There has been a resurgence of interest in hypertrophic cardiomyopathy (HCM) in recent years due to improved anatomical delineation using cardiac MR (CMR), as well as improvements in invasive techniques and the advent of implantable cardiac defibrillators (ICDs). Image-based phenotyping has enabled better identification of those at risk and reassurance of those spared.1 Dedicated HCM centres are gaining prominence and facilitating centralised access to all aspects of diagnosis, treatment and prevention. While many aspects of HCM are becoming better understood, there are still many unanswered questions related to the field.

The rare, but tragic, consequences of sudden cardiac death (SCD) in HCM mean that every effort needs to be made to accurately stratify those at risk. The difficulty in this delineation is highlighted by the multiple parameters currently recommended for risk classification. No single parameter is able to provide with certainty an accurate and reliable measure to calibrate SCD risk. While ICDs have revolutionised the management of this patient cohort, there are associated problems related to device infection, inappropriate firing and cost, which preclude ICD adoption as a general panacea. The exact cause of SCD in this population remains incompletely defined. This relates in part to the heterogeneous nature of disease expression. In subjects with severe LV hypertrophy and severe symptomatic LV outflow tract (LVOT) obstruction, the cause of their hemodynamic instability is clear, and ICD implantation and invasive therapies to relieve LVOT obstruction are easy to justify. However, other variants are less clear-cut and important questions remain. What is the prognosis for subjects with minimal hypertrophy but dynamic LVOT obstruction with systolic anterior motion of the mitral valve (SAM) and provocable gradients with exercise or amyl nitrate? Does apical hypertrophy have a lower risk of SCD due to less LVOT obstruction? What is the significance of isolated papillary …