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Blends of two elastomeric ethylene-octene copolymers with similar octene contents having a random (ORC) and a blocky architecture (OBC) are prepared by melt mixing. The thermal and mechanical properties of ORC, OBC and their blends are investigated by DSC, dynamic mechanical analysis and tensile tests. The morphology of the semi-crystalline samples is studied by AFM and WAXS. Two types of crystals have been observed: (i) Orthorhombic crystals forming lamellae with an estimated thickness of about 13 nm composed mainly of long polyethylene-like sequences of OBC that melt a temperature of about 120 degrees C and (ii) fringed micellar crystals with a thickness of 2-4 nm formed basically by short polyethylene-like sequences of ORC that have melting temperatures between 30 and 80 degrees C. The amorphous phase contains a relatively homogeneous mixture of segments of both components indicated by the relatively uniform shape of the loss modulus peaks from dymamic-mechanical measurements for all investigated copolymers and blends. ORC crystallization is hindered in blends as indicated by lower melting enthalpies. This might be related to the high octene content of the amorphous phase at the relevant crystallization temperature as well as geometrical constraints since ORC crystallization occurs in an already semi-crystalline polymer. The results of tensile tests show that the mechanical behavior can be tailored via blend composition and morphology of the semi-crystalline material. The findings clearly indicate that blending is a powerful strategy to optimize the properties of polyolefin-based copolymers.

In this study the effects of crystal habit, crystallinity and superstructure on the modulus of elasticity of isotactic polypropylene films were analyzed by atomic force microscope (AFM) nanoindentation. The modulus of elasticity, evaluated on the nanometer scale by AFM, showed a qualitatively similar dependence on the crystal habit, crystallinity and superstructure as the modulus of elasticity measured by dynamic-mechanical analysis and tensile testing. The observed values of both the surface stiffness measured by AFM and the macroscopic/bulk stiffness were distinctly larger in the presence of non-isometric lamellae organized in spherulite than in the presence of isometric nodular crystals, not organized in a spherulitic superstructure. The experimental data showed that the modulus of elasticity is not primarily influenced by the presence or absence of spherulite but by the molecular-deformation constraint associated to the crystal habit.

Congenital anomalies of the aortic arch that present in the first 30 days of life include clinically significant lesions such as coarctation of the aorta and interruption of the aortic arch. Other anomalies of aortic arch position may present as part of a larger congenital complex. Knowledge of the embryology and anatomy of these structures is essential to the understanding of this class of defects. A systematic and careful two-dimensional echocardiographic examination of the arch structures from suprasternal and high parasternal views should reveal the anatomy. A careful Doppler examination using pulsed- and continuous-wave Doppler, as well as color flow imaging, is used to delineate the presence and severity of obstructive lesions. This review discusses the anatomy and echocardiographic techniques that may be used to demonstrate this group of lesions. Noninvasive echocardiographic examination of the aortic arch complex in the neonate should be sufficient to make the diagnosis of most aortic arch anomalies. (ECHOCARDIOGRAPHY, Volume 8, July 1991)

We reviewed our experience over a 10-year period to determine whether children with Down’s syndrome and complete atrioventricular canal develop pulmonary vascular obstructive disease earlier than children with normal chromosomes and this defect. Comparisons were made between Down’s syndrome and normal chromosome children regarding (1) pulmonary blood flow and pulmonary vascular resistance at initial catheterization, (2) operability as related to elevation in pulmonary vascular resistance, and (3) age at diagnosis of fixed pulmonary vascular obstructive disease. The 45 patients with Down’s syndrome catheterized under 1 year of age had a lower mean pulmonary blood flow (3.2 versus 5.7; p = 0.0001) and higher mean pulmonary vascular resistance (8.3 versus 4.6 Wood units · m2; p = 0.0003) than their 34 normal chromosome counterparts. When all ages were included, 38 of 81 (47 %) of the children with Down’s syndrome and 32 of 40 (80 %) of the normal children were considered operable. Non-Down’s syndrome patients who had operations had a higher pulmonary blood flow (5.8 versus 3.3; p = 0.004) and lower pulmonary vascular resistance (3.6 versus 6.0 Wood units · m2; p = 0.005) than Down’s syndrome patients. Of the 34 patients who did not have operations because of pulmonary vascular obstructive disease, 31 had Down’s syndrome. In 10 of 81 children with Down’s syndrome, fixed pulmonary vascular obstructive disease was diagnosed before the age of 1 year, while this was found in none of 40 normal children. Our data demonstrate that Down’s syndrome patients with complete atrioventricular canal have a greater degree of elevation of pulmonary vascular resistance in the first year of life and more rapid progression to fixed pulmonary vascular obstructive disease than children with normal chromosomes.

