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Biomedical subjects

A R Snider

Publications and source records attributed to A R Snider.

At least 73 records · Page 4Linked to original sources
PubMed1986

Pulsed Doppler findings in patients with coarctation of the aorta.

We used combined two-dimensional and pulsed Doppler echocardiography to examine 37 infants and children with coarctation of the aorta and 19 normal subjects. The ages ranged from 1 day to 16 years. We compared the differences between the Doppler flow signal from the ascending aorta and the descending aorta below the coarctation in each patient, as well as the differences between the corresponding flow signals in the aorta of patients with coarctation and normal subjects. Six variables were measured from each Doppler signal: acceleration slope (peak rate of acceleration), acceleration time (time from onset of flow to the peak systolic frequency), antegrade flow time, peak systolic frequency, peak velocity of flow, and deceleration slope (peak rate of deceleration). In patients with coarctation, each of these variables was significantly different in the descending aorta compared with the ascending aorta. There was a decrease in the acceleration slope (14 +/- 13 vs 87 +/- 67 kHz/sec) (mean +/- SD), peak systolic frequency (1.8 +/- 1.0 vs 5.2 +/- 1.9 kHz), peak velocity of flow (0.70 +/- 0.40 vs 1.4 +/- 0.44 m/sec), and deceleration slope (11 +/- 11 vs 27 +/- 12 kHz/sec). There was also a prolongation of the acceleration time (140 +/- 50 vs 88 +/- 22 msec) and antegrade flow time (330 +/- 120 vs 270 +/- 50 msec). In addition, these variables in the descending aorta of patients with coarctation were significantly different from those in the descending aorta of normal subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Doppler evaluation of left ventricular diastolic filling in children with systemic hypertension.

To assess left ventricular (LV) diastolic function in children with systemic hypertension, 11 patients with hypertension (mean blood pressure 99 mm Hg) and 7 normal patients (mean blood pressure 78 mm Hg) underwent M-mode echocardiography and pulsed Doppler examination of the LV inflow. From a digitized trace of the LV endocardium and a simultaneous phonocardiogram, echocardiographic diastolic time intervals, peak rate of increase in LV dimension (dD/dt), and dD/dt normalized for LV end-diastolic dimension (dD/dt/D) were measured. Doppler diastolic time intervals, peak velocities at rapid filling (E velocity) and atrial contraction (A velocity), and the ratio of E and A velocities were measured. The following areas under the Doppler curve and their percent of the total area were determined: first 33% of diastole (0.33 area), first 50% of diastole, triangle under the A velocity (A area), and the triangle under the E velocity (E area). The A velocity (patients with hypertension = 0.68 +/- 0.11 m/s, normal subjects = 0.49 +/- 0.08 m/s), the 0.33 area/total area (patients with hypertension = 0.49 +/- 0.09, normal subjects = 0.58 +/- 0.08), the A area (patients with hypertension = 0.17 +/- 0.05, normal subjects = 0.12 +/- 0.03), and the A area/total area (patients with hypertension = 0.30 +/- 0.11, normal subjects = 0.20 +/- 0.07) were significantly different between groups (p less than 0.05). M-mode and Doppler time intervals, (dD/dt)/D, E velocity, and the remaining Doppler areas were not significantly different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1985

Results of balloon valvuloplasty in the treatment of congenital valvar pulmonary stenosis in children.

Transluminal balloon valvuloplasty was used in the treatment of congenital valvar pulmonary stenosis in 19 children, aged 5 months to 18 years. The right ventricular (RV) systolic pressure and RV outflow tract gradient decreased significantly immediately after the procedure (95 +/- 29 vs 59 +/- 14 mm Hg, p less than 0.01, and 78 +/- 27 vs 38 +/- 13 mm Hg, p less than 0.01). Seven of these patients were evaluated at cardiac catheterization 1 year after balloon valvuloplasty. No significant change occurred in RV systolic pressure or RV outflow tract gradient at follow-up evaluation compared with measurements immediately after balloon valvuloplasty (60 +/- 5 mm Hg vs 56 +/- 12 mm Hg and 39 +/- 5 vs 38 +/- 10 mm Hg). In addition, follow-up evaluation was performed using noninvasive methods and included electrocardiography (n = 13), vectorcardiography (n = 11) and Doppler echocardiography (n = 11) Doppler echocardiography in 11 patients 15 +/- 9 months after balloon valvuloplasty showed a continued beneficial effect with a mild further decrease in RV outflow tract gradient. Thus, balloon valvuloplasty is effective in the relief of pulmonary stenosis.

