Value of Pulse Wave Velocity

Cardiovascular disease is a major cause of death in patients with a kidney transplant. This should be no surprise as many of these patients get transplanted with a significant history of traditional as well as non-traditional risk factors related to CKD or wait-time on dialysis.  I encourage all my patients to exercise and stay active in the first year after transplant, but don’t know exactly how much or what type of exercise is required to provide an unclear amount of cardiovascular benefit.

In ESRD patients, aerobic training has been shown to reduce the pulse wave velocity (PWV), which is a non-invasive measure of arterial stiffness that has been positively correlated with mortality in kidney transplant recipients.  Several small studies have found that aerobic training or aerobic plus resistance exercise training improves cardiorespiratory fitness, quality of life, and hand strength, but none have evaluated the impact on cardiovascular measures. However, a new study in AJKD by Greenwood et al measured the effect of three exercise programs on pulse wave velocity, cardiorespiratory fitness, and serum inflammatory markers. This trial randomized 60 adult kidney transplant recipients within the first year of transplant to one of three arms: an individualized aerobic training program, a resistance-training program, or usual care. The intervention groups were both required to attend twice-weekly outpatient exercise and education sessions, and to also undergo a home-based exercise session once a week for a total of 12 weeks.  The study measured PWV, VO2peak and serum inflammatory markers before and after the 12-week period.

Compared to usual care, the mean difference in PWV was significantly lower at 12 weeks in patients who completed either the aerobic training or resistance training (both with P<0.001).  Both exercise interventions were also associated with significant improvements in the relative and absolute VO2peak. There were no significant differences in inflammatory markers between the three groups. Overall, this suggests that a supervised exercise program using either aerobic or resistance training improves cardiorespiratory fitness and reduces arterial stiffness. One caveat to this conclusion is that both exercise intervention groups had 7 participants (35% of each arm) who were lost to follow up because they needed to return to work and presumably could not attend the outpatient sessions. This suggests that the exercise program required to meet these outcomes may be too cumbersome for patients who are further from surgery and returning to work. The analysis only included patients who completed the trial, and exclusion of the dropouts may have biased the results. Despite the small sample sizes in this pilot study, it seems that in the short term, adhering to a rigorous exercise program reduces the PWV and improves fitness in kidney transplant recipients. It is unknown if the PWV returned to baseline in those patients who stop exercising. An intense 12-week regimen seems to be beneficial, but we should also think about exercise interventions that are sustainable for the long-term as well.

John K. Roberts, MD, MS
Duke University Medical Center

To view the article abstract or full-text (subscription required), please visit AJKD.org.

 

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