A 56-year-old woman is evaluated during an appointment to establish care. She has a developmental delay, and she is known to have pulmonary hypertension due to a congenital cardiac condition. There is no history of cardiac surgery. She is on low-dose aspirin and thyroid replacement therapy.
On physical examination, blood pressure is 110/70 mm Hg, pulse rate is 68/min and regular, and respiration rate is 18/min. BMI is 32. The central venous pressure is elevated with a prominent a wave. The apical impulse is normal. There is a prominent parasternal impulse at the left sternal border. The S1 is normal; the S2 is loud. There is a grade 1/6 holosystolic murmur at the left lower sternal border. The toes demonstrate cyanosis and digital clubbing; her hands appear normal. The remainder of the physical examination is unremarkable.
Which of the following is the most likely cause of this patient's pulmonary hypertension?