In vitro flow experiments for determination of optimal geometry of total cavopulmonary connection for surgical repair of children with functional single ventricle

Objectives.This study sought to evaluate the effect of offsetting cavopulmonary connections at varying pulmonary flow ratios to determine the optimal geometry of the connection.Background.Previous investigators have demonstrated energy conservation within the streamlined contours of the total cavopulmonary connection compared with that of the atriopulmonary connection. However, their surgical design of connecting the two cavae directly opposite each other may result in high energy losses. Others have introduced a unidirectional connection with some advantages but with concerns about the formation of arteriovenous malformation in the lung excluded from hepatic venous return. Thus, an optimal surgical design has not been determined.Methods.In the present models, the caval connections were offset through a range of 0.0 to 2.0 diameters by 0.5 superior cava diameter increments. Flow ratios were fixed for superior and inferior cavae and varied for right and left pulmonary arteries as 70:30, 60:40, 50:50, 40:60 and 30:70 to stimulate varying lung resistance. Pressure measurements and flow visualization were done at steady flows of 2, 4 and 6 liters/min to simulate rest and exercise.Results.Our data show that the energy losses at the 0.0diameter offset were double the losses of the 1.0 and 1.5 diameters, which had minimal energy losses. This result was attributable to chaotic patterns seen on flow visualization in the 0.0-diameter offset. Energy savings were more evident at the 50:50 right/left pulmonary artery ratio. Energy losses increased with increased total flow rates.Conclusions.The results strongly suggest the incorporation of caval offsets in future total cavopulmonary connections

Right ventricular outflow reconstruction with cryopreserved homografts in pediatric patients: Intermediate-term follow-up with serial echocardiographic assessment

AbstractObjectives. This study was performed to assess by echocardiography the intermediate-term outcome of cryopreserved homografts employed in pulmonary outflow reconstruction in children and to validate the reliability of Doppler echocardiography in their evaluation.Background. Cryopreserved homografts have become the most widely used pulmonary conduits. Previous reports have shown the occurrence of homograft regurgitation in the immediate postoperative period and the propensity of regurgitation to progress. Although Doppler echocardiography has been useful in assessing extracardiac valved conduit stenosis, its reliability in assessing a large series of cryopreserved homografts has not been documented.Methods. Echocardiograms of 41 patients (43 homografts) who underwent operations between December 1986 and October 1992 were retrospectively reviewed. The median age of patients at operation was 37.5 months (range 3 to 333), and the median duration of follow-up was 28.5 months (range 1 to 68). Homograft regurgitation was classified on a scale of 0 to 4+. Pressure gradients across the homografts measured in 23 catheterizations were correlated with corresponding echocardiographic gradients.Results. Regurgitation: Homograft regurgitation occurred in 100% of patients at follow-up. Progression of severity >2 grades occurred during follow-up in 35% and was associated with operation before age 18 months (p < 0.002) and stenosis progression (p < 0.05) but not with homograft type (aortic or pulmonary). These data predict that 50% of patients operated on before 18 months of age will have severe regurgitation by 15 months postoperatively compared with only 15% operated on after 18 months. Stenosis: At follow-up, 51% of homografts had a stenotic gradient ≥25 mm Hg predominantly at the distal anastomosis, and stenosis progression was related to young age at operation (<18 months, p < 0.005) and small conduit size (p < 0.01). Fifty percent of conduits implanted before age 18 months could be predicted to stenose by 21.8 months compared with only 5% of those implanted after age 18 months. The gradient measured from Doppler echocardiography correlated well with the catheterization gradient (r = 0.86).Conclusions. Cryopreserved homograft dysfunction is frequent and progressive. Young age at operation (<18 months) predicts more rapid deterioration. Doppler echocardiography is reliable in assessing the systolic gradients across homografts. Serial echocardiographic assessment in the follow-up of these patients accurately characterizes these problems

Fatal COVID-19 outcomes are associated with an antibody response targeting epitopes shared with endemic coronaviruses

The role of immune responses to previously seen endemic coronavirus epitopes in severe acute respiratory coronavirus 2 (SARS-CoV-2) infection and disease progression has not yet been determined. Here, we show that a key characteristic of fatal coronavirus disease (COVID-19) outcomes is that the immune response to the SARS-CoV-2 spike protein is enriched for antibodies directed against epitopes shared with endemic beta-coronaviruses, and has a lower proportion of antibodies targeting the more protective variable regions of the spike. The magnitude of antibody responses to the SARS-CoV-2 full-length spike protein, its domains and subunits, and the SARS-CoV-2 nucleocapsid also correlated strongly with responses to the endemic beta-coronavirus spike proteins in individuals admitted to intensive care units (ICU) with fatal COVID-19 outcomes, but not in individuals with non-fatal outcomes. This correlation was found to be due to the antibody response directed at the S2 subunit of the SARS-CoV-2 spike protein, which has the highest degree of conservation between the beta-coronavirus spike proteins. Intriguingly, antibody responses to the less cross-reactive SARS-CoV-2 nucleocapsid were not significantly different in individuals who were admitted to ICU with fatal and non-fatal outcomes, suggesting an antibody profile in individuals with fatal outcomes consistent with an original antigenic sin type-response