High-risk features include A family history of premature sudden cardiac arrest Left ventricular wall thickness > 3 cm Delayed enhancement on cardiac MRI Unexplained syncope Survival after a cardiac arrest due to ventricular arrhythmia Multiple burst of nonsustained ventricular tachycardia (NSVT) Left ventricular ejection fraction (LVEF) < 50% (end-stage disease) Left ventricular aneurysm Myomectomy and alcohol ablation have been used to decrease outflow obstruction and relive symptoms.