Uric acid: a prognostic marker not only before but also after heart transplantation

Early diagnosis of rejection after heart transplantation is mandatory, since even mild rejection can rapidly progress to more severe rejection. However, the identification of patients at high risk of acute cellular rejection and their non-invasive diagnosis remains a challenge. To identify patients with a high risk of acute cellular rejection during the first post-transplantation year.

A retrospective study of 114 consecutive patients submitted to first heart transplantation (between November 2003 and January 2008). The International Society for Heart and Lung Transplantation (ISHLT) grading system was used for the classification of endomyocardial biopsies. Patients were divided into two groups: group A (non-rejecting)--90 patients who had no significant rejection episodes (ISHLT grade <2R); and group B (rejecting)--included 24 patients with moderate or severe rejection episodes (grade > or =2R) during a 1-year post-transplantation follow-up. The Kaplan-Meier method was used for cumulative survival analysis with the Breslow test for assessing statistical differences between curves.

The group B patients tended to have more ischaemic aetiology (42% vs 26%, p=0.13) and lower baseline triglycerides (99.1+/-34.2 vs 117.9+/-63.6 mg dl(-1), p=0.17), tended to receive less cardiac allografts from donors of the same ABO blood type (83% vs 92%, p=0.25) and to have longer cardiopulmonary bypass times (108+/-64 min vs 94+/-26 min, p=0.12). Significantly, they had more hyperuricaemia (71% vs 43%, p=0.02) and longer mechanical ventilation times (19.2+/-17.9h vs 14.3+/-5.3h, p=0.031). During follow-up, the group B patients tended to have more severe infections (46% vs 31%, p=0.16), to be more frequently Quilty-positive (50% vs 30%, p=0.073) and to have a higher 1-year mortality (8% vs 2%, p=0.18). Uric acid levels higher than 7.2 mg dl(-1) were identified as the optimal cut-off value to predict acute rejection after heart transplantation (with a sensitivity of 71%, a specificity of 62% and an area under the curve of 0.64).

Our work suggests that hyperuricaemia may be a marker of acute cellular rejection that could be another tool helping to identify acute rejection during the follow-up of cardiac-transplanted patients.