Early intertwin differences in myocardial performance during the twin-to-twin transfusion syndrome.

BACKGROUND: In the twin-to-twin transfusion syndrome (TTTS), pressure rather than volume overload is increasingly considered as a key factor in the pathogenesis of the cardiomyopathy of the recipient twin. If this is the case, cardiac dysfunction should be among the first signs observed with TTTS. The objective of this study was to determine whether intertwin differences in myocardial function are modified early in the course of TTTS and whether they can help to differentiate this condition from intrauterine growth restriction (IUGR). METHODS AND RESULTS: Eight variables were analyzed on the first fetal echocardiography on 21 pairs of twins with TTTS and 11 with IUGR. No difference was found between the 2 groups for the cardiothoracic ratio, pulsatility indices in the umbilical and middle cerebral arteries, and peak velocity of the middle cerebral artery. Significant difference was found for ventricular septal thickness, but with no association with the conditions under study. With TTTS, left ventricular shortening fraction was consistently greater in the donor twins, and myocardial performance indices (MPIs) were elevated in the recipient twins. This increase in MPI was caused by a lengthening of the isovolumic periods compared with those of the donor twin: left ventricular and right ventricular isovolumic periods 0.105+/-0.047 and 0.097+/-0.026 seconds, respectively, for the recipient twins versus 0.0561+/-0.46 and 0.065+/-0.03 seconds, respectively, for the donor twins (P<0.001). These changes in the isovolumic periods were mainly due to significant prolongation of isovolumic relaxation times. A change in left ventricular MPI > or =0.09 combined with a change in right ventricular MPI > or =0.05 would identify a TTTS with a sensitivity of 75% and a false-positive rate of 9%. CONCLUSIONS: The observed diastolic function impairment goes along with the pressure-overload pathogenic concept proposed in TTTS. Assessment of intertwin difference in MPI is a valuable tool for early differential diagnosis between TTTS and isolated IUGR.

Management of fetal tachyarrhythmia based on superior vena cava/aorta Doppler flow recordings.

OBJECTIVE: To evaluate a management protocol of fetal supraventricular tachycardia (SVT) based on prior identification of the underlying mechanism. DESIGN AND SETTING: Prospective study in a mother-child tertiary university centre. PATIENTS: During a consecutive 36 month period, 18 fetuses with sustained SVT underwent a superior vena cava/ascending aorta (SVC/AA) Doppler investigation in an attempt to determine the atrioventricular (AV) relation and to treat the arrhythmia according to a pre-established management protocol. MAIN OUTCOME MEASURE: Rate of conversion to sinus rhythm. RESULTS: Seven fetuses had short ventriculoatrial tachycardia, five of these with a 1:1 AV conduction suggesting re-entrant tachycardia. The first choice drug was digoxin and all were converted. One fetus had AV dissociation leading to the diagnosis of junctional ectopic tachycardia, which was resistant to digoxin and sotalol; amiodarone achieved postnatal conversion. One fetus had SVT and first or second AV block; the diagnosis was atrial ectopic tachycardia (AET), which responded to sotalol given as a drug of first choice. Seven fetuses had long ventriculoatrial tachycardia: one with sinus tachycardia (no treatment), one with permanent junctional reciprocating tachycardia (PJRT), and three with AET. The first choice drug was sotalol and all were converted. One AET was classified postnatally as PJRT. Six fetuses had intra-atrial re-entrant tachycardia: five with 2:1 AV conduction and one with variable block. The first choice drug was digoxin. Conversion was achieved in all but one, who died after birth from advanced cardiomyopathy. CONCLUSION: The electrophysiological mechanisms of fetal SVT can be clarified with SVC/AA Doppler. The proposed management protocol has so far yielded a good rate of conversion to sinus rhythm.

A single dose of an effective whole cell pertussis vaccine does not significantly increase protection in children primed with a less effective vaccine.

We evaluated if a single dose of a protective whole cell pertussis vaccine given before school entry to children primed with a less effective vaccine would increase their protection. A school cohort including 3876 students and a family cohort including 162 children were assessed. Although there was a trend toward increased protection. the better vaccine did not provide a significant improvement. These results suggest that a single dose of an effective vaccine given to children primed with a less effective one does not raise the protection to at level similar to that provided by three doses of the better vaccine.

T cell subsets in the thymus of graft-versus-host immunosuppressed mice. Sensitivity of the L3T4+Lyt-2- subset to cortisone.

We have investigated the effects of graft-versus-host disease on T cell differentiation in the murine thymus. We previously reported that GVH-induced thymic dysplasia results in a T cell immunodeficiency associated with a lack of IL-2 production. This deficiency in IL-2 production may be the result of a reduction in the number of L3T4+Lyt-2- IL-2-producing cells or of a functional defect in this population. To test these two alternatives, flow cytometry analysis of L3T4 and Lyt-2 antigen expression on thymocytes along with immunofluorescence microscopy were employed to assess T cell phenotypes in thymuses of GVH mice. GVH reactions were induced by injecting 40 x 10(6) C57BL/6 (B6) or A strain lymphoid cells into C57BL/6xAF1 (B6AF1) mice. Thymocyte populations were quantitated on different days after GVH induction. In the normal thymus, the ratio of L3T4/Lyt-2 single positive cells was greater than 2:1. In contrast, such a ratio was less than 1:1 in the atrophic GVH thymus, owing to a selective reduction in the number of L3T4+Lyt-2- cells. Following cortisone treatment the ratio of L3T4/Lyt-2 single positive thymocytes in normal F1 mice was approximately 3:1, whereas in GVH animals this ratio was reversed (1:2). This reversal was due to a selective reduction in the absolute numbers of L3T4+Lyt-2- cells. In adrenalectomized GVH animals, thymic cortical atrophy was prevented and normal ratios of L3T4/Lyt-2 single positive cells were observed. However, when these animals were treated with cortisone, the L3+T4/Lyt-2- population was more sensitive than was the L3T4- Lyt2+ population, thereby resulting in a 1:2 L3T4/Lyt-2 ratio. These results demonstrate that single positive L3T4 cells are present in the murine GVH thymus, yet they have not acquired cortisone resistance, a trait normally attributed to this mature thymic subset. It appears that the GVH dysplastic thymus can support the differentiation of L3T4+Lyt-2- cells--however, such a thymus is unable to confer cortisone resistance upon this population. Consequently, these cells appear to be eliminated when exposed to corticosteroids in peripheral lymphoid tissue.