Is liver transplantation a risk factor for cardiovascular disease? A meta-analysis of observational studies

Up to two-thirds of patients develop metabolic syndrome within the first 5 years after orthotopic liver transplantation (OLT). However, data on overall cardiovascular (CV) morbidity and mortality among OLT recipients and particularly those who develop metabolic syndrome remain elusive. A literature search using MEDLINE, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and meeting abstracts (along with their bibliographies) was performed to identify studies. Data on ischemic CV events were extracted from each study and were used for pooled analyses. Overall pooled estimates and 95% confidence intervals (CIs) for the incidence of CV events and deaths were obtained with a random effects model. Twelve observational studies reporting CV outcomes for 4792 post-OLT recipients who were followed for 28,783 person-years were included. Pooled estimates showed that the 10-year risk of developing CV events among the post-OLT recipients was 13.6% (95% CI = 9%-8.1%). Pooled estimates from case-control studies showed that the post-OLT group had an approximately 64% greater risk of experiencing CV events than controls (standardized incidence ratio = 1.64, 95% CI = 1.18-2.20). Among OLT recipients, those with metabolic syndrome were approximately 4 times more likely to have a CV event [odds ratio (OR) = 4.01, 95% CI = 1.94-8.32] without any significant increase in all-cause mortality (OR = 1.15, 95% CI = 0.63-2.10). In conclusion, this systematic review suggests that OLT recipients and particularly those with metabolic syndrome have a high risk for CV events. However, the literature is limited and lacks high-quality studies. Future prospective studies are warranted to confirm these findings and determine whether aggressive risk-reduction strategies can attenuate the increased CV risk seen in this population.