Background: We investigated the potential of conversion to sirolimus (SRL) as a primary immunosuppressant in attenuating cardiac allograft vasculopathy progression.
Methods and results: Twenty-nine cardiac transplant recipients were converted to SRL 3.8+/-3.4 years after transplantation with complete calcineurin inhibitor (CNI) withdrawal. Secondary immunosuppressants (azathioprine or mycophenolate) and steroids remained unchanged. Forty patients (controls) 4.8+/-4.0 years from transplantation were maintained on CNIs. Three-dimensional intravascular ultrasound studies were performed at baseline and 12.1+/-2.6 months later. Mean plaque (media and intima) volume (PV) and plaque index (PI) (PV/vessel volume percent) increased significantly in the CNI group (1.28+/-2.86 mm(3)/mm, P=0.004; and 6+/-8%, P=0.0001) but not in the SRL group (0.1+/-1.13 mm(3)/mm, P=0.63; and 0.1+/-8%, P=0.94). In patients enrolled within 2 years after transplantation, the increases in PV (0.06+/-1.06 versus 1.77+/-1.65 mm(3)/mm; P=0.0081) and PI (0+/-9% versus 10+/-8%; P=0.0145) were smaller in the SRL group (n=11) than in the CNI (n=12) group. In patients enrolled >/=2 years after transplantation, the increase in PI was less in the SRL group compared with the CNI group (0.1+/-6.5% versus 5+/-8%; P=0.033), but changes in PV did not differ significantly. Treatment with azathioprine or mycophenolate did not affect PV or PI in either the SRL group (PV: 0.22+/-0.66 versus 0.05+/-1.45 mm(3)/mm, P=0.46; PI: 1.5+/-6% versus -1.6+/-8.5%, P=0.29) or the CNI group (PV: 1.42+/-1.39 versus 1.06+/-2.28 mm(3)/mm, P=0.49; PI: 7.8+/-8.7% versus 4.8+/-7.3%, P=0.23).
Conclusions: Substituting CNI with SRL as primary immunosuppression attenuates cardiac allograft vasculopathy progression.