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Biomedical subjects

D J Sahn

Publications and source records attributed to D J Sahn.

At least 163 records · Page 9Linked to original sources
PubMed1988

One-year follow-up of cardiac and coronary artery disease in infants and children with Kawasaki disease.

Of 75 patients meeting clinical criteria for Kawasaki disease, 67 patients were followed with serial ECG and echocardiograms (echo) for at least 1 year. Sixteen patients had coronary artery aneurysms and three had dilated coronary arteries as assessed by initial two-dimensional (2D) echo and/or angiocardiographic studies. ECG findings of first and second-degree heart block and ST-T wave changes (36%) as well as M-mode echo abnormalities (45%) including pericardial effusion, decreased ventricular septal motion, and decreased left ventricular function were all normalized by 6 months, except in two infants who continued to have decreased function and flat ventricular septal motion. In four patients with single proximal coronary aneurysm and two with dilated coronary artery, resolution of lesions occurred by 1 year. Among 11 patients with multiple coronary aneurysms discovered by initial studies, the 2D echo became normal in seven and showed aneurysms in four as corroborated by angiogram. One patient with an isolated distal coronary aneurysm, not seen by initial or serial echo, had a normal follow-up angiogram. Our study suggests that in Kawasaki disease careful, serial, 2D echo is sufficient to monitor the course of coronary artery disease that tends to regress and follow a benign course. However, the long-term effects of this disease on cardiac and coronary arteries remain to be elucidated.

Child↗
PubMed1988

Noninvasive Doppler color flow mapping for detection of anomalous origin of the left coronary artery from the pulmonary artery and for evaluation of surgical repair.

Anomalous origin of the left coronary artery from the pulmonary artery is a rare but important cause of congestive heart failure in infancy and of sudden death at all ages. Diagnosis is often missed when based solely on physical examination and noninvasive methods. A 4 year old patient is presented in whom mitral regurgitation was noted by a referring physician and an anomalous left coronary artery was found by Doppler color flow mapping upon referral and verified at cardiac catheterization. Doppler color flow mapping was also used intraoperatively using a gas-sterilized transducer to further clarify the hemodynamics and assess the surgical result. After creation of an intrapulmonary artery tunnel from the ostium of the left coronary artery to the aorta, anterograde coronary artery flow and absence of a residual left to right pulmonary artery shunt were verified during surgery by Doppler flow mapping. Postoperatively, residual mitral regurgitation and patency of the left coronary artery graft have been followed up serially by Doppler flow mapping. Therefore, Doppler color flow mapping is useful in the diagnosis and intraoperative and postoperative management of this important and potentially life-threatening abnormality.

Blood Vessel Prosthesis↗
PubMed1988

Instrumentation and physical factors related to visualization of stenotic and regurgitant jets by Doppler color flow mapping.

Major clinical uses of the new Doppler color flow mapping technologies involve the imaging of disturbed flow through cardiac defects or valves. Nevertheless, there is little general understanding of the determinants of flow and of how flow is imaged by these new systems. This review will attempt to relate the hydrodynamics through a simplified stenotic or regurgitant orifice with the physics and sampling theories relevant to the functioning of Doppler color flow mapping systems. The goal will be to characterize the velocity resolution, spatial resolution, sensitivity and performance of these systems so that clinicians can understand why flow looks the way it does on Doppler color studies and which aspects of flow mapping can be expected to become more quantifiable than they are at present.

Blood Circulation↗
PubMed1988

Cine magnetic resonance imaging for evaluation of congenital heart disease: role in pediatric cardiology compared with echocardiography and angiography.

Cine magnetic resonance imaging was used for preoperative and postoperative evaluation of 91 patients with congenital heart disease. Their ages ranged from 6 weeks to 14 years. The quality of study was excellent in 81% of the cases, in which it provided complete documentation of diagnostic features; substantial diagnostic information was provided in another 14%, and the study was nondiagnostic in only 5%. This technique was most useful for evaluating areas of the right ventricle (95%), great arteries (95%), vena cava (94%), and pulmonary venous system (91%). The anatomic delineation of these areas was comparable to that obtained by cineangiography and was superior to echocardiography, especially in postoperative patients. For complex venous anomalies, magnetic resonance imaging provided better anatomic details than did angiography or echocardiography. The capability of multiplanar imaging allows complex angled views through the desired planes of the heart and great vessels. Proper sedation is essential to obtain maximum diagnostic information. Our preliminary experience suggests that this new modality provides excellent anatomic information in infants and children with congenital cardiac defects and will play an increasing role in pediatric cardiac diagnosis.

