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Biomedical subjects

D J Sahn

Publications and source records attributed to D J Sahn.

At least 181 records · Page 10Linked to original sources
PubMed1986

Noninvasive assessment of indomethacin therapy in patent ductus arteriosus in preterm infants.

We performed 138 serial two-dimensional (2-D), M-mode, and Doppler echocardiographic studies to assess the efficacy of intravenous indomethacin (INDO) therapy for patent ductus arteriosus (PDA) in 41 preterm infants. Nine infants expired without sufficient echo data to warrant inclusion in the study. Of the remaining 32 infants, 12 (Group 1) required ligation despite INDO therapy, 18 (Group 2) responded to INDO or spontaneously closed their PDAs, and 2 were transferred to other hospitals with their PDAs still open and were lost to follow-up. The presence of PDA was verified by 2-D echo visualization of the ductus (high parasternal short-axis views) and Doppler demonstration of high velocity ductal flow toward the main pulmonary artery. The ratio of PDA lumen to aortic root inner diameter (Ao) was measured as well. Indication for surgical ligation was failure of the PDA to close after 3 or more courses of INDO. In Group 1, the PDA/Ao ratio was 0.45 +/- 0.10 standard error of the mean (SEM) pre-INDO, and 0.40 +/- 0.12 SEM post-INDO (immediately before ligation). In Group 2, the PDA/Ao ratio was 0.42 +/- 0.11 SEM pre-INDO, and 0.19 +/- 0.14 SEM at the end of INDO course (p less than 0.001), with 12 infants showing no ductal flow by Doppler. Follow-up six months after INDO therapy has shown no residual murmurs or other evidence of PDA in any INDO-closed infant. Five of the 18 infants have undergone repeated echocardiographic studies, all of which were negative for PDA patency or flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗
PubMed1986

Steady flow velocity measurements in a pulmonary artery model with varying degrees of pulmonic stenosis.

Velocity and flow visualization studies were conducted in an adult size pulmonary artery model with varying degrees of valvular stenosis, using a two dimensional laser Doppler anemometer system. Velocity measurements in the main, left and right branches of the pulmonary artery revealed that as the degree of pulmonic stenosis increased, the jet type flow created by the valve hit the distal wall of the LPA farther downstream from the junction of the bifurcation. This in turn led to higher levels of turbulent and disturbed flow, and larger secondary flow motion in the LPA compared to the RPA. The high levels of turbulence measured in the main and left pulmonary arteries with the stenotic valves, could lead to the clinically observed phenomenon of post stenotic dilatation in the MPA extending into the LPA.

Blood Flow Velocity↗
PubMed1986

Doppler echocardiographic studies of diastolic function in the human fetal heart: changes during gestation.

With the combined use of two-dimensional ultrasound and Doppler echocardiography, noninvasive examination of the human fetal heart and circulation has recently become possible. These techniques were employed to investigate diastolic atrioventricular valve flow in the fetal heart in 120 fetuses studied between 17 and 42 weeks of gestation. Two-dimensional ultrasound was used to examine fetal and intrauterine anatomy, and estimates of gestational age were made based on biparietal diameters and femur lengths. Doppler echocardiography was performed with a 3.5 or 5 MHz Doppler sector scanner. Flow velocity patterns were obtained through the tricuspid and mitral valves during diastole. Peak flow velocity during late diastole or atrial contraction (A) was compared with peak flow velocity during early diastole (E) in four groups of fetuses: Group 1, 17 to 24 weeks of gestation; Group 2, 25 to 30 weeks; Group 3, 31 to 36 weeks; and Group 4, 37 to 42 weeks. The ratio of A to E decreased significantly as gestational age advanced, from 1.56 +/- 0.06 (+/- SE) to 1.22 +/- 0.03 across the tricuspid valve (p less than 0.001) and from 1.55 +/- 0.04 to 1.22 +/- 0.06 across the mitral valve (p less than 0.001). In tricuspid valve measurements, peak flow velocity during early diastole increased from 26.3 +/- 2.0 cm/s in Group 1 to 36.5 +/- 1.7 cm/s in Group 4 (p less than 0.001), whereas peak flow velocity during atrial contraction did not change.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1986

Doppler-detected paradoxus of mitral and tricuspid valve flows in chronic lung disease.

