James W. Mathewson

Energy-efficient knee-ankle-foot orthosis: A case study

The energy required to walk using a newly designed knee-ankle-foot orthosis (KAFO) has been evaluated. The new KAFO locks the knee during stance and allows free-knee motion during the swing phase of gait. The energy required for gait on level ground and on a slope with a 5-percent incline was evaluated in a postpolio subject. Comparisons were made between the standard locked-knee KAFO and the free-knee (unlocked) configuration. The oxygen consumption rate (ml/kg/min) and energy cost (ml/kg/m) were significantly lower during free-knee gait. The results of the study show that a KAFO design that allows free-knee motion during swing is effective in lowering the energy required for walking.

Balloon dilatation of porcine bioprosthetic valves in the pulmonary position.

Balloon dilatation (BD) of bioprosthetic valves was investigated in vivo and in vitro. Four children with stenotic bioprosthetic porcine valves in the pulmonary position underwent BD of the valve 10 to 24 months after its insertion. Average valve gradient was reduced from 47.5 to 27 mm Hg. Obstruction at the conduit-branch pulmonary artery connection became apparent after dilatation of the valve. These distal stenoses were also dilated. BD technique was tested in vitro with the use of nonstenotic valves in fresh conduits. No damage to the valve or to the conduit was found when oversized balloons were used in a standard fashion or intentionally inflated until rupture. It is concluded that conduit replacement may be deferred by balloon dilatation of obstructed biological valves and/or a stenotic conduit-pulmonary artery anastomosis.

Reconstruction of Stenotic or Occluded Iliofemoral Veins and Inferior Vena Cava Using Intravascular Stents: Re-establishing Access for Future Cardiac Catheterization and Cardiac Surgery

OBJECTIVES The study evaluated the safety and efficacy of stent reconstruction of stenotic/occluded iliofemoral veins (IFV) and inferior vena cava (IVC). BACKGROUND Patients with congenital heart defects and stenotic or occluded IFV/IVC may encounter femoral venous access problems during future cardiac surgeries or catheterizations. METHODS Twenty-four patients (median age 4.9 years) underwent implantation of 85 stents in 22 IFV and 6 IVC. Fifteen vessels were severely stenotic and 13 were completely occluded. Although guide wires were easily passed across the stenotic vessels, occluded vessels required puncture through the thrombosed sites using a stiff wire or transseptal needle. Once traversed, the occluded site was dilated serially prior to stent implantation. RESULTS Following stent placement, the mean vessel diameter increased from 0.9 +/- 1.6 to 7.4 +/- 2.6 mm (p < 0.05). Twenty-one of 28 vessels had long segment stenosis/occlusion requiring two to seven overlapping stents. Repeat catheterizations were performed in seven patients (9 stented vessels) at mean follow-up of 1.6 years. Seven vessels remained patent with mean diameter of 6.4 +/- 2.0 mm. Two vessels were occluded, but they were easily recanalized and redilated. Echocardiographic follow-up in two patients with IVC stents demonstrated wide patency. In four additional patients, a stented vessel was utilized for vascular access during subsequent cardiac surgery (n = 3) and endomyocardial biopsy (n = 1). Therefore, 13 of 15 stented vessels (87%) remained patent at follow-up thus far. CONCLUSIONS Stenotic/obstructed IFV and IVC may be reconstructed using stents to re-establish venous access to the heart for future cardiac catheterization and/or surgeries.

Percutaneous use of stents to correct pulmonary artery stenosis in young children after cavopulmonary anastomosis

Pulmonary artery distortion is a risk factor among candidates for the Fontan procedure. In 57 patients evaluated by catheterization after successful cavopulmonary anastomosis, 8 had proximal left pulmonary artery (LPA) stenosis, either discrete (4 patients) or long segment (4 patients). Median age was 27 months (range 19 to 60 months). Median weight was 11.4 kg (range 9.1 to 20.0). Mean diameter at LPA stenosis was 4.4 +/- 0.4. Proximal right pulmonary artery mean diameter was 10.4 +/- 1.0 mm. After angiographic and hemodynamic assessment, short 11F sheaths were placed in the right internal jugular (6 patients) or subclavian veins (2 patients). Pulmonary artery angioplasty and stent placement were performed. LPA stenoses were enlarged using 10 Palmaz stents dilated to 10 mm (7 patients) or to 12 mm (3 patients). Poststent angiograms showed that narrowest LPA dimensions were significantly enlarged to 9.9 mm +/- 1.0 mm, p < 001). There were no complications. Follow-up studies (catheterizations in 4 patients, echocardiograms in 8 patients) were performed 4 to 9 months after stent implantation. No restenosis was observed. Five patients had completion of their Fontan procedures; three patients are pending Fontan completion. This study demonstrates the efficacy and safety of the percutaneous use of Palmaz stents to correct pulmonary artery stenosis in young children after cavopulmonary anastomosis.

Surgical closure of the tricuspid valve for pulmonary atresia, intact ventricular septum, and right ventricle to coronary artery communications

SummaryA surgical approach is reported for a patient with pulmonary atresia, intact ventricular septum, and right ventricle to coronary artery communications through sinusoids. A shunt procedure was performed at two days of age; the right ventricular outflow tract was not opened. At subsequent catheterization, the tricuspid valve was temporarily closed with a balloon catheter and no change was seen in the ECG. At five months of age, the right ventricle was plicated and a patch was sewn over the tricuspid valve. One year after surgery, neither the right ventricular cavity nor the sinusoids could be demonstrated at angiocardiography; ECG changes of left ventricular ischemia have resolved, and the child is growing normally.