Multiple cardiac rhabdomyomas in a neonate with tuberous sclerosis were first described by Von Recklinghausen in 1862. These hamartomas are the cardiac tumors most frequently encountered during infancy and childhood. Rhabdomyomas account for 45% of primary heart tumors in children and represent 53% of primary benign childhood cardiac tumors. 1 Approximately 30% of patients with tuberous sclerosis have cardiac rhabdomyomas. 2 Their natural history is unclear because most reviews on this subject are based on autopsy data. The prognosis for cardiac rhabdomyomas is believed to be grim because of reported fatality rates of 53% by the first week of life and 78% by 1 year of age. 2,3 With widespread use of echocardiography in pediatrics during the last 2 decades, it has become clear that rhabdomyomas result in a wide spectrum of clinical manifestations, ranging from a total absence of symptoms to intrauterine or sudden postnatal death. Also reported are hydrops fetalis, dysrhythmias, inflow or outflow obstruction, congestive heart failure and possibly cerebral embolization. Histologic examination of these masses in 1923 was suggestive of spontaneous regression. 4 Isolated clinical reports of spontaneous regression have recently appeared. 5 We now describe a series of 5 infants with tuberous sclerosis who had close documentation of the size of their 13 tumors.

Between 1972 and 1990, 18 patients (median age 3 years, range 0.1-14 years) with coronary artery fistulae (CAF) were seen at this institution. Of the 16 patients without associated heart defects, two patients presented with congestive heart failure and the remaining 14 were asymptomatic. Fifteen patients had normal origin of two coronary arteries. Two patients had atresia of the proximal right coronary artery and, in one patient, the right coronary artery originated from the left main coronary artery. The QP/QS ranged between 1.0 and 2.8, with a mean of 1.4. Fifteen patients underwent operative closure without any deaths. One patient is being followed medically at present. Two patients showed spontaneous clinical improvement of CAF (complete closure in one and near complete in the other) and remained asymptomatic during a decade of follow-up. Review of the literature suggests operative closure of symptomatic and asymptomatic small CAF during childhood. However, the natural history of minute CAF remains unclear. In addition, symptoms from CAF may spontaneously improve with time.

To evaluate a possible neural or renal contribution to the hypertension that occurs in some patients following coarctation of aorta repair, 35 patients underwent graded bicycle exercise with serial measurements of plasma norepinephrine concentrations and plasma renin activity. Sixteen patients with coarctectomy who had systolic or diastolic hypertension at peak exercise were compared with 19 normotensive patients with coarctectomy. The average time interval between coarctation repair and study was significantly longer (p less than 0.05) in the hypertensive group than in the normotensive patients (12.8 +/- 4.8 versus 8.7 +/- 2.2 years). The heart rate response to exercise was similar for both patient groups. The systolic blood pressure in the hypertensive group was higher than in the normotensive group at rest in the supine and upright positions and at 5 minutes of recovery, in addition to peak exercise, and the diastolic blood pressure was increased at peak exercise. Plasma norepinephrine concentrations were significantly higher at peak exercise and during recovery in the hypertensive group than in the normotensive patients. Plasma renin activity was also significantly higher in the hypertensive group at peak exercise. These data suggest that patients with coarctectomy who have a hypertensive response to exercise have an augmented sympathetic nervous system output and increased plasma renin activity that may lead to peripheral vasoconstriction at peak exercise and that may contribute to the development of their hypertension.