An echocardiographic Doppler study in a patient with pulsus paradoxus of respiratory origin demonstrated a large inspiratory increase of tricuspid flow velocity and a corresponding decrease of mitral flow velocity. This "flow paradoxus" is therefore not specific for cardiac tamponade, and provides evidence that decreased left ventricular filling is an important mechanism of pulsus paradoxus observed in severe chronic lung disease.

Aged↗
PubMed1986

Real-time Doppler color flow mapping for detection of patent ductus arteriosus.

In this study, ultrasound Doppler color flow mapping systems were utilized to examine flow in the pulmonary artery in 31 premature and term infants (aged 4 hours to 9 months) with patent ductus arteriosus accompanying respiratory distress syndrome, as an isolated lesion, or with patent ductus in association with other cyanotic or acyanotic congenital heart disorders. The flow mapping patterns were compared with those of a control population of 15 infants who did not have patent ductus arteriosus. In unconstricted ductus arteriosus, the flow from the aorta into the pulmonary artery was detected in late systole and early diastole and was distributed along the superior leftward lateral wall of the main pulmonary artery from the origin of the left pulmonary artery back in a proximal direction toward the pulmonary valve. In constricted patent ductus arteriosus, or especially in a ductus in association with cyanotic heart disease, the position of the ductal shunt in the pulmonary artery was more variable, often directed centrally or medially. Waveform spectral Doppler sampling could be performed in specific positions guided by the Doppler flow map to verify the phasic characteristics of the ductal shunt on spectral and audio outputs. Shunts through a very small patent ductus arteriosus were routinely detected in this group of infants, and right to left ductal shunts could also be verified by the Doppler flow mapping technique. This study suggests substantial promise for real-time two-dimensional Doppler echocardiographic flow mapping for evaluation of patent ductus arteriosus in infants.

Blood Flow Velocity↗
PubMed1986

Cardiac Doppler flow velocities in human fetuses.

Cardiac Doppler flow velocity studies were performed in normal human fetuses between 18 and 40 weeks of gestation. Two-dimensional linear array and sector scanning techniques were used for the initial evaluation of the fetuses, which included a standard ultrasound examination to determine normal anatomy and estimated gestational age and weight. Fetal cardiac ultrasound examination was then performed, with four-chamber, short-axis/great vessel, long-axis/left ventricular outflow tract, and aortic arch views obtained. Pulsed echo Doppler instrumentation was used to obtain flow velocity measurements through the tricuspid, pulmonary outflow, mitral, and aortic outflow regions. Calculation of transvalve volume flow for mitral and tricuspid valves was performed by combining the valve anulus sizes and calculated mean temporal velocities for the valves. Maximal flow velocities were greater through the tricuspid (mean maximal velocity 51 +/- 1.2 [SE] cm/sec) than through the mitral (47 +/- 1.1 cm/sec; p less than .05) valve regions, with a wide range of scatter for results between fetuses but less than 6% average variation in the individual fetuses during gestation. For 18 fetuses, right heart dimensions and volume flows (mean 307 + 30 ml/kg/min) were greater than left heart dimensions and volume flows (232 +/- 25 ml/kg/min). Doppler echocardiography may prove to be useful as an adjunct to imaging echocardiography for evaluation of fetal cardiac anatomy and function.

Aorta↗
PubMed1986

Studies in vitro of the relationship between ultrasound and laser Doppler velocimetry and applicability to the simplified Bernoulli relationship.

While there has been wide general acceptance of Doppler methods that use the simplified Bernoulii relationship to estimate pressure gradients across stenotic orifices, there is still ongoing controversy related to potential sources of error in the method. In this study we tested accuracy o ultrasound Doppler measurements of flow velocity when compared with the gold standard of laser light Doppler anemometry in a pulsatile flow model of pulmonic stenosis in vitro. We tested two commercially available Doppler systems and examined steered and nonsteered, parallel and off-axis and angle-corrected velocity determinations using continuous-wave and high-pulse repetition frequency (HPRF) methods. We also examined the potential range of error in the simplified Bernoulli method. One hundred and twenty individual flow states were examined with three stenotic valve orifices (3.0, 1.0, and 0.5 cm2 flow area) to measure velocities up to 620 cn/sec. A very high correlation coefficient was obtained for the comparison of laser Doppler anemometric and ultrasound velocity recordings by the nonsteered continuous-wave technique (r= .99, SEE = 17.9 cn/sec), but there was a tendency for underestimation of higher velocities when the transducer was positioned at 30 degrees and the ultrasound beam was steered so as to be parallel to the visualized flow jet (r = .98, SEE = 29.6 cn/sec). The HPRF ultrasound Doppler technique was also highly accurate in this optimized setting for measuring velocities (r = .99, SEE = 17 cm/sec), but also slightly underestimated the highest velocities. Our results also verified the accuracy of the simplified Bernoulli equation for converting instantaneous velocity measurements to estimated peak instantaneous gradient (r = .97, SEE = 8.4 mm Hg).

