Biomedical subjects
Publications and source records attributed to D A Redel.
Cardiac traumatization may lead to severe complications. Transcatheter closure of a postraumatic ventricular septal defect (VSD) was successfully done using an Amplatzer septal occluder in a man who had previously undergone surgery for myocardial fissure and mitral valve dysfunction. In selected cases, the percutaneous approach may be a valuable option to close muscular VSDs.
In two-dimensional echocardiography the sonographer must synthesize multiple tomographic slices into a mental three-dimensional (3D) model of the heart. Computer graphics and virtual reality environments are ideal to visualize complex 3D spatial relationships. In augmented reality (AR) applications, real and virtual image data are linked, to increase the information content. In the presented AR simulator a 3D surface model of the human heart is linked with echocardiographic volume data sets. The 3D echocardiographic data sets are registered with the heart model to establish spatial and temporal congruence. The heart model, together with an animated ultrasound sector represents a reference scenario, which displays the currently selected two-dimensional echocardiographic cutting plane calculated from the volume data set. Modifications of the cutting plane within the echocardiographic data are transferred and visualized simultaneously and in real time within the reference scenario. The trainee can interactively explore the 3D heart model and the registered 3D echocardiographic data sets by an animated ultrasound probe, whose position is controlled by an electromagnetic tracking system. The tracking system is attached to a dummy transducer and placed on a plastic puppet to give a realistic impression of a two-dimensional echocardiographic examination.
Augmented reality (AR) applications link real with virtual image data, in order to increase their information content. In medicine they are especially useful for education and for supporting the interpretation of three-dimensional (3D) image data. Simulators are used to train risky or expensive procedures. In the AR application EchoCom2 a 3D surface model of the human heart is linked with echocardiographic volume data sets. The 3D echocardiographic data sets are registered with the heart model to synchronize it's temporal and spatial orientation. The heart model together with an animated ultrasound sector represents a reference scenario, which displays the currently selected cutting plane within the echocardiographic volume data set. Modifications of the cutting plane within the echocardiographic data are transferred simultaneously and in real time to the reference scenario. The AR application is used as a simulator to train two-dimensional echocardiographic examinations and as an orientation and navigation aid for the exploration of 3D echocardiographic data sets. Beginners in echocardiography have only a rudimentary conception of the spatial relationship between the actual ultrasound image and the 3D anatomy of the heart. They are unable to translate multiple two-dimensional slices into a coherent 3D mental image of the heart. In EchoCom2 the trainee can interactively explore the 3D heart model and the registered 3D echocardiographic data sets by the animated ultrasound sector, whose position is controlled by an electromagnetic orientation and position system (EPOS). The data from the EPOS are used to calculate the echocardiographic images that are analogue to the position of the animated ultrasound sector. EchoCom2 is also used to support the interpretation of 3D echocardiographic data sets. The analysis of 3D echocardiographic data has to be done during a post processing. Defining the exact position of a cutting plane within the volume is difficult due to the lack of a standardized representation, the independence of the cutting plane of any transducer position and the possibility to calculate an indefinite number of views. The simultaneous representation of the current cutting plane both in the volume data, and in the heart model enables the examiner ad hoc to recognize it's position and the visualized structures.
Color Doppler echocardiography of tricuspid valve regurgitation (TR) is a valid, noninvasive method of determining systolic pulmonary artery pressure (SPAP). In a prospective study the authors examined 56 healthy full-term newborns (group I), 36 healthy preterm newborns (group II), and 10 preterm newborns with severe respiratory distress syndrome requiring surfactant replacement therapy (group III). Doppler studies were repeated until the transtricuspid gradient was < 20 mm Hg. In 83.3% of children a reproducible spectral curve was recorded at least once. The authors estimated the transtricuspid gradient delta p (RV-RA) by using the modified Bernoulli equation. Within the first twenty-four hours delta p (RV-RA) was < 20 mm Hg in 72.7%, 50%, and 25% of children with measurable TR in groups I, II, and III, respectively, increasing to 91.1%, 78.6%, and 55.6% within forty-eight hours. There was no significant correlation between SPAP and gestational age, birth weight, mode of delivery, and ductal closing time. Continuous holosystolic envelope tracing of TR was recorded in 16.6%. In these patients delta p (RV-RA) was measured markedly higher (mean of 30.1 mm Hg) than in the others (mean 17.3 mm Hg). The authors conclude that there is a high prevalence of TR in neonates, which allows estimation of SPAP in > 80% of newborns without considerable impairment. Normalization of SPAP takes place within four days in most patients, but there is a delay in preterm infants with severe respiratory distress syndrome.