Adolescent↗
PubMed1985

Hemodynamic determinants of exercise-induced ST-segment depression in children with valvar aortic stenosis.

To evaluate the hemodynamic factors associated with treadmill-induced ST-segment depression in children with valvar aortic stenosis, 12 patients (mean age 13 years) with ST-segment depression during treadmill exercise and 5 patients (mean age 13 years) without ST-segment depression during treadmill exercise underwent exercise testing during cardiac catheterization. The left ventricular (LV) systolic pressure and LV outflow tract gradient at rest (177 +/- 25 vs 138 +/- 8 mm Hg and 59 +/- 18 vs 23 +/- 7 mm Hg, respectively) and corresponding pressures during maximal supine exercise (248 +/- 37 vs 189 +/- 17 mm Hg and 112 +/- 34 vs 52 +/- 14 mm Hg) were significantly greater (p less than 0.01) in the patients with exercise-induced ST-segment depression, although overlap existed. The LV-O2 supply-demand ratio during maximal supine exercise was significantly less (6.4 +/- 2.7 vs 11.8 +/- 0.7; p less than 0.005) in patients with than in those without exercise-induced ST-segment depression. In fact, an LV-O2 supply-demand ratio less than 11.0 was 100% sensitive and specific in predicting treadmill-induced ST-segment depression. These results suggest that although the development of ST-segment depression during treadmill exercise is related to LV systolic pressure and LV outflow gradient, its major hemodynamic determinant is the LV-O2 supply-demand ratio.

Adolescent↗
PubMed1985

Echocardiographic detection of anomalous course of the left innominate vein.

Anomalous course of the left innominate vein beneath the aortic arch is a rare congenital anomaly. We report the case of a 3 year old child in whom this defect was detected by two-dimensional and Doppler echocardiography. The echocardiographic appearance of the anomalous course of the left innominate vein is illustrated and the importance of identifying this rare systemic venous anomaly is discussed.

Aorta, Thoracic↗
PubMed1985

Atrial overdrive pacing for conversion of atrial flutter in children.

Twenty-three successive patients with 27 different episodes of sustained atrial flutter were treated with atrial pacing for conversion of the tachyarrhythmia; 15 patients with 16 episodes of atrial flutter underwent intracardiac right atrial pacing and eight patients with 11 episodes of atrial flutter were treated with transesophageal atrial pacing. Ten of sixteen episodes (63%) and eight of 11 episodes (73%) were successfully converted using intracardiac and transesophageal techniques, respectively. Mean flutter cycle length for all 27 episodes was 219 ms (mean heart rate 274 beats per minute); successful pacing conversion cycle length (n = 15) was 72% of the flutter cycle length. Hemodynamic, electrophysiologic, and roentgenographic data were not predictive of conversion by either technique. Induction of localized atrial fibrillation or failure to meet critical pacing criteria may explain pacing failures. Based on this experience, a trial of transesophageal atrial pacing for acute conversion of any episode of atrial flutter in children prior to direct current cardioversion is recommended.

Adolescent↗
PubMed1984

Use of balloon angioplasty to treat peripheral pulmonary stenosis.

