In contract with the previous observations, some studies go against the idea that PSA or other kallikreins play an active role in the pathophysiology of AF: infusion of the general kallikrein/serine protease inhibitor aprotinin was not associated with a significant reduction in post-operative AF in patients undergoing cardiothoracic surgery (Gillespie, 2005). The gene discussed is KLK4; the disease is atrial fibrillation.