OBJECTIVES: We attempted to evaluate the efficacy and tissue reaction of a new miniature interventional ductal occlusion device in neonatal pigs. BACKGROUND: A variety of devices are used to close persistent ductus arteriosus (PDA) by interventional measures. Because of the size of these devices, they have not been applied to term or preterm neonates. Newborn piglets are comparable in size and fragility to human term and preterm neonates. METHODS: Memory-shaped double-cone stainless steel coils were mounted on a titanium-nickel core wire. A snap-in mechanism attaches the coil to the delivery wire, allowing intravascular coil retrieval and repositioning. The system was placed through a 3F Teflon catheter. Two piglet models of PDA were used: 1) ductal patency maintained by stents (n = 6), and 2) ductal patency produced by angioplasty (n = 7) to avoid stent-coil interaction. RESULTS: Placement of the coils within the PDA was possible in all piglets. Before final detachment, the coils were retrieved or repositioned, or both, up to eight times. In all but two piglets the ductus was closed within 1 h of the procedure. The coils were never dislocated and caused no infections or relevant aortic and pulmonary artery obstruction (95% confidence interval for missing complications [0 of 13] extends to 23%). Histologic and electron microscopic studies revealed endothelial coverage of the implants and histiocytic reaction but no local or systemic inflammation or erosion of the implant. CONCLUSIONS: The device was effective in experimental models of PDA. The information obtained warrants initial trials of the device in neonates.
Two children underwent interventional closure of a modified Blalock-Taussig shunt using a new detachable coil system (Duct-Occlud). This procedure has advantages over currently available materials to occlude these and other communications between the systemic and pulmonary circulations.
Segmented 2D times-of-flight (TOF) magnetic resonance angiography (MRA) with ECG gating is a suitable adjunct to conventional magnetic resonance tomography. Based on our experience with 106 patients, cardiovascular MRA primarily aids in the diagnosis of congenital heart disease, but is of minor importance for the evaluation of acquired cardiovascular disease, such as aortic aneurysms. Changes in flow dynamics as a result of spin dephasing may render partial signal loss. Due to flow turbulence and resulting signal loss distal to stenoses, difficulties may arise in correctly determining the degree of stenosis and differentiating between partial thrombosis and slowly flowing blood. The most promising approach for optimizing 2D TOF MRA is enhancement of the intravascular signal and suppression of background signal. For the equipment we use with a 0.5 Tesla scanner, the most powerful combination to enhance intravascular signal and suppress back-ground noise was applying a flip angle of 65 degrees and a short inversion prepulse. The influence of the flip angle and prepulse on the intravascular signal varies, dependent on the flow velocities and heart rates. Secondary reconstructions, such as the MIP technique, contribute to better spatial orientation by using rotating projection views. To avoid overprojection artifacts and loss of diagnostic information, 2D single slices should be the primary source of image analysis.
A longitudinal study was performed in nine nonhydropic and nine hydropic fetuses with supraventricular tachycardia (SVT). First, because of a lack of reference methods in utero, the validity of spatial (length and area) and temporal parameters for semiquantitative grading of atrioventricular (AV) valve regurgitation by color Doppler flow mapping and M-Q mode imaging was evaluated by a longitudinal intraindividual study before and after drug-induced cardioversion to sinus rhythm and by correlation with the severity of hydrops and the time required for complete remission of hydrops. Second, with the demonstration of AV valve incompetence and changes in venous blood flow velocity wave forms, new data were collected concerning chronic SVT in the fetus. AV valve incompetence occurred in eight fetuses: during SVT only in three severely hydropic fetuses, during sinus rhythm in one nonhydropic fetus, and in seven hydropic fetuses including those previously mentioned, where AV incompetence outlasted tachycardia. The length and area of the regurgitant jet as imaged by color Doppler flow mapping and the temporal duration of regurgitation in relation to the systolic phase as measured by M-Q mode continuously diminished intraindividually but with great interindividual differences in the time span required for complete remission, which ranged from 5 to 42 days. Pulsed-wave Doppler studies of blood flow in the inferior vena cava and left hepatic vein demonstrated normal biphasic forward flow with a systolic and a diastolic surge during sinus rhythm in all fetuses and in two instances also during SVT of 190 and 195 beats/min, respectively. In all cases a pulsatile reversal of blood flow with systolic forward flow and diastolic reverse flow was observed during tachycardia greater than 220 beats/min. Thus the presence of functional AV valve incompetence as a result of annular enlargement seems to be a sign of SVT-induced "cardiomyopathy" during fetal life. AV valve incompetence during SVT was always associated with extremely severe hydrops and seemed to indicate the most severe degree of ventricular dysfunction, which could influence the selection of antiarrhythmic drugs. After termination of SVT, severe AV valve insufficiencies also occurred in other cases of hydrops, probably because of the markedly increased diastolic filling distending the already enlarged annular ring. The observed great interindividual differences in time required for disappearance of AV valve incompetence and hydrops could be explained by a different state of progression of tachycardia-induced "cardiomyopathy" at the time of drug-induced cardioversion.(ABSTRACT TRUNCATED AT 400 WORDS)
A rare case of aorta to right ventricle tunnel with associated pulmonary stenosis was corrected on cardiopulmonary bypass in a 3-month-old infant. Both the aortic and ventricular openings were closed with a patch. Although the repair was successful and the child was discharged from the hospital, septicemia developed and she died later. Early repair of this defect is recommended.