Balloon angioplasty was attempted in 13 children with peripheral pulmonary arterial (PA) stenosis. In 5 patients, angioplasty was successful in relieving the peripheral PA stenosis as judged by an increase in PA size of more than 75% over the predilatation size and a more than 50% reduction in the distal PA to main PA peak systolic pressure gradient. Each child has been followed for 6 to 30 months. All remain well, without signs of subsequent deterioration, and follow-up angiograms in 2 patients (at 10 and 12 months) showed persistence of anatomic and hemodynamic improvement. In 8 patients, angioplasty was unsuccessful: In 4 patients, stenosis at the site of a previous systemic-to-PA shunt could not be dilated and in 4 patients, angioplasty could not be performed because of technical difficulties. Thus, we could not dilate the stenosis in more than 60% of the patients; we also had a significant complication with the angioplasty procedure (perforation of a distal branch of the right pulmonary artery). Thus, although balloon angioplasty was not effective in all patients, it did provide significant improvement in some patients in whom traditional operative management is usually unsuccessful.

Adolescent↗
PubMed1984

Two-dimensional echocardiographic determination of aortic and pulmonary artery sizes from infancy to adulthood in normal subjects.

The aorta, right pulmonary artery and pulmonary trunk were measured from the 2-dimensional echocardiogram (2-D echo) of 110 normal subjects aged 1 day to 18 years. The vessel diameters were measured from the parasternal short-axis view, the suprasternal long-axis view and the suprasternal short-axis view. Measurements were made at end-systole and at end-diastole and in both an axial and lateral direction where possible. When analyzed with respect to body surface area (BSA), the echocardiographic measurements were linearly related to the square root of the BSA, and there was inequality of variance around the relation. To establish a range of normal values for each vessel dimension, a weighted regression analysis was used to produce estimates of the regression line and a set of tolerance intervals. The systolic vessel dimension was larger than the diastolic vessel dimension and the measurement of a vessel in an axial direction was larger than the measurement of the same vessel in a lateral direction. In general, when a vessel was measured in several views, the largest diameter was obtained using the view that imaged the vessel in cross section. These data on normal values for the echocardiographic measurement of the aorta and pulmonary arteries at different BSAs should be useful for identifying patients with abnormalities in arterial size and for the serial assessment of arterial size in children who have undergone surgical or medical therapy.

Adolescent↗
PubMed1984

Use and abuse of the echocardiogram.

Echocardiography is a valuable noninvasive technology that has profoundly influenced the standards of medical and surgical care of infants and children with cardiac disease. The correct and efficient utilization of this technology requires a knowledge of the structures that can be visualized on the echocardiogram, the limitations of the technique, and the factors that influence the quality of the echocardiographic examination. This article includes specific examples of the uses and abuses of the echocardiogram in (1) the determination of the anatomic diagnosis, (2) the assessment of the hemodynamic severity of the defect, and (3) the assessment of cardiac function.

Aorta↗
PubMed1982

Ventricular septal defect with silent discrete subaortic stenosis.

Subaortic stenosis is rarely mentioned as a lesion that may be associated with a ventricular septal defect. We have encountered 4 patients with discrete subaortic stenosis adjacent to a ventricular septal defect, all of whom posed significant problems in diagnosis. In all 4 patients the subaortic stenosis was silent clinically and in 3 cases the obstruction was also not detected at the initial cardiac catheterization and angiocardiography. In the latter 3 cases, after surgical closure of the ventricular septal defect, there was a loud systolic murmur initially thought to be due to a small residual ventricular septal defect. In time, the clinical findings became more typical of isolated subaortic stenosis. In each of these cases the obstruction was verified at cardiac catheterization with peak systolic pressure gradients of 145, 45, and 70 mmHg. During reoperation, a discrete subaortic shelf was found opposite the patch used to close the ventricular septal defect. In the 4th case, the subaortic stenosis was unsuspected by clinical evaluation but was diagnosed by echocardiography as well as at cardiac catheterization, and both the ventricular septal defect and subaortic stenosis were corrected at the initial operation. A discrete subaortic shelf situated adjacent to a ventricular septal defect may be "silent," producing minimal, if any, pressure gradient and may pose diagnostic difficulties. Failure to recognize such a shelf and to remove it at the time of surgical closure of the ventricular septal defect, may result in the creation of a severe subaortic obstruction.

