Association of LVOT Gradient and LA Strain with Cardiac Events in Pediatric HCM

In adults with hypertrophic cardiomyopathy (HCM), left ventricular outflow tract (LVOT) obstruction on exercise stress echocardiography (ESE) and reduced left atrial (LA) strain increase heart failure and cardiac outcome risk. However, limited pediatric data exist. We evaluated the association of exercise-induced LVOT obstruction and LA strain with cardiac events in young HCM patients. Patients who underwent ESE (n = 114, 32%F, median = 17 yrs) from 2014-2022 at a single center 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). LA reservoir (LASr), conduit (LAScd), and contractile strain were analyzed with TOMTEC AutoStrain LA. Composite cardiac event included: heart failure, non-sustained/sustained ventricular tachycardia, cardiac syncope, heart transplantation, and HCM-related death. At follow-up (median = 2.0 years), there was a greater hazard of the composite event in Group 3 vs. 2 (hazard-ratio [HR] = 4.97, p = 0.013). Severe events were rare and largely observed in Group 3. Increased HR was seen in Group 2 vs. 1 but the difference was not significant. Adjusting for LVOT gradient (Group 3), lower LASr or LAScd or increased LA stiffness (E/e' to LASr ratio) were associated with composite event (HR LASr = 1.57; LAScd = 1.70; LA stiffness = 1.31; all p < 0.01). Concordance indices were similar for these three strain/stiffness models (0.81-0.82) and higher than in models including LVOT group with traditional diastolic indices (LA volume index or E/e'; c-index = 0.76). In one of the largest pediatric HCM cohorts undergoing ESE, reduced LA strain demonstrated greater incremental value to LVOT gradient than traditional diastolic indices when evaluating association with cardiac events.