Subcutaneous implantable cardiac defibrillator parameters after 65 kg weight gain – not what they were – a case report

Subcutaneous implantable cardiac defibrillator (SICD) efficacy can be affected by increased body habitus due to R wave undersensing and unsuccessful defibrillation from ineffectual current delivery.

Our patient underwent SICD implantation for idiopathic VF. Appropriate shocks were delivered over the next 4 years for episodes of VF storm. However, following this his weight increased from 102 to 167 kg. With this his R wave values in all vectors fell, and device impedance rose to 210Ω. This value was outside manufacturer recommendations and where its efficacy in treating ventricular arrhythmia is unknown. Due to this concern, a full system revision procedure occurred, following which his impedance fell to 80Ω, and he successfully underwent defibrillation testing. At follow up he had remained arrhythmia free with normal device parameters and had commenced a weight loss programme.

Increased body habitus can have profound effects of SICD parameters due to the high resistance of adipose tissue. Parameters and device efficacy can be optimized with device and lead placement adjacent to the chest wall and sternum respectively.