• Cardioverter
• defibrillator
• HCM
• ICD
• implantable cardioverter defibrillator (ICD)
• sudden cardiac death
• ventricular fibrillation
• ventricular tachycardia

The sudden and unexpected death of an often young and otherwise healthy person with hypertrophic cardiomyopathy (HCM) due to a ventricular arrhythmia is a tragic but preventable occurrence. Wider availability of the implantable cardioverter defibrillator (ICD), a reliable and effective therapy that can detect and successfully terminate a spontaneous sustained ventricular arrhythmia, remains one of the most important additions to the therapeutic armamentarium of clinicians who care for patients with HCM in the past 25 years or so and is recommended for those individuals deemed at highest risk.1

Although initially thought to be a disease of the young with high mortality, HCM is now widely recognised as having a relatively benign clinical course for the majority of patients, but remains the most common cause of sudden death in younger patients (age <25 years) and athletes.2 Importantly, however, sudden death also occurs in older individuals perhaps due to a change in risk profile such as the development of coronary disease and in 3–5% of patients without identifiable risk factors.3

A major hurdle in the selection of individuals who might benefit from ICD therapy is not only the low incident rate of sudden death, especially in the general (non-referral) community, but the enormous heterogeneity of the phenotype.4 5 As a result of these difficulties, and despite decades of research, no wholly reliable or accurate means of identifying individuals most at risk of sudden cardiac arrest currently exists.6 Despite the lack of an individualised risk score or a sensitive and specific marker of risk, general agreement exists that ICD implantation should be recommended in individuals who present with sudden cardiac arrest or a sustained ventricular arrhythmia, and those with one or more ‘high risk’ trait(s): a close family history of cardiac arrest due to HCM, massive left ventricular hypertrophy, cardiogenic …