• A 21-month-old infant presented with simultaneous localized scleroderma and severe cardiomyopathy with heart failure. Cardiac abnormalities and serological changes (positive rheumatoid factor assay, elevated IgM and IgG levels, and elevated erythrocyte sedimentation rate) reverted to normal with prednisone therapy, and there was substantial, though incomplete, resolution of her skin changes during the same period. To our knowledge, this is the first patient with definite, clinically significant cardiac involvement associated with focal scleroderma. The possibility of internal organ involvement, including cardiac involvement, must be considered with focal scleroderma as well as with progressive systemic sclerosis. ( AJDC . 1991;145:229-231)

One hundred twenty patients with dextro-transposition of the great arteries (TGA) underwent intra-arterial baffle repair using thin Dacron fabric from 1971 to 1979. The ages of the patients ranged from 29 days to 17 years (mean age 28 months). Thirty-five patients had undergone 49 preliminary palliative operations. Early postoperative mortality was 4.8% for patients with simple TGA but was higher among patients with associated ventricular septal defect (26%), VSD and left ventricular outflow tract obstruction (28.5%) and intact ventricular septum with left ventricular outflow tract obstruction (12.5%). Early nonfatal postoperative complications included low cardiac output (23.3%), respiratory insufficiency (35.8%), junctional rhythm (34.1%), superior vena caval (SVC) obstruction (9.1%), and chylothorax (7.5%). Late postoperative mortality for all groups was 7.5% (nine patients). Late cardiac dysrhythmias occurred in 33 patients (40.7%). Normal sinus rhythm has been preserved in all patients since direct, high SVC cannulation was instituted. Late postoperative hemodynamic and angiographic evaluation in 61 patients revealed severe to total SVC obstruction in 12 patients (20.2%) and pulmonary venous obstruction in four patients (6.5%). Among the latter, two patients died following reoperation and another patient died without operation. SVC obstruction was clinically important in only three patients, two of whom have undergone successful reoperation. All other late survivors are acyanotic and clinically well. The Mustard operation has dramatically improved the survival rate and quality of life for patients with TGA. However, postoperative caval and pulmonary venous obstruction are problems which require additional technical modifications and stimulate the search for alternative corrective operations.

Ultrasonic studies were performed in 19 neonates with the hypoplastic left heart syndrome whose diagnosis was confirmed at angiography or autopsy, or both. The patients were classified in two echocardiographic groups: Group I, 10 infants whose ventricular septum could be recorded, and Group II, 9 infants whose septum could not be recorded. The findings in these groups were compared with those in 60 neonates without congenital heart disease also studied with ultrasound. Two additional neonates who presented with signs of shock were also studied. The diagnostic echocardiographic features of hypoplastic left heart syndrome were: (1)a left ventricular end-diastolic dimension of less than 9 mm; (2)an aortic root diameter of less than 6 mm; (3)a ratio of left ventricular end-diastolic to right ventricular end-diastolic dimension of less than 0.6; and (4)a mitral valve echo that is absent or greatly distorted and of small amplitude. These echocardiographic criteria differed significantly from findings in the normal group (P less than 0.01). Echocardiography proved valuable in neonates with shock. It is a safe, reliable technique that can be used to delineate the intracardiac anatomy in sick neonates with the hypoplastic left heart syndrome.

One hundred nine consecutive patients underwent 115 palliative shunts between 1971 and 1979 for the initial management of symptomatic tetralogy of Fallot. A single Blalock-Taussig shunt was done in 78 patients, including 38 infants below 12 months of age, with two deaths (2.5% mortality rate). Thirty-two patients underwent a Waterston shunt, with one death (3.1% mortality rate). The total early shunt mortality rate was 2.7% (three deaths among 109 patients). There was one late noncardiac death and one instance of nonfatal brain abscess between the two stages. Fifty-nine of the previously shunted patients have undergone total correction at a mean post shunt interval of 37.1 months, with one early postoperative death (1.6% mortality rate). The mean patient age at total repair was 4.8 years. The two-stage combined operative mortality rate was 3.6% (four deaths among 109 patients). The Waterston shunt is considered undesirable because it complicated the total repair and was associated with a high incidence of residual right pulmonary artery obstruction at postoperative cardiac catheterization. The Blalock-Taussig shunt had a low mortality rate, high long-term patency rate, absence of interval complications, and no adverse effect at the time of total correction. It is considered the shunt of choice in all symptomatic infants and small children with tetralogy of Fallot. Our experience suggests that, at the present time, the two-stage surgical approach compares favorably with primary total correction, especially in infants under 1 year of age.

