Abstract 2438: Radiofrequency Catheter Ablation of Septal Hypertrophy in Children With Hypertrophic Cardiomyopathy: Initial Experience.
Objectives: To describe the initial results and early follow-up data after radiofrequency catheter ablation (RFA) of septal hypertrophy in children with hypertrophic obstructive cardiomyopathy (HOCM).
Methods: 11 children (5 female; age range 5–17 years; weight range 17–52 kg) with symptomatic HOCM underwent RFA for septal reduction. After initial left ventricular angiography to delineate the anatomic extent of the obstruction, sequential AV pacing at varying AV delays was performed to determine whether the LVOT gradient could be influenced by pacing techniques. If this was not the case, RFA was performed. The His bundle was plotted and marked using the LocaLisa navigation system (Medtronic, Minneapolis). Using an 8F cooled tip catheter (Sprinklr, Medtronic) with an infusion rate of 300 ml/hour during RFA, ablation was commenced at the most apical extent of the hypertrophied septum. Three lines of contiguous RF lesions were made, extending upto just under the aortic valve. Care was taken to stay away from the His bundle during RFA. At putative ablation sites where His signals were recorded, the RF catheter was disengaged and an adjacent site without a definite His signal was sought. The number of RF lesions ranged between 10 and 50.
Results: The LVOT peak Doppler gradient changed from a median of 80 (50 –112) mm Hg pre-RFA to 30 (20 –50) mm Hg at 72 hours post-procedure. Cardiac troponin T (5.1– 8.6 micrograms/L; baseline value <0.1) and CK-MB (45–397 units/L; baseline value <20) were significantly elevated at 24 hours post-ablation, confirming myocardial necrosis. All patients had abolition of symptoms at 6 weeks’ follow-up. Recurrence of obstruction, or incomplete relief of obstruction was seen in 3 patients, within 6 months of RFA; 1 underwent re-do RFA with success; 1 patient opted for surgery which was successfully undertaken, and in 1 patient (who remains symptom-free, but has echo-Doppler gradient of >50 mm Hg) no decision has been made concerning further therapy.
Conclusions: RFA for symptomatic HOCM produces acute relief of LVOT obstruction with resolution of symptoms. It avoids AV block, and can be repeated. Further studies, and longer-term follow-up will determine the place of this modality in the therapeutic algorithm for HOCM in childhood.