A 60-year-old man is admitted to ICU with fever, confusion, and a new heart murmur. Transthoracic echocardiography shows a 15 mm vegetation on the mitral valve with severe mitral regurgitation. Blood cultures grow Staphylococcus aureus (MSSA). He is started on IV flucloxacillin. According to ESC/BSE guidelines, which of the following is an indication for urgent surgical intervention in infective endocarditis?