Impaired myocardial reserve underlies reduced exercise capacity and heart rate recovery in preterm-born young adults

AIMS : We tested the hypothesis that the known reduction in myocardial functional reserve in preterm-born young adults is an independent predictor of exercise capacity (peak VO(2)) and heart rate recovery (HRR). METHODS AND RESULTS : We recruited 101 normotensive young adults (n = 47 born preterm; 32.8 ± 3.2 weeks’ gestation and n = 54 term-born controls). Peak VO(2) was determined by cardiopulmonary exercise testing (CPET), and lung function assessed using spirometry. Percentage predicted values were then calculated. HRR was defined as the decrease from peak HR to 1 min (HRR(1)) and 2 min of recovery (HRR(2)). Four-chamber echocardiography views were acquired at rest and exercise at 40% and 60% of CPET peak power. Change in left ventricular ejection fraction from rest to each work intensity was calculated (EFΔ40% and EFΔ60%) to estimate myocardial functional reserve. Peak VO(2) and per cent of predicted peak VO(2) were lower in preterm-born young adults compared with controls (33.6 ± 8.6 vs. 40.1 ± 9.0 mL/kg/min, P = 0.003 and 94% ± 20% vs. 108% ± 25%, P = 0.001). HRR(1) was similar between groups. HRR(2) decreased less in preterm-born young adults compared with controls (−36 ± 13 vs. −43 ± 11 b.p.m., P = 0.039). In young adults born preterm, but not in controls, EFΔ40% and EFΔ60% correlated with per cent of predicted peak VO(2) (r(2) = 0.430, P = 0.015 and r(2) = 0.345, P = 0.021). Similarly, EFΔ60% correlated with HRR(1) and HRR(2) only in those born preterm (r(2) = 0.611, P = 0.002 and r(2) = 0.663, P = 0.001). CONCLUSIONS : Impaired myocardial functional reserve underlies reductions in peak VO(2) and HRR in young adults born moderately preterm. Peak VO(2) and HRR may aid risk stratification and treatment monitoring in this population.