Different patterns of heparin resistance: Therapeutic implications

Heparin resistance (HR) during cardiac operations is a common feature. Its aetiology often recognizes a decrease in circulating antithrombin III (AT III) due to a preoperative heparin treatment. Nevertheless, some papers high-lighted the existence of HR in patients with normal values of AT III. This paper was designed in order to identify this subgroup of AT III-independent heparin-resistant patients. Five hundred consecutive patients scheduled for coronary revascularization with cardiopulmonary bypass were enrolled in this prospective trial. HR was identified in 104 (20.8%) patients. Thirty-six of them (7.2% of the total population) had a preoperative AT III activity ≥100%, and were defined as AT III-independent heparin-resistant patients. This subgroup significantly differs from the AT III-dependent heparin-resistant group being affected by a less severe degree of HR and including less patients pretreated with heparin. Unlike the other heparin-resistant patients, these subjects do not respond to AT III supplementation aimed at reaching supranormal AT III activity values.