A young woman suffering from congenital hypertrophic obstructive cardiomyopathy (HOCM) received a transcoronary ablation of the septal hypertrophy (TASH) and an automated Cardioverter/Defibrillator (AICD) for the relief of progressive symptoms of heart failure. She developed an acute heart failure in the perioperative period and had to be put on veno-arterial extracorporeal membrane oxygenation. Following this the patient developed a nearly complete thrombosis of the left-sided cardiac chambers, despite successful laboratory anticoagulation.