Adults born preterm exhibit bi‐ventricular hypercontractility and inefficiency

Abstract

IntroductionIn the US, prematurity accounts for approximately 10% of all live births. Infants born preterm are at an increased risk of cardiopulmonary disease. Until recently, little was known about the long‐term sequelae in the myocardium in adult survivors of prematurity. One study demonstrated that adults born preterm had larger left (LV) and right ventricular (RV) masses, and lower RV ejection fraction compared to term born controls. To date, there is a paucity of information on the potential mechanism of altered ventricular mechanics in adult survivors of prematurity. Therefore, we hypothesized that preterm subjects would display reduced RV and LV strain.MethodsPreterm subjects were recruited from a prospectively followed cohort at UW‐Madison. Gestational ages for the preterm subjects were 28.2 ± 0.84 weeks and they weighed < 1500 grams. Term‐born subjects were recruited from the general public. Cardiac magnetic resonance imaging (MRI) was used to determine myocardial strain and stroke volume (SV) in adults born preterm (n = 10, age = 26.9 ± 0.3 years) and age‐matched term born controls (n = 12, age = 25.8 ± 0.2 years). Three slices from the RV and LV (apex, mid and base) short‐axis cine MR images were used to analyze RV and LV circumferential and LV radial dimensions (mean peak strain, systolic and diastolic strain rate). SV was obtained from the main pulmonary artery (MPA) and aorta (Ao) 2‐D phase contrast images. SV was normalized to body surface area (SVI) and was divided by peak RV and LV circumferential strain to obtain RV and LV efficiency. All MRI analysis was performed using Segment (http://segment.heiberg.se). A Mann‐Whitney test was performed to test differences between groups (p < 0.05).ResultsPreterm subjects demonstrated increased peak RV circumferential (−11.36 % ± 1.90 vs. −8.83 % ± 1.95; p = 0.003) and LV circumferential (−20.15 % ± 2.29 vs. −17.96 % ± 1.96; p = 0.025) strain compared to controls, respectively. Additionally, RV circumferential systolic strain rate, LV circumferential systolic and diastolic strain rate, and LV radial diastolic strain rate were greater (p < 0.05) in preterm adults as compared to controls. SVI as measured from the MPA and Ao flow was not different between groups. Preterm subjects exhibited reduced (p < 0.05) RV and LV (p = 0.06) efficiency as compared to controls.DiscussionWe used MRI to measure RV and LV strain, which is a measure of ventricular displacement during the cardiac cycle. Contrary to our hypothesis, these results demonstrate that adults born preterm exhibit a hypercontractile myocardium (increased strain) under resting conditions. The increased bi‐ventricular strain in the circumferential dimension in preterm born adults occurred despite no differences in SVI between groups. This results in reduced RV and LV efficiency in preterm subjects compared to controls, suggesting increased cardiac work may be required in adults born preterm for the same SVI. The implications for life‐time cardiovascular risk merit further study.Support or Funding InformationProject supported by funding from the National Institutes of Health: 1RO1 HL086897 (MWE) and RO1 HL38149 (MWE). Kara Goss is supported by the University of Wisconsin Clinical and Translational Science Award (CTSA) program, through the NIH National Center for Advancing Translational Sciences (NCATS), grant NIH UL1TR000427 (PI Drezner; 4KL2TR000428‐‐10).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.