High molecular weight kininogen deficiency: A patient who underwent cardiac surgery

A 66 year old male, referred for cardiac surgery, was found to have high mo lecular weight kininogen deficiency (activity <l%). Apart from activated pa rtial thromboplastin time (APTT) >300 s, tests of haemostasis were otherwis e normal (factors VIII, IX, XI, XII and prekallikrein). No inhibitor of coa gulation was found. The activated coagulation time (ACT) was 800 s pre-operatively and >1000 s after heparin. Heparin levels were measured directly by an anti-Xa chromoge nic assay, with values of between 2.9 and 3.2 u/ml during cardiopulmonary b ypass. Thrombin-antithrombin levels rose from 2.3*g/l before surgery to a p eak of 83.5*g/l at the end of cardiopulmonary bypass. Cross linked fibrin d -dimers (XDP) levels rose from 100 ng/ml before operation to 600 ng/ml afte r protamine administration. The patient had no excess bleeding and no throm botic complications from surgery. This patient shows that high molecular weight kininogen is not required for thrombin formation or fibrinolysis during cardiac surgery and illustrates the need to measure heparin directly in patients with such contact factor d eficiencies.