CTS Collaborative Transplant Study
Dear Colleagues,
Blood pressure management is a fundamental aspect of post-transplant care in kidney transplantation. Therefore, since the establishment of the CTS, analyses of the impact of hypertension (HT) on graft and patient outcomes have been a central focus of our reports, based on the data generously contributed by hundreds of transplant centers worldwide. The paper by Opelz G, Wujciak T, and Ritz E, titled "Association of chronic kidney graft failure with recipient blood pressure", published in Kidney International in 1998, was a landmark study that highlighted the critical relationship between blood pressure and long-term outcomes of kidney transplantation. In 1998, hypertension was defined as a blood pressure of ≥140/90 mmHg according to the Joint National Committee (JNC) and others. In 2017, the American College of Cardiology (ACC) and the American Heart Association (AHA) lowered the threshold for the definition of hypertension to 130/80 mmHg. The 2017 ACC/AHA guidelines introduced the following categories for blood pressure:
In a very recent study, we analyzed the impact of the new classification of blood pressure in the cohort of kidney transplant patients. The results were published in late 2024 by the authors Speer C, Benning L, Morath C, Zeier M, Frey N, Opelz G, Döhler B, and Tran TH for the Collaborative Transplant Study in Kidney International Reports (Kidney Int Rep, https://doi.org/10.1016/j.ekir.2024.12.004). In this newsletter, we aim to highlight the key findings of this publication and examine them from a slightly different perspective. For better visualization, selected results are presented here using Kaplan-Meier curves. For detailed analyses, including multivariable Cox regression and hazard ratios with 95% confidence intervals, please refer to Kidney Int Rep.
The analyses were based on data from more than 60,000 kidney transplants performed from 2000 to 2021 in adult patients for whom 1-year blood pressure values were available. Figure 1 shows the distribution of hypertension categories in the study population according to the ACC/AHA guidelines. This means that, according to the 2017 ACC/AHA criteria, more than three-quarters (77.4 %) of all kidney transplant patients had inadequately controlled blood pressure at year 1 post-transplant – a quite remarkable finding.
How does blood pressure affect graft outcome?
Figure 2 highlights the relatively small, yet statistically significant impact of hypertension stage 1 on 10-year death-censored graft survival. It also demonstrates that there is no significant difference between the categories “Elevated” and “Normal” so that we combined these two groups to one category of “No Hypertension” (<130/80 mmHg) for further analyses.
Are there specific subgroups of transplant patients particularly at risk for hypertension?
Figure 3 illustrates that hypertension had a stronger impact on female recipients compared to male recipients. Cox regression analysis demonstrated that even at hypertension stage 1, there was a 20 % higher risk of graft failure for female patients (hazard ratio [HR] = 1.20, P = 0.007). A similarly elevated risk at hypertension stage 1 was observed in retransplants (HR = 1.21, P = 0.069), sensitized patients (HR = 1.26, P = 0.018), and living donor transplants (HR = 1.22, P = 0.020; Kidney Int Rep, Table 2).
Can the negative impact of hypertension be reversed by improving blood pressure control?
To answer this question, we used blood pressure values recorded at year 1 and year 2 post-transplant to analyze 10-year follow-up data. Here, we summarized the results for nine combinations of blood pressure categories: no hypertension, hypertension stage 1, and hypertension stage 2, each at post-transplant years 1 and 2. Since no significant differences in 10-year death-censored graft survival were observed between “no hypertension” and “hypertension stage 1”, these two groups were combined as “no hypertension stage 2” (–HT2) and compared to “with hypertension stage 2” (+HT2) in the Kaplan-Meier analysis of Figure 4.
Figure 4 provides the following conclusions:
We sincerely thank all centers that have contributed data over decades, making this study possible. We hope that the results of our analyses will contribute to optimizing hypertension management in kidney transplant recipients, ultimately improving their long-term graft outcomes.
The next shipping date of
Serum and DNA Studies is
April 18, 2025.
Thank you for your continued support and best wishes,
Hien Tran
| For the CTS Executive Board and CTS Team in Heidelberg | |||
| Axel Roers | Klemens Budde | Martin Zeier | Hien Tran |