Abstract 16461: Are Inducible Exercise Left Ventricular Outflow Tract Gradients Associated With Adverse Outcomes in Pediatric Hypertrophic Cardiomyopathy?

Abstract

Introduction: Adverse outcomes in hypertrophic cardiomyopathy (HCM) includes arrhythmias, myocardial fibrosis, heart failure, and sudden cardiac arrest (SCA). These are well documented in children. Exercise stress echocardiography (ESE) can identify the severity and mechanism of left ventricular outflow tract (LVOT) obstruction that may not be present at rest. Our aim was to compare clinical outcomes in pediatric patients with varying severity of LVOT obstruction. Methods: We reviewed records of patients < 22 years with HCM who underwent staged ESE Jan 2009 - Dec 2019 at our center. Patients were divided into 3 groups: no resting or exercise LVOT gradient (Group 1), no resting gradient with LVOT gradient > 30 mmHg at peak exercise (Group 2), and resting LVOT gradient > 30 mmHg (Group 3). We assessed echocardiographic indices, advanced imaging, and clinical data. Statistical analysis performed with p-value <0.05. Results: 93 patients met inclusion criteria. 6 SCA events occurred, though not during ESE.. Patients in Group 3 were classified less often as NYHA Class 1 compared to Group 1 or Group 2, (p < 0.01). Group 3 had the highest rate of myectomy (p=0.005) and ICD placement (p=0.003). There was no significant difference in exercise symptoms, peak oxygen consumption, or ischemic changes during ESE between the groups. Peak heart rate was also higher in Group 2 with no difference in blood pressure response. Groups were not associated with family history of disease, positive gene status, SCA, or the presence of fibrosis (Table). LVOT gradients differed as early as Stage 1 in Groups 1 & 2. Inducible LVOT obstruction was most commonly midcavitary in Group 2. Conclusion: The presence of resting versus inducible LVOT obstruction in pediatric HCM does not appear associated with adverse outcomes. This may be hampered by the rarity of events in pediatrics. The predominant mechanism of inducible LVOT obstruction was midcavitary, which has a link to adverse long-term outcomes in adult HCM.