Goss, Kara N

Introduction: Individuals born premature have smaller ventricular chambers volumes and a reduced cardiac reserve during exercise. Epidemiologic studies demonstrate increased risk of developing heart failure by young adulthood, though whether this is due primarily to systolic or diastolic dysfunction remains unresolved. Hypothesis: We hypothesize that either systolic or diastolic function, quantified as intraventricular kinetic energy (KE) during systolic and diastolic phases, respectively, will be altered in both ventricles of young adults born premature. Methods: A total of 56 young adults participated in this observational cardiac MRI study: 35 subjects born moderately to extremely premature (birth weight <1500 g or gestational age ≤32 weeks), and 21 age-matched term-born subjects. Each subject underwent cardiac MRI, including cine cardiac structure/function assessment and four-dimensional flow-encoded MRI (4D flow MRI). Five 4D flow parameters, normalized by end diastolic volume (EDV) to control for heart size, were extracted from each ventricle’s KE-time curve: average KE/EDV, peak systolic KE/EDV, early diastolic (E-wave) KE/EDV, late diastolic (A-wave) KE/EDV, and the ratio of E-wave KE to A-wave KE. Results: Average KE/EDV and peak systolic KE/EDV were similar between term and preterm subjects. Preterm-born subjects had increased A-wave KE/EDV in the RV and decreased E/A KE ratio in both ventricles (Table 1), indicating subtle diastolic dysfunction. The E/A KE ratio was moderately correlated with stroke volume index in both ventricles (LV: R=0.37, P=0.005; RV: R=0.32, P=0.02). Conclusions: Our results suggest that diastolic dysfunction, along with reduced chamber size, contributes to the reduced stroke volume seen in individuals born premature. In addition, diastolic dysfunction may further limit cardiac functional reserve and increase early heart failure risk in this population.

We assessed the effect of right ventricular afterload reduction with sildenafil and heart rate reduction with metoprolol on cardiac hemodynamics and function in young adults born premature using 4D flow MRI. Metoprolol depressed cardiac function, whereas sildenafil improved cardiac function including right ventricular direct flow fraction by 4D flow, consistent with hemodynamic improvement. This suggests that the preterm heart is dependent on heart rate and sensitive to right ventricular afterload changes.Listen to this article's corresponding podcast at https://ajpheart.podbean.com/e/behind-the-bench-episode-9 .