Case report: septal radiofrequency ablation for sigmoid ventricular septum-related dynamic obstruction: with observations suggesting left bundle branch block as a potential therapeutic collaborator

Abstract Background Sigmoid ventricular septum (SVS) can cause dynamic left ventricular outflow tract obstruction (LVOTO) during stress. Radiofrequency ablation (RFA) has been used for septal reduction in hypertrophic obstructive cardiomyopathy, but its application in SVS is limited and the underlying mechanisms remain poorly understood. Results A 77-year-old woman with symptomatic dynamic LVOTO secondary to SVS underwent endocardial RFA after failing medical therapy. Dobutamine stress echocardiography (DSE) before ablation provoked severe obstruction (peak gradient 210 mmHg) with systolic anterior motion (SAM) of the mitral valve and a large systolic vortex on blood speckle imaging (BSI). After targeted RFA of the basal septum, the patient developed new-onset complete left bundle branch block (CLBBB). Repeat DSE demonstrated resolution of SAM and obstruction (peak gradient 14 mmHg), with BSI showing restoration of laminar flow. Strain analysis revealed reduced, delayed, and post-systolic contraction of the basal septum. At 3-month follow-up, the patient remained asymptomatic. Conclusions This case raises the hypothesis that CLBBB may have contributed synergistically to obstruction relief in RFA treatment for SVS-related dynamic LVOTO.