Inclusion Criteria:

• All patients 18 years or older that were evaluated at the Mayo Cardiomyopathy Clinic and underwent septal ablation between 1998 – 02/28/2019 at Mayo Clinic.
• Each patient met the following criteria to be considered for septal ablation:
  • severe, drug-refractory cardiovascular symptoms, which was defined New York Heart Association class III/IV dyspnea, Canadian Cardiac Society angina class III/IV, or disabling syncope; 
  • dynamic LVOT obstruction due to systolic anterior motion of the mitral valve, with an LVOT gradient ≥ 30 mm Hg at rest or ≥ 50 mm Hg with provocation (e.g., Valsalva strain, amyl nitrate inhalation, and postectopic beat analysis); 
  • ventricular septal thickness ≥ 15 mm; 
  • no significant intrinsic mitral valve disease; 
  • absence of need for concomitant cardiac surgical procedure (e.g., bypass grafting and valve replacement);
  • suitable coronary anatomy; and 
  • informed patient consent.
  • The choice of alcohol septal ablation or surgical myectomy was made through a shared decision-making process after discussion of the risks of benefits of each alternative.

Exclusion Criteria: 

• Patients who underwent septal ablation for purposes other than relieving severe dynamic LVOT obstruction (e.g., in preparation of transcatheter mitral valve replacement).