Q. An 18-year-old female presents to your clinic with a fever, erythematous rash, joint pain and swelling in multiple joints. The patient describes a history of a sore throat that began 2 weeks ago. She also reports having had a similar episode of sore throat and joint pain 4 years ago, which was diagnosed as rheumatic fever. On physical examination, the patient has a fever of 39.5 degrees Celsius (103 degrees Fahrenheit), a diffuse erythematous rash, and joint pain and swelling in her knees, wrists, and ankles. Cardiac assessment reveals a pericardial friction rub and an enlarged, tender precordium. You order an electrocardiogram (see image), and bloodwork. The patient's laboratory workup reveals an elevated erythrocyte sedimentation rate and C-reactive protein, as well as a positive antistreptolysin O titer. You choose to treat her with high-dose aspirin, oral corticosteroids, and antibiotics to eradicate the underlying streptococcal infection. You also refer her to a rheumatologist for long-term management of her condition. The patient is counseled on the importance of preventative measures, such as prompt treatment of a sore throat with antibiotics and regular follow-up appointments to monitor for any recurrence of her symptoms. Based on the patient’s diagnosis, which of the following is she at the greatest risk of developing?