The burden of inappropriate shocks in young people and how to avoid them

Implicated in up to half of all cardiovascular mortality among developed nations worldwide,w1 w2 sudden cardiac death (SCD) is associated with approximately 450 000 deaths annually in the USA and >700 000 deaths in Europe.w3 w4 In 23% of out-of-hospital and 17% of inhospital cardiac arrests, the initial observed rhythm was ventricular tachycardia (VT) or ventricular fibrillation (VF), both potentially treatable with defibrillation.w5 w6 Large scale trials have also demonstrated that implantable cardioverter defibrillators (ICDs) can improve survival through terminating malignant ventricular arrhythmias, particularly among SCD survivorsw7 and heart failure patients with systolic dysfunction.w8–w12 Based on these data, there has been a dramatic surge in the utilisation of ICDs over the past two decades, with 116 000 ICD device implantations in the USA in 2009 alone, of which 53 000 (46%) were implanted in patients younger than the age of 65 years.w6 With increasing use of ICDs, there has also been heightened awareness of device-related complications and associated risk–benefit trade-offs. Specifically, although it is clear that appropriate ICD therapies extend survival, inappropriate ICD shocks are common and occur in a similar magnitude of patients.w12 w13 Frequent ICD shocks are associated with diminished quality of life,w14 w15 and significant anxiety, depression and post-traumatic stress in a minority of patients.w16 w17 In addition, inappropriate ICD shocks have been linked to the possibility of proarryhthmiaw18–w20 and are associated with increased mortality in some patients, although any causal relationship remains controversial.1–3 w21–w23 Conversely, interventions to prevent inappropriate ICD shocks reduce morbidity,4 and also have been shown to reduce heart failure hospitalisation.5 As the use of ICDs continues to expand further into primary prevention and younger patient populations, identifying at-risk patients and devising a treatment plan for patients suffering from inappropriate shocks are critical. Strategies to avoid inappropriate …