Blood Flow Velocity↗
PubMed1986

Ultrasound Doppler methods for calculating cardiac volume flows, cardiac output, and cardiac shunts.

The variety of volume flow calculation methods described for determination of cardiac output by Doppler and the controversy surrounding their relative accuracy is to some extent a result of how difficult they are to use and the fact that they break down in patients whose anatomic and physiologic flow cross sections do not match, in patients who may have flow in vessels with flow profiles that are not flat, and in patients who are difficult to examine in one view or another or who do not give clean Doppler waveforms. Nonetheless, most of the methods work to some extent in most patients. Discovering those patients who do not fit the assumptions in these methods and whose cardiac output can therefore not be accurately calculated will probably be a major contribution of the new flow mapping Doppler technologies. We believe these new technologies may provide more sophisticated methods for calculating volume flows, cardiac outputs, regurgitant fractions, and shunt volumes.

Algorithms↗
PubMed1985

Echocardiographic ventricular shape analysis in congenital heart disease with right ventricular volume or pressure overload.

In this 2-dimensional (2-D) echocardiographic study, a computerized Fourier analysis technique refined from one that allows quantification of changes in septal shapes in normal fetuses, newborns and infants allowed analysis of left ventricular (LV) shapes in 14 patients with right ventricular (RV) volume overload (atrial septal defects), 5 with volume and pressure overload (total anomalous pulmonary venous connection), and 10 with pressure overload (complete transposition of the great arteries [TGA] with intact ventricular septum). Diastolic shape factors in the 3 groups were significantly different from those of normal subjects (p less than 0.01). Highest diastolic values were found in patients with TGA (mean 4.59 +/- 1.28). Systolic shape factors were similar in patients with atrial septal defect and normal subjects. Significant differences existed between normal subjects and patients with total anomalous pulmonary venous connection, with the greatest differences in systolic shape factor being 5.61 for TGA vs 1.87 (p less than 0.005) for normal subjects. Shape factor correlated well with hemodynamic data for RV/LV systolic pressure ratios (r = 0.93, p less than 0.001) for normalized interventricular pressure differences (r = -0.95, p less than 0.001). The lower the normalized systolic pressure difference or the higher the RV/LV ratio, the more the septum encroached into the LV cavity. Significant but weaker correlations were noted for values during diastole. Quantitative application of Fourier shape factor analysis to LV shapes allows numerical expression of visually interpreted distortions over a wide range of geometric alterations.

Cardiac Volume↗
PubMed1985

Transducers in medical ultrasound: Part Three. Transducer applications in echocardiology.

A comparison is made between phased arrays and mechanical sector scanners in transcutaneous echocardiographic applications. Aspects such as contact area, beam control, side lobes, grating lobes and image quality are discussed in the context of transducer frequency. The incorporation of simultaneous acquisition of Doppler velocity information and display of M-mode signals is considered. Transoesophageal and intraoperative scanning systems for cardiology are also compared, in particular linear arrays, phased arrays and mechanical scanners, and their advantages and disadvantages in relation to the above mentioned aspects are discussed. The general conclusion is that electronic sector scanners may have a considerably improved cost/benefit ratio in the near future and thereby will become the leading systems for echocardiography.

Coronary Vessels↗
PubMed1985

Resolution and display requirements for ultrasound Doppler/evaluation of the heart in children, infants and the unborn human fetus.

Technical considerations and the instrumentation used for pediatric two-dimensional echocardiography and Doppler examination are reviewed. The configurations of sector scanners, the function of the mechanical versus phased array systems and considerations related to lateral, axial and azimuthal resolution requirements are discussed. The performance and requirements for echocardiographic cardiographic scan converters and the requirements for pediatric display are reviewed. Methods of performing quantitative Doppler echocardiography are discussed because this technique provides new and important types of information for the evaluation of congenital heart disease. Considerations of Doppler velocity, Doppler spatial resolution and Doppler display requirements are presented. Characteristics of ultrasonic imaging devices for use in fetal echocardiography and fetal Doppler study are reviewed, and a brief overview of techniques for the extraction of information about the nature of ultrasound scatterers (that is, tissue signature) is presented. It is the purpose of this technically oriented discussion to present the capabilities, trade-offs and needs for future development relevant to pediatric echocardiography in 1983.

