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Biomedical subjects

H D Allen

Publications and source records attributed to H D Allen.

At least 91 records · Page 5Linked to original sources
PubMed1985

Doppler echocardiographic estimation of systolic pulmonary artery pressure in pediatric patients with interventricular communications.

The purpose of this study was to evaluate a noninvasive method for estimation of pulmonary artery pressures in infants and children with interventricular communications. Systolic pulmonary artery pressures measured by cardiac catheterization were compared with those estimated by Doppler echocardiography. Pressure drops were measured by Doppler study (modified Bernoulli equation) and were referenced to systolic systemic arterial pressure measured by sphygmomanometry. All 25 patients in this study had either a ventricular septal defect or a single ventricle. The systolic pulmonary artery pressure measured by cardiac catheterization ranged from 15 to 100 mm Hg (mean +/- SD 44 +/- 26) and that measured by Doppler echocardiography ranged from 5 to 100 mm Hg (mean 43 +/- 26) (p = NS; r = 0.92; SEE = 9.9; slope = 0.92; y intercept = 4.7). Systolic pulmonary artery to aortic pressure ratio measured by cardiac catheterization ranged from 0.2 to 1.0 (mean 0.5 +/- 0.3) and that measured by Doppler echocardiography ranged from 0.1 to 1.0 (mean 0.5 +/- 0.3) (p = NS; r = 0.94; SEE = 0.09; slope = 0.90; y intercept = 0.04). This study demonstrates that Doppler echocardiography can closely approximate systolic pulmonary artery pressure in patients with interventricular communications.

Blood Pressure↗
PubMed1985

Ruptured mitral chordae tendineae may be a frequent and insignificant complication in the mitral valve prolapse syndrome.

In this study, we performed 512 echocardiographic studies on 264 consecutive unselected patients with the idiopathic mitral valve prolapse syndrome. Twenty-eight patients (10.6%) had evidence of ruptured chordae tendineae of the mitral valve on M-mode examination and in 24 the diagnosis was confirmed by two-dimensional echocardiography. Mild to severe mitral insufficiency was proven in all of them by left ventriculography during cardiac catheterization. Eight patients underwent surgery to relieve symptomatic severe mitral regurgitation. At operation all had myxomatous degeneration of the mitral valve, two patients were found to have rupture of anterior mitral chordae, and six had rupture of posterior mitral chordae. Twenty (71%) patients with chordal rupture had either mild symptoms or were completely asymptomatic. It is concluded that chordal rupture in patients with the mitral valve prolapse syndrome may be present in asymptomatic patients and go undetected clinically in a substantial number of patients unless a high index of suspicion is maintained. Serial M-mode and two-dimensional echocardiographic studies are of importance in identifying the progression of prolapse findings and may reveal the natural history of this pathologic condition in asymptomatic patients.

Adolescent↗
PubMed1984

Factors affecting accuracy of in vitro valvar pressure gradient estimates by Doppler ultrasound.

Doppler ultrasound is used successfully in clinical situations for noninvasive measurement of pressure changes across stenotic cardiac valves. However, situations that might lead to errors in measurement have not been identified. This study determines the effect of flow rate, viscosity, orifice shape and size on the calculation of Doppler transvalvar gradient. Pressure gradient is usually computed from the equation P1-P2 = 4 X Vmax2, where P1-P2 is the gradient and Vmax is the maximal jet velocity measured by Doppler ultrasound. An in vitro model was developed with interchangeable orifices that permitted the jet to be detected by an in-line Doppler transducer. The model allowed alteration of flow rates, viscosities and pressure gradients. When P1-P2 as predicted by Doppler was compared with that measured by manometers (PM), excellent correlations were obtained for triangular orifices of areas as small as 78.5 mm2 (r = 0.95) and for circular and elliptical orifices to as small as 50.2 mm2 (r = 0.99). For smaller orifices, P1-P2 correlated poorly with PM. Good correlation was found between P1-P2 and PM, with flow rates ranging from 0.7 to 8.4 liters/min (r = 0.97) with a 10-mm diameter circular orifice (area = 78.5 mm2). No observable differences were found in the accuracy of the equation between high and low flow rates. Viscosity had no effect on the accuracy of the P1-P2 comparison with PM over the range evaluated (1 to 10 cp). It is concluded that the modified Bernoulli Doppler gradient equation provides accurate results in the usual clinical situation when an orifice permits true jet formation.

