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Biomedical subjects

H D Allen

Publications and source records attributed to H D Allen.

At least 109 records · Page 6Linked to original sources
PubMed1983

Two-dimensional echocardiographic study of right ventricular outflow and great artery anatomy in pulmonary atresia with ventricular septal defects and in truncus arteriosus.

In this study, we reviewed M-mode and two-dimensional (2DE) echocardiographic observations in 13 patients with pulmonary atresia with ventricular septal defect and in six patients with truncus arteriosus in order to attempt to identify echocardiographic features distinguishing these two abnormalities in which no anatomic connection exists between the right ventricle and the pulmonary artery. M-Mode features compatible with the diagnosis of pulmonary atresia with a ventricular septal defect (VSD) were a small but identifiable space anterior to the aorta and/or immobile pulmonic valve echoes appearing to open during diastole rather than systole. By 2DE, the proximal and distal segments of the right ventricular outflow tract could be imaged and the length of the atretic segment estimated. In truncus arteriosus, no outflow tract of the right ventricle could be identified by 2DE or M-mode echocardiography, and the origin of the pulmonary artery from the truncus could be imaged directly in four patients with type I and in one patient with type II truncus. Abnormalities of the truncal valve were also present and were imaged by 2DE in three of our five patients. Our study identified specific echocardiographic criteria for diagnosing truncus arteriosus and pulmonary atresia with VSD and for differentiation between them.

Child↗
PubMed1983

Detection of deterioration or infection of homograft and porcine xenograft bioprosthetic valves in mitral and aortic positions by two-dimensional echocardiographic examination.

Results of two-dimensional echocardiographic examinations were compared with angiographic, hemodynamic and surgical results in 44 patients with bioprosthetic valves in mitral and aortic positions who were undergoing elective or urgent reinvestigation 24 to 87 months (mean 34) after implantation. In these patients, there were 18 homograft aortic valves in the aortic position, 9 stent-mounted homograft aortic valves in the mitral position, 13 porcine xenograft valves in the mitral position and 12 in the aortic position. Poor cusp support, gross fluttering and prolapse of cusps behind or below the anulus identified aortic insufficiency by two-dimensional echocardiography in six patients with an aortic homograft and four patients were identified with insufficiency of a stent-mounted aortic homograft in the mitral position. Two-dimensional echocardiographic examination revealed mitral stenosis in three patients with a porcine xenograft valve in the mitral position and suggested mitral insufficiency in two others. Bacterial endocarditis on homograft or porcine xenograft valves was associated with easily imaged vegetations by two-dimensional echocardiography in 10 patients. Despite difficulties in imaging valve cusps, and the skill required to obtain good echocardiographic images of bioprosthetic valves, significant valve deterioration or infected prostheses were quite effectively imaged by two-dimensional echocardiography in this study.

Adolescent↗
PubMed1983

Serial left ventricular wall measurements in Duchenne's muscular dystrophy.

In 19 patients with Duchenne's muscular dystrophy, left ventricular wall thickness in end-systole and end-diastole was determined serially every 12 months by echocardiography and compared with ventricular wall growth in normal subjects. In the normal subjects, left ventricular wall thickness increased linearly with increasing body surface area. A control group of wheelchair-bound patients with a variety of neurologic disorders, although not followed serially, had a distribution of end-diastolic wall thickness values similar to that of the normal subjects. In patients with muscular dystrophy, wall thickness increased linearly with respect to body surface area for some time and then began to thin. The time at which thinning began was not directly related to age, although it was more common in older than in younger patients. Those patients who died demonstrated marked deviation from normal wall growth. Free wall thinning is probably a result of fibrosis and loss of myofibrils.

Adolescent↗
PubMed1983

The effect of variations of pulsed Doppler sampling site on calculation of cardiac output: an experimental study in open-chest dogs.

