SAN FRANCISCO – Monitoring plasma vascular endothelial growth factor A (VEGF-A) may help identify pediatric heart transplant patients who are at increased risk for poor outcomes, according to a study reported at the 2014 World Transplant Congress.
"Cardiac allograft vasculopathy [CAV] remains the leading cause of chronic allograft failure after heart transplantation. ... Therefore, it’s important for us to be able to anticipate the development of CAV and open up a therapeutic window," said Dr. Kevin P. Daly of Harvard Medical School and Boston Children’s Hospital.
Dr. Kevin Daly
"Our pilot data suggest that plasma VEGF-A levels below 90 pg/mL identify a low-risk patient population in whom a decreased frequency of coronary angiography can be considered. Future studies are needed to determine if using plasma VEGF-A levels to modify CAV screening frequency results in equivalent patient outcomes, with decreased resource utilization and improved quality of life," Dr. Daly commented at the congress, which was sponsored by the American Society of Transplant Surgeons.
As the vascular endothelium is the primary target of the immune response in CAV, the researchers hypothesized that VEGF-A likely contributes to an inflammatory cycle that leads to vascular damage and occlusion in the graft.
Participants in the single-center prospective cohort study were 44 consecutive children aged 2 years or older who were at least 18 months (median, 6 years) out from heart transplantation. They were scheduled for routine annual screening coronary angiography during 2009, and had no or mild CAV.
Moderate or severe CAV developed in 32% of patients who had VEGF-A values above the median value at baseline (90 pg/mL), compared with 5% of patients who had VEGF-A values below the median level (P = .02). Patients who developed this vasculopathy were more likely to die (38% vs. 0%), undergo retransplantation (38% vs. 0%), experience a myocardial infarction (12% vs. 0%), and be listed for retransplantation (12% vs. 0%).
"While this is a biomarker and we have shown it is associated with CAV, we have not shown that it is causal," Dr. Daly cautioned. Any treatment directed against VEGF would have to be conducted in the context of a clinical trial to assess its impact.
A subset of patients becomes nonadherent to therapy; a subset that is highly sensitized before transplant may have donor-specific antibody, Dr. Daly said. So "we don’t think we fully understand the inciting event, ... [but] VEGF-A has been shown before to be elevated in antibody-mediated rejection, so it’s not surprising to see this association."
"We didn’t have these data available clinically because it was all a research study, so we didn’t intervene on any of the patients in this cohort. But we have started to think about whether or not we could use VEGF-A levels at least in our ... patients who might not have arterial access, and it might be difficult to survey them for CAV. I think in order to really understand the appropriate way to use it, we would need a larger study," he remarked.
Dr. Daly disclosed that he had no conflicts of interest relevant to the study.