EFFECT OF WARFARIN ON REGIONAL LEFT ATRIAL COAGULATION ACTIVITY IN MITRAL-STENOSIS

Increased regional left atrial (LA) coagulation activity has recently been implicated in the pathophysiology of LA thrombus and systemic emb olism in mitral stenosis (MS). Anticoagulation with warfarin reduces t he risk of such thromboembolism, but the effect of warfarin on LA coag ulation activity is unknown. We have addressed this question in MS pat ients with normal or prolonged clotting times. Peripheral venous and L A coagulation activities were measured in MS patients on long-term ora l anticoagulation, who were predisposed tb increased LA coagulation ac tivity because of the presence of LA spontaneous echo contrast. Patien ts ceased warfarin 4 days before percutaneous balloon mitral valvulopl asty, and had either a normal (n = 15) or prolonged (n = 8) Internatio nal Normalized Ratio (INR) at valvuloplasty. Coagulation activity was assessed during the valvuloplasty procedure, but before valve dilation , by measuring levels of prothrombin fragment 1 + 2 (F1 + 2), a marker of thrombin generation. The LA F1 + 2 level exceeded the peripheral v enous level in patients with a normal INR (p < 0.001), but these level s were similar in patients with a prolonged INR (p = 0.16). Moreover, the LA (p < 0.005) and peripheral venous (p < 0.03) F1 + 2 levels, as well as the LA-peripheral venous F1 + 2 difference (p < 0.03) were low er in patients with a prolonged INR. These results suggest that antico agulation with warfarin in MS not only reduces systemic coagulation ac tivity but is associated with a greater reduction in LA coagulation ac tivity. The latter may contribute to the reduced risk of LA thrombus f ormation that accompanies warfarin therapy in MS. (C) 1997 by Excerpta Medica, Inc.