. Beats of interest are labelled 1-10.