Biomedical subjects

N H Silverman

Publications and source records attributed to N H Silverman.

At least 73 records · Page 4Linked to original sources

PubMed1996

Assessment of flow events at the ductus venosus-inferior vena cava junction and at the foramen ovale in fetal sheep by use of multimodal ultrasound.

BACKGROUND: Previous techniques for the study of the fetal circulation did not permit assessment of phasic events associated with the cardiac cycle. We used multimodal ultrasound techniques to examine flow events that occur in the major veins and across the foramen ovale in the circulation of the fetal lamb. METHODS AND RESULTS: We studied eight fetal lambs instrumented with catheters in the superior and inferior venae cavae and a peripheral umbilical vein and performed ultrasound studies that included M-mode and two-dimensional imaging, pulsed and Doppler color flow ultrasound, and contrast echocardiography to evaluate flow in the ductus venosus, in both venae cavae, and through the foramen ovale. Two blood streams of different flow velocities were identified within the cephalic portion of the inferior vena cava. The stream that originated from the narrowed ductus venosus had a higher velocity than that from the caudal inferior vena cava (mean velocity, 57 +/- 13 versus 16 +/- 3 cm/s; P < .0002). Facilitated by the eustachian valve and the septum primum, the ductus venosus stream preferentially passed through the foramen ovale to the left atrium. This flow occurred during most of the cardiac cycle, except for 19.6 +/- 2.3% of the cycle when the foramen ovale was closed during atrial contraction. Superior vena cava flow passed almost exclusively into the right atrium and tricuspid valve; a small amount that was refluxed from the right atrium into the inferior vena cava subsequently passed through the foramen into the left atrium. CONCLUSIONS: Visualization of fetal circulatory streaming at the venous sites by ultrasound techniques aids in understanding the function of the fetal circulation and may be helpful in detecting the human fetus that is hemodynamically compromised.

Animals↗

PubMed1996

Comparison of cleft and papillary muscle position in cleft mitral valve and atrioventricular septal defect.

Differentiation of cleft mitral valve from atrioventricular septal defect (AVSD) is surgically important because of different conduction pathways. The purpose of this study was to find echocardiographic markers for differentiating cleft mitral valve from AVSD. We examined 11 children with cleft mitral valve, 11 children with AVSD, and 11 normal children. We defined a fixed reference point (0 degrees of arc) at the medial junction of the right ventricular free wall with the posteroinferior ventricular septum. Left ventricular papillary muscle and cleft position was measured clockwise in degrees of arc from 0 degrees around a point representing the center of the left ventricle in the parasternal short-axis views. Mural leaflet size was expressed by the arc between the bases of the papillary muscles. Papillary muscle position in cleft mitral valve was similar to that in normals (anterolateral ventricular papillary muscle:cleft mitral valve 194 +/- 10 degrees, normals 191 +/- 8 degrees; posteromedial ventricular papillary muscle:cleft mitral valve 329 +/- 10 degrees, normals 329 +/- 14 degrees). In AVSD, both left ventricular papillary muscles originated closer to each other and were rotated counterclockwise (anterolateral papillary muscle: 182 +/- 7 degrees; posteromedial papillary muscle: 287 degrees +/- 17 degrees). The mural leaflet size was similar in cleft mitral valve and in normal children. In AVSD, the mural leaflet was significantly smaller than in cleft mitral valve and in normals. The cleft position did not permit distinction between cleft mitral valve and AVSD. In conclusion, echocardiographic measurements of papillary muscle position and mural leaflet size permit differentiation of cleft mitral valve from AVSD.

Child↗

PubMed1996

Transesophageal echocardiography in fetal sheep. A monitoring tool for open and fetoscopic cardiac procedures.

