Video-assisted thoracoscopic division of a vascular ring in an infant: a new operative technique

We report the first successful use of thoracoscopy and video-assisted thoracic surgery (TVATS) techniques to relieve extrinsic tracheoesophageal compression produced by a vascular ring. The patient was a 3-month-old infant with postprandial regurgitation and a diagnosis of double aortic arch. After an uncomplicated operation and recovery, the infant was discharged on the second postoperative day. Refinement of technique and instrumentation may allow wider application of video-assisted thoracoscopic techniques in pediatric patients.

Real-time gas-exchange measurement of oxygen consumption in neonates and infants after cardiac surgery

OBJECTIVES

The purposes of this study were: a) to measure oxygen consumption (VO2) in ventilated neonates and infants after cardiac surgery, utilizing a real-time gas exchange system; and b) to assess this new method by comparing the measured VO2 with calculated VO2 (using the Fick equation and simultaneously determined thermodilution cardiac output, measured hemoglobin, and measured mixed venous and arterial saturations).

DESIGN

Prospective, comparison study. Comparison of measured VO2 and calculated VO2 using correlation coefficient, linear regression analysis, and bias and precision.

SETTING

Cardiac intensive care unit in a children's hospital.

PATIENTS

A total of 60 direct comparisons were made between measured and calculated VO2 in 15 patients (ages ranging from 4 days to 14.1 months with median age of 2.4 months) who were receiving mechanical ventilation after undergoing corrective cardiac surgery.

INTERVENTIONS

a) Direct measurement of VO2 using gas exchange method involving a pneumotachograph and a gas sampling system; b) determination of cardiac output by the thermodilution technique; c) measurement of arterial and mixed venous oxygen content by blood sampling.

MEASUREMENTS AND RESULTS

The absolute measured VO2 ranged from 19 to 154 mL/min with a mean of 52 +/- 32 mL/min (when indexed, the range was 81 to 367 mL/min/m2 with mean 185 +/- 69 mL/min/m2, or range 4.7 to 18.8 mL/min/kg with mean 10.4 +/- 3.3 mL/min/kg). While 34 (57%) of 60 measured VO2 values were within 10% of their respective calculated VO2 values, 58 (97%) of 60 were within 25%; the mean percent difference between measured and calculated VO2 values was 10.6 +/- 7.7%. In comparing the measured VO2 and calculated VO2, the correlation coefficient was good (r2 = .87; p < .01) and the linear regression equation was: measured VO2 = 1.1 x calculated VO2 -9.0 mL/min/m2. The mean difference, or bias, was 0 mL/min/m2 with precision of 26 and 52 mL/min/m2 (at 1 and 2 SD). As an alternative means of examining the measured VO2 data, we also directly compared the thermodilution cardiac output with cardiac output derived by using the measured VO2 and the Fick equation. The range of Fick-derived cardiac output was between 1.69 to 8.11 L/min/m2 (mean 3.72 +/- 1.56) and the range of thermodilution cardiac output was between 1.75 to 7.42 L/min/m2 (mean 3.71 +/- 1.36). The correlation coefficient between thermodilution cardiac output and Fick-derived cardiac output was good with r2 = .88 (p < .01) and the linear regression equation was: thermodilution cardiac output = 0.81 x Fick-derived cardiac output + 0.71 L/min/m2. The bias was -0.01 L/min/m2 with a precision of 0.54 L/min/m2 at 1 SD (or 1.08 L/min/m2 for 2 SD).

CONCLUSIONS

Measured VO2 using a gas-exchange system compared favorably with calculated VO2 values using the Fick equation and simultaneously obtained thermodilution cardiac output and arterial and venous oxygen concentrations. By employing this breath-by-breath gas-exchange system, real-time VO2 measurement in ventilated neonates and infants is now feasible.