Child↗
PubMed1985

Prediction of gradients in fibrous subaortic stenosis by continuous wave two-dimensional Doppler echocardiography: animal studies.

The purpose of this study was to assess the accuracy of continuous wave, two-dimensional Doppler echocardiography for predicting pressure gradients across discrete subaortic stenoses. Twenty-three Newfoundland dogs with subaortic stenosis were studied by closed chest Doppler interrogation of aortic velocity from an apical view of the left ventricular outflow tract simultaneously with measurements of pressure gradient during cardiac catheterization. Continuous mode Doppler interrogation was used with two-dimensional echographic guidance (Irex model IIIB) to compare the Doppler-derived maximal velocity with the pressure gradient across the obstruction at rest and after provocation with amyl nitrite inhalation and isoproterenol infusion. The maximal velocities recorded by Doppler ranged from 98 to 539 cm/s and correlated with hemodynamic gradients ranging from 3 to 123 mm Hg (r = 0.92, SEE = 37 cm/s). Doppler velocities were converted to gradients using a simplification of the Bernoulli relation (gradient = 4 X maximal velocity2); the resulting Doppler-derived gradients also correlated closely with the catheterization-measured pressure gradients (r = 0.95, SEE = 7.1 mm Hg). The predictive capability of Doppler echocardiography for estimating the pressure gradient across fibromuscular subaortic obstructions in this group of dogs with a spectrum of disease similar to that found in human beings was validated. The results also indicate that Doppler methods may have clinical applications in patients with subaortic stenosis.

Amyl Nitrite↗
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↗
PubMed1985

In-vitro pulsatile flow visualization studies in a pulmonary artery model.

In-vitro pulsatile flow visualization studies were conducted in an adult-sized pulmonary artery model to observe the effects of valvular pulmonic stenosis on the flow fields of the main, left and right pulmonary arteries. The flow patterns revealed that as the degree of stenosis increased, the jet-type flow created by the valve became narrower, and it impinged on the far (distal) wall of the left pulmonary artery further downstream from the junction of the bifurcation. This in turn led to larger regions of disturbed turbulent flow, as well as helical-type secondary flow motions in the left pulmonary artery, compared to the right pulmonary artery. The flow field in the main pulmonary artery also became more disturbed and turbulent, especially during peak systole and the deceleration phase. The flow visualization observations have been valuable in helping to conduct further quantitative studies such as pressure and velocity field mapping. Such studies are important to understanding the fluid mechanics characteristics of the main pulmonary artery and its two major branches.

Adult↗
PubMed1985

A Doppler echocardiographic method for calculating volume flow across the tricuspid valve: correlative laboratory and clinical studies.

In this study we tested a two-dimensional Doppler echocardiographic method for measuring volume flow across the tricuspid valve. Five anesthetized, open-chest dogs had a calibrated electromagnetic flow probe placed on the ascending aorta. Volume flow across the tricuspid valve was controlled by creating a variable femoral-to-pulmonary arterial shunt. Since no standard plane provided a direct view of the tricuspid valve orifice, tricuspid flow area was estimated by calculating a fixed circular flow orifice from the maximal late diastolic diameter of the tricuspid anulus in a four-chamber view. Doppler-determined velocities across the tricuspid valve and tricuspid anulus images in the four-chamber view were obtained in inspiration and expiration. For 24 cardiac outputs (0.6 to 4.0 liters/min), inspiratory tricuspid flow determined by the Doppler method correlated minimally better (r = .90, SEE = 0.30 liter/min) than did expiratory measurements (r = .89, SEE = 0.35 liter/min) with the time-averaged systemic flow determined electromagnetically. Doppler-determined tricuspid volume flows in four-chamber and short-axis two-dimensional echocardiographic views from 10 children were then compared with values determined simultaneously by thermodilution during cardiac catheterization. In the children, Doppler-determined flows in short-axis and four-chamber views, both in inspiration and expiration, were similar; when results for the two views were averaged in inspiration and expiration, the tricuspid flows predicted by the Doppler method were highly correlated (r = .98, SEE = 0.48 liter/min) with the results of thermodilution. The two-dimensional Doppler echocardiographic method provides a means of estimating volume flow across the tricuspid valve noninvasively.

Adolescent↗