A 32-year-old man comes to the physician for a 4-day history of worsening shortness of breath. At the age of 3 years, he underwent successful repair of a ventricular septal defect. He is a non-smoker. Pulse is irregularly irregular. Physical examination shows perioral cyanosis and mild peripheral edema at the ankles. Lungs are clear to auscultation. A 3/6 pan-systolic murmur is auscultated at the left sternal border. Which of the following is the most likely explanation for these findings?
Decreased pulmonary arterial blood flow
Decreased pulmonary arterial resistance
Decreased systemic vascular resistance
Increased pulmonary arterial blood flow
Increased pulmonary arterial resistance
Increased systemic vascular resistance