BACKGROUND: Cardiac procedures in exteriorized fetuses or assisted by fetoscopy require monitoring capabilities not attended by conventional maternal transabdominal echocardiography. METHODS: We, therefore, assessed the potential of fetal transesophageal echocardiography (TEE) utilizing an intravascular ultrasound catheter (IVUC) for fetal cardiac monitoring. We inserted a 10-F-10-MHz IVUC into the esophagus in 12 exteriorized fetal sheep and by a fetoscopic approach in 4 fetal sheep. Cardiac events were observed. Heart rate, cardiac rhythm, patency of the foramen ovale and ductus arteriosus, and the width of the branch pulmonary arteries could be assessed in all fetuses. Ventricular contractility could be assessed only in fetuses weighing less than 2.5 kg. Larger fetuses did not allow adequate imaging of the apical portion of the ventricles because of limited tissue penetration of the IVUC. Fetal TEE permitted placing small guide wires in the cardiac atria and left ventricle. Short-lived premature beats following intracardiac manipulations of these wires could be observed by fetal TEE in all cases. RESULTS: At autopsy, no complications from IVUC insertion were observed in the exteriorized fetuses. Fetoscopic placement of the IVUC resulted in minor perioral skin erosion in two nonexteriorized fetuses. CONCLUSIONS: In conclusion, fetal TEE can be achieved with minor fetal injury and may provide useful information during open and fetoscopic cardiac procedures. Further improvements in IVUC design will permit the application of this technique to monitor human fetal cardiac procedures.

Animals↗

PubMed1996

Intraatrial baffle repair of isolated ventricular inversion with left atrial isomerism.

Isolated ventricular inversion with left atrial isomerism, partial anomalous pulmonary venous connection, and interruption of the inferior vena cava with azygos continuation to a right superior vena cava was diagnosed by echocardiography in a neonate. At 48 days of age, the patient underwent successful anatomic correction with redirection of flow from the superior vena cava and hepatic veins to the left-sided tricuspid valve, and flow from the pulmonary veins to the right-sided mitral valve. In the present report, the surgical techniques of this case are described, along with a survey of the surgical literature covering anatomic repair of isolated ventricular inversion.

Echocardiography↗

PubMed1996

Reversed shunting across the ductus arteriosus or atrial septum in utero heralds severe congenital heart disease.

OBJECTIVES: This study was performed to define the significance of Doppler color flow mapping in demonstrating reversal of the direction of the normal physiologic flow across the atrial septum and ductus arteriosus in the human fetus. BACKGROUND: Reversal of the physiologic shunting across the ductus arteriosus or atrial septum in utero (i.e., left to right) can be readily identified by Doppler color flow mapping, complemented by pulsed and continuous wave Doppler information. METHODS: We reviewed echocardiograms recorded at our three institutions from 1988 to 1993, which displayed reversal of flow by Doppler color flow in 53 fetuses of gestational age 18 weeks to term. The diagnoses were confirmed by postnatal echocardiography, operation or autopsy. Reversal of shunting was consistently associated with severe heart disease. RESULTS: Reversed atrial shunting was found with severe left heart obstructive lesions, including 19 with hypoplastic left heart syndrome, 3 with critical aortic stenosis, 2 with double-outlet right ventricle and 1 each with an interrupted aortic arch, atrioventricular septal defect and severe left ventricular dysfunction due to dilated cardiomyopathy. Reversed ductus arteriosus shunting was found with severe right heart obstructive lesions, including nine fetuses with pulmonary atresia, six with severe obstructive tricuspid valve abnormalities, five with severe tetralogy of Fallot, four with Ebstein's anomaly and two with single ventricle and pulmonary stenosis. Associated cardiac lesions were common in both groups. Only 3 of the 15 infants who were delivered alive from the reverse ductus arteriosus shunt group and 4 of 12 from the reverse atrial shunt group still survive. CONCLUSIONS: The finding of reversed flow by Doppler color flow mapping during fetal life provides a key to subsequent accurate diagnosis and denotes a spectrum of diseases with a very poor prognosis.

Ductus Arteriosus↗

PubMed1996

Regression of tricuspid regurgitation after two-stage arterial switch operation for failing systemic ventricle after atrial inversion operation.