Adolescent↗
PubMed1988

Factors influencing late right ventricular ejection.

Forward flow from the right ventricle into the pulmonary artery continues longer than contraction in the right ventricular free wall. The momentum of blood flow, contraction of other areas of the right ventricular free wall, and movement of the interventricular septum are possible mechanisms regulating late right ventricular ejection. In this study the changes in shortening in right ventricular free wall and in free wall to septum distance were measured using sonomicrometry. Right ventricular free wall shortening was studied in both outflow and inflow regions in hoop and apex to base axes. Pulmonary artery flow was simultaneously measured using an electromagnetic flowmeter. Right ventricular free wall in the hoop axis was motionless during late ejection. The inflow segment in the hoop axis stopped shortening before all other segments (p less than 0.01). Both outflow and inflow segments in the hoop axis lengthened after the end of shortening. Both shortening of the right ventricular free wall in the apex to base axis and decrease in free wall to septum distance were continued until the end of ejection (p less than 0.01). Compared with the right ventricular outflow segment, the inflow segment shortened for a longer duration. It is concluded that forward flow during late right ventricular ejection is associated with continued shortening of the free wall in the apex to base axis. However, the results of this study do not exclude the role of septal bulge into the right ventricle during late ejection.

Animals↗
PubMed1988

Cine magnetic resonance imaging after surgical repair in patients with transposition of the great arteries.

Cine magnetic resonance imaging (MRI) was used for postoperative evaluation of eight patients who underwent intra-atrial baffle procedure for surgical repair of D-transposition of the great arteries (D-TGA). Their ages ranged from 9 months to 8 years. Younger patients were sedated with chloral hydrate (80 to 100 mg/kg) orally. MRI was performed with use of a General Electric Signa system operating at a field strength of 1.5 tesla. A body or head coil was used depending on the size of the patient. Images were obtained by use of a technique of gradient-recalled acquisition in steady state (GRASS) that utilizes a low flip angle and shorter repetition and echo times. Five patients had widely patent venae cavae and three had superior vena caval obstruction at the junction of the right atrium with a dilated azygos vein. There was no evidence of pulmonary venous obstruction in any of the patients. Right ventricular function was assessed in four patients and their ejection fractions ranged from 58% to 81%. Tricuspid and mitral regurgitation were observed in three and two patients, respectively. Both right and left ventricular outflow tracts were well visualized and showed no evidence of obstruction. Cine MRI is an entirely noninvasive, nonionizing, and safe procedure in young patients and appears to be a valuable alternative method for evaluating patients after surgical repair of D-TGA. With advancing technologies and an accumulation of experience with cine MRI, it appears that this new technique will play an important role in patient care for children with congenital heart disease.

Child↗
PubMed1988

Color Doppler flow mapping in patients with coarctation of the aorta: new observations and improved evaluation with color flow diameter and proximal acceleration as predictors of severity.

We performed color Doppler flow mapping in 15 patients, 1 week to 17 years old (mean 42 months), with coarctation of the aorta that was confirmed subsequently by angiography and/or surgery. Twelve patients had native coarctation and three had mild recoarctation after surgical repair. Color Doppler flow maps were analyzed with a digital analysis package and a Sony computer system. The diameter in the region of coarctation from the color Doppler flow map (mean = 2.0 +/- 0.8 mm [SD]) correlated well with the coarctation diameter measured at angiography (mean = 1.8 +/- 0.8 mm; r = .83, SEE 0.43 mm) in the 10 patients with native coarctation undergoing angiography, but the coarctation diameter measured by two-dimensional echocardiography (3.9 +/- 1.5 mm) was poorly predictive of the angiographic severity (r = .23). Additionally, spatial acceleration was seen in all patients proximal to the coarctation site, with an aliased and accelerating stream narrowing progressively as it proceeded toward the coarctation site, a pattern that is not seen in healthy subjects. Computer analysis of the color Doppler images provided pseudo three-dimensional and digital velocity maps for blue, red, and green (turbulent) flow velocities to allow an enhanced appreciation of the accelerating stream, easily separating this from normal descending aortic aliasing patterns. The narrowing of the acceleration area in the proximal descending aorta (distal/proximal acceleration zone ratio) was also predictive of the angiographic severity of coarctation (r = .83). The distribution of low-level turbulence seen proximally paralleled the distribution of the proximal accelerating stream.(ABSTRACT TRUNCATED AT 250 WORDS)

Aorta↗
PubMed1988

Cine magnetic resonance imaging for evaluation of anatomy and flow relations in infants and children with coarctation of the aorta.

