Abstract 4147433: Left Ventricular Outflow Tract Gradient and Left Atrial Strain Predict Cardiac Outcomes in Young Hypertrophic Cardiomyopathy Patients

Background: In adults with hypertrophic cardiomyopathy (HCM), left ventricular outflow tract (LVOT) obstruction and reduced left atrial strain (LAS) predict heart failure and cardiac event risk. However, data in children are limited. Hypothesis: LVOT gradient and LAS together determine cardiac outcome risk in children and young adults with HCM. Methods: All HCM patients with exercise stress echocardiography (ESE) from 2014-2022 at a single center were included. Patients were stratified by LVOT gradients: Group 1 (n=44, rest/exercise gradients < 30mmHg); Group 2 (n=41, rest < 30mmHg; exercise ≥ 30mmHg); Group 3 (n=29, rest/exercise ≥ 30mmHg). Composite cardiac outcome included cardiac syncope, non-sustained/sustained ventricular tachycardia, cardiac arrest, NYHA heart failure class ≥ II, heart transplantation, and HCM-related death. LA reservoir (LASr) and conduit (LAScd) strain were analyzed with TOMTEC AutoStrain LA. Cumulative incidence of composite outcome by LVOT group was estimated by Kaplan-Meier method. Multivariable Cox regression was used to evaluate the effect of adding LAS to a model containing only LVOT group. Model discrimination was assessed using the concordance (c) index. Results: 114 patients (32%F, median age 17 years) formed the cohort. At median 2.1 years follow-up [IQR: 1.0, 3.4] composite cardiac outcome risk was higher in Group 3 vs. 2 (HR=4.97, p=0.013, Figure 1). Composite cardiac outcome risk was lower in Group 1 vs. 2, but not significant (HR=0.70, p=0.66). Adjusting for LVOT group, lower LASr and LAScd were associated with greater cardiac outcome risk (per 5% LAS decrease: LASr HR=1.56, p=0.008; LAScd HR=1.77, p=0.002, Table 1). C index increased with inclusion of LASr or LAScd in the model (Table 1). Conclusion: In one of the largest young HCM cohorts evaluated with ESE, cardiac outcome risk increased with resting LVOT obstruction and reduced LA strain. LA strain demonstrated additive value for prediction of cardiac outcomes in children.