Expression of merosin in the thymus and its interaction with thymocytes

Merosin is a 700 kDa multichain protein that has several properties in common with laminin, one of the major extracellular matrix proteins present in basement membranes. Both contain B1 and B2 light chains, but merosin has a distinct M-chain compared with the laminin A-chain. Merosin is present in the basement membrane of placenta, striated muscle, and peripheral nerve. Using the RT-PCR assay, we demonstrate that merosin, but not laminin, is also expressed in the thymus. A partial cDNA sequence of the mouse merosin M-chain was 88% identical to the human M-chain, and the deduced amino acid sequences were 95% identical. 18-24% of adult mouse thymocytes bound to human merosin in vitro. Mg2+, but not Ca2+, was essential for binding. Binding was inhibited by antibodies recognizing VLA alpha 6 or beta 1, suggesting that the VLA-6 integrin is a merosin receptor. An anti-beta 4 integrin subunit mAb failed to inhibit binding, suggesting that the alpha 6 beta 4 integrin was not involved. Thymocytes were fractionated into immature and mature populations based on their expression of the heat stable antigen, recognized by the J11d mAb. Virtually all thymocytes expressed VLA-6, but only immature thymocytes (J11d+) bound to meroson. PMA treatment did not significantly increase the binding of J11d+ thymocytes nor did induce binding in the mature J11d- population. In constrast, both splenic T cells and unseparated lymph node cells showed enhanced binding to merosin after PMA stimulation. The expression of merosin in the thymus and its selective interaction with immature thymocytes suggest that thymocyte-merosin interactions may play a role in T cell development.

Expression of merosin in the thymus and its interaction with thymocytes

Merosin is a 700 kDa multichain protein that has several properties in common with laminin, one of the major extracellular matrix proteins present in basement membranes. Both contain B1 and B2 light chains, but merosin has a distinct M-chain compared with the laminin A-chain. Merosin is present in the basement membrane of placenta, striated muscle, and peripheral nerve. Using the RT-PCR assay, we demonstrate that merosin, but not laminin, is also expressed in the thymus. A partial cDNA sequence of the mouse merosin M-chain was 88% identical to the human M-chain, and the deduced amino acid sequences were 95% identical. 18-24% of adult mouse thymocytes bound to human merosin in vitro. Mg2+, but not Ca2+, was essential for binding. Binding was inhibited by antibodies recognizing VLA alpha 6 or beta 1, suggesting that the VLA-6 integrin is a merosin receptor. An anti-beta 4 integrin subunit mAb failed to inhibit binding, suggesting that the alpha 6 beta 4 integrin was not involved. Thymocytes were fractionated into immature and mature populations based on their expression of the heat stable antigen, recognized by the J11d mAb. Virtually all thymocytes expressed VLA-6, but only immature thymocytes (J11d+) bound to meroson. PMA treatment did not significantly increase the binding of J11d+ thymocytes nor did induce binding in the mature J11d- population. In constrast, both splenic T cells and unseparated lymph node cells showed enhanced binding to merosin after PMA stimulation. The expression of merosin in the thymus and its selective interaction with immature thymocytes suggest that thymocyte-merosin interactions may play a role in T cell development.

Tissue factor pathway inhibitor reduces mortality from Escherichia coli septic shock

This study was designed to test the hypothesis that tissue factor pathway inhibitor (TFPI) plays a significant role in vivo in regulating coagulation that results from exposure of blood to tissue factor after vascular injury as in the case of gram negative sepsis. Highly purified recombinant TFPI (6 mg/kg) was administered either 30 min or 4 h after the start of a lethal intravenous Escherichia coli infusion in baboons. Early posttreatment of TFPI resulted in (a) permanent seven-day survivors (5/5) with significant improvement in quality of life, while the mean survival time for the controls (5/5) was 39.9 h (no survivors); and (b) significant attenuations of the coagulation response and various measures of cell injury, with significant reductions in pathology observed in E. coli sepsis target organs, including kidneys, adrenals, and lungs. TFPI administration did not affect the reduction in mean systemic arterial pressure, the increases in respiration and heart rate, or temperature changes associated with the bacterial infusion. TFPI treated E. coli infected baboons had significantly lower IL-6 levels than their phosphate buffered saline-treated controls, however tumor necrosis factor levels were similarly elevated in both groups. In contrast to the earlier 30-min treatment, the administration of TFPI at 4 h, i.e., 240 min, after the start of bacterial infusion resulted in prolongation of survival time, with 40% survival rate (2/5) and some attenuation of the coagulopathic response, especially in animals in which fibrinogen levels were above 10% of normal at the time of TFPI administration. Results provide evidence for the significance of tissue factor and tissue factor pathway inhibitor in bacterial sepsis, and suggest a role for blood coagulation in the regulation of the inflammatory response.

