We have investigated genetic and clinical factors associated with hyperdynamic state (HS) after heart surgery with extracorporeal circulation (ECC). We performed a prospective cohort study of consecutive patients who underwent elective heart surgery with ECC. HS was defined as hyperthermia (>38 degrees C), cardiac index (CI) >3.5 l/min/m(2) and systemic vascular resistance index (SVRI) <1600 dynes x s/cm(5) x m(2). The study included demographic variables, gene polymorphisms A/G of tumor necrosis factor-beta (TNFbeta+250), G/A-1082 of interleukin-10 (IL-10), polymorphism of interleukin-1 receptor antagonist (IL-1ra), comorbidity, type of surgery, serum levels of interleukin-6 (IL-6), and postoperative course. We used Pearson chi(2) or Fisher exact test, and Student t-test for univariate analysis, with forward stepwise logistic regression for multivariate adjustment. Eighty patients were studied, of whom 22 (27.5%) developed HS. The presence of allele G of TNFbeta+250 polymorphism was associated with an increased incidence of HS (68% vs. 37%; P=0.011). In the multivariate analysis, a longer duration of ECC, and the presence of the G allele, were associated with the development of HS. The G allele of TNFbeta+250 polymorphism, and prolonged extracorporeal circuit times, may favor the development of a hyperdynamic state after heart surgery with ECC.