We measured aortic flow by two-dimensional Doppler echocardiography in an open-chest dog model to examine how variations in Doppler sample volume length and position influence aortic hemodynamic flow calculations. Fourteen dogs underwent right-heart bypass, in which venous return from the venae cavae drained by gravity to a reservoir. A variable-speed roller pump returned the blood to the pulmonary artery, fixing left-sided cardiac input and output. Echo Doppler measurements were performed using a 3.5 MHz transducer placed directly on the aortic arch to determine internal aortic cross-sectional area. The transducer was then directed to image the aortic arch for Doppler velocity measurements and the various sampling sites were investigated. Doppler cardiac output could then be determined for each of the various sample volumes over a range of known roller pump settings. Doppler velocity was analyzed using fast Fourier transform spectral analysis. Mean velocity over the cardiac cycle was obtained by planimetry of the area under the Doppler velocity curve with a minicomputer. Doppler-derived determinations of cardiac output achieved a correlation of r = 0.98-0.99 to values obtained by the roller pump over a range of cardiac outputs from 0.75-5 l/min. The standard error of the estimate was 0.21/min. In this laminar flow model, there was no difference between the predictive accuracy of any of the sampling sites over the range of roller pump flows. Our study shows that Doppler velocity measurements can be used to quantify aortic flow over a clinically useful range and that variations of sample length and position did not produce significant differences in calculated flows.

Animals↗
PubMed1983

Noninvasive prediction of transvalvular pressure gradient in patients with pulmonary stenosis by quantitative two-dimensional echocardiographic Doppler studies.

Recent studies suggest that maximal Doppler velocities measured within the jets that form downstream from stenotic valves can be used to predict aortic valve gradients. To test whether the Doppler method would be useful for evaluation and management of pediatric patients with right ventricular outflow obstruction, we evaluated pulmonary artery flow before catheterization in 16 children with pulmonary valve stenosis. We used a 3.5-MHz, quantitative, range-gated, two-dimensional, pulsed, echocardiographic Doppler scanner with fast Fourier transform spectral output and a 2.5-MHz phased array with pulsed or continuous-mode Doppler. Peak systolic pulmonary artery flow velocities in the jet were recorded distal to the domed pulmonary valve leaflets in short-axis parasternal echocardiographic views. The pulsed Doppler scanner, because of its limitations for resolving high velocities, could quantify only the mildest stenoses; but, especially with the continuous Doppler technique, a close correlation was found between maximal velocity recorded in the jet and transpulmonary gradients between 11 and 180 mm Hg. A simplified Bernoulli equation (transvalvular gradient = 4 x [maximal velocity]2) proposed by Hatle and Angelsen could be used to predict the gradients found at catheterization with a high degree of accuracy (r = 0.98, SEE = +/- 7 mm Hg). Our study shows that recording of maximal Doppler jet velocities appears to provide a reliable measure of the severity of valvular pulmonic stenosis.

Adolescent↗
PubMed1983

The mitral valve orifice method for noninvasive two-dimensional echo Doppler determinations of cardiac output.

We developed and validated a mitral valve orifice method for Doppler cardiac output determination. In 15 open-chest dogs, cardiac output was controlled and measured by a roller pump interposed between the right atrium and pulmonary artery as a right-heart bypass. Left heart flows were measured in the open-chest dog model by Doppler measurements at the mitral valve orifice and compared not only to volume flow measured by the roller pump, but to electromagnetic flow meters as well. The maximum mitral valve orifice area was measured off short-axis two-dimensional echocardiographic views by planimetry. The maximal orifice was then adjusted for its diastolic variation in size by calculating a ratio of mean-to-maximal mitral valve separation on a derived M-mode echocardiogram. Flow was sampled parallel to mitral valve inflow in a four-chamber plane. The multiplication of mean flow throughout the cardiac cycle by the mean mitral valve area after correction for diastolic size variation yielded a cardiac output determination that could be compared to the roller pump measurement. Fifty-two cardiac output determinations over roller pump values of 1-5 l/min yielded a high correlation between roller pump flows and Doppler (r = 0.97 +/- 0.23 l/min). Our study shows that the mitral valve orifice provides an accurate site for Doppler cardiac output measurements.

Animals↗
PubMed1983

Prediction of the severity of left ventricular outflow tract obstruction by quantitative two-dimensional echocardiographic Doppler studies.