Incidental vesicoureteral reflux in neonates with antenatally detected hydronephrosis and other renal abnormalities

Postnatal imaging findings were reviewed in 130 neonates and young infants referred for imaging evaluation of antenatally detected renal abnormalities. All children underwent voiding cystourethrography and upper urinary tract imaging with sonography and/or renal scintigraphy. Vesicoureteral reflux was present in 49 patients (38%) and was bilateral in 24. All grades of reflux were observed. Reflux occurred in 41 of 98 neonates (42%) in whom postnatal imaging revealed persistent upper tract abnormalities (eg, hydronephrosis, cysts, renal agenesis) and in eight of 32 (25%) with normal findings at postnatal sonography and/or renal scintigraphy. Reflux was the single most common urologic diagnosis and was the only postnatal abnormality in 12 patients (9%). The authors conclude that neonates with antenatally detected hydronephrosis should be routinely screened for reflux with voiding cystography. Detection and aggressive management of reflux in the asymptomatic neonate in whom renal growth and function are unimpaired theoretically offer the best opportunity for preventing renal injury later in childhood.

Semiquantitative assessment of mitral regurgitation by Doppler color flow imaging in patients aged < 20 years

Doppler color flow imaging is a rapid, noninvasive method to estimate the severity of mitral regurgitation (MR) in adult patients; theoretically, it should be possible to use the technique at least as successfully in infants and children, because problems with beam penetration should be diminished. Doppler color flow studies in 27 pediatric patients (age range 12 days to 17 years, median 7 months) with various degrees of MR (but without coexistent aortic regurgitation or intracardiac shunt) were analyzed. All patients underwent left ventriculography within 2 weeks of their color Doppler examination. Three sets of parameters were investigated, including: (1) maximal length of regurgitant jet: by itself, and indexed to cube root of body surface area (BSA) and to left atrial depth; (2) proximal width of jet; by itself, and indexed to cube root of BSA and to diameter of mitral annulus; and (3) regurgitant jet area (RJA): by itself, and indexed to BSA and left atrial area (LAA). Of these parameters, RJA indexed to BSA, and the ratio of RJA/LAA had the best correlation with angiographic grading (r = 0.84 and 0.92, respectively). With our instrumentation, the "cutoff" values in infants and children separating mild, moderate and severe MR appear to be 4 and 10 cm2/m2 for RJA/BSA, and 30 and 50% for RJA/LAA, respectively. Both inter- and intraobserver correlations were good for RJA (r = 0.95 and 0.94, respectively), and the ratio of RJA/LAA (r = 0.92 and 0.94, respectively). Semiquantitative assessment of MR appears to be possible in pediatric patients, using 1 instrument and a standardized technique.

Molecular characterization of a murine homologue of alpha 2C4 adrenoceptor subtype gene

A clone MA2C4 encoding the murine homologue of adrenoceptor alpha 2C4 was identified, amplified and purified from a mouse genomic library (EMBL-3). The Pstl-EcoRl digested fragment (2409 base pairs) of the clone contains the nucleotide sequence encoding a putative receptor protein (458 amino acids), which is highly homologous in the transmembrane and G protein-coupling domains to the human and rat isoceptors. The 5' untranslated region (0.4kb) is characterized by high GC content and CpG island count whereas a polyadenylation signal (AATAAA) is located 481 base pairs downstream from the termination codon in the 3' untranslated region (0.6kb).