Sixteen cine magnetic resonance imaging (MRI) studies were performed in 14 patients aged 1 week to 17 years (mean age, 46 months), who had coarctation of the aorta confirmed at angiography or surgery. Conventional echocardiographic-gated MRI was first performed in axial and rotated sagittal views and was used to identify the slice locations for cine MRI. Cine MRI was performed by gradient-recalled acquisition in steady state with a 30 degree flip angle, 12-msec echo time, 22-msec pulse repetition time, and a 128 x 256 acquisition matrix. Coarctation anatomy was extremely well defined in all but one patient who had vascular clips at the coarctation repair site. The smallest descending aortic flow diameter on cine MRI showed excellent agreement with angiography (r = 0.90). Lucent jets of high-velocity flow through the site of coarctation were imaged in eight patients, and jet length correlated well with the angiographic severity of coarctation (r = -0.81). Two patients were restudied after surgery, and they exhibited excellent repair and normal flow patterns. Cine MRI provides high-resolution imaging of coarctation anatomy with a dynamic spatial and temporal visualization of flow and with excellent detail of vascular anatomy and flow both proximal and distal to the coarctation.

Adolescent↗
PubMed1987

A simplified mitral valve method for two-dimensional echo Doppler blood flow calculation: validation in an open-chest canine model and initial clinical studies.

Quantitative two-dimensional Doppler echocardiography is increasingly used for the calculation of cardiac blood volumes. This study evaluates a simplified method for measuring volume flow at the mitral valve orifice. In four open-chest dogs the simplified mitral valve method was compared to a previously described mitral orifice method for Doppler volume flow calculation and to data obtained by electromagnetic flow measurement. Cardiac output varied from 1.4 to 7.7 L/min. Correlation for both the Doppler method and the electromagnetic meter volume flows was r = 0.98 to 0.99, and there was no significant difference between the two methods. In a clinical pilot study, 10 children were studied in the catheterization laboratory, and the simplified Doppler flow method was compared to thermodilution cardiac output measurements with good results. The study indicates that the simplified mitral valve method provides acceptable accuracy for Doppler cardiac output measurement.

Animals↗
PubMed1987

In vitro methods for studying the accuracy of velocity determination and spatial resolution of a color Doppler flow mapping system.

We tested a color Doppler flow mapping system (Aloka 880, 3.5 mHz) to image the steady flow of a suspension of cornstarch (0.1% to 1.75%) in water, flowing at known velocities through a series of Tygon tubing with internal diameters of 1.6 to 4.8 mm and latex rubber tubing (7.9 to 15.9 mm) in a water tank. Flow through the tubes was imaged at 2 to 12 cm and 2 to 18 cm distances from the transducer, by the use of the near and far focus settings of the instrument. First, the color flow diameters were compared to the known internal diameters of the tubing oriented at a 30- to 70-degree flow angle to the direction of interrogation to test axial resolution as well as lateral resolution. For the near transmit focus setting, the color diameters increasingly overestimated the actual flow diameters as the distance from the transducer increased progressively beyond 6 cm (i.e., overestimation of up to 25 mm or 500% for the 4.8 mm tubing and 250% for the 9.5 mm tubing at 16 cm from the transducer). For the far transmit focus setting and for distances within 10 cm, the color diameters did not differ significantly (i.e., more than 1 mm) from the actual diameter. The lowest velocity color encoded by the instrument was 3 cm/sec for a pulse repetition frequency of 4 kHz. At a flow velocity of about 50 cm/sec, 6 cm distance from the transducer and mid gain settings, flow through the 1.6 mm tube barely color coded, while flow through 2.4, 3.2, and 4.8 mm tubes was easily imaged.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Flow Velocity↗
PubMed1987

Pediatric Doppler echocardiography 1987: major advances in technology.

The major advances in the capabilities of pediatric cardiologists to evaluate the heart by ultrasound that have occurred in the last 5 years have been reviewed. In addition to the new Doppler methods, the evolution of higher resolution echo techniques have provided a comprehensive means of evaluating the heart noninvasively. This information has relegated catheterization to a more therapeutic arena, leaving ultrasound as the major diagnostic technique for evaluation of congenital heart disease, both before and after birth.

