A new topical hemostatic agent composed of a specifically-formulated porous collagen matrix, coated on one side with a thin protein bonding layer (known as NHS-PEG) has been reported to be extremely effective, in addition to traditional means, in terminating bleeding during cardiac operations with control rates as high as 97,5%. The investigators compared such hemostatic agent (Hemopatch; Baxter Inc, Deerfield, IL) with traditional optimized hemostasis routine.