Six patients with cor triatriatum underwent surgical correction. They ranged for 1.5 to 93 months old (mean, 22 months). Congestive heart failure was present in 3 patients. Cardiomegaly and increased pulmonary vascularity were evident roentgenographically in all patients. Cardiac cineangiography demonstrated the subdividing left atrial membrane in 5 patients and suggested the correct diagnosis by revealing an abnormal configuration of the left atrium in the other patient. The opening in the anomalous left atrial membrane was stenotic in every instance. The proximal left atrial chamber communicated with the right atrium through an atrial septal defect in 5 patients and with the systemic venous circuit through a persistent left superior vena cava in the other patient, in whom the atrial septum was intact. A right atrial-transseptal approach provided ample exposure for complete excision of the obstructing membrane and repair of the atrial septum in all patients. One patient died of low cardiac output during the early postoperative period. The other 5 are alive and well at an average of 48 months after operation.

A prospective comparison of physiologic response to single-rate ventricular and dual-chamber atrioventricular pacing was conducted in 14 pediatric patients (age 1 to 24 years, median 14) with symptomatic nonsurgical second- or third-degree atrioventricular block. All patients were studied acutely during cardiac catheterization before and after 1 hour of both pacing modes. Following pacemaker implant, eight patients were reevaluated after 1 month of each mode with symptom questionnaire, resting ECG, resting echocardiogram, and Doppler cardiac output measurement at rest and at peak treadmill exercise. Cardiac outputs (mean +/- standard error) increased acutely (n = 14) with both ventricular (32 +/- 12%) and dual-chamber (39 +/- 10%) pacing over intrinsic rhythm values (p less than 0.01 in both). During chronic pacing (n = 8), symptoms were reported only with the ventricular mode. Dual-chamber synchronous pacing was associated with improved mean resting shortening fraction and cardiac output, slower mean resting sinus rate (89 +/- 5 compared to 73 +/- 4 bpm (p less than 0.02), and a 23% increase in mean excerise cardiac output (4.2 +/- 0.4 compared to 3.4 +/- 0.3 L/min/m2) compared to single-rate ventricular pacing. Exercise-induced dysrhythmias occurred only with ventricular pacing. This study demonstrates that pediatric patients with nonsurgical atrioventricular block can compensate for loss of atrioventricular synchrony at rest but exhibit improved cardiac function with chronic dual-chamber atrioventricular compared to single-rate ventricular pacing.

Case histories of 53 patients with surgically treated vascular rings are presented. The diagnosis was strongly suggested in all patients by symptoms of tracheoesophageal obstruction and was confirmed by barium esophagogram, which showed typical bilateral and posterior indentations in the esophagus. Angiography was rarely used although it is helpful in doubtful cases. Endoscopic studies were considered unnecessary and potentially harmful. A left posterolateral thoracotomy afforded ample access for division of the ring in all patients. Two patients died who were operated upon during the early experience. There were no postoperative deaths among the last 45 consecutive patients. All survivors had excellent symptomatic relief although complete resolution of symptoms took several months in some patients. The importance of early diagnosis and prompt surgical division is emphasized.

Case histories of five children with primary cardiac tumors are presented. The clinical and pathological features of the most frequent cardiac neoplasms in childhood are also reviewed. Cardiac tumors should be suspected in any child with unexplained heart murmurs, congestive heart failure, or cardiac arrhythmias. Echocardiography, cardiac catheterization, and biplane cineangiograms provide diagnostic confirmation. Prompt surgical resection is indicated in all symptomatic patients and in those with significant inflow and outflow tumor-related obstruction. Complete resection is not possible in many patients with cardiac rhabdomyoma or lipoma but removal of the obstructive portion of the tumor frequently provides long-term symptomatic relief.

