122Left atrial diameter predicted from left atrial volume in the risk assessment of sudden cardiac death in hypertrophic cardiomyopathy - potential clinical consequence for the individual patient

Background: Hypertrophic cardiomyopathy (HCM) is an inherited disease with variable clinical manifestations ranging from no symptoms to syncope, dyspnoea and sudden cardiac death (SCD). Estimating the risk of SCD and the indication for an implantable cardioverter-defibrillator (ICD) is an important part of the management of HCM patients. A clinical risk prediction model assessing the 5-year risk of SCD was presented in 2014 as a result of the HCM Risk-SCD study and is used in daily clinical practice. The model includes seven clinical predictors including left atrial diameter (LAd). LAd is however a one-dimensional estimate of a three-dimensional structure and recent echocardiographic guidelines therefore suggest biplane estimation of LA volume (LAv). Purpose: First, we aimed to determine the relation between LAd and LAv in HCM. Second, we aimed to assess what impact the use of LAd predicted from LAv instead of measured LAd has on the assessment of SCD risk. Methods: We prospectively collected clinical, echocardiographic and Holter data from patients with HCM. Patients with chronic atrial fibrillation were excluded. Antero-posterior LAd was measured in the parasternal long-axis window and LAv was estimated using biplane method of disks in the apical two- and fourchamber views. The ESC HCM-risk calculator was used to estimate the 5-year risk of SCD by measured LAd and by LAd predicted from LAv, respectively.