In this study we explored the use of continuous wave Doppler echocardiography guided by simultaneous two-dimensional echocardiographic imaging as a method for noninvasively estimating pressure gradients in patients with discrete forms of left ventricular outflow tract obstruction. We studied 16 children, ages 6 months to 17 years, with valvular aortic stenosis (n = 12) or with discrete subaortic stenosis (n = 4) and compared maximal Doppler velocities in the aorta with pressure gradients obtained at cardiac catheterization. Examinations could be performed from the suprasternal notch view or from the apical left ventricular outflow tract view with equal accuracy for the study of flow in the left ventricular outflow tract, and results were comparable in both views. With a simplified Bernoulli relationship (gradient = 4 X [maximal velocity]2), results suggested that Doppler echocardiography could be used to predict the severity of obstruction in our patients with a correlation coefficient of r = .94 (SEE +/- 7.5 mm Hg) between Doppler-estimated gradients and gradients obtained at catheterization. The method appears promising for initial evaluation and for serial management of patients with discrete forms of left ventricular outflow tract obstruction.

Adolescent↗
PubMed1983

Analysis of ventricular shape by echocardiography in normal fetuses, newborns, and infants.

Qualitative and quantitative changes in left ventricular shapes were analyzed in 14 normal fetuses, 29 normal newborns, and 12 normal infants. Qualitative observations demonstrated that most fetuses and newborns with dominant right ventricles had flattened or even indented interventricular septae, which changed left ventricular shape into an ellipse. In contrast, left ventricular shapes in infants were round, similar to shapes described in older children and adults. When changes in shape or septal distortions were gross, interobserver agreement was 100%; when changes were less altered from a circular shape, interobserver agreement was 78%. To avoid subjective misinterpretations, quantitative analyses were performed, including M mode echocardiographic comparisons of right ventricular/left ventricular dimensions and left ventricular cavity anterior-posterior/lateral diameters, as well as Fourier analysis of digitized tracings of the entire left ventricular shape. The right ventricular/left ventricular ratio, determined by M mode echocardiography, showed significant differences between fetuses (1.07 +/- 0.07) and newborns (0.62 +/- 0.12) (p less than .001). Infants had a significantly lower right ventricular/left ventricular ratio (0.45 +/- 0.01) when compared with newborns (p less than .01). Ratios of left ventricular anterior-posterior/lateral diastolic diameters were significantly lower (p less than .001) in newborns (0.66 +/- 0.08) when compared with those of infants (0.82 +/- 0.10). All diameters tended to increase (toward roundness) with systole and with aging. Fourier analysis allowed evaluation of the entire left ventricle, including that portion of the septum that qualitatively appeared most indented and could not be analyzed by either of the above techniques. Shape factor derived from idealized shapes ranging from a circle to an indented ellipse allowed comparison with digitized left ventricular tracings. This technique allowed accurate quantitation of the observed changes in shape. Fetuses had the highest diastolic shape factor (7.47 +/- 0.92), whereas infants' shape factors were lowest (2.12 +/- 0.41). A tendency toward roundness and loss of distortion occurred with aging. Systolic shape factor was lower with aging in each group studied. The Fourier technique used in this study allows evaluation of an arbitrarily large number of components of a shape, and thus a complete description of that shape is permitted. Comparisons of right ventricular/left ventricular diastolic dimensions and left ventricular anterior-posterior/lateral comparisons are subsets of this technique, which allow evaluation of only two points (circular component-first harmonic) or four points (elliptical component-second harmonic) of an overall shape.(ABSTRACT TRUNCATED AT 400 WORDS)

Echocardiography↗
PubMed1982

A new technique for noninvasive evaluation of femoral arterial and venous anatomy before and after percutaneous cardiac catheterization in children and infants.

A new ultrasonic method was applied to image the femoral artery and vein in children for evaluation of short- and long-term effects of cardiac catheterization with femoral percutaneous cannulation. Sixty-six children and infants (aged 5 days to 20 years) were studied with a 9 megahertz electronically focused real time scanner. Adequate studies were obtained in 46 patients before catheterization, in 26 of 30 short-term follow-up studies and in 14 long-term follow-up studies. Femoral arterial size could be quantitatively measured at the inguinal ligament and a correlation existed between imaged femoral arterial diameter and body weight (r = +0.82) or body surface area (r = +0.80). Short-term follow-up ultrasonic imaging studies allowed diagnosis of spasm and other complications of percutaneous femoral arterial puncture. Long-term follow-up studies were performed 4 months to 3 years after catheterization in 14 patients who had no complications recorded at the time of catheterization. These revealed significant differences between vessels on the catheterized and uncatheterized (control) sides in only 3 of the 14. High resolution ultrasonic imaging can provide anatomic and functional information about femoral arteries and veins and appears to be of assistance in planning cardiac catheterization and in studying the short- and long-term effects of percutaneous femoral cannulation.