From 1981 to 1990, 60 fetuses with tachyarrhythmia (21-39 weeks of gestation) were treated in utero. Of these, 54 were cases of supraventricular tachycardia, and six of atrial flutter. Non-immune fetal hydrops was present in 21 cases with supraventricular tachycardia and in five cases with atrial flutter, a total of 26 cases.Transplacental treatment by maternally administered antiarrhythmic drugs (digoxin only or in combination with verapamil) produced good results in non-hydropic fetuses. In this group, all 34 fetuses survived. In fetuses with hydrops, 20 out of 26 survived. In 13 fetuses of the 26 with hydrops, direct fetal therapy was performed in addition to the transplacental therapy when the tachyarrhythmia was refractory to transplacental treatment. During the 9 years of this study, a variety of direct treatment regimes have been used consisting of intraperitoneal and/or umbilical intravenous administrations of different drugs. Since 1988, umbilical vein punctures have shown that the transplacental passage of digoxin (and amiodarone) is hampered in the presence of hydrops, and direct treatment may he necessary in these cases. Amiodarone seems to he the drug of choice for direct therapy. It is highly effective in supraventricular tachycardia and atrial flutter. The long elimination half-time of amiodarone reduces the number of umbilical cord punctures needed to maintain the therapeutic drug level in the fetus.
Fourteen fetuses with atrioventricular canal malformations were examined by two-dimensional echocardiography, pulsed-wave Doppler echocardiography, and color Doppler flow mapping. Eleven fetuses had complete and three fetuses had partial atrioventricular canal malformations. Nonimmune hydrops fetalis was associated with six cases, and fetal arrhythmia was seen in three cases. With two-dimensional echocardiography, the atrioventricular canal malformations could be diagnosed accurately. The inclusion of color Doppler flow mapping, however, provided additional hemodynamic information that was important from the prognostic point of view. Incompetence of atrioventricular valves could be demonstrated in 10 of 14 cases by Doppler echocardiography. In nine cases, detailed Doppler echocardiographic evaluation of the regurgitation jet was possible. The proportion of systolic time during which atrioventricular valve insufficiency was demonstrated was related to the occurrence of nonimmune hydrops fetalis. When insufficiency of atrioventricular valves was associated with hydrops (four cases), a pansystolic insufficiency was always present. In cases without hydrops (five), regurgitation was confined to early systole. Thus a reliable method for semiquantitative evaluation of the degree of insufficiency seems to have been found. Moreover, an association appeared to exist between the occurrence of hydrops fetalis and the proportion of atrial area that was taken up by regurgitant jet area, as determined by planimetry in the four-chamber view. Prenatal diagnosis was confirmed by autopsy or neonatal cardiac evaluation. Only one neonate survived in our series. Two were stillborn, four died during the neonatal period, two died during infancy, and pregnancy was electively terminated prematurely in five cases. Eight fetuses were found to have a karyotypic abnormality.
Color Doppler flow mapping of fetal heart was performed in 582 fetuses between 16 and 38 weeks of gestation. Congenital heart diseases were excluded in 522 fetuses correctly. In 59 fetuses structural and/or functional cardiac abnormalities were diagnosed. In one fetus small multiple ventricular septal defects were missed. The most important additional information obtained by color Doppler flow mapping was: (1) Diagnosis of insufficiencies of atrioventricular valves; (2) Demonstration of turbulent high velocity jet in stenosis of semilunar valve; (3) Reverse flow in ascending aorta in atresia of aortic valves and on ductus arteriosus and main pulmonary artery in atresia of pulmonary valves; (4) Reverse perfusion of ductus arteriosus and main pulmonary artery as well as an antegrade turbulent high velocity jet in severe pulmonary stenosis as part of tetralogy of Fallot; (5) Bidirectional interventricular shunting of blood in ventricular septal defect. Color Doppler flow mapping allows rapid screening for flow abnormalities of the fetal heart. Exact localisation of sample volume by pulsed wave Doppler in area of abnormal flow pattern is possible, thus significantly reducing the Doppler examination time. The accuracy of prenatal diagnosis of congenital heart diseases is improved by application of color Doppler flow mapping, in particular in presence of complex cardiac defects.