The Damus-Fontan procedure

The Damus-Kaye-Stansel operation is a useful technique for the treatment of complex cyanotic congenital heart disease when there is obstruction between the systemic ventricle and the aorta. Modifications of the technique include transection of the aorta and the pulmonary artery, anastomosis of the contiguous aortic and pulmonary walls, and connection of the distal aorta to the perimeter of the new bivalved proximal great artery. In addition, the bidirectional cavopulmonary shunt technique can be used with or without the Fontan procedure. Six patients underwent a Damus-Fontan operation, and all survived. Two patients underwent the Damus-cavopulmonary shunt (hemi-Fontan) procedure, and 1 survived. The postoperative status of the 7 survivors is good to excellent. Follow-up ranges from 2 months to 7 1/2 years.

Congenital heart disease and pulmonary artery hypertension. I. pulmonary vasoreactivity to 15% oxygen before and after surgery

Pulmonary vasoreactivity at sea level was studied in 22 children before and in 15 children after corrective cardiac surgery for congenital heart disease and pulmonary artery hypertension; 8 children were studied both before and after cardiac surgery. During cardiac catheterization in 28 children, pulmonary and systemic hemodynamics were determined in room air and during breathing of 15% oxygen, which corresponds to a maximal hypoxic level commonly encountered during airplane travel. Before surgery, 19 of 22 children tolerated 15% oxygen (O2), which caused the following hemodynamic changes from room air status: the ratio of pulmonary to systemic arterial pressure increased from 0.70 to 0.78 (p less than 0.05), the ratio of pulmonary to systemic flow decreased from 2.2 to 2.0 (p greater than 0.05) and the ratio of pulmonary to systemic vascular resistance increased from 0.33 to 0.40 (p less than 0.02). In two children, severe pulmonary vasoconstriction developed within 5 minutes of 15% oxygen administration, requiring immediate discontinuation of hypoxia; neither patient had lasting deleterious effects. There was no evidence of increased pulmonary vasoreactivity in children with Downs syndrome compared with genetically normal children. After corrective surgery in 15 children (including both of the hyperreactors), no significant pulmonary vascular response to 15% oxygen was found. It is concluded that, in a small number of children with unrepaired congenital heart disease and pulmonary artery hypertension, pulmonary vascular hyperreactivity can be induced by breathing 15% oxygen; this reaction is life-threatening but reversible with the administration of 100% oxygen.(ABSTRACT TRUNCATED AT 250 WORDS)

Psychological preparation of mothers of preschool children undergoing cardiac catheterization

Abstract Three methods of preparing mothers for the hospitalization of their preschool age children scheduled for cardiac catheterization were compared. Fifty mothers participated in varying combinations of education and hospital orientation, stress management training, and brief supportive psychotherapy. This design allowed for the measurement of both individual and cumulative effects. Behavioral responses of children and their mothers and self-reports of mothers were measured. Mothers who received stress management training and their children evidenced significantly more adaptive behaviors at key stress points and these children adapted more positively at home following the catheterization. Mothers who received education and hospital orientation reported significantly less anxiety and tension and expressed greater competence in caring for their children. Possible explanations for these results are discussed.

Shared coronary arteries and coronary venous drainage in thoracopagus twins

A pair of type B thoracopagus twins with complex cyanotic heart disease had shared coronary arteries and coronary venous drainage. Surgical separation was not attempted and the twins died at 10.5 months of age. Antemortem angiography demonstrated that Twin As right coronary artery supplied Twin Bs diaphragmatic and anterior ventricular myocardial free wall. A midline communication existed between each twins right atrium at a common coronary sinus. The crossing coronary artery coursed alongside this connection and was visualized echocardiographically. At postmortem examination, the great cardiac vein of Twin A drained into the orifice of the common coronary sinus on Twin Bs side of the midline. In five of six previously reported cases, the children died at attempted separation shortly after ligation of the interatrial communication. This may have been because of occlusion of a coronary artery or acute obstruction of a coronary vein. Consideration of separation of type B thoracopagus twins requires anatomic delineation of the coronary arteries and veins.

Separation of omphalopagus twins : Unique reconstruction using syngeneic cryopreserved tissue

Omphalopagus twin girls were admitted for evaluation of possible separation and repair at age 7 days. Prenatal sonographic diagnosis occurred late in the third trimester and was followed by cesarean section delivery shortly thereafter. Results of extensive evaluation over the next 7 days including x-rays, computed tomography and ultrasound scan of the head and torso, and cardiac catheterization showed: the gastrointestinal tracts were separate and normal, the livers were joined but had separate biliary and vascular systems, and the hearts were separate with vastly different anatomy and function. One twin (twin A) had a normal heart with a small insignificant VSD. Twin B had a single ventricle, an incompetent A-V valve, stenotic pulmonic valve, ASD, PDA, and congenital heart block. Hemodynamic support of twin B was almost entirely from twin A. The vascular communications between the two consisted of a major connection between the internal mammary arteries and large arterial and venous connections traversing the joined livers. Because of continued deterioration of twin B, separation was undertaken at age 15 days. The separation included dividing the liver and the multiple large vascular connections. Two teams then reconstructed each twin separately. Twin B began showing signs of cardiac decompensation shortly after separation in spite of placement of a pacemaker, pulmonary artery banding, and ligation of the PDA. Cardiac function rapidly deteriorated and she died. Tissue from her chest wall was cryopreserved and placed in the tissue bank. Twin A underwent closure of her abdomen, and received a temporary bovine pericardial patch over the chest defect. She subsequently underwent placement of a graft of twin Bs rib cage to bridge the bony chest defect and skin flap closure. She is presently taking a normal diet and thriving at home at age 18 months. The use of cryopreserved tissue from a syngeneic source provides a unique method of reconstruction in this situation.