Blood Flow Velocity↗
PubMed1984

In vitro verification of Doppler prediction of transvalve pressure gradient and orifice area in stenosis.

This study was designed to analyze the validity of application of the modified Bernoulli equation (pressure gradient = 4.0 X velocity2) for estimating the pressure drop and valve orifice area from the jet velocity measured by Doppler ultrasound. We used an in vitro model which permitted interchangeable orifices, accurate measurement of the valve area and pressure drop across the valve. An in-line Doppler ultrasound transducer measured jet velocity (VEL D) at various water flow rates at an incident angle of 180 degrees beyond the various tested orifices. Jet velocity was also determined independently by application of a modified Bernoulli equation using the experimentally measured pressure drop (VEL P) and by a standard continuity equation (VEL Q). VEL P correlated very closely with VEL D (r = 0.981, standard error of the estimate [SEE] = 17.0 and slope of the regression = 0.988). VEL Q, corrected for vena contracta effects, correlated with VEL P (r = 0.986, SEE = 21.6), but had a slope of 0.673. To experimentally determine the exponent of velocity in the Bernoulli equation, we plotted pressure drop against VEL D and found a value of 2.11; theory predicts 2.0. Experimental coefficient of velocity was 3.36 torr/m (standard deviation = 0.52), whereas theory predicts 3.75 for water. Orifice area, calculated using VEL D and the continuity equation, was consistently overestimated by 3 to 12% for flows that produced laminar jets. The pressure gradient and orifice areas calculated from Doppler-derived data accurately predict actual pressure gradients and orifice areas.

Constriction, Pathologic↗
PubMed1984

Doppler echocardiographic prediction of pulmonary arterial hypertension in congenital heart disease.

This study determines the accuracy of Doppler echocardiography (echo) for predicting the presence of pulmonary artery (PA) hypertension from Doppler PA velocity traces. The patient group included 17 patients with congenital cardiac disease who had undergone catheterization. The control group was composed of 15 normal subjects. Doppler traces were analyzed qualitatively and quantitatively. Qualitative assessment included evaluation for a negative presystolic velocity that was the equivalent of the pulmonary a wave detected by M-mode echo. Quantitative assessment included measurement of the following time intervals and ratio of intervals: preejection period (PEP), time to peak velocity (TPV), right ventricular ejection time (RVET), PEP/RVET and TPV/RVET ratios. In the patient group, systolic PA pressure ranged from 22 to 90 mm Hg (mean 50 +/- 23), and mean PA pressure ranged from 12 to 60 mm Hg (mean 32 +/- 17). Five patients had systolic PA pressures of less than or equal to 30 mm Hg and 12 had systolic PA pressures greater than 30 mm Hg. Of 15 control subjects, 14 had a negative presystolic a wave. Of 5 patients with PA pressure less than or equal to 30 mm Hg, 4 had a presystolic negative velocity, and all with higher pressures had no presystolic negative velocity. One patient with pressure less than 30 mm Hg and 2 with PA pressure greater than 30 mm Hg had indeterminate status of presystolic velocity pattern because of turbulence or baseline blanking. The best quantitative indexes for separating patients with normal PA pressure from those with elevated PA pressure were TPV and TPV/RVET, which respectively correlated negatively with systolic PA pressure (r = -0.82, standard error of the estimate [SEE] = 0.02; and r = -0.70, SEE = 0.05). These measurements also correlated negatively with mean PA pressure (r = -0.75, SEE = 0.02; and r = -0.76, SEE = 0.05). Other intervals and ratios had enough individual variability to make them less useful as predictors of PA hypertension.

Adolescent↗
PubMed1984

Two-dimensional echo Doppler study of congenital disorders of the mitral valve.

To define the use of two-dimensional echocardiography (2DE) and Doppler methods for diagnosis of forms of congenital mitral stenosis, we studied 16 children, age range 2 months to 13 years, with congenital deformities of the mitral valve documented at cardiac catheterization. Thirteen had additional congenital heart defects, most commonly aortic stenosis or aortic coarctation. In eight patients features of mitral valve anatomy were observed and described during cardiac surgery and in one child the anatomy was verified by postmortem examination. 2DE studies allowed anatomic subclassification of 10 valves which had asymmetric or single dominant papillary muscles (parachute) and six which had arcade mitral valve attached by short chords to multiple diminutive papillary muscle heads. All patients' echoes exhibited shortened and thickened mitral chordae and doming of the mitral leaflets during diastole, and seven children had restricted mitral orifices imaged on the short-axis imaging plane. All seven of the patients studied by Doppler echocardiography had increased maximal transmitral inflow velocity (range 111 to 260 cm/sec) greater than the 95% confidence limits for mitral flow velocities in 34 normal children who served as the control group. Our study suggests that 2DE studies, especially when combined with Doppler interrogation, are sensitive for defining forms of congenital mitral stenosis.

