Transthoracic echocardiography guided percutaneous laser ablation of the interventricular septum: A successful sheep model for septal thickness reduction and one year follow-up.

Background: Hypertrophic cardiomyopathy (HCM) is a common genetic cardiovascular disease, causing breathlessness, chest pain, syncope and sudden death. One-year outcome of echo-guided transthoracic percutaneous laser ablation (TPLA) of the sheep interventricular septum was studied as a novel treatment to reduce the septal thickness. It may partially address the limitations of surgical myectomy and alcohol septal ablation in terms of trauma, safety, and efficacy.

Methods: Twelve healthy adult sheep were randomly categorized into two groups: with and without the laser application of TPLA of the interventricular septum (IVS) at the energy level of 5 W for 3 min. Echocardiography, electrocardiography (ECG), cardiac magnetic resonance (CMR), serological and pathological examinations were performed over a 12-month follow-up.

Results: After the laser ablation all animals survived with normal cardiac function; No severe complications or bundle branch block were noted. The septal thickness (3.11 ± 1.14 vs. 8.40 ± 0.45 mm, p < 0.05), regional movement of ablated IVS and longitudinal strain significantly decreased when comparing the experimental and control groups. The Troponin I level was significantly elevated after the operation, which validated immediate cardiac coagulation necrosis. On cardiac magnetic resonance (CMR) imaging, the ablated myocardium showed significant fibrosis evidenced by late gadolinium enhancement. Pathological results revealed damaged ultra-structure of the ablated myocardium and development of fibrosis.

Conclusions: TPLA is a safe and effective minimally invasive method to reduce IVS thickness in the long term, making it a potential alternative for HOCM treatment.