When ICDs Do Not Deliver: The Unseen Burden of Untreated Arrhythmias

ICDs are implanted to treat sudden arrhythmic death by treating episodes of ventricular arrhythmia (VA). Despite this primary function, patients can still die with a functioning ICD due to untreated VA. The purpose of this review is to examine the causes and implications of ICD failures in detection and therapy delivery during VA and assess post-mortem interrogation practices and literature. The literature, adverse event reports, and the authors' own internal data were reviewed to identify causes of ICD non-therapy. Signal-related, functional, algorithmic and myocardial undersensing were identified as contributors, along with episodes of failed defibrillation/cardioversion. Contemporary ICD programming prioritises specificity but may compromise sensitivity. Post-mortem interrogation is rare, under-utilised and has no standardisation, despite reports of ICD failure being the cause of death in up to 25% of cases. To conclude, failure to interrogate ICDs after death risks missing fatal undersensing. Systematic post-mortem analysis is proposed as the cardiac equivalent of aviation's black box, which is critical for learning and sudden arrhythmic death prevention.