Multiple changes in VLA protein glycosylation, expression, and function occur during mouse T cell ontogeny

VLA molecules (beta 1 integrins) are cell-surface alpha beta heterodimers that bind to extracellular matrix (ECM) proteins such as fibronectin, laminin, and collagen. We analyzed the expression, structure, and function of VLAs on mouse thymocytes, as a first step toward understanding their role in T cell development. Two major forms of beta 1 were detected, which differed in their extent of N-glycosylation and sialylation. No evidence for alternative splicing of beta 1 mRNA was obtained by PCR analyses. The larger (135 kDa, nonreduced) more basic beta 1 was the only form on nonmature (J11d+) adult thymocytes, with 135 kDa and larger beta 1-chains expressed on fetal thymocytes from day 14 of gestation through birth. The smaller (120 kDa, nonreduced), more acidic beta-chain was found exclusively on mature (J11d-) thymocytes and peripheral lymphocytes. VLA alpha-chain expression was also analyzed. Virtually all thymocytes were VLA-alpha 4+, -alpha 6+. VLA-alpha 5 was detected in both J11d+ and J11d- thymocytes by immunoprecipitation, but could not be analyzed in detail because of the lack of an appropriate mAb for flow cytometry. VLA-alpha 1 and -alpha 2 were immunoprecipitated only from cells within the J11d- population. Only J11d+ thymocytes (12 to 15%) bound to fibronectin (via VLA-4 and VLA-5) and binding to laminin (via VLA-6) was two to fourfold higher in J11d+ compared with J11d- thymocytes (60 to 80% vs 20 to 30%). The high percentage of J11d+ thymocytes adhering to laminin suggests that VLA-6 exists in an activated state on most thymocytes, in contrast to resting peripheral T cells. These data show that major changes in VLA glycosylation, expression, and ECM-binding capacity occur as thymocytes mature, supporting the hypothesis that VLA-ECM interactions play a role in T cell ontogeny.

Multiple changes in VLA protein glycosylation, expression, and function occur during mouse T cell ontogeny

VLA molecules (beta 1 integrins) are cell-surface alpha beta heterodimers that bind to extracellular matrix (ECM) proteins such as fibronectin, laminin, and collagen. We analyzed the expression, structure, and function of VLAs on mouse thymocytes, as a first step toward understanding their role in T cell development. Two major forms of beta 1 were detected, which differed in their extent of N-glycosylation and sialylation. No evidence for alternative splicing of beta 1 mRNA was obtained by PCR analyses. The larger (135 kDa, nonreduced) more basic beta 1 was the only form on nonmature (J11d+) adult thymocytes, with 135 kDa and larger beta 1-chains expressed on fetal thymocytes from day 14 of gestation through birth. The smaller (120 kDa, nonreduced), more acidic beta-chain was found exclusively on mature (J11d-) thymocytes and peripheral lymphocytes. VLA alpha-chain expression was also analyzed. Virtually all thymocytes were VLA-alpha 4+, -alpha 6+. VLA-alpha 5 was detected in both J11d+ and J11d- thymocytes by immunoprecipitation, but could not be analyzed in detail because of the lack of an appropriate mAb for flow cytometry. VLA-alpha 1 and -alpha 2 were immunoprecipitated only from cells within the J11d- population. Only J11d+ thymocytes (12 to 15%) bound to fibronectin (via VLA-4 and VLA-5) and binding to laminin (via VLA-6) was two to fourfold higher in J11d+ compared with J11d- thymocytes (60 to 80% vs 20 to 30%). The high percentage of J11d+ thymocytes adhering to laminin suggests that VLA-6 exists in an activated state on most thymocytes, in contrast to resting peripheral T cells. These data show that major changes in VLA glycosylation, expression, and ECM-binding capacity occur as thymocytes mature, supporting the hypothesis that VLA-ECM interactions play a role in T cell ontogeny.

