No increased extracellular volume fraction or conduction time after childhood septal myectomy

OBJECTIVES: The aim of this study was to assess the effect of surgical septal myectomy performed during early childhood for severe, drug-refractory hypertrophic cardiomyopathy with left ventricular outflow tract obstruction on the extent of septal myocardial extracellular volume fraction and the potential risk of developing atrioventricular cardiac conduction system disease. METHODS: In this retrospective study, data from 30 patients with a confirmed diagnosis of childhood-onset hypertrophic cardiomyopathy were reviewed including cardiovascular magnetic resonance (CMR) with myocardial T1 mapping and late gadolinium enhancement, histopathology of myocardial specimens, transthoracic echocardiography, electrocardiography, 24-h Holter and cardiopulmonary exercise testing. Eighteen patients without were compared to 12 patients with prior septal myectomy performed during childhood (non-operated versus myectomy patients). RESULTS: Late gadolinium enhancement on CMR as a correlate for focal myocardial fibrosis was found in 53% of patients, predominantly located in the septal region, with no difference between groups. As compared to non-operated patients, those after myectomy showed a similar amount of total and septal extracellular volume fraction, as calculated from pre- and post-contrast CMR T1 mapping, which is a correlate for diffuse interstitial myocardial fibrosis. PQ-intervals or the occurrence of higher degree conduction system disease were equal between the 2 groups. CONCLUSIONS: Data from CMR and electrocardiography suggest that surgical septal myectomy performed during early childhood for severe obstructive hypertrophic cardiomyopathy does not cause an increased septal extracellular volume fraction or delayed atrioventricular conduction time on long-term follow-up.