Background: Metabolic syndrome (MetS) is increasingly prevalent globally and is linked to inflammation in cardiac tissues. Cardiac allograft vasculopathy (CAV) is a significant inflammatory condition and a leading cause of graft failure after orthotopic heart transplantation (OHT). The relationship between MetS and CAV remains poorly understood.

Methods: A literature search was conducted from inception to September 2024, including studies that reported associations between MetS or its components (obesity, hypertension, dyslipidemia, and diabetes mellitus) and CAV. The primary endpoint was the development of CAV after OHT. Results were presented as odds ratios (OR) or hazard ratios (HR) with 95% confidence intervals (CI), employing both random and fixed-effect models based on heterogeneity.

Results: A total of 16 studies involving 3,366 patients were included. The prevalence of MetS was high before OHT (32%, 95% CI: 24-41%, I2 = 75%) and increased after OHT (37%, 95% CI: 18-61%, I2 = 83%). MetS was significantly associated with CAV (OR = 1.99, 95% CI: 1.28-3.09, I2 = 36%). Key components of MetS linked to CAV included obesity (OR = 1.54, 95% CI: 1.11-2.13, I2 = 0%) and dyslipidemia (OR = 1.87, 95% CI: 1.49-2.36, I2 = 0%). New-onset diabetes mellitus after transplantation increases the risk of CAV with an HR of 1.71 (95% CI: 1.56-1.88, I2 = 0%).

Conclusion: The high prevalence of MetS both before and after OHT is associated with an increased risk of CAV, highlighting the need for targeted interventions to manage MetS in heart transplant recipients.