To evaluate the incidence of cytomegalovirus (CMV) infection in the early postoperative period following pediatric heart transplantation, and to explore the association between CMV infection and peripheral blood lymphocyte subsets.

A retrospective study analyzed 60 pediatric recipients who underwent heart transplantation between 2021 and 2024 in Fuwai Hospital, Chinese Academy of Medical Sciences. The recipients could be categorized into two groups depending on CMV-DNAemia occurred in the early postoperative period (within 180 days) following pediatric heart transplantation (CMV infection group, n=24; non- CMV infection group: n=36), and the differences of lymphocyte subsets (CD4⁺ T cells, CD8⁺ T cells, CD4⁺ /CD8⁺ ratio, CD19⁺ B cells, CD56⁺ NK cells) were compared at different time points (preoperation, postoperative 1, 3, 7, 14, 30, 90, 180 days). The recipients could be categorized into two groups depending on pretransplant serologic recipient CMV status (CMV-IgG positive group, n=47; CMV-IgG negative group, n=13), and the differences of CMV infection incidence were compared. For the comparison between groups, the Wilcoxon rank-sum test was used for non-normally distributed continuous data, and the chi-square test was used for categorical data. P<0.05 was considered statistically significant.

The incidence of postoperative CMV infection was 40.0% (24/60) in the early postoperative period following pediatric heart transplantation, and more common at 30-90 days. There were no statistically significant differences in preoperative general data (age, weight, height, BMI, disease type, degree of heart failure, immunosuppressive therapy, and length of stay) between infection and non-infection groups (χ²/Z=0.188, -0.417, -0.294, -0.936, -0.589, 1.405, 0.188, 0.262, and -1.238; all P>0.05). The CD4⁺ /CD8⁺ ratio in the CMV infection group was lower at 180 days after surgery (Z=-2.233), and the absolute value of CD56⁺ NK cells was higher (Z=-2.414, -2.535), and the differences were statistically significant (all P<0.05). The proportion of positive CMV DNAemia in the preoperative CMV-IgG positive group and the negative group was 17/47 and 7/13, respectively, and there was no statistically significant difference (χ²=1.326, P>0.05).

CMV infection is common in pediatric heart transplantation. A decrease in the CD4⁺ /CD8⁺ ratio in pediatric recipients with early CMV infection indicates the immunosuppression. Recipients with negative pre-transplant CMV-IgG antibody have a higher risk of CMV infection after surgery. Children who have undergone heart transplantation can have their lymphocyte subsets regularly monitored to assess their immune function and predict the risk of CMV infection.