Molecular cloning and characterization of a mouse alpha 2C2 adrenoceptor subtype gene

A clone MA2C2 encoding the murine homologue of adrenoceptor alpha 2C2 was isolated from a mouse genomic library using a subtype specific probe. The nucleotide and the deduced amino acid sequences derived from an ApaI fragment (2 kb) of the clone reveal a single open reading frame encoding a putative receptor protein of 455 amino acids. The 5' untranslated region (0.5 kb) sequenced is characterized by high GC content and CpG island count.

Reactions of thrombin-serpin complexes with thrombospondin

Activated platelets release proteins that form stable complexes with thrombin (J. J. Miller, P. C. Browne, and T. C. Detwiler, Biochem. Biophys. Res. Commun. 151, 9-15, 1988). A working model for the reaction (P. C. Browne, J. J. Miller, and T. C. Detwiler, Arch. Biochem. Biophys. 265, 534-538, 1988) includes a dissociable complex of thrombin with released platelet protease nexin, leading to formation of a nondissociable thrombin-nexin complex that then becomes disulfide linked to thrombospondin. This disulfide-linked complex is converted back to the thrombin-nexin complex by reduction of disulfide bonds. Results that allow elaboration on this model are presented. After longer periods of incubation or after incubation with higher concentrations of thrombin, the amount of thrombin complexed with thrombospondin exceeded the amount of thrombin-nexin complex recovered after reduction of disulfide bonds. When the reaction mixture included inhibitors of formation of the thrombin-nexin complex, a slow formation of the thrombin-thrombospondin complex was observed. It was concluded that there is a nexin-independent as well as the faster nexin-dependent disulfide linkage of thrombin to thrombospondin. Addition of thrombin-antithrombin III complexes to the supernatant solution of activated platelets also led to complexes with thrombospondin, demonstrating that serpins other than platelet protease nexin facilitate incorporation of thrombin into complexes with thrombospondin. By heparin affinity chromatography, it was shown that thrombin-nexin complexes dissociably associate with thrombospondin prior to formation of disulfide-linked complexes. These observations are incorporated into a more detailed model of the reaction.

Surgical management of late right ventricular failure after Mustard or Senning repair

BACKGROUND

Information on surgical management and outcome in patients who develop symptomatic right ventricular failure after prior Mustard or Senning operations is limited.

METHODS AND RESULTS

From March 1987 to March 1991, 10 patients 3.6-23.5 years old (median, 7.0 years) with transposition of the great arteries and prior Mustard (six patients) or Senning (four patients) repairs (performed at ages 2 months to 5 years; median, 6 months) underwent surgical intervention for symptomatic right ventricular failure. In five of 10 patients, anatomic correction with either an arterial switch operation (three patients) or a pulmonary artery-to-aorta anastomosis and right ventricle-to-pulmonary artery conduit (two patients) was performed. Before anatomic correction in these five patients, four of five patients had a pulmonary artery band to prepare the left ventricle. The interval between preparation and correction ranged from 8 days to 12 months (median, 2 months). One patient died after an arterial switch operation. In the remaining five patients, coexisting left ventricular dysfunction precluded anatomic correction; all five patients survived cardiac transplantation. Survival for the entire group of 10 patients is 90%, and the median postoperative hospital stay was 17 days. During follow-up (12-62 months; median, 27 months), there were no deaths. Neoaortic insufficiency after anatomic correction was common (mild in one patient, moderate in two patients, and severe in one patient who required aortic valve replacement 4 months after surgery). In the transplantation group, one patient developed lymphoma 3 months after transplantation but is currently in remission after reduction of immunosuppression.

CONCLUSIONS

In patients who develop late right ventricular failure after Mustard or Senning repair, surgical intervention with either anatomic correction or cardiac transplantation can be done with acceptable morbidity and low mortality. Neoaortic valve insufficiency demands close follow-up after anatomic correction.