The cases of five patients with previous Senning (n = 4) or Mustard (n = 1) operations and failing systemic ventricles in whom banding of the pulmonary artery was performed as an interim step toward an arterial switch procedure are reported. The rise in the ratio of left to right mean systolic ventricular pressure, from 0.35 before operation to 0.90 during operation and 0.80 on the first postoperative day, caused a shift of the ventricular septum from a leftward to a midline or nearly midline position. This shift was associated with a reduction of tricuspid regurgitation. At a median interval of 5.1 months after pulmonary artery banding, the mean left ventricular posterior wall thickness had increased to 8.2 mm, versus 5 mm before operation, and the mean left ventricular myocardial mass index had increased to 90 gm/m2, versus 55.6 gm/m2 before operation. After the arterial switch operation, which was performed in four patients, the tricuspid regurgitation decreased to a trivial amount (n = 1) or disappeared completely (n = 3).

Adult↗

PubMed1996

Electrophysiologic study and radiofrequency ablation in patients with intracardiac tumors and accessory pathways: is the tumor the pathway?

INTRODUCTION: There is a strong association of cardiac rhabdomyomas with the Wolff-Parkinson-White syndrome. This report describes the results of investigations in two patients with accessory pathway-mediated AV reciprocating tachycardia coexisting with intracardiac tumors. METHODS AND RESULTS: Two patients with intracardiac tumors had mapping of the accessory pathway. Echocardiograms obtained in the electrophysiology laboratory while the ablation catheter was at the site of successful radiofrequency ablation demonstrated a close correspondence between the site of intracardiac tumor and the location of the accessory pathway. CONCLUSIONS: These results lend support to the hypothesis that accessory pathways in patients with intracardiac tumors, such as rhabdomyomas, are not typical Kent bundles, but instead are either part of the intracardiac tumor or are closely related to the tumor. Ablation is possible in at least some patients with accessory pathways associated with intracardiac tumors.

Adolescent↗

PubMed1996

Evaluation of umbilical venous blood flow by Doppler color flow mapping and conventional ultrasonographic methods.

Ultrasonographic measurement of umbilical venous blood flow as a reflection of placental blood flow has been used for assessment of fetal well-being. Because fetal and maternal factors may prevent satisfactory measurement of umbilical venous diameter and flow velocity, an alternative method would be helpful. We found that, in 35 human fetuses between 18 and 35 weeks of gestation, that both variables for umbilical venous flow calculation can be measured from a single Doppler color frame with close measurement agreement to conventional combined cross-sectional pulsed Doppler ultrasonographic measurements. Thus, this method provides an alternative to the conventional method or may be used for a cross-check and has the potential for automated flow calculation.

Blood Flow Velocity↗

PubMed1996

Pediatric cardiac imaging--an historical perspective and future challenges.

This report defines the events that shaped the development of echocardiography and those studies that established the discipline of pediatric echocardiography, by noting the major contributions that defined the development of the craft. From the present perspective, future developments appear promising for providing even greater morphologic and physiologic information.

Child↗

PubMed1995

Pathologic elucidation of the echocardiographic features of Ebstein's malformation of the morphologically tricuspid valve in discordant atrioventricular connections.

We defined the morphology of the left atrioventricular valve in Ebstein's malformation associated with congenitally corrected transposition to elucidate the approach to diagnosis by echocardiography. We found 14 unequivocal cases out of a total of 3,720 specimens. We noted the atrial arrangement, displacement, and nature of the tricuspid leaflets, and axis of the plane of the tricuspid orifice. We constructed ratios of volume of the atrialized to the functional right ventricle, and of the right to left ventricle, as well as distances of the septal attachments of the atrioventricular junctions to the respective ventricular apices. Three specimens had abnormalities of cardiac position, and 8 had ventricular septal defect. The tricuspid valve plane was rotated 47 +/- 21 degrees from its usual position into the ventricle. The tricuspid valvar tissue was variably attached to the underlying myocardium, with the most severely affected lesion being the mural leaflet followed by the septal leaflet, and the anterior leaflet attachment the least affected. Abnormalities of the tendinous cords and the effective valvar orifice occurred in 3 specimens. The ratio of the atrialized to the functional right ventricular volume was 0.74 +/- 0.49; the ratio of the fetal right to left ventricular volume was 1.18:1 +/- 0.70:1. These data suggest that plastic repairs of the right ventricle would leave a small functional right ventricle, but that valve replacement could restore the volume of the ventricle. Thus, the plane of displacement of the valve in corrected transposition appears less amenable to 4-chamber echocardiography than other forms of Ebstein's malformation. Changes in the echocardiographic planes should display the morphology and also provide some hemodynamic information.