Adolescent↗
PubMed1982

Use of echocardiography in newborns with patent ductus arteriosus: a review.

Assessment of the contribution of left-to-right shunted ductal flow to the clinical state of a newborn with respiratory distress syndrome is difficult. Echocardiography has aided in the bedside diagnosis and management of these infants. M-mode echocardiography allows evaluation of left atrial dimension in both precordial and suprasternal planes, left ventricular dimension, and indices of function. M-mode echocardiography combined with saline contrast aortic injections allows a very sensitive demonstration of the presence of left-to-right shunting patent ductus arteriosus even if no murmur is present. Two-dimensional echocardiography demonstrates the physical appearance of the ductus and helps rule out associated congenital cardiac lesions. Incorporation of venous and arterial contrast injections help demonstrate flow direction as well. Range gated pulsed Doppler echocardiography helps evaluate flow characteristics and aids in differential diagnosis. In the future, ultrasonic evaluation will probably combine Doppler echocardiography with two-dimensional echocardiography allowing clearer noninvasive definition of anatomy and flow direction. None of these techniques should be used by itself. Careful clinical assessment by standard techniques along with judicious use of ultrasonic methodology should result in improved diagnosis and management.

Ductus Arteriosus, Patent↗
PubMed1982

Preclinical abnormal segmental cardiac manifestations of thalassemia major in children on transfusion-chelation therapy: echographic alterations of left ventricular posterior wall contraction and relaxation patterns.

The purpose of this study was to evaluate young asymptomatic patients with thalassemia major by utilizing an echocardiographic technique which traces an expanded image of the left ventricular posterior wall (LVPW). This technique separates global cardiac function from segmental changes in LV free wall thickness during systole and diastole. The study population consisted of 13 patients aged 2 to 15 years with classical homozygous beta-thalassemia. Thirty-one normal healthy individuals age 4 to 13 years served as controls. Echocardiograms, height, weight, and blood pressure were measured in all patients at their lowest hemoglobin level. Traces of the expanded LVPW were analyzed and measured; while total net thickening relative to baseline was similar in both groups at all times during systole and diastole, the LVPW in children with thalassemia was statistically thinner than in controls (p less than 0.001). Contraction was a nearly linear process in controls, but for patients with thalassemia, it was significantly faster at 50% and 75% of systolic time (p less than 0.05). Relaxation, on the other hand, was not linear for either controls or thalassemic patients. In both groups, diastolic thinning was biphasic; however, LV walls of thalassemic children thinned more slowly than normal for each time point in diastole (p less than 0.001). These results demonstrate that young children with thalassemia major, even if kept at strict transfusion and chelation regimens, have defects in LV segmental wall motion which antedate the appearance of clinical symptoms.

Adolescent↗
PubMed1982

Range gated echo-Doppler velocity and turbulence mapping in patients with valvular aortic stenosis.

Flow beyond a stenotic aortic valve (AS) is dynamically complex. Numerous hydraulic studies have demonstrated that at least four well-known major flow areas occur distal to a stenotic valve. These include a jet, an area alongside the jet (the parajet), an area of flow disturbance, and an area in which disturbed flow again becomes laminar downstream. Of these, only the flow disturbance area has markedly turbulent flow, although some turbulence can be at times detected in the area beside the jet. The purpose of this investigation was to test a technique of patient examination that might allow a range-gated pulsed Doppler to detect each of these known areas in the aorta (Ao) of valvular AS patients. A method for mapping flow in the lumen of the Ao root and ascending Ao is detailed. The transverse Ao arch was studied in the standard manner. With this mapping method, 14 patients with AS were studied. We were able to identify the jet in 13 of 14 as a high velocity, narrow-width signal in the Ao root. The parajet area was characterized by no detectable or low flow in 12 of 14, but two patients had late systolic flow disturbance in the parajet area. All patients had a strong flow disturbance detected; 3 of 14 were first detected in the Ao root and the remainder were first detected higher in the ascending Ao. The area of relaminarization was not addressed in this study. This investigation demonstrates that a proper interpretation of range-gated pulsed Doppler recordings from areas distal to AS requires knowledge of flow dynamics beyond an obstruction and a methodical range-gated pulsed Doppler examination technique.

Aorta↗