Meta-Analysis of Cardiorespiratory Fitness Impairment in Pediatric Heart Transplant Recipients

Pediatric heart transplant (PHTR) recipients have reduced cardiorespiratory fitness (VO₂peak); however, the magnitude of this impairment and its underlying central hemodynamic mechanisms remain poorly characterized. This systematic review and meta-analysis quantified differences in VO₂peak and peak exercise central hemodynamics between PHTR recipients and age-matched healthy controls (CON). MEDLINE (PubMed) was searched for studies comparing VO₂peak in PHTR recipients and CON. Pooled effect sizes were expressed as weighted mean differences (WMD) using a DerSimonian-Laird random-effects model, and weighted least-squares meta-regression assessed the moderating effects of age and time post-transplant. Seven unique studies (PHTR n = 90; CON n = 118) reported VO₂peak and peak HR. PHTR had significantly lower VO₂peak (WMD  =  -9.5 mL/kg/min), peak HR (WMD: -30 bpm), and CO (n = 3 studies, WMD: -2.5 L/min), with no difference in peak SBP (n = 3 studies). Meta-regression revealed no significant moderating effect of age or time post-transplant on the VO₂peak deficit. The markedly reduced VO₂peak in PHTR recipients is driven primarily by impaired peak CO and persistent chronotropic incompetence, consistent with cardiac allograft sympathetic denervation.