Adult↗

PubMed1995

Echocardiographic evaluation of congenital mitral valve anomalies in children.

Congenital mitral valve anomalies were diagnosed in 65 children, whose ages ranged from newborn to 18 years, using 2-dimensional, color, pulsed-, and continuous-wave Doppler ultrasound. Data were collected over 7.5 years from 13,400 new studies. Data in these patients were compared with those obtained by cardiac catheterization, cardiac surgery, and autopsy. We detected 4 different lesions: (1) congenital mitral stenosis with 2 papillary muscles (n = 24); (2) parachute mitral valve, with a single papillary muscle (n = 24); (3) isolated cleft in the mitral valve (n = 10); and (4) double-orifice mitral valve (n = 7). A supravalvar mitral ring was detected in 21 patients with mitral stenosis; however, it never occurred as an isolated lesion and was invariably associated with some other left ventricular inflow or outflow obstruction. The supravalvar ring was associated with a parachute deformity of the mitral valve in 17 patients; in only 4 was this abnormality associated with mitral stenosis with 2 papillary muscles. In patients with congenital mitral stenosis, the peak and mean transmitral Doppler velocities were increased significantly compared with those in controls (peak velocity 1.53 +/- 0.74 vs 0.86 +/- 0.25 m/s, respectively, p < 0.01; mean velocity 1.13 +/- 0.61 vs 0.58 +/- 0.11 m/s, respectively, p < 0.01). The correlation between mean transmitral pressure gradient obtained by Doppler and cardiac catheterization was fair (r = 0.75). However, the correlation between the mitral valve areas calculated by the Doppler pressure half-time method and by the Gorlin formula was poor (r = 0.57).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1995

Determination of ventricular volumes in human fetal hearts by two-dimensional echocardiography.

In conclusion, ventricular volume calculation from 2DE is feasible in the human fetus and improves the ability to calculate fetal ventricular size and ejection fraction. The right ventricle is clearly dominant at midgestation, but approaches left ventricular size at term. Calculation of the ventricular output from 2DE volume measurements is an accurate alternative to Doppler measurements.

Echocardiography↗

PubMed1995

Development of pulmonary arteriovenous fistulae in children after cavopulmonary shunt.

BACKGROUND: The cavopulmonary shunt procedure is now used for palliation of complex congenital heart lesions in infants. While pulmonary arteriovenous fistulae (PAVF) are a well-known complication of this surgery in older patients, no study of the prevalence of this condition in children and young infants has been reported. METHODS AND RESULTS: We compared 29 patients with cavopulmonary shunts or total caval exclusion with 53 control subjects evaluated by contrast echocardiography at the University of California, San Francisco. The primary cardiac lesion, age at the time of surgery, type of right heart bypass procedure, provision of auxiliary pulmonary blood flow, and changes in oxygen saturation over time were compared. The prevalence of PAVF in children after cavopulmonary anastomosis is 60%, higher than previously reported. The prevalence is significantly higher in infants < 6 months old and in those with a heterotaxy syndrome. The provision of an additional source of pulsatile, pulmonary blood flow appears to have little effect on the development of PAVF. Patients who developed PAVF had arterial oxygen saturations at the time of discharge from surgery similar to those who did not develop them. Those with PAVF had significantly lower arterial and pulmonary venous oxygen saturations at follow-up as a result of their intrapulmonary shunt. CONCLUSIONS: Contrast echocardiography provides a sensitive method for the detection of PAVF. While the origins, natural history, and ultimate clinical significance of PAVF in children after cavopulmonary anastomosis are unclear, surveillance by contrast echocardiography is indicated for all patients who have had this procedure because PAVF may cause significant intrapulmonary right-to-left shunting in some patients.