Lethal Staphylococcus aureus-induced shock in primates: prevention of death with anti-TNF antibody

A successful experimental treatment for gram-positive sepsis to our knowledge has not been achieved. The objectives of this study were to develop a nonhuman primate model of lethal gram-positive sepsis employing the micro-organism Staphylococcus aureus and to determine the efficacy of treatment using monoclonal antibody (MAb) to tumor necrosis factor alpha (TNF). The antibody was administered intravenously, 15 mg/kg, 30 minutes after the beginning of a 2-hour infusion of S. aureus, 4 x 10(10) colony forming units/kilogram. The baboons infused with S. aureus demonstrated the release of the cytokines TNF and interleukin-6 (IL-6), but endotoxin was not observed in the plasma at any time. Treatment with antibody to TNF abolished the rise in serum TNF levels and reduced the increased levels of IL-6. Treatment with MAb to TNF prevented multiple organ failure and achieved permanent (> 7 day) survival of all baboons.

Prognostic determinants in hypertrophic cardiomyopathy. Prospective evaluation of a therapeutic strategy based on clinical, Holter, hemodynamic, and electrophysiological findings

BACKGROUND

Patients with hypertrophic cardiomyopathy (HCM) frequently have arrhythmias and hemodynamic abnormalities and are prone to sudden death and syncope. An important need exists for improved risk stratification and definition of appropriate investigation and therapy.

METHODS AND RESULTS

The relation of 31 clinical, Holter, cardiac catheterization, and electrophysiological (EP) variables to subsequent cardiac events in 230 HCM patients was examined by multivariate analysis. Studies were for cardiac arrest (n = 32), syncope (n = 80), presyncope (n = 52), ventricular tachycardia (VT) on Holter (n = 36), a strong family history of sudden death (n = 9), and palpitations (n = 21). Nonsustained VT on Holter was present in 115 patients (50%). Sustained ventricular arrhythmia was induced in 82 patients (36%). Seventeen cardiac events (eight sudden deaths, one cardiac arrest, and eight syncope with defibrillator discharges) occurred during a follow-up of 28 +/- 19 months. The 1-year and 5-year event-free rates were 99% and 79%, respectively. Two variables were significant independent predictors of subsequent events: sustained ventricular arrhythmia induced at EP study (beta, 3.5; p = 0.002) and a history of cardiac arrest or syncope (beta, 2.9; p less than 0.05). Only two of 66 patients without symptoms of impaired consciousness had a cardiac event (3-year event-free rate, 97%). In contrast, nonsustained VT on Holter was associated with a worse prognosis only in patients with symptoms of impaired consciousness: 11 of 79 symptomatic patients with VT on Holter (14%) had events versus only four of 85 symptomatic patients without VT on Holter (5%) (p = 0.057). Notably, none of 51 patients without symptoms of impaired consciousness in whom VT was not induced at EP study had a cardiac event.

CONCLUSIONS

In HCM, VT on Holter is of benign prognostic significance in the absence of symptoms of impaired consciousness and inducible VT, and sustained VT induced at EP study, especially when associated with cardiac arrest or syncope, identifies a subgroup at high risk for subsequent cardiac events.

Characterization of a glial associated antigen GA-1 by monoclonal antibody

A glial antigen (GA-1) was identified by monoclonal antibodies (MAb) raised against C6 rat glioma cells. MAb-7D3 (IgG2a kappa) revealed GA-1 as a single protein band with a Rf value of 0.09 by the use of basic-PAGE Western blot. SDS-PAGE Western blot and radioimmunoprecipitation (RIP) further resolved GA-1 into two subunits with a molecular weight of 200 and 78 kDa respectively. Subcellular localization by immunocytochemical staining revealed its cytosolic presence with a punctate pattern perinuclearly. Significant expression of GA-1 may be detected in 4 glioma or glial cell lines derived from rat brain. However, no expression may be detected in the rest of the 18 mammalian cell lines or primary neural cell cultures examined. All of the above data thereby suggest that GA-1 may be glial specific whereas the epitope of GA-1 defined by MAb-7D3 is species (rat) specific.