Adolescent↗
PubMed1982

Abnormal cerebral blood flow patterns in preterm infants with a large patent ductus arteriosus.

To determine whether there are significant alterations in cerebral blood flow patterns in infants with a patent ductus arteriosus and whether these alterations correlate with alterations in aortic blood flow, we performed range-gated pulsed-Doppler examinations of the aorta and cerebral arteries in 20 infants. Ten infants had a PDA and ten control infants did not. We analyzed these flow patterns quantitatively by calculating the pulsatility index (peak systolic frequency minus trough diastolic frequency)/peak systolic frequency. In the ten control infants and in three infants with a small PDA, there was no significant diastolic flow in the descending aorta; flow in the cerebral arteries was antegrade throughout systole and diastole (PI = 0.75 +/- 0.03 for control infants and 0.73 +/- 0.07 for small PDA infants). In seven infants with a large PDA, there was retrograde diastolic flow in the descending aorta. This pattern was not seen after PDA closure. In the cerebral arteries of the seven infants with a large PDA, diastolic flow was retrograde in three and decreased or absent in four, and PI was significantly higher (PI = 0.96 +/- 0.06. P less than 0.001 vs controls). After PDA closure, cerebral diastolic flow was antegrade in all seven infants (PI = 0.74 +/- 0.04). We conclude that a large PDA can cause abnormal flow patterns in the descending aorta and cerebral arteries. These flow patterns may predispose these infants to CNS ischemia or intraventricular hemorrhage.

Aorta, Thoracic↗
PubMed1982

Evaluation of infradiaphragmatic total anomalous pulmonary venous connection with two-dimensional echocardiography.

In three newborn infants with infradiaphragmatic total anomalous pulmonary venous connection, the common pulmonary vein was visualized with two-dimensional echocardiography and validated with saline contrast injections. The transducer was placed in the subcostal region in a sagittal body plane so as to image the descending aorta and the vertebral column. The common pulmonary vein, which connected the pulmonary veins to a systemic vein in the abdomen, was seen lying parallel and anterior to the descending aorta and to the left of the inferior vena cava. With peripheral venous contrast injections, contrast echoes first filled the inferior vena cava and then the descending aorta because of obligatory right-to-left atrial shunting. The common pulmonary vein was the only structure that remained free of contrast echoes. Thus, contrast echocardiography provided a method for identifying the site of pulmonary venous drainage and for distinguishing the common pulmonary vein from other structures such as the inferior vena cava. In cyanotic infants with respiratory distress, two-dimensional contrast echocardiography permits a rapid diagnosis of infradiaphragmatic total anomalous pulmonary venous connection.

Diaphragm↗
PubMed1981

Suprasternal notch echocardiography: a two-dimensional technique for evaluating congenital heart disease.

Two-dimensional suprasternal notch echocardiography was performed in 1033 patients, ages 1 day to 18 years. For the long-axis suprasternal notch view, the transducer was positioned in the suprasternal notch and angled to obtain a plane passing between the right nipple and left scapular tip. In this view, the entire aortic arch, vessels to the head and neck, right pulmonary artery and right bronchus were imaged. The long-axis view was useful for evaluating coarctation and interruption of the aorta, hypoplastic left heart, aortic and pulmonic stenosis and cervical aortic arch. For the short-axis suprasternal notch view the transducer was positioned in the suprasternal notch and angled to obtain a coronal body plane. In this view the transverse aorta, right pulmonary artery, left atrium, innominate veins and superior vena cava were imaged. The short-axis view was useful in the evaluation of children with increased or decreased pulmonary blood flow, persistent left superior vena cava, total anomalous pulmonary venous return to the right superior vena cava, and superior vena caval obstruction after Mustard's operation. In the evaluation of children with congenital heart disease, the suprasternal notch views added significant information to the two-dimensional echocardiographic examination.

