Cardiorespiratory Optimisation By Arteriovenous fistula Ligation after renal Transplantation (COBALT): study protocol for a multicentre randomised interventional feasibility trial

Veena Surendrakumar, Emma Aitken, Patrick B. Mark, Reza Motallebzadeh, James Hunter, Aimen Amer, Dominic Summers, Kirsten Rennie, Leila Rooshenas, Madalina Garbi, Karl Sylvester, Cara Hudson, Jennifer Banks, Anna Sidders, Andrew Norton, Matthew Slater, Matthew Bartlett, Simon Knight, Gavin Pettigrew*

*Corresponding author for this work

Research output: Contribution to journalProtocol


INTRODUCTION: Cardiovascular events are a major cause of mortality following successful kidney transplantation.Arteriovenous fistulas (AVFs) are considered the best option for haemodialysis, but may contribute to this excess mortality because they promote adverse cardiac remodelling and ventricular hypertrophy. This raises the question whether recipients with a well-functioning kidney transplant should undergo elective AVF ligation.

METHODS AND ANALYSIS: The COBALT feasibility study is a multicentre interventional randomised controlled trial (RCT) that will randomise renal transplant patients with stable graft function and a working AVF on a 1:1 basis to standard care (continued conservative management) or to AVF ligation. All patients will perform cardiopulmonary exercise testing (CPET) on recruitment and 6 months later. Daily functioning and quality of life will be additionally assessed by questionnaire completion and objective measure of physical activity. The primary outcome-the proportion of approached patients who complete the study (incorporating rates of consent, receipt of allocated intervention and completion of both CPETs without withdrawal)-will determine progression to a full-scale RCT. Design of the proposed RCT will be informed by an embedded qualitative assessment of participant and healthcare professional involvement.

ETHICS AND DISSEMINATION: This study has been approved by the East Midlands-Derby Research Ethics Committee (22/EM/0002) and the Health Research Authority. The results of this work will be disseminated academically through presentation at national and international renal meetings and via open access, peer-reviewed outputs. Existing networks of renal patient groups will also be used to disseminate the study findings to other key stakeholders.


Original languageEnglish
Article numbere067668
JournalBMJ Open
Issue number2
Publication statusPublished - 9 Feb 2023

Bibliographical note

Funding Information:
This work was supported by National Institute for Health Research (NIHR) Research for Patient Benefit Funding grant (NIHR202255) with further support from the Addenbrooke’s Kidney Patient Association and Cambridge University Hospitals NHS Foundation Trust. KLR is supported by the National Institute of Health Research (NIHR) Biomedical Research Centre in Cambridge (IS-BRC-1215-20014).

Publisher Copyright:
© 2023 BMJ Publishing Group. All rights reserved.


  • Humans
  • Kidney Transplantation
  • Feasibility Studies
  • Kidney
  • Renal Dialysis
  • Arteriovenous Fistula
  • Randomized Controlled Trials as Topic
  • Multicenter Studies as Topic


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