Anticoagulant and fibrinolytic activities are promoted, not retarded, in vivo after thrombin generation in the presence of a monoclonal antibody that inhibits activation of protein C

This study examines the assumption that both the anticoagulant and fibrinolytic activity that follow the generation of thrombin induced by infusion of factor Xa/PCPS are due to generation of activated protein C. Untreated controls or animals given unrelated antibody were compared with animals pretreated with a specific monoclonal antibody to protein C (HPC4). Compared with untreated controls excess HPC4 substantially reduced the level of protein C activation as observed by protein C immunoblotting and enzyme-linked immunosorbent assay for antitrypsin/activated protein C complexes. Despite this, the anticoagulant activity as reflected by the decline of factors Va and VIIIa levels (as observed by coagulation assays and by factor V immunoblotting) was significantly greater than controls. The fibrinolytic activity (as observed by assays of tissue plasminogen activator, D-Dimer, alpha 2-antiplasmin) also was significantly greater than controls. We conclude that neutralization of the protein C anticoagulant system while resulting in a significantly more intense coagulant response to Xa/PCPS does not preclude inactivation of factors Va and VIIIa and the full expression of the fibrinolytic response. We conclude further that after thrombin generation in vivo, protein C activation is not a prerequisite for the promotion of the fibrinolytic response previously observed, and that the inactivation of factors Va/VIIIa may be mediated by enzymes other than activated protein C. The reduction in alpha 2-antiplasmin levels in association with increased tissue plasminogen activator activity suggests that plasmin is a likely candidate.

Role of peptido-leukotrienes in the genesis of early ventricular arrhythmias during acute myocardial ischaemia in rats

Changes in cardiac ventricular concentrations of peptidoleukotrienes (peptido-LTs) following coronary artery ligation and the effects of lipoxygenase inhibition and leukotriene antagonism on the cardiovascular responses to acute myocardial ischaemia were studied in pentobarbitone-anaesthetised rats. It was found that the left ventricular peptido-LT levels significantly increased at 2.5 and 5 min after left coronary artery ligation while the changes in right ventricle were not statistically significant. Pretreatment with nordihydroguaiaretic acid 25, 50 or 100 mg/kg caused marked depletion of ventricular peptido-LT content, but did not significantly prevent the blood pressure or heart rate changes, the occurrence of ventricular tachycardia or fibrillation, or the mortality of the animals following coronary artery ligation. Administration of SK&F 102922, even at doses which caused marked decreases in blood pressure and heart rate, also did not significantly alter the cardiovascular changes and the mortality rate induced by left coronary artery ligation. It is, therefore, suggested that the occurrence of ventricular arrhythmias and haemodynamic changes during the early phase of acute myocardial ischaemia may not be due to the augmented synthesis of peptido-LTs in cardiac tissue.

Outcome and assessment after the modified Fontan procedure for hypoplastic left heart syndrome

BACKGROUND

We reviewed the outcome of 76 consecutive patients (age range, 5 months to 6 years; median age, 19 months) who underwent a modified Fontan procedure after initial palliative surgery for hypoplastic left heart syndrome (HLHS) between January 1984 and December 1989.

METHODS AND RESULTS

Modifications of the Fontan procedure included transatrial baffle of pulmonary venous return to the tricuspid valve (n = 10) or inferior vena cava baffle within the right atrium to the superior vena caval-pulmonary artery anastomosis, with pulmonary artery augmentation (n = 66). Actuarial survival rates were 74% (1 month), 58% (12 months), 56% (2 years), and 52% (4 years). Of the 43 survivors, 25 patients have returned for postoperative cardiac catheterization at a medium of 13 months after the Fontan procedure. Mean +/- SD hemodynamic values were cardiac index, 2.8 +/- 0.6 l/min/m2; right arterial pressure, 11 +/- 2 mm Hg; pulmonary artery wedge pressure, 6 +/- 3 mm Hg; and arterial oxygen saturation, 94 +/- 3%. No patient had significant tricuspid or native pulmonary valve insufficiency.

