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Biomedical subjects

A R Snider

Publications and source records attributed to A R Snider.

85 records · Page 5Linked to original sources
PubMed1979

Echocardiographic evaluation of ventricular septal aneurysms.

The spontaneous closure of ventricular septal defects is frequently associated with septal aneurysm formation. In this paper we discuss the M-mode and two-dimensional echocardiographic findings in nine children with aneurysms of the ventricular septum in association with ventricular septal defects. In all patients the diagnosis was confirmed by angiography. The ventricular septal aneurysms were detected by both M-mode and two-dimensional echocardiography. With M-mode echocardiography, septal aneurysms could be recognized by a pattern of multiple systolic echoes within the right ventricle. With two-dimensional echocardiography, the protrusion of the septal aneurysm into the right ventricle could be seen from several views and the location and the relative size of the aneurysm assessed. Echocardiographic techniques useful in the detection of ventricular septal aneurysms are discussed and examples presented.

Adolescent↗
PubMedDate not supplied

Isolated ventricular inversion: two-dimensional echocardiographic findings and a review of the literature.

In a cyanotic newborn infant, the diagnosis of isolated ventricular inversion in situs solitus was made from the two-dimensional echocardiographic examination and later confirmed at cardiac catheterization and surgery. The four-chamber views were especially useful for identifying the normal atrial situs and discordant atrioventricular connections in this infant. The normal relationships of the great arteries to each other (aortic valve rightward, posterior, and inferior to the pulmonary valve; great arteries coiled around each other) and to the ventricles (mitral-aortic fibrous continuity, well-developed subpulmonic conus) were well defined in the subcostal views. A review of the medical literature revealed a total of 12 cases of isolated ventricular inversion, most of which were diagnosed only at postmortem examination. The two-dimensional echocardiogram provides a rapid, safe technique for prompt diagnosis in these very sick cyanotic infants.

Cardiac Catheterization↗
PubMedDate not supplied

The use of Doppler ultrasonography for the evaluation of cerebral artery flow patterns in infants with congenital heart disease.

With the use of a two-dimensional range-gated pulsed-Doppler ultrasound system, Doppler examinations of the aorta and cerebral arteries were performed in 20 normal newborn infants and in 54 infants with various forms of congenital heart disease (i.e. patent ductus arteriosus, coarctation of the aorta, critical aortic stenosis, pulmonary atresia, truncus arteriosus). In the cerebral artery Doppler recordings of the normal infants, there was antegrade flow throughout systole and diastole. In the cerebral artery Doppler recordings of the infants with cardiac disease, various abnormal flow signals (i.e. retrograde or absent diastolic flow signals, increased systolic and diastolic flow signals, etc.) were found. Furthermore, the changes in the cerebral artery Doppler recordings were concomitant with changes in the aortic Doppler flow signals and the arterial blood pressure. Representative examples of the normal and abnormal Doppler flow patterns that were observed in the aorta and cerebral arteries are presented, and the mechanisms that could lead to these flow patterns are discussed.

Aorta↗
PubMedDate not supplied

In vitro evaluation of volumetric flow from Doppler power-weighted and amplitude-weighted mean velocities.

Ultrasound theory suggests that the volume of flow is directly related to the power and amplitude of the backscattered Doppler signals. To evaluate the accuracy of volume flow calculated with power-weighted and amplitude-weighted mean velocities (PWMV and AWMV), volume flows were measured in a pulsatile flow-tank system equipped with a 1.25 cm diameter simulated femoral artery. Analyses were performed throughout a range of physiologic flows, mean driving pressures, and pulse rates. At each hemodynamic setting, volume flow in the simulated artery was measured with an electromagnetic flow probe and with pulsed Doppler echocardiography by use of 7.0 and 3.5 MHz transducers. In addition, to determine the effects of vessel size and parabolic flow on the accuracy of the Doppler volumes, volume flow was evaluated in several differently sized vessels at sampling distances of 20 times the vessel diameter downstream from the orifice. On the ultrasound system, PWMV was calculated as the sum of the individual velocities multiplied by their respective power fractions (the fraction of the total instantaneous power represented by the individual signal power). The instantaneous PWMV was plotted continuously in time and superimposed on the spectral recording. Similarly, AWMV was calculated with amplitudes measured as the square root of the signal power. The PWMV and AWMV were integrated over the flow period and multiplied by the known cross-sectional area of flow to obtain the Doppler volume. In all analyses performed, volumetric flows calculated with Doppler echocardiography with PWMV and AWMV correlated extremely well with those measured with the electromagnetic flow probe. Thus, over a wide range of physiologic conditions, transducers frequencies, and vessel sizes, volume flow can be accurately calculated from PWMV and AWMV Doppler data. This technique provides an accurate, automatic method for on-line determination of volumetric flow.