Adolescent↗
PubMed1984

Left ventricular wall motion abnormalities in Kawasaki's disease.

Two-dimensional (2DE) and M-mode echocardiographic examinations were reviewed for 21 patients with Kawasaki's disease. Cardiac catheterization including coronary angiography was performed in 14 patients. 2DE detected regional myocardial contraction deficits in four patients later proven to have coronary disease. Coronary aneurysms were detected by echocardiography in two of four patients with proven coronary lesions. Although a minor pericardial effusion was detected in two patients and an increased left ventricular (LV) cavity dimension was found in one patient, M-mode function studies were not helpful for detection of cardiac involvement. ECG and chest x-ray examination were also noncontributory. We conclude that 2DE detection of LV wall contraction abnormalities may be a sensitive method for detecting cardiac contraction abnormalities may be a sensitive method for detecting cardiac involvement in Kawasaki's disease. 2DE may be better for assessing LV contraction than for imaging aneurysms in Kawasaki patients.

Aneurysm↗
PubMed1984

Noninvasive quantification of stenotic semilunar valve areas by Doppler echocardiography.

Fourteen patients, aged 1 month to 13 years, with congenital semilunar valve stenosis (11 pulmonary and 3 aortic) were studied for orifice area quantification calculated from a Doppler echocardiographic equation: Area = SV/0.88 X V2 X VET, where SV = stroke volume, V2 = maximal velocity and VET = ventricular ejection time. Results from individual measurements used in this formula and derived area were compared with individual results from cardiac catheterization and valve area derived from the Gorlin formula. Ventricular ejection time by cardiac catheterization ranged from 0.17 to 0.44 second (mean +/- standard deviation [SD] 0.27 +/- 0.09), and by Doppler study from 0.20 to 0.41 second (mean +/- SD 0.29 +/- 0.06) (r = 0.65, standard error of the estimate [SEE] = 0.03, y = 0.149 + 0.528x). Pressure gradient by catheterization ranged from 30 to 125 mm Hg (mean +/- SD 56.6 +/- 33.1), and by Doppler study from 17.6 to 100 mm Hg (mean +/- SD 46.8 +/- 27.9) (r = 0.91, SEE = 8.8, y = 1.23 + 0.904x). Stroke volume was measured by Doppler study simultaneously with cardiac catheterization in nine patients; results at cardiac catheterization with thermodilution measurements (cardiac output/heart rate) ranged from 5.5 to 53.4 cc (mean +/- SD 24.7 +/- 20), and by Doppler study from 5.8 to 46.9 cc (mean +/- SD 23 +/- 18) (r = 0.96, SEE = 3.5). Area quantification was performed in two ways. In Group 1, heart rate-matched stroke volumes from cardiac catheterization were used in the derived equation for Doppler study (all patients). In Group 2, the stroke volume used was that obtained by Doppler study, which was performed simultaneously with cardiac catheterization (nine patients).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Doppler echocardiographic comparison of flows distal to the four cardiac valves.

Cardiac flows measured by the Doppler technique and invasive methods correlate well, but no prior study has correlated Doppler flows obtained distal to the four cardiac valves in the same individual. The purpose of this investigation was to measure the four flows in normal subjects using the range-gated pulsed Doppler echocardiographic technique. Velocities were obtained from 22 subjects aged 4 to 29 years at a beam-flow intercept angle close to 0 degree in the ascending aorta, distal main pulmonary artery and the tricuspid and mitral valve outflow areas. Vessel and orifice sizes of the ascending aorta, main pulmonary artery and tricuspid valve orifice were measured directly from two-dimensional echocardiographic images. The mitral valve orifice was measured by a previously described method. Results show that flow values for the ascending aorta, main pulmonary artery and tricuspid valve inflow area were similar in absolute magnitude and correlated strongly (r = 0.93 to 0.98). Slopes for these relations were approximated at 1.0. The absolute magnitude of mitral valve flows was highly variable and showed the poorest correlation with flows from the other areas (r = 0.59 to 0.67). The high correlation of ascending aorta, main pulmonary artery and tricuspid valve outflow areas was considerably assisted by recording of velocity at a verified angle near 0 degree and obtaining accurate vessel and valve diameters. Improved angle accuracy was possible in the ascending aorta with the use of a new transducer designed to image anteroinferiorly from the suprasternal notch. A relatively simple method for measuring tricuspid flow was developed.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1984

Normal intracardiac and great vessel Doppler flow velocities in infants and children.

