A 24-year-old female graduate student repos increasing shoness of breath with exercise and has recently noticed dyspnea on mild activity. One day before presenting at the office, she experienced sudden loss of consciousness while shopping at a grocery store. On physical examination, vital signs are: pulse 88 bpm; temperature 97.8degF; respirations 18/min; blood pressure 100/70 mm Hg. BMI is 34. ABGs on RA: pH 7.43; PCO2 36 mm Hg; PO2 87 mm Hg. Chest x-rays are shown in.The clinical and chest radiographic diagnosis may be commonly associated with