Blood Flow Velocity↗
PubMedDate not supplied

Echocardiographic indexes of allograft rejection in pediatric cardiac transplant recipients.

To determine the usefulness of echocardiographic indexes of left ventricular (LV) function as possible predictors of cardiac rejection, 12 transplant recipients (ages 3 to 17 years) underwent a total of 52 serial echocardiographic examinations and cardiac biopsies. The results were compared to those of 12 normal children (ages 2 to 17 years). Biopsies were graded as no rejection (n = 23), mild rejection (cellular infiltrate, n = 13), and moderate rejection (myocyte necrosis, n = 16). LV dimensions, percent shortening fraction, indexed LV mass, and ejection fraction were measured from M-mode and two-dimensional echocardiography. From the mitral valve Doppler tracing, the following measurements were made: isovolumic relaxation time, peak E and peak A velocities, and the fraction of filling under the E and A waves as well as in the first third of diastole. Compared with normal subjects, transplant recipients with no rejection had higher heart rates (95 +/- 15 vs 80 +/- 17 beats/min), longer isovolumic relaxation time (68.8 +/- 11.2 vs 51.5 +/- 13.6 msec), decreased first third area fraction (0.48 +/- 0.10 vs 0.57 +/- 0.10), and similar shortening fraction, LV mass, and peak E and A velocities (p less than 0.03). Compared with transplant recipients with no rejection, patients in whom mild rejection developed also had decreased shortening fraction (31% +/- 10% vs 37% +/- 8%) and decreased peak E velocity (0.68 +/- 0.19 vs 0.88 +/- 0.15 m/s) (p less than 0.03). From mild to moderate rejection, no further changes were noted in any echocardiographic indexes measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMedDate not supplied

Two-dimensional echocardiographic features of double outlet left ventricle.

In a cyanotic newborn infant, the diagnosis of double outlet left ventricle was made from the two-dimensional echocardiographic examination. The diagnosis was later confirmed at cardiac catheterization and surgery. The parasternal and subcostal views were especially useful for identification of the origin of both great arteries from the morphologic left ventricle. A review of the medical literature since 1967 revealed 77 cases of double outlet left ventricle, most of which were diagnosed only at surgery or postmortem examination. The anatomic features demonstrated with two-dimensional echocardiography in this case are representative of the findings cited most often in the cases reported in the medical literature.

Double Outlet Right Ventricle↗
PubMedDate not supplied

Doppler evaluation of normalized peak filling rate in normal children and children with left ventricular outflow obstruction.

To evaluate the early diastolic peak filling rate of the left ventricle, three groups of children (normal children, patients with aortic valvular stenosis, and patients with aortic coarctation) were examined with the peak filling rate normalized to stroke volume calculated from the mitral valve inflow Doppler recording as the peak E velocity divided by the velocity time integral. The normal value for this index in children was 6.78 +/- 0.99 SV/sec and did not vary with age, weight, body surface area, or heart rate. Compared with normal subjects, both patients with aortic stenosis and patients with coarctation had increased left ventricular mass, but patients with aortic stenosis had decreased normalized peak filling rates (5.3 +/- 0.84 SV/sec, p < 0.01), while patients with coarctation had normal rates (6.79 +/- 0.98 SV/sec, p = 0.97). Compared with patients with aortic coarctation, patients with aortic stenosis had higher Doppler gradients. Thus the Doppler index of peak filling rate normalized to stroke volume is particularly useful in children because it is independent of heart rate, age, weight, and body surface area. Patients with coarctation may have normal peak filling rates normalized to stroke volume despite increased left ventricular mass because of milder obstruction or better coronary artery perfusion compared with that of patients with aortic stenosis.

Adolescent↗
PubMedDate not supplied

Doppler systemic venous flow patterns: changes in children with mild/moderate pulmonic stenosis.

To determine the usefulness of systemic venous flow patterns in patients with mild/moderate right ventricular hypertension, 17 patients with isolated mild/moderate pulmonic stenosis and 17 age-matched normal children were evaluated with pulsed Doppler echocardiography. Tricuspid valve, superior vena caval, and hepatic vein pulsed Doppler recordings were obtained with simultaneous respirometry and electrocardiography. Peak velocities and velocity-time integrals were measured for Doppler signals corresponding with ventricular systole, ventricular diastole, ventricular end systole, and atrial systole. The groups were similar in weight, heart rate, tricuspid inflow Doppler echocardiograms, and cardiac indexes. Compared with normal subjects, patients showed changes in respiratory variation for some superior vena caval and hepatic vein indexes. In addition, hepatic vein measurements made at ventricular end systole were significantly lower and measurements made at atrial systole were significantly higher in patients than in normal subjects. These changes in systemic venous flow patterns may provide a sensitive indicator of early right-sided heart dysfunction.

Adolescent↗