In a fetus with ventricular extrasystoles a congenital aneurysm of the left ventricle was diagnosed prenatally. At 32 weeks of gestation, echocardiography showed a large apical left ventricular aneurysm with a thin, hypokinetic wall. Congestive heart failure did not occur. Prenatal and postnatal examinations did not detect the aetiology of the aneurysm, but excluded the majority of possible causes. The 2-year-old child is now asymptomatic and normally developed. Neither medication nor surgical treatment have been necessary, except for antithrombotic prophylaxis with low-dose aspirin.
Improving techniques in fetal echocardiography have important implications in the field of clinical genetics. 1) Fetal echocardiography in pregnancies with families with increased recurrence risks for congenital heart disease (CHD): In 473 pregnancies with increased recurrence risks for CHD second-trimester fetal echocardiography was performed. In 11 cases (2.3%) cardiac malformations were present that could be diagnosed in five cases prenatally (hypoplastic left heart, complete atrioventricular canal defect with hypoplastic left ventricle, preductal coarctation of aorta, tetralogy of Fallot, complete atrioventricular canal defect). In six cases the prenatal diagnosis could not be performed (total anomalous pulmonary venous connection [one case], secundum atrial septal defect [two cases], ventricular septal defect [three cases]). The recurrence risk in families with one previously affected child was 1.4% (5/364), and 17.6% (3/17) in families with two previously affected children. In two out of 44 cases with one affected parent a CHD could be diagnosed, in both cases one previous child was already affected. 2) Congenital heart defect as a common symptom in malformation syndromes: CHD is common as a symptom in malformation syndromes. The demonstration of a fetal CHD can lead to diagnosis of a complex malformation syndrome and it is integral in prenatal diagnosis in cases with increased recurrence risks for a complex malformation syndrome. The sonographic diagnosis of a CHD may signal associated chromosomal disorders. Between January 1986 and December 1988 in 433 cases with prenatally diagnosed congenital malformation and/or severe fetal growth retardation a prenatal chromosome analysis was performed. Within this group 77 fetuses demonstrated a CHD and 28 (36%) out of these revealed a chromosomal disorder. The genetic basis of CHD, the most common complex syndromes with CHD, and the principles of genetic counseling in families with CHD are summarized.
In patients with VSD right ventricular pressure can be determined noninvasivly by subtracting the VSD-gradient from the systolic blood pressure. Using a stand-alone continuous-wave Doppler the VSD-gradient may be underestimated due to a large angle theta caused by the various VSD locations and the often atypical VSD-jet directions. Therefore Color-Doppler was used to visualize the VSD-jet and to align (angle less than 15 degrees) the continuous-wave Doppler beam. 37 patients, who underwent catheterization were studied. By VSD-jet visualization 3 patients were correctly identified in whom the VSD gradient would have been underestimated due to a large angle 0. They were excluded from this study because of the resulting error. In the remaining 34 patients VSD-gradients up to 105 mmHg were measured. A good correlation was found between the noninvasively an invasively determined right ventricular pressures: r = 0.93; y = 1.06x -2.4. One source of error in this method is the difference between the maximal instantaneous and the peak to peak VSD-gradient. Differences of up to 39 mmHg were found when the maximal instantaneous gradient occurred either very early or very late in systole. In these cases the midsystolic gradient should be used. It is concluded that the presented method is easy to perform and permits a reliable noninvasive estimation of the right ventricular pressure in patients with VSD.
One hundred and fifty fetuses between 16 and 38 weeks of gestation were studied by fetal echocardiography using colour-coded two-dimensional Doppler echocardiography. Two-dimensional, M-mode, and Doppler spectral analyses were also performed. In 14 fetuses, structural and/or functional abnormalities were detected. Abnormalities were correctly ruled out in all the other fetuses. The advantages of two-dimensional Doppler echocardiography are (1) rapid screening for flow abnormalities in the fetal heart, and thus shortening of the Doppler examination time; (2) rapid diagnosis of valvular regurgitation, valvular stenosis, and abnormal shunting of blood across the interatrial and interventricular septa; and (3) facilitation of the diagnosis of complex congenital heart defects which in certain cases is possible only by using two-dimensional Doppler echocardiography.
The fetuses of 352 patients at between 16 and 38 weeks of gestation were studied by using two-dimensional Doppler echocardiography (2-DDE). In 32 fetuses, structural and/or functional abnormalities were detected. The advantages of 2-DDE are, in particular, rapid screening for flow abnormalities and, thus, shortening of the Doppler examination time. Further benefits include a rapid diagnosis of valvular regurgitation, valvular stenosis, and abnormal shunting of blood across the cardiac septa. The diagnosis of complex heart defects is facilitated by and, in certain cases, only possible at all using 2-DDE.
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