Normal two-dimensional pulsed Doppler echocardiographic velocity profiles for sites within the heart and great vessels in a group of 102 normal infants and children are presented. Qualitatively, waveforms mimic expected hemodynamic events at the various sites. All waveforms had a rapid initial deflection followed by spectral broadening after attainment of peak velocity. Quantitative angle-corrected peak velocities were generally lower on the right side than on the left side of the heart. Differences in tricuspid (mean 61.8 cm/s) versus mitral (mean 81.1 cm/s) outflow and pulmonary (mean 76.1 cm/s) versus aortic (mean 88.5 cm/s) outflow were significant (p less than 0.01). The only significant age-related differences were in the pulmonary artery (mean for newborns 67.7 cm/s versus 79.6 cm/s for older children, p less than 0.01). Aortic data obtained from interrogation sites in which flow was close to 0 or 180 degrees were similar, whereas aortic peak velocity data obtained from apical long-axis or subcostal views were greater. These differences were probably induced from inaccuracies in azimuthal (elevational) angles that cannot be measured. These normal Doppler data should be useful for comparisons with data obtained for children with various forms of congenital heart disease that affect flow dynamics.

Adolescent↗
PubMed1984

Clinical utility of two-dimensional doppler echocardiographic techniques for estimating pulmonary to systemic blood flow ratios in children with left to right shunting atrial septal defect, ventricular septal defect or patent ductus arteriosus.

Range gated two-dimensional Doppler echocardiographic methods were evaluated for quantifying pulmonary (QP) to systemic (QS) blood flow ratios. Twenty-one patients were studied, 4 with patent ductus arteriosus, 6 with atrial septal defect and 11 with ventricular septal defect. The Doppler pulmonary to systemic flow (QP:QS) estimation method involved calculating volume flow (liters/min) at a variety of intracardiac sites by using imaging information for flow area and Doppler outputs to calculate mean flow velocity as a function of time. Area volume flows were combined to yield QP:QS ratios. The sites sampled were main pulmonary artery, ascending aorta, mitral valve orifice and subpulmonary right ventricular outflow tract. The overall correlation between Doppler QP:QS estimates and those obtained at cardiac catheterization (n = 18) or radionuclide angiography (n = 3) was r = 0.85 (standard error of the estimate = 0.48:1). These preliminary results suggest that clinical application of this Doppler echocardiographic method should allow noninvasive estimation of the magnitude of cardiac shunts.

Adolescent↗
PubMed1983

Two-dimensional echocardiographic evaluation of dilated cardiomyopathy in children.

This study examines and quantitates left ventricular (LV) short-axis 2-dimensional (2-D) echocardiograms of 16 normal control subjects and 19 patients who presented with clinical features suggestive of myocarditis leading to severe myocardiopathy. Of the 19 patients, 8 died or had cardiac transplantation: 9 were studied in the chronic phase and 10 in the acute phase. The endocardial surface of the LV short-axis image was digitized at chordal level at end-diastole and end-systole. Digitized traces in systole and diastole were superimposed. The cavity area of systole and diastole was determined and expressed as the percent systolic area reduction ratio. In the control subjects, the left ventricles were round in systole and diastole, contracted concentrically, and had a mean percent systolic area reduction of 53% (range 43 to 67). The left ventricle was not round in systole in the patients with myocarditis, and in 15, only the ventricular septum contracted significantly. Three patients had nonconcentric contraction, and regional contraction was more difficult to judge. The systolic area reduction ratio for the patients was 11% (range 1 to 33), with no overlap with control subjects (p less than 0.001). Our results suggest that myocarditis more severely affects the LV free wall than the septum. In chronic patients, LV contraction remained markedly impaired. Quantitative evaluation of short-axis 2-D echocardiograms is a useful and sensitive technique for assessing damage due to presumed myocarditis.

Adolescent↗