Delayed Reduction in the Left Ventricular Outflow Tract Gradient After Endocardial Radiofrequency Ablation for Septal Hypertrophy in a Patient With Hypertrophic Obstructive Cardiomyopathy: A Case Report.

We report a case of a 79-year-old female with hypertrophic obstructive cardiomyopathy (HOCM) who demonstrated a delayed reduction in the left ventricular outflow tract (LVOT) gradient following endocardial radiofrequency ablation of septal hypertrophy (ERASH). The patient presented with diffuse interventricular septal thickening and systolic anterior motion (SAM) of the anterior mitral valve leaflet, with a markedly reduced six-minute walking distance of less than 50 meters. To minimize procedural risks, ERASH was performed using the CARTO3 (Biosense Webster, Inc., Irvine, California, USA) and CARTOSOUND systems (Biosense Webster, Inc., Irvine, California, USA). Intraoperatively, SAM resolved and the LVOT gradient showed an immediate decline (93 mmHg to 43 mmHg). The patient experienced gradual improvement in functional status and remained asymptomatic post-procedure. Interestingly, four days post-procedure, follow-up transthoracic echocardiography (TTE) demonstrated a delayed, further reduction in the LVOT gradient. This case highlights the potential for delayed hemodynamic improvement following ERASH, potentially attributable to transient post-ablation myocardial edema, as evidenced by the increase in end-diastolic interventricular septum thickness detected by TTE. Further studies are needed to assess procedural factors such as ablation power settings, ablation lesion size, and age-related myocardial degeneration.