Prognostic Importance of Atrial Fibrillation in Kidney Transplant Recipients

Atrial fibrillation (AF) affects three to six million people in the United States, and nearly 30 million people worldwide. AF is associated with higher risk of mortality and adverse cardiovascular events including stroke. Among patients with end-stage renal disease (ESRD), the prevalence of AF is particularly high compared to the general population. In addition, the 1-year mortality risk of patients with ESRD with AF is two times higher than in those without AF.

Compared with dialysis, kidney transplantation is the treatment of choice for ESRD, improving survival and quality of life for the majority of patients with ESRD. Advances in immunosuppression and in surgical techniques have improved the short-term allograft survival in renal transplant patients; however, long-term allograft survival remains a concern. The incidence and potential consequences of AF may be affected by the improvement of renal function following transplantation; conversely, immunosuppressive agents, insulin resistance, and metabolic syndrome following transplantation may have an impact on those potential consequences.

Charat Thongprayoon, MD, and colleagues recently conducted a meta-analysis designed to summarize available data on (1) the prevalence of pre-existing AF and/or the incidence of post-transplantation AF; (2) outcomes of kidney transplant recipients with AF; and (3) the trends of the estimated incidence of AF after kidney transplantation over time. Results of the meta-analysis were reported online in the Journal of Clinical Medicine [doi:10.3390/jcm7100370].

The researchers performed a systematic literature search of MEDLINE (1946 to March 2018), EMBASE (1988 to March 2018), and the Cochrane Database of Systematic Reviews (database inception to March 2018) using a search strategy that combined the terms of “kidney” or “renal” AND “transplant” OR “transplantation” AND “atrial fibrillation.” Eligibility criteria for studies were clinical trials or observational studies (cohort, case-control, or cross-sectional), and reporting the prevalence of pre-existing AF or the incidence of AF after kidney transplantation or outcomes of kidney transplant recipients with AF. Eligible studies had to provide data on prevalence or incidence or effect estimates relative risks, odds ratios (OR), or hazard ratios (HR) with 95% confidence intervals (CI).

The search revealed 399 potentially eligible articles. Following exclusion of 382 articles based on the title and abstract not meeting inclusion criteria, 17 articles underwent full review. Of those, six were excluded due to lack of data on the outcome of interest and three were excluded due to study design, resulting in a final analysis of eight cohort studies representing 137,709 kidney transplant recipients.

The pooled estimated prevalence of pre-existing AF in patients undergoing kidney transplantation was 7.0% (95% CI, 5.6%-8.8%, I2=86%); the pooled estimated incidence of AF after kidney transplantation was 4.9% (95% CI, 1.7%-13.0%;, I2=99%). After limiting the data to new-onset AF after kidney transplantation, the pooled estimated incidence of new-onset AF was 4.2% (95% CI, 1.6%-10.6%, I2=94%).

Results of meta-regression analyses did not show significant correlations between year of study and either prevalence or pre-existing AF or AF following kidney transplantation.

Risk factors for AF after kidney transplantation included older recipient age, higher body mass index, and a history of coronary artery disease/acute myocardial infarction. The pooled OR of mortality among kidney transplant recipients with AF was 1.86 (three studies; 95% CI, 1.03-3.35; I2=98%). Among the population of kidney transplant recipients, AF was associated with death-censored loss of allograft (two studies; OR, 1.55; 95% CI, 1.02-2.35; I2=94%) and stroke (three studies; OR, 2.54; 95% CI, 1.11-5.78; I2=83%).

Limitations to the study cited by the researchers included (1) the presence of statistical heterogeneities, (2) relatively short follow-up periods in the studies analyzed, (3) the inability to determine whether outcomes would be improved with the use of anticoagulation (warfarin and other agents) in kidney transplant recipients, and (4) due to the observational design of the included studies, the meta-analysis could only reveal association rather than a causal-effect relationship between kidney transplantation and AF.

In conclusion, the researchers said, “In spite of progress in transplant medicine, incidence of AF following kidney transplants does not seem to decrease over time. When compared to those without AF, this meta-analysis shows that kidney transplant recipients with AF may carry higher risks of mortality, renal allograft loss, and stroke.”

Takeaway Points

  1. Among kidney transplant recipients, those with atrial fibrillation (AF) face a 1-year mortality risk that is twice as high than among those without AF.
  2. Researchers conducted a systematic review and meta-analysis to examine data on the prevalence of pre-existing AF and/or the incidence of AF after transplantation; outcomes of transplant recipients with AF; and trends in estimated incidence of AF post-transplantation.
  3. The risks of mortality, renal allograft loss, and stroke appear to be higher among kidney transplant recipients with AF compared with those without AF.