Association Between Preterm Birth and Arrested Cardiac Growth in Adolescents and Young Adults

Importance

Premature birth is associated with substantially higher lifetime risk for cardiovascular disease, including arrhythmia, ischemic disease, and heart failure, although the underlying mechanisms are poorly understood.

Objective

To characterize cardiac structure and function in adolescents and young adults born preterm using cardiac magnetic resonance imaging (MRI).

Design, Setting, and Participants

This cross-sectional cohort study at an academic medical center included adolescents and young adults born moderately to extremely premature (20 in the adolescent cohort born from 2003 to 2004 and 38 in the young adult cohort born in the 1980s and 1990s) and 52 age-matched participants who were born at term and underwent cardiac MRI. The dates of analysis were February 2016 to October 2019.

Exposures

Premature birth (gestational age ≤32 weeks) or birth weight less than 1500 g.

Main Outcomes and Measures

Main study outcomes included MRI measures of biventricular volume, mass, and strain.

Results

Of 40 adolescents (24 [60%] girls), the mean (SD) age of participants in the term and preterm groups was 13.3 (0.7) years and 13.0 (0.7) years, respectively. Of 70 adults (43 [61%] women), the mean (SD) age of participants in the term and preterm groups was 25.4 (2.9) years and 26.5 (3.5) years, respectively. Participants from both age cohorts who were born prematurely had statistically significantly smaller biventricular cardiac chamber size compared with participants in the term group: the mean (SD) left ventricular end-diastolic volume index was 72 (7) vs 80 (9) and 80 (10) vs 92 (15) mL/m2 for adolescents and adults in the preterm group compared with age-matched participants in the term group, respectively (P < .001), and the mean (SD) left ventricular end-systolic volume index was 30 (4) vs 34 (6) and 32 (7) vs 38 (8) mL/m2, respectively (P < .001). Stroke volume index was also reduced in adolescent vs adult participants in the preterm group vs age-matched participants in the term group, with a mean (SD) of 42 (7) vs 46 (7) and 48 (7) vs 54 (9) mL/m2, respectively (P < .001), although biventricular ejection fractions were preserved. Biventricular mass was statistically significantly lower in adolescents and adults born preterm: the mean (SD) left ventricular mass index was 39.6 (5.9) vs 44.4 (7.5) and 40.7 (7.3) vs 49.8 (14.0), respectively (P < .001). Cardiac strain analyses demonstrated a hypercontractile heart, primarily in the right ventricle, in adults born prematurely.

Conclusions and Relevance

In this cross-sectional study, adolescents and young adults born prematurely had statistically significantly smaller biventricular cardiac chamber size and decreased cardiac mass. Although function was preserved in both age groups, these morphologic differences may be associated with elevated lifetime cardiovascular disease risk after premature birth.

A novel in vivo approach to assess radial and axial distensibility of large and intermediate pulmonary artery branches

Pulmonary arteries (PAs) distend to accommodate increases in cardiac output. PA distensibility protects the right ventricle (RV) from excessive increases in pressure. Loss of PA distensibility plays a critical role in the fatal progression of pulmonary arterial hypertension (PAH) toward RV failure. However, it is unclear how PA distensibility is distributed across the generations of PA branches, mainly because of the lack of appropriate in vivo methods to measure distensibility of vessels other than the large, conduit PAs. In this study, we propose a novel approach to assess the distensibility of individual PA branches. The metric of PA distensibility we used is the slope of the stretch ratio-pressure relationship. To measure distensibility, we combined invasive measurements of mean PA pressure with angiographic imaging of the PA network of six healthy female dogs. Stacks of 2D images of the PAs, obtained from either contrast enhanced magnetic resonance angiography (CE-MRA) or computed tomography digital subtraction angiography (CT-DSA), were used to reconstruct 3D surface models of the PA network, from the first bifurcation down to the sixth generation of branches. For each branch of the PA, we calculated radial and longitudinal stretch between baseline and a pressurized state obtained via acute embolization of the pulmonary vasculature. Our results indicated that large and intermediate PA branches have a radial distensibility consistently close to 2%/mmHg. Our axial distensibility data, albeit affected by larger variability, suggested that the PAs distal to the first generation may not significantly elongate in vivo, presumably due to spatial constraints. Results from both angiographic techniques were comparable to data from established phase-contrast (PC) magnetic resonance imaging (MRI) and ex vivo mechanical tests, which can only be used in the first branch generation. Our novel method can be used to characterize PA distensibility in PAH patients undergoing clinical right heart catheterization (RHC) in combination with MRI.

Advanced multimodality imaging of an anomalous vessel between the ascending aorta and main pulmonary artery in a dog

A 1-year-old male German shorthaired pointer was referred for evaluation of tachypnea and hemoptysis. A grade VI/VI left basilar continuous murmur was ausculted. Multimodality imaging consisting of thoracic radiographs, transthoracic and transesophageal echocardiography, fluoroscopy-guided selective angiography, computed tomography angiogram (CTA) and magnetic resonance angiogram (MRA), was performed on this patient. The defect included a left-to-right shunting anomalous vessel between the ascending aorta and main pulmonary artery, along with a dissecting aneurysm of the main and right pulmonary artery. An MRA post-processing technique (PC VIPR) was used to allow for high resolution angiographic images and further assessment of the patient's hemodynamics prior to surgical correction. This case report describes the clinical course of a canine patient with a rare form of congenital cardiac disease, and the multiple imaging modalities that were used to aid in diagnosis and treatment.

Acute megakaryocytic leukemia: the Eastern Cooperative Oncology Group experience

Acute megakaryocytic leukemia (AMegL) is a rare subtype of acute myeloid leukemia (AML) evolving from primitive megakaryoblasts. Because of its rarity and the lack of precise diagnostic criteria in the past, few series of adults treated with contemporary therapy have been reported. Twenty among 1649 (1.2%) patients with newly diagnosed AML entered on Eastern Cooperative Oncology Group (ECOG) trials between 1984 and 1997 were found to have AMegL. The median age was 42.5 years (range 18-70). Marrow fibrosis, usually extensive, was present in the bone marrow. Of the 8 patients who had cytogenetic studies performed, abnormalities of chromosome 3 were the most frequent. The most consistent immunophenotypic finding was absence of myeloperoxidase in blast cells from 5 patients. In the most typical 3 cases, the leukemic cells were positive for one to 2 platelet-specific antigens in addition to lacking myeloperoxidase or an antigen consistent with a lymphoid leukemia. Myeloid antigens other than myeloperoxidase and selected T-cell antigens (CD7 and/or CD2) were frequently expressed. Induction therapy included an anthracycline and cytarabine in all cases. Complete remission (CR) was achieved in 10 of 20 patients (50%). Two patients remain alive, one in CR at 160+ months. Resistant disease was the cause of induction failure in all but 3 patients. The median CR duration was 10.6 months (range 1-160+ months). The median survival for all patients was 10.4 months (range 1-160+ months). Although half of the patients achieved CR, the long-term outcome is extremely poor, primarily attributable to resistant disease. New therapeutic strategies are needed.

The separation of the alpha-chains of collagen by free-flow electrophoresis

1. The separation of the alpha-components of codfish-skin and calf-skin collagen from the higher-molecular-weight components was accomplished by gel filtration with Bio-Gel P-300 resin in 5m-lithium chloride and at pH7.4. 2. From this fraction three distinct alpha-components, corresponding to the alpha1-, alpha2- and alpha3- chains of collagen, were isolated by free-flow electrophoresis in 6m-urea at 4 degrees . At the temperatures and pH values used there was no detectable degradation of the alpha-chains.