We report here a 75-year-old male with hypertrophic obstructive cardiomyopathy of de novo sustained monomorphic ventricular tachycardia (VT) after successful percutaneous transluminal alcohol septal myocardial ablation (PTSMA). In this case history, the necrotic induced by the PTSMA procedure might represent a region of slow conduction that is a circuit of re-entry and therefore stimulation might be spread around. Therefore, the basis of the sustained monomorphic VT was thought to be the presence of a focal necrotic area, itself a complication arising from the PTSMA procedures. In conclusion, the PTSMA procedure may have caused a de novo episode of ventricular arrhythmia.