Longer Ischemic Time is Associated with Increased Ventricular Stiffness as Measured by Pressure–Volume Loop Analysis in Pediatric Heart Transplant Recipients

Background: The purpose of this study was to investigate the associations between clinical factors and cardiac function as measured by pressure–volume loops (PVLs) in a pediatric heart transplant cohort. Methods: Patients (age < 20 years) who underwent heart transplantation presenting for a clinically indicated catheterization were enrolled. PVLs were recorded using microconductance catheters (CD Leycom^®, Zoetermeer, Netherlands). Demographic data, serum B-type natriuretic peptide (BNP), time from transplant, ischemic time, presence of transplant coronary artery disease, donor-specific antibodies, and history of rejection were recorded at the time of catheterization. PVL data included contractility indices: end-systolic elastance and preload recruitable stroke work; ventricular–arterial coupling index; ventricular stiffness constant, Beta; and isovolumic relaxation time constant, tau. Associations between PVL measures and clinical data were investigated using non-parametric statistical tests. Results: A total of 18 patients were enrolled. Median age was 8.7 years (IQR 5–14 years). There were ten males and eight females. Six patients had a history of rejection and ten had positive donor-specific antibodies. There was no transplant coronary artery disease. Median BNP was 100 pg/mL (IQR 46–140). Time from transplant to PVL obtained during catheterization procedure was 4.1 years (IQR 1.7–7.8 year). No single clinical characteristic was statistically significant when correlated with PVL data. However, longer ischemic time was associated with worse Beta (r = 0.49, p = 0.05). Conclusions: Our study found that longer ischemic times are associated with increased left ventricular stiffness. No other single clinical variable is associated with cardiac dysfunction as determined by PVL analysis.