Transluminally placed endovascular grafts to exclude undesirable intracardiac vascular communications.

PURPOSE: In this report, we summarize our early experience using transluminally placed endovascular grafts (TPEG) to close intracardiac communications within surgically created conduits. MATERIALS AND METHODS: Three patients with surgically corrected congenital heart disease were treated in this study. All three patients had intracardiac conduits [Modified Fontan (n = 2) or Mustard procedure (n = 1)]. All three patients had intracardiac shunts causing hypoxemia. The shunts were caused by a surgically created fenestration (n =1), a leak at a surgical anastomosis (n = 1) and perforations of a pericardial baffle (n = 1). All three patients were treated percutaneously from venous side approaches. The TPEG devices were constructed of pre-expanded polytetrafluoroethylene (PTFE) sutured to a Palmaz stent. RESULTS: In the two patients with the modified Fontan procedures, the leaks were completely excluded; in the patient with the Mustard procedure, the perforations in the baffle were not completely excluded. All patients experienced immediate improvements in oxygen saturation ranging from 17Eth 26% (mean, 20.3%). The improvements in oxygen saturation were sustained with values ranging from 12Eth 22% (mean, 17.3%) at the time of clinical follow-up. Clinical follow-up has ranged from 13Eth 19 months (mean, 15 months) and has demonstrated improved exercise tolerance and weight gain. Echocardiographic follow-up has shown no complications of TPEG stenoses, occlusions or migrations. There were no immediate or delayed complications associated with the TPEG devices. CONCLUSION: We report our experience using TPEG devices to exclude intracardiac communications in 3 patients with surgically corrected congenital heart disease. The preliminary results are encouraging and suggest that further investigation in this area should be done.

The mechanisms of nonheme iron uptake determined in IEC-6 rat intestinal cells.

The mechanisms of iron absorption, which control total body iron stores, are not fully understood. We have defined an in vitro model using rat small intestinal cells (IEC-6) to study nutrient uptake by the intestine and have characterized the mechanisms of nonheme iron uptake in this model. IEC-6 cells were grown to confluency, and then 59Fe solutions were layered on the cells, allowing iron uptake to occur through the apical surface. Iron uptake increased over time and comparable results were seen with either 59Fe(II) or 59Fe(III). Two types of 59Fe(II) binding sites were detected, a high affinity site with a dissociation constant of 1 x 10(-8) mol/L and 5 x 10(5) sites per cell, and a lower affinity site with a dissociation constant of 2 x 10(-6) mol/L and 2.6 x 10(6) sites per cell. The 59Fe uptake was inhibited by low temperature, low and high pH, prior iron loading of the cells, high osmotic concentrations, and by N,N'-dicyclohexylcarbodiimide, tannic acid, bathophenanthroline and colchicine. Uptake was not inhibited by vinblastine or verapamil. Transferrin mRNA was not detected in IEC-6 cells grown under normal growth conditions but could be induced under some other conditions. IEC-6 cell proteins that bind iron were detected in a subcellular vesicle fraction having estimated molecular weights of 120,000, 95,000, 55,000 and 35,000. These studies confirm iron uptake studies by other models and demonstrate that IEC-6 cells possess iron-binding moieties, a regulated iron uptake process, and little or no transcription of the transferrin gene under normal growth conditions.

Caco-2 cell line: a system for studying intestinal iron transport across epithelial cell monolayers.

Iron transport across polarized intestinal epithelium was studied by using Caco-2 cells grown in bicameral chambers. When cells were grown under conditions of low, normal, or high iron concentration not only was the iron content of the cells markedly altered but the low iron cells exhibited a nearly 2-fold increase in transepithelial electrical resistance (TEER). 59Fe uptake from the apical surface into cells and transport into the basal chamber was affected both by the valency of the iron and the iron status of the cells. Uptake from 59Fe(II)-ascorbate was about 600 pmol 59Fe/h per mg protein, increased about 2-fold in low iron cells, and was about 13-200-fold greater than uptakes from 59Fe(III) chelated to nitrilotriacetic acid, BSA, or citrate. Transport into the basal chamber from 59Fe(II)-ascorbate was 3.7 +/- 1.7 pmol/h per cm2 for Fe-deficient cells vs. 0.72 +/- 0.1 pmol/h per cm2 for normal-Fe cells and from 59Fe(III)-BSA 1.1 +/- 0.2 pmol/h per cm2 vs. 0.3 +/- 0.03 pmol/h per cm2 for deficient vs. normal iron cells, respectively. The greater transport of iron both from Fe(II) and in iron deficient cells supports the use of the Caco-2 cells as a model for iron transport.