Age Factors↗

PubMed1995

Surgical closed atrial septotomy under transesophageal guidance.

An infant with pulmonary atresia and intact ventricular septum is presented who, after initial patch reconstruction of the right ventricular outflow tract and bidirectional cavopulmonary anastomosis through a fifth median sternotomy, underwent an echocardiographically guided closed atrial septotomy, which resulted in marked long-term clinical improvement. The technique of intraoperative transesophageal echocardiography as used in the presented case represents an expanded role for this diagnostic modality in congenital cardiac surgery.

Ductus Arteriosus, Patent↗

PubMed1995

Extending the limits of the Ross procedure.

BACKGROUND: The potential for growth and the proven long-term durability of the native pulmonary valve make it ideal for replacement of the diseased aortic valve, especially in growing children. The use of the autologous pulmonary valve can be further extended to patients with complex left ventricular outflow tract obstruction and to neonates and infants. METHODS: Between June 1993 and May 1995, 35 patients underwent the Ross procedure at our center. Of these, 15 (43%) had complex left ventricular outflow tract obstruction and 7 (20%) were infants, including 3 neonates. The autologous pulmonary valve was implanted as a root replacement with coronary reimplantation in all patients. Additional left ventricular outflow tract procedures performed were ventricular myectomy in 7 patients and a Konno type aortoventriculoplasty in 11 patients. RESULTS: There was one early death in a patient with borderline hypoplastic left heart syndrome. At a median follow-up of 9 months (range, 0.2 to 22 months) there were no late deaths or reinterventions. The autologous pulmonary valve function was excellent, with 1 (2.8%) patient having moderate insufficiency. CONCLUSIONS: Autologous pulmonary valve is an excellent option for aortic valve replacement in all age groups. Its use can be readily extended to neonates, infants, and patients with complex left ventricular obstruction requiring additional left ventricular outflow tract procedures.

Adolescent↗

PubMed1995

Fibrous obstruction within the left ventricular outflow tract associated with ventricular septal defect: a pathologic study.

OBJECTIVES: We examined the nature of ridges within the left ventricular outflow tract associated with ventricular septal defects that might be found by echocardiography. BACKGROUND: Echocardiography displays even small ridges well. Surgical removal of such ridges at the time of defect closure is recommended. METHODS: We examined 37 heart specimens with ventricular septal defects with a ridge, noting its nature and relation to the defect and adjacent valves. We excluded left ventricular outflow tract obstruction associated with complex lesions. RESULTS: Defects were perimembranous in 25 specimens, muscular in 8 and part of an atrioventricular septal defect in 5. Some hearts had multiple defects. Many of the original reports had not mentioned ridges. Three distinct ridge patterns were found. The first (n = 18) was a fold of endocardial tissue related to the membranous septum. The second (n = 12) was a defect of a fibrous nature; in 8 this was a discrete, protuberant fibrous ridge, and in 4 the obstruction was diffuse, which we termed keloidal. The third pattern (n = 7) lay circumferentially around the ventricular septal defect, seemingly associated with the defect's attempted spontaneous diminution in size. Endocardial folds were not found in specimens from patients > 5 years old. Fibrous and keloidal lesions, which may represent a continuum of progression, generally were found in specimens from older patients. Histologic studies of 17 specimens confirmed the morphologic findings. The endocardial folds were endothelial tissue, whereas the fibrous and keloidal ridges were of fibrous tissue, as were circumferential lesions. All specimens had mitral-semilunar valvular continuity. CONCLUSIONS: Endocardial fold and circumferential lesions appear to be benign. The endocardial folds arose from the membranous ventricular septum, were not protuberant and usually were found in younger patients. The fibrous ridges, in contrast, were protuberant and were always associated with the underlying muscle of the outlet septum. These pathologic distinctions may facilitate echocardiographic diagnosis and prognosis.

