[Post-cardiac Surgery Pulmonary Hypertension Improved by High-flow Arteriovenous Shunts Closure]

High-flow arteriovenous fistulas (AVFs) in hemodialysis patients can cause significant hemodynamic stress by increasing venous return and right ventricular preload, sometimes leading to pulmonary hypertension (PH) and high-output heart failure. We report two hemodialysis patients who underwent cardiac surgery and unremitting exertional dyspnea and intradialytic hypotension despite improved leftheart function. In case 1, a 74-year-old man demonstrated an AVF flow of 2.91 l/min with a resistance index of 0.47. In case 2, a 74-year-old man had an AVF flow of 3.84 l/min and resistance index of 0.46. Both patients underwent surgical closure of the high-flow AVF. Following intervention, estimated pulmonary artery systolic pressure decreased from 55 to 25 mmHg in case 1 and from 35 to 25 mmHg in case 2. In both cases, patients became hemodynamically stable during dialysis sessions without need for vasopressors. These outcomes underscore that persistent PH after cardiac surgery in dialysis patients may be attributable to excessive AVF flow, which is a potentially manageable factor. Quantitative flow measurement (Qa) and the Qa/cardiac output ratio should be incorporated into routine evaluation, and timely intervention should be considered. Our experience highlights the clinical importance of recognizing high-flow access as a treatable cause of post-cardiac surgery PH.