Hereditary hemochromatosis: pathogenesis and clinical features of a common disease.

Hereditary hemochromatosis (HHC) is a common inherited disorder of iron metabolism characterized by excessive iron absorption and the toxic accumulation of iron in parenchymal cells. Homozygous inheritance of an abnormality on chromosome 6 causes this disorder by increasing the intestinal absorption of iron, which is slowly deposited in parenchymal cells of the liver, heart, pancreas, and other endocrine organs. Symptoms develop only after the marked accumulation of iron stores develop, which causes functional insufficiency of these organs. The symptoms are often variable, nonspecific, and attributed to other diseases. Early diagnosis requires a high index of suspicion and an awareness of the clinical features of HHC. Serum iron, total iron-binding capacity (TIBC), and ferritin levels are useful screening studies, but liver biopsy with quantitative chemical determination of iron concentration is essential to evaluate histopathological changes and to help distinguish hereditary hemochromatosis from secondary iron overload. Treatment with weekly phlebotomy frequently results in some clinical improvement in patients with established disease, and if initiated early, organ damage can be prevented and a normal life-span can be expected. The hereditary nature of the disease mandates familial screening of index cases.

Percutaneous cardiac catheterization and atrial balloon septostomy in pediatrics.

Between November, 1971, and July, 1975, 688 patients ranging in age from six hours to 21 years have undergone percutaneous transfemoral venous and/or arterial catheterization at the University of Oregon Health Sciences Center. This represents 93% of all venous catheterizations of the right side of the heart and 97% of all arterial catheterizations of the left side of the heart in the pediatric age range. One hundred and ninety-five patients (29% of the group) weighed 5 kg or less and 133 (20% of the group) were neonates. There were virtually no complications following the venous studies. The complication rate following percutaneous arterial studies is lower than is the reported experience with cut-down arteriotomies. Long-term survival following percutaneous atrial balloon septostomy in D-transposition of the great arteries was comparable to that following cut-down balloon septostomy. The ease of accomplishment, significantly lower complication rate, and successful accomplishment of atrial balloon septostomy prompt us to advocate that the percutaneous technique of cardiac catheterization be extended to include the neonate and young infant who weighsless than 5 kg.

Aortico-left ventricular tunnel. Recognition and repair in infancy.

An infant with an aortico-left ventricular tunnel underwent surgery at the age of five months. There was clinical and electrocardiographic improvement, and postoperative cardiac catheterization demonstrated obliteration of the aortic end of the tunnel, normalization of systemic pulse pressure, mild residual aortic valvular insufficiency, and a decrease in the left ventricular end-diastolic volume index. Early surgery may limit the progression of aortic valvular insufficiency secondary to turbulent aortic-root blood flow.

Postoperative hemodynamic and electrophysiologic evaluation of the interatrial baffle procedure.

Hemodynamic and electrophysiologic studies were performed in 11 children with dextrotransposition of the great arteries an average of 26 months after the interatrial baffle procedure and, in 2 patients, additional closure of a ventricular septal defect. All children are clinically well. Right to left shunts ranging from 28 to 63 percent of systemic blood flow were found at the superior vena caval-baffle junction in four children. The superior vena caval-baffle gradient averaged 7 mm Hg (range 0 to 22). Right ventricular stroke work index averaged 39 g-m/beat per m2 and right ventricular end-diastolic pressure 9 mm Hg. These values were not significantly different from the values for the systemic left ventricle in a comparable group of normal children (average left ventricular stroke work index 45 g-m/beat per m2 and average left ventricular end-diastolic pressure 8 mm Hg). Cardiac index, heart rate and arteriovenous oxygen difference were also normal. No child has complete heart block. His bundle recording demonstrated normal H-V intervals (range 27 to 40 msec); 4 of the 11 had a prolonged A-H interval. Left ventricular systolic pressure was less than 40 mm Hg in all but two children who had significant subpulmonary stenosis. Pulmonary vascular resistance averaged 1.9 units and was decreased in all children. We conclude that up to 37 months postoperatively, despite some residual abnormalities, the clinical and hemodynamic condition of these children is excellent.