Abstract Body (Do not enter title and authors here): Background
Subaortic membrane (SAM) is a fibromuscular ridge beneath the aortic valve that causes fixed left ventricular outflow tract (LVOT) obstruction. Surgical resection is the standard treatment for symptomatic patients or those with high gradients; however, recurrence occurs in up to 14% of adults within 5 years. While radiofrequency ablation (RFA) is well-established in arrhythmia management, its role in treating SAM has not been previously described.

Case Information
53-year-old man with HTN, BMI 51.7, and well-controlled OSA presented with worsening exertional dyspnea and fatigue in April 2024. He had prior surgical SAM resection in 2018, complicated by third-degree AV block requiring pacemaker implantation. Follow-up echocardiography revealed SAM recurrence with peak LVOT gradient of 52 mmHg. Given elevated surgical risk, a novel catheter-based RFA approach was pursued.

In July 2024, the patient underwent catheter-based RFA under general anesthesia. A ThermoCool SmartTouch SF catheter was advanced retroaortically across the aortic valve toward the subaortic ridge, guided by CARTO 3 with CartoSound. A semi-circular lesion set was delivered to the septum inferior to the membrane. Two steam pops occurred during ablation in this area.

Serial transthoracic echocardiograms at 3 and 8 months demonstrated sustained LVOT gradient reduction, from 52 mmHg pre-ablation to 49 mmHg and 38 mmHg, respectively. Left ventricular ejection fraction (EF) remained stable at 61%, with no new wall motion abnormalities or pericardial effusion. The patient reported marked improvement in symptoms and normalization of daily activity tolerance. No procedural complications or hospital readmissions occurred.

Decision-Making
Given the patient’s high surgical risk and recurrent symptoms, the multidisciplinary team determined that repeat sternotomy carried elevated morbidity. RFA offered a targeted, minimally invasive solution that leveraged electrophysiology tools and preserved structural integrity while maximizing safety.

Conclusions
This first-in-human case illustrates the feasibility of intracardiac RFA for recurrent SAM. The patient experienced sustained LVOT gradient reduction, preserved EF, and marked symptomatic improvement. This novel approach may offer a viable option for select patients with recurrent subaortic obstruction and prior sternotomy, warranting further investigation to define lesion durability, depth of tissue effect, and conduction system safety.