CONCLUSIONS

Survival after the Fontan procedure in patients with HLHS is comparable to survival after a Fontan procedure in patients with other complex congenital heart lesions. In the subgroup of patients with HLHS who survived both reconstructive surgery and a Fontan procedure and have been evaluated by cardiac catheterization after a Fontan procedure, the use of the right ventricle as the systemic ventricle yielded excellent intermediate results for Fontan physiology.

Diagnosis, transport, and outcome in fetuses with left ventricular outflow tract obstruction

Between March 1986 and April 1990, 22 consecutive fetuses (at gestational ages of 21 to 38 weeks) with a suspected diagnosis of critical (ductus-dependent) left ventricular outflow tract obstruction on fetal echocardiogram were referred to our center for delivery and surgical treatment. Diagnoses were hypoplastic left heart syndrome (n = 16), valvular aortic stenosis (n = 2), common atrioventricular canal with subaortic stenosis (n = 3), and single ventricle with subaortic stenosis (n = 1). Postnatal echocardiography revealed that fetal echocardiography was correct in predicting left ventricular outflow tract obstruction to be critical in all but one patient, for a positive predictive value of 96%. Of the 21 patients with true, critical left ventricular outflow tract obstruction, 17 patients underwent cardiac surgery as neonates (birth to 6 days of age, median 2 days); 13 (or 77%) survived and were discharged from the hospital. In addition, one patient underwent successful balloon aortic valvotomy for critical valvular aortic stenosis but later died of sepsis. Lethal chromosomal and congenital abnormalities should be sought and are contraindications for this approach. In utero transport of fetuses with suspected critical left ventricular outflow tract obstruction to a neonatal cardiac surgical center can result in improved neonatal condition and may improve overall survival.

Comparison of rejection in the atrioventricular node and bundles with the working myocardium in transplanted hearts

At present the monitoring of heart transplant patients for rejection is done by endomyocardial biopsy. It has been proposed that ECG assessments of conduction delay may provide a noninvasive means of detecting rejection. To determine whether rejection in the atrioventricular node and conduction bundles reflects rejection in the working myocardium, we studied 21 transplanted hearts from 21 cardiac allograft recipients. Twenty of the hearts were obtained at autopsy, and one was obtained from a patient who underwent a second transplant procedure. The atrioventricular conduction tissues, the ventricular and atrial free walls, and the interventricular and interatrial septa from these hearts were examined for histologic evidence of rejection. Of the 21 hearts, 17 showed histologic changes of acute allograft rejection. Of the 17, rejection involved the conducting system and the myocardium equally in 11. In 6 of the 17 hearts, rejection involved the working myocardium more severely than it did the conducting system. Of interest, nonrejection pathologic changes were also noted in the conducting systems of several hearts. Severe accelerated arteriosclerosis was found in the artery to the atrioventricular node in one case, and lesser degrees of accelerated arteriosclerosis in this artery were found in two additional cases. In one case, lymphoid infiltrates, consistent with posttransplant lymphoproliferative disorder, were noted in the vicinity of the atrioventricular node, and several hearts demonstrated operative trauma or ischemic changes that appeared to involve the conducting system. These results suggest that although there may be a morphologic basis for using electrophysiologic changes in the conducting system to monitor heart allograft recipients for rejection, caution should be exercised in interpreting these changes.

Bleomycin resistance as a selectable marker for transformation of the eukaryote, Dictyostelium discoideum

An expression cassette was constructed, which has the bacterial bleomycin (Bm) resistance-encoding gene (ble) fused to the Dictyostelium discoideum actin-6 promoter, with a segment of 3'-flanking DNA from the actin-8-encoding gene placed downstream from the ble gene to serve as a transcription terminator. Plasmid pMUW161, which contains this cassette and the D. discoideum plasmid Ddp2 origin of DNA replication, transformed D. discoideum with high efficiency under Bm selection. Hence, this construct is useful as a dominant selectable marker for D. discoideum.