Adolescent↗
PubMed1981

Detection of intracranial arteriovenous fistula by two-dimensional ultrasonography.

Three newborn infants who had severe congestive heart failure caused by an arteriovenous malformation of the vein of Galen were evaluated by two-dimensional ultrasonography. Examination of the heart from standard echocardiographic planes showed right atrial and right ventricular dilatation. The superior vena cava, ascending aorta and the vessels to the head and neck were enlarged. Contrast two-dimensional echocardiography from a peripheral vein showed right-to-left atrial shunting and early superior vena cava recirculation. With the transducer positioned in the anterior fontanel or against the temporal bone, two-dimensional sector scans of the brain were obtained in the coronal, sagittal and transverse planes. A large echo-free space that represented an aneurysm of the vein of Galen was seen within the brain. During contrast injection into a peripheral vein, microcavitations that passed from right to left at the atrial level were seen filling the vein of Galen aneurysm. In two infants in whom beryllium wire was placed in the fistula to induce thrombosis, postoperative ultrasonography showed a dense mass of echoes arising from the wire and persistent left-to-right shunting through the fistula. In infants presenting in the first week of life with congestive heart failure and cyanosis of unknown etiology, two-dimensional ultrasonography provides a rapid, safe method for detecting intracranial arteriovenous malformation.

Brain↗
PubMed1981

Superior vena caval obstruction after Mustard's operation: detection by two-dimensional contrast echocardiography.

To assess superior vena caval (SVC) obstruction after the Mustard operation for transposition of the great arteries, we performed two-dimensional contrast echocardiography (2-D contrast echo) in 18 patients, ages 1-9 years. Sterile saline was injected into a peripheral scalp or arm vein while the junction of the inferior vena cava (IVC) and the systemic venous atrium (SVA) was imaged from the subcostal long-axis plane. The results of 2-D contrast echo were compared with those obtained at cardiac catheterization. In nine patients, contrast passed from the SVC to the SVA and the IVC remained free of contrast echoes. At catheterization, these patients had no SVC obstruction by angiography and minor SVC-SVA mean pressure differences (0-4 mm Hg). In five patients, contrast passed from the SVC into the SVA. Within a few cardiac cycles, contrast from azygos-IVC collateral vessels flowed in the IVC toward the SVA. At catheterization, these patients had partial SVC obstruction by angiography and SVC-SVA mean pressure differences of 9-13 mm Hg. In four patients, the SVA was filled only by contrast arriving from the IVC by way of azygos-IVC collateral vessels. At catheterization, these patients had complete SVC obstruction and SVC-SVA mean pressure differences of 14-20 mm Hg. Two-dimensional contrast echocardiography is a simple, accurate, noninvasive method for detecting SVC obstruction after Mustard's operation and allows differentiation of complete from partial SVC obstruction.

Cardiac Catheterization↗
PubMed1980

Congenital left ventricular inflow obstruction evaluated by two-dimensional echocardiography.

Several forms of congenital heart disease that cause left ventricular inflow obstruction have similar M-mode findings, and frequently the exact anatomic diagnosis cannot be made by M-mode echocardiography alone. We examined five children with various forms of left ventricular inflow obstruction using two-dimensional echocardiography. The diagnosis was confirmed by cardiac catheterization and surgery in all five patients. In one patient with congenital mitral valve stenosis, a thick mitral valve with two papillary muscles was imaged. This patient was easily distinguished from a second child with parachute deformity of the mitral valve in whom a single papillary muscle arising from the left ventricular apex was seen. These two patients with mitral valve stenosis were easily differentiated from the three patients in whom the left ventricular inflow obstruction was caused by a membrane within the left atrium. The membrane could be seen in several spatial planes; however, we could not distinguish by two-dimensional echocardiography one child who had cor triatriatum from the other two patients who had a supravalvar mitral ring. Because of its spatial anatomic display, the two-dimensional echocardiogram provides information for a more detailed anatomic diagnosis in children with congenital left ventricular inflow obstruction.

Adolescent↗