Percutaneous transluminal septal myocardial ablation: past, present, and future.

About 30% of patients with hypertrophic cardiomyopathy have a significant left ventricular pressure gradient at rest, and 60%-70% of these patients are diagnosed with hypertrophic obstructive cardiomyopathy (HOCM) because an induced pressure gradient is also present. Percutaneous transluminal septal myocardial ablation (PTSMA) is a procedure in which ethanol is used to ablate the portion of the septal myocardium that is involved in the pathogenesis of the left ventricular outflow tract pressure gradient (LVOT PG). In 1995, Sigwart et al. reported three cases of PTSMA in The Lancet. The introduction of PTSMA into clinical practice has enabled the reduction of LVOT PG and improvement of heart failure symptoms in elderly and high-risk patients with symptomatic, drug-refractory HOCM. In 1998, Faber et al. published a report in Circulation on selective septal myocardial ablation using myocardial contrast echocardiography (MCE). MCE-guided PTSMA is now recognized as the standard method of PTSMA in many countries and regions, including Europe, North America, and Asia, and is estimated to be performed on about 300 to 400 patients per year in Japan based on reports from the Japanese Circulation Society's Clinical Practice Survey. The current problems with this technique are: 1) the outcome is greatly influenced by operators' and institutional experience, and 2) it is difficult to determine in advance whether the patient is a PTSMA responder or not. Recently, advancements in imaging modalities, including cardiac computed tomography and magnetic resonance imaging, have facilitated clarification of the mechanisms of LVOT obstruction. Therefore, more appropriate decisions regarding PTSMA and surgical myectomy (SM) are now made. Better treatment selection will undoubtedly improve the prognosis of patients with drug-refractory HOCM complicated by heart failure, and further elucidation of the pathogenesis of LVOT obstruction and technical advances in PTSMA and SM are eagerly awaited.