Adolescent↗

PubMed1995

The levoatriocardinal vein: morphology and echocardiographic identification of the pulmonary-systemic connection.

OBJECTIVES: This study considers the array of pulmonary-systemic connections made by the levoatriocardinal vein. The primary and associated lesions that play a role in forming this vein are examined, and echocardiography is discussed as a method for its rapid identification. BACKGROUND: The levoatriocardinal vein is a pulmonary-systemic connection that provides an alternative egress for pulmonary venous blood in left-sided obstructive lesions. It is thought to result from the persistence of anastomotic channels that connect the capillary plexus of the embryonic foregut to the cardinal veins. Only 12 cases of levoatriocardinal vein have been reported since its first description in 1926. A comprehensive description of the morphology and echocardiographic identification of this lesion has been unavailable because of its rarity. METHODS: A retrospective study was performed in 13 patients with a levoatriocardinal vein from the University of California, San Francisco. Echocardiographic findings were compared with those obtained by angiography or at necropsy. In addition, the details of 12 previously published case reports were reviewed. Age at presentation, primary obstruction to pulmonary venous return, integrity of the atrial septum and origin and drainage of the levoatriocardinal vein were compared. RESULTS: Patient age at presentation was < 2 years, with most patients presenting before age 6 months. Variations of the hypoplastic left heart syndrome accounted for the majority of primary defects encountered, although multiple but less severe left-sided lesions were seen. The atrial septum was functionally intact in most patients. The levoatriocardinal vein, defined echocardiographically, originated predominantly from the smooth-walled left atrium and drained to the superior vena cava or innominate vein; however, variations of this pattern existed. CONCLUSIONS: As a physiologic entity, the levoatriocardinal vein provides a mechanism for decompression of pulmonary venous return primarily in patients with left ventricular inflow obstruction. A levoatriocardinal vein is thought to form when the atrial septum fails to provide an alternate egress for left atrial blood. However, when a septal defect or alternative shunt occurs in conjunction with a levoatriocardinal vein, the clinical presentation may be postponed. Echocardiography provides a rapid, noninvasive modality for identifying the pulmonary-systemic connection, which may masquerade as the vertical vein in anomalous pulmonary venous connection or act as an occult source of left to right shunting in patients undergoing surgery for hypoplastic left heart syndrome.

Coronary Circulation↗

PubMed1995

Is a cleft in the anterior leaflet of an otherwise normal mitral valve an atrioventricular canal malformation?

OBJECTIVES: This study sought to ascertain the surgical anatomy of a cleft in the left atrioventricular (AV) valve. BACKGROUND: Important morphologic differences exist between hearts with a cleft in the anterior leaflet of an otherwise normal mitral valve and those with a so-called cleft in the left AV valve when there is an AV septal defect, but it has been customary to link the lesions together on developmental grounds. METHODS: Eight autopsied specimens with a cleft in the aortic (or anterior) leaflet of the mitral valve were studied in detail, and echocardiograms from 21 patients with such a cleft were compared with the specimens and with findings typical of the so-called partial AV canal and other forms of AV septal defect. RESULTS: The structure and direction of the cleft, location of the papillary muscles within the left ventricle and AV junctional morphology of hearts with an otherwise normally structured mitral valve were significantly different from typical findings in hearts with AV septal defects. CONCLUSIONS: It is necessary to distinguish morphologically a cleft in an otherwise normally structured mitral valve in hearts with separate right and left AV junctions from the trifoliate left component of a common AV valve in hearts with an AV septal defect and a common AV junction because the disposition of the AV conduction tissues varies markedly between the lesions.

Autopsy↗