Background: Advances in the diagnosis and treatment of congenital heart diseases (CHDs) have resulted in improved survival rates for CHD patients. Up to 90% of individuals with mild CHD and 40% with complex CHD now reach the age of 60. Previous studies have indicated an elevated risk of atherosclerotic cardiovascular disease (ASCVD) and associated risk factors, morbidity, and mortality in adults with congenital heart disease (ACHD). However, there were no comprehensive guidelines for the prevention and management of acquired cardiovascular diseases (CVDs) in ACHD populations until recently. Case presentation: A 55-year-old man with Eisenmenger syndrome and comorbidities (arterial hypertension, heart failure, dyslipidemia, hyperuricemia, and a history of pulmonary embolism (PE)) presented with progressive breathlessness. The electrocardiogram (ECG) revealed signs of right ventricle (RV) hypertrophy and overload, while echocardiography showed reduced RV function, RV overload, and severe pulmonary hypertension (PH) signs, and preserved left ventricle (LV) function. After ruling out a new PE episode, acute coronary syndrome (ACS) was diagnosed, and percutaneous intervention was performed within 24–48 h of admission. Conclusions: This case highlights the importance of increased awareness of acquired heart diseases in patients with pulmonary hypertension due to CHD.