Posterior wall thickness is associated with outcomes after septal myectomy in childhood hypertrophic obstructive cardiomyopathy.

Abstract

The impact of high left ventricular posterior wall thickness (PWT) on outcomes after septal myectomy in young children and infants with hypertrophic obstructive cardiomyopathy (HOCM) is unknown. This study sought to correlate PWT z-score with mid-term outcomes following septal myectomy in such patients with HOCM. This cohort study included 80 consecutive children and infants who underwent septal myectomy for HOCM between January 2013 and December 2023. Postmyectomy outcomes were compared between patients with a high PWT z-score (group A) and those with a low PWT z-score (group B). The mean duration of follow-up among 97.4% (n = 75) of hospital survivors was 51.18 ± 31.83 months. Fifty children (62.5%) were diagnosed in infancy. The mean age at myectomy was 5.73 ± 3.87 years. Freedom from death or transplantation was 98.5% at 1 year, 96.4% at 3 years, and 88.4% at 5 years. The rate of composite events was significantly higher in group A compared to group B (35% [n = 7/20] vs 7.1% [n = 4/56]; P = .008). Six of 7 late deaths were classified as sudden cardiac death (SCD). In-hospital mortality was associated with age at procedure <2 years (hazard ratio [HR], 0.953; 95% confidence interval [CI], 1.087-14.370; P = .037), PWT z-score ≥9 (HR, 4.600; 95% CI, 1.231-17.195; P = .023) and biventricular obstruction (HR, 4.880; 95% CI, 1.325-17.978; P = .017). SCD was associated with PWT z-score ≥9 (HR, 8.800; 95% CI, 1.377-56.247; P = .022). Midterm survival after surgery in children with HOCM is lower than that in adult patients. A higher PWT z-score is a novel risk factor for worse postmyectomy outcomes. The most common cause of death in these patients is SCD.