Recipients of older-donor kidneys had significantly worse stiffness a year after transplantation
Transplantation of kidneys from older donors is followed by increased stiffening of the recipient’s aorta, which may help to explain the higher rates of CVD and death in patients receiving kidneys from expanded criteria donors, according to French researchers.
The investigators, who published their findings in Journal of the American Society of Nephrology (2008; published online ahead of print), used a technique called carotid-femoral pulse wave velocity to measure aortic stiffness in 74 patients who had received kidney transplants from deceased donors.
Twenty-four patients were younger than 41 years (mean age 28.3 years), 27 were aged 41-53 years (mean 48.1 years), and 23 were older than 53 years (mean 59.6 years). Fifteen donors (20.3%) met the ECD criteria (donor age 60 years and older or 50-59 years old with at least two of the following conditions: cerebrovascular cause of death, history of hypertension, and serum creatinine level greater than 130 µmol/L).
When first measured three months after transplantation, aortic stiffness was related exclusively to characteristics of the transplant recipient. The aorta was stiffer in transplant recipients who were male, older, and had higher BP. When the measurement was repeated after 12 months, aortic stiffness had signif-icantly worsened in patients who received kidneys from the older donors (53-70 years old).
“We found that donor age emerged as a strong and independent determinant of recipient aortic stiffness one year post-transplantation,” said lead investigator Michel Delahousse, MD, head of nephrology and the transplant unit at Foch Hospital in Paris. In contrast, for patients receiving kidneys from younger donors, aortic stiffness decreased.
For recipients of older-donor kidneys, pulse wave velocity was increased by one meter per second. “This is a very significant finding,” Dr. Delahousse said. “Indeed, such an increase was previously associated with a 39% increase in overall risk of death in end-stage renal disease patients.”
Study results could be a significant step toward targeted interventions after kidney transplantation, with the goal of reducing cardiovascular risk and cardiovascular mortality and improving long-term results, Dr. Delahousse said. Patients with worsening arterial disease earlier after transplantation could benefit from drug treatments to reduce arterial stiffness if they are identified more quickly. Prospective studies are needed to further investigate this.
Dr. Delahousse said these new study findings also provide an intriguing new piece of evidence regarding the interrelationships between kidneys and cardiovascular system. “Our study provides the first strong cause-and-effect evidence of the impact of kidney characteristics upon the mechanical properties of large arteries,” Dr. Delahousse said. “The results suggest that the kidney could be involved, normally or otherwise, in the process of arterial stiffening that is the hallmark of aging of the large arteries.”
The results do not challenge the increasingly common practice of transplantation from expanded criteria donors (ECD). These donors have certain characteristics, such as older age, high BP, or slightly de-creased kidney function that make them less than ideal as organ donors, but ECD transplantation still confers a significant survival advantage compared with remaining on dialysis and waiting for a standard kidney.
He and his colleagues acknowledge some limitations of their study, including its small size and a potential but “reasonably low” risk of selection bias.
“We were surprised that the impact of donor age remained after adjustment for allograft function,” Dr. Delahousse told Renal & Urology News.
“This suggests that some other age-related metabolic or endocrine function of the kidney could affect in some way the process of vascular aging. The simple use of pulse wave velocity could help to identify recipients with an increasing arterial stiffness and higher risk for cardiovascular disease.”