Child↗
PubMed1987

Continuous-wave Doppler velocities and gradients across fixed tunnel obstructions: studies in vitro and in vivo.

The simplified Bernoulli relationship appears to be quite accurate for predicting gradients across discrete valvular obstructions. Controversy exists about how accurately it predicts the severity of disease in longer segment obstructions. In this study we constructed a pulsatile model of subvalvular pulmonary stensosis in vitro to study nine custom-made subvalvular tunnels 2, 4, and 7 mm in length with flow cross sections of 0.5 to 1.5 cm2 and with the stenotic segment proximal to a nonstenotic bioprosthetic valve, and a pulsatile model in vitro of a 16 mm long tunnel-like ventricular septal defect (VSD) of varying cross-sectional area (0.20 to 0.64 cm2). We also compared the observations in vitro with those in an open-chest dog preparation with a tunnel-like interventricular communication. In the subpulmonic stenosis model, for each individual tunnel, 10 instantaneous peak gradients between 15 to 105 mm Hg were available. The pressure gradients across the tunnel alone, measured in the subvalvular area, were consistently higher than the measured gradients across the tunnel plus valve, suggesting some relaminarization of flow (i.e., a decrease in velocity) and pressure recovery (i.e., an increase in pressure) distal to the obstruction. Continuous-wave Doppler velocities across the 4 and 7 mm tunnels for the highest gradients were slightly lower than for the 2 mm tunnel at the same gradients, and it was only for the 0.5 cm2 cross section, 4 and 7 mm tunnels that there was a suggestion of minor viscous energy loss. For all the subvalvular tunnels studied, the Bernoulli relationship accurately predicted the results of the pressure drop across the tunnel only, while the gradient across tunnel plus valve was consistently lower. For the VSD tunnel model in vitro, the Doppler-derived gradients were approximately 40% higher than the measured gradients. The findings for the subvalvular and VSD tunnels in vitro and similar findings in the open-chest dogs with VSD suggest that relaminarization of flow and recovery of pressure occurred distal to the tunnel orifice, whereas continuous-wave Doppler findings correlate with the highest instantaneous gradients measured in the lowest pressure areas at the vena contracta of the tunnel.

Animals↗
PubMed1987

Cardiac Doppler flows during fetal arrhythmias: physiologic consequences.

Eighty-six fetuses of 21-41 weeks' gestation with arrhythmias were studied with ultrasound and heart rate monitoring. The type of arrhythmia was identified by M-mode studies and was confirmed by postnatal electrocardiogram in 70 infants. The most common arrhythmia was premature atrial contractions (76), followed by premature ventricular contractions (five), paroxysmal supraventricular tachycardia (four), and atrial fibrillation/flutter (one). Doppler echocardiography was performed in 54 fetuses to measure flow velocities across the atrioventricular and semilunar valves. After isolated premature atrial and ventricular contractions, post-extrasystolic potentiation was demonstrated by an increase in fractional shortening (N = 32) of 49 +/- 6% in the right ventricle and 64 +/- 7% in the left ventricle. When post-extrasystolic beats were compared with normal beats, Doppler-determined time-velocity integrals increased 43% across the tricuspid valve, 41% across the mitral valve, 34% across the pulmonary valve, and 38% across the aortic valve. Mean velocity increased significantly after conversion to normal sinus rhythm in the five fetuses with supraventricular tachycardia (P less than .05). By studying the physiologic consequences of fetal arrhythmias using two-dimensional Doppler and M-mode ultrasound, we have documented the presence of post-extrasystolic potentiation after premature contractions, the existence of the Frank-Starling mechanism, and an increase in mean velocity (and therefore in cardiac output) after conversion of fetal tachyarrhythmias to normal sinus rhythm.

Arrhythmias, Cardiac↗
PubMed1987

Two-dimensional Doppler color flow mapping for detecting atrial and ventricular septal defects. Studies in an animal model and in the clinical setting.

In experimental studies in six dogs as well as in clinical studies in eleven patients with atrial septal defect and 27 patients with ventricular septal defect, the diagnostic usefulness of color Doppler echocardiography in detection of small septal defects and multiple defects was analyzed. The study showed that atrial or ventricular septal defects with a size of 2.5 to 3 mm or more, which eluded detection with two-dimensional echocardiography, were easily identified with the color Doppler method. Additionally, multiple defects were reliably demonstrated. In atrial septal defects, according to the results of this study, the shunt area in the color Doppler image enables a semiquantitative estimation of the shunt volume.

Adolescent↗