Long-term cardiovascular adverse events in liver transplant recipients with over 10 years of survival: incidence, temporal pattern and preoperative risk factors

Technical Summary: Long-term Cardiovascular Adverse Events in Liver Transplant Recipients with Over 10 Years of Survival

Problem Statement
While liver transplantation has achieved remarkable success in short-term patient and graft survival, long-term outcomes are increasingly compromised by non-graft-related causes of mortality, particularly cardiovascular diseases (CVD). Existing literature predominantly focuses on cardiovascular events occurring within the first five years post-transplantation. There is a significant gap in understanding the incidence, temporal distribution, and predictive risk factors for Major Adverse Cardiovascular Events (MACE) in "ultra-long-term" survivors (those surviving beyond 10 years). The specific trajectory of atherosclerotic progression and the role of preoperative baseline factors in this late-stage period remain incompletely characterized.

Methodology
This study employed a single-center, retrospective cohort design conducted at Beijing Friendship Hospital.

• Cohort: The study enrolled 52 primary liver transplant recipients who underwent surgery between April 2013 and December 2015. Inclusion criteria required age ≥18, successful primary isolated liver transplantation, and complete clinical follow-up exceeding 10 years. Patients with re-transplantation, combined multi-organ transplants, or pre-existing severe cardiovascular/cerebrovascular/peripheral arterial disease were excluded.
• Data Collection: Researchers extracted preoperative, intraoperative, and long-term follow-up data from electronic medical records and dedicated databases. Variables included demographics, laboratory biomarkers (e.g., MELD score, lipid profiles, glucose), comorbidities, surgical parameters, and immunosuppressive regimens.
• Endpoint Definition: The primary endpoint was MACE, defined as new-onset coronary heart disease (≥50% stenosis confirmed by CCTA or CAG), ischemic cerebrovascular disease (stroke, TIA, hemorrhage confirmed by CT/MRI), or peripheral arterial occlusive disease (≥50% stenosis confirmed by ultrasound, CTA, or DSA).
• Statistical Analysis:
  • Survival analysis utilized the Kaplan–Meier method with log-rank tests to compare event-free survival across subgroups.
  • Given the limited number of endpoint events (n=7), the study utilized Firth-corrected univariable and multivariable binary logistic regression (via the logistf package in R) to mitigate estimation bias caused by small sample sizes and complete data separation.
  • Fisher's exact test was used to assess associations between immunosuppressive regimens and MACE incidence.

Key Results

• Incidence and Temporal Distribution: Among the 52 ultra-long-term survivors, the cumulative incidence of MACE was 13.5% (7 patients, 8 documented vascular events). The temporal distribution revealed that the peak incidence window occurred between 5 and 10 years post-transplantation (57.1% of events). Notably, 28.6% of new MACE cases emerged beyond the 10-year mark, indicating that cardiovascular risk persists and progresses even in patients with sustained postoperative remission.
• Survival Rates: The cardiovascular event-free survival rates were 98.1% at 5 years, 90.4% at 10 years, and 85.5% for the post-10-year period.
• Risk Factor Analysis:
  • Univariate Analysis: Preoperative hypertension (P=0.015) and hyperlipidemia (P=0.049) showed significant associations with MACE.
  • Multivariate Analysis: After adjusting for confounders (age, gender, BMI, smoking, diabetes, etc.), preoperative hypertension was confirmed as the sole independent risk factor for long-term MACE (Odds Ratio = 15.16; 95% CI: 1.96–219.90; P=0.009).
  • Immunosuppression: No statistically significant difference in MACE incidence was observed across different immunosuppressive regimens (P=0.590), though the study noted limited statistical power due to sample size.
• Demographics: The cohort had a median age of 52 years. Preoperative comorbidities included hypertension (11.5%), type 2 diabetes (17.3%), and hyperlipidemia (1.9%).

Significance and Claims
The authors claim that this study provides rare real-world evidence regarding the late-stage cardiovascular trajectory of liver transplant recipients. The primary significance lies in demonstrating that:

1. Persistent Risk: Cardiovascular injury is a progressive pathological process; a substantial proportion of atherosclerotic events occur more than a decade after transplantation, challenging the notion that long-term survivors are free from acute cardiovascular threats.
2. Predictive Value: Preoperative hypertension is a critical, independent predictor of ultra-long-term cardiovascular complications, aligning with general population risk factors but highlighting its specific weight in this transplant context.
3. Clinical Implications: The findings support the necessity of lifelong standardized cardiovascular surveillance and intensive blood pressure control. The authors suggest that clinical monitoring intensity should not be reduced based on long-term postoperative disease-free status and that intensified screening should be initiated around the 5-year post-transplant mark to capture the peak incidence window.

Limitations
The authors acknowledge the study's limitations, including its single-center retrospective nature, small sample size (n=52), and the lack of serial postoperative blood pressure and lipid measurements, which prevented the evaluation of post-transplant metabolic control impacts. Consequently, the statistical power for subgroup analyses (particularly regarding immunosuppressive regimens) was limited.