Two hundred and nine patients underwent total repair of tetralogy of Fallot without congenital pulmonary atresia from 1971 to 1979. The age of the patients ranged from 22 months to 27 years (mean 6.8 years). Previous palliative shunts were present in 130 patients (62.2%). The right ventricular outflow tract obstruction was relieved by infundibulectomy in 31 patients (14.8%), by transannular patching in 142 patients (67.9%), and by insertion of a right ventricular-to-pulmonary artery prosthetic conduit in 10 patients (4.7%) with associated coronary artery anomalies. A porcine valve was inserted after transannular patching only in patients with undersized pulmonary arteries, unilateral pulmonary artery, or congenitally absent pulmonary valve. There were 10 early postoperative deaths (4.7%). Previous palliative shunts did not adversely affect early postoperative mortality rate. Surgically induced permanent complete heart block occurred in one patient (0.4%). Six patients (3%) died in the late postoperative period, three of them of unrelated causes. Late results were good in 170 patients (87%), fair in 10 patients (5.1%), and poor in 15 patients (7.6%). Poor results were due to residual stenosis at the origin of the pulmonary arteries in 13 patients (6.5%) and to residual ventricular septal defect in two patients (1%). The mean cardiothoracic ratio was 0.61 for patients with poor results and 0.54 for the entire group. Pulmonary valvular insufficiency was well tolerated postoperatively in the absence of distal pulmonary artery obstruction. This experience supports a policy of aggressive relief of the right ventricular outflow tract obstruction including liberal use of transannular patching and, when indicated, extensive reconstruction of the pulmonary artery branches. We also recommend a two-stage treatment program for symptomatic infants with unfavorable anatomy consisting of initial Blalock-Taussig shunt followed by total repair at about 3 years of age.

A fourth case is presented of propagation of Wilms' tumor to the right atrium through the inferior vena cava. Ultrasonic examination of the heart was diagnostic of the tumor and the diagnosis was confirmed by angiographic studies and surgical exploration. This report provides the first echocardiographic description of a right atrial tumor in a child.

Intrapericardial teratoma is a rare, congenital, pedunculated tumor, usually attached to the ascending aorta and associated with massive pericardial effusion, cardiac compression, and severe cardiorespiratory distress in infants and young children. Echocardiography and cardiac cineangiography are diagnostic and should be used promptly. The tumor is generally benign and early surgical removal is curative. The case reports of two infants who underwent successful surgical removal of their lesions are presented.

Four patients with tetralogy of Fallot (TF) and complete atrioventricular canal (CAVC) underwent successful intracardiac repair. All patients had undergone preliminary palliative shunts. Associated cardiovascular lesions included muscular ventricular septal defect (VSD) and left superior vena cava (one patient), bilateral main pulmonary artery stenosis (one patient), and right aortic arch (two patients). The diagnosis was suspected clinically by electrocardiographic evidence of right ventricular hypertrophy and left anterior hemiblock, by echocardiographic findings suggestive of CAVC with aortic dextroposition, and by the association with trisomy 21. The diagnosis was confirmed by cardiac catheterization and cineangiography. Total correction consisted of closure of the VSD and atrial septal defect (ASD), reconstruction of the atrioventricular valves, and relief of the right ventricular outflow tract obstruction (RVOTO). There were no early or late postoperative deaths. Surgically induced complete heart block did not occur. One patient underwent successful reoperation for residual VSD and right ventricular outflow aneurysm. Late hemodynamic evaluation revealed good results in all patients. We recommend a staged treatment plan consisting of preliminary systemic--pulmonary artery shunting for symptomatic children under 4 to 5 years of age and total correction for older children. With proper preoperative diagnosis and accurate intracardiac repair, good results may be obtained after total correction of TF and CAVC.

A total of 297 consecutive classic systemic artery-pulmonary artery shunts were performed in 281 patients over the past 9 years. This experience includes 200 Blalock-Taussig shunts (67.3%), 84 Waterston shunts (28.2%), and 13 Potts shunts (4.3%). The overall early mortality after the Blalock-Taussig shunt (5.5%) was significantly lower (p less than 0.02) than for the Waterston shunt (13%). The early mortality after either the Blalock-Taussig or Waterston shunt was not statistically related to the age of the patient at operation. Both the Blalock-Taussig and Waterston shunts demonstrated a higher mortality (p less than 0.02) among patients in Group II (complex defects) than in patients in Group I (tetralogy of Fallot and pulmonary atresia with ventricular septal defect [VSD]). However, the Blalock-Taussig shunt had a significantly lower (p less than 0.04) probability of early postoperative death than the Waterston shunt among patients with complex lesions. The Blalock-Taussig shunt also revealed a lower incidence of important late postoperative complications and did not affect adversely the hemodynamic result after intracardiac correction, as evidenced by late postoperative cardiac catheterization. This study also confirms the feasibility of the Blalock-Taussig shunt during the neonatal period without significantly increased age-related risk of postoperative death (p = 0.13) and with good early and late long-term patency rates.