THE HAEMODYNAMICS OF COMPLETE TRANSPOSITION OF THE GREAT VESSELS

OpenModelica-based virtual simulator for the cardiovascular and respiratory physiology of a neonate

There is a lack of medical simulation tools that can be understood and used, at the same time, by researchers, teachers, clinicians and students. Regarding this issue, in this work we report a virtual simulator (developed in OpenModelica) that allow to experiment with the fundamental variables of the cardiovascular and respiratory system of a neonate. We extended a long-tested lumped parameter model that represents the cardiovascular and respiratory physiology of a neonate. From this model, we implemented a physiological simulator using Modelica. The fidelity and versatility of the reported simulator were evaluated by simulating seven physiological scenarios: two of them representing a healthy infant (newborn and 6-months old) and five representing newborns affected by different heart diseases. The simulator properly and consistently represented the quantitative and qualitative behaviour of the seven physiological scenarios when compared with existing clinical data. Results allow us to consider the simulator reported here as a reliable tool for researching, training and learning. The advanced modelling features of Modelica and the friendly graphical user interface of OpenModelica make the simulator suitable to be used by a broad community of users. Furthermore, it can be easily extended to simulate many clinical scenarios.

Complete transposition of the aorta and pulmonary artery in a Belgian Blue crossbreed calf: a case report

BACKGROUND

Complete transposition of the great arteries is a congenital cardiac malformation occasionally encountered in cattle and other species. The objective of the present report was to provide a detailed clinical, echocardiographic and post mortem description of a calf presenting with this condition.

CASE PRESENTATION

A 6-week old male Belgian Blue cross-breed calf was examined for respiratory distress and exercise intolerance. The patient was bright, alert and responsive without any neurologic abnormalities but was exercise intolerant, had marked cyanosis, tachycardia, tachypnea, a pansystolic heart murmur as well as a bilaterally palpable thrill over the heart. Arterial blood gas analysis revealed marked hypoxemia (PaO(2)=23 mmHg, O(2)sat=41.1%), mild hypercapnia and compensated respiratory acidosis. Echocardiographic examination revealed a complete transposition of the great arteries in combination with a ventricular septal defect through which blood shunted bidirectionally. Cardiac catheterization confirmed that arterialization of blood of the systemic circulation solely occurred in the right ventricle through blood shunting from the left into the right ventricle. Results of post mortem examination are presented.

CONCLUSION

Complete transposition of the great arteries is a cyanotic congenital anomaly repeatedly reported in calves that should be considered as differential diagnosis in patients presenting with hypoxemia more severe than commonly encountered with other congenital cyanotic heart conditions. We give a comprehensive summary of the clinical presentation, diagnostic work-up and post mortem examination of a Belgian Blue cross-breed calf with complete transposition of the great arteries.

Plain-film assessment of the neonate with D-transposition of the great vessels

The presenting chest radiographs of 27 new-born patients with D-transposition of the great vessels (D-TGV) were evaluated for the degree of pulmonary flow as well as other findings classically described in D-TGV (narrow superior mediastinum, radiographically absent thymus, inapparent main pulmonary artery, non-visualization of the malpositioned aortic arch, asymmetric pulmonary blood flow, and cardiomegaly). Of the 27 patients, 22 (82%) demonstrated normal or decreased flow. The majority of the D-TGV patients also failed to demonstrate any of the other classically described radiographic findings. A normal chest radiograph is the most common presenting scenario in the neonate with D-TGV.

Hemodynamics in transposition of the great arteries with comparison to ventricular septal defect

This paper uses a mathematical model of the circulations to study the hemodynamics of transposition of the great arteries (TGA) with comparison to ventricular septal defect (VSD). Computer experiments are conducted to determine the influence of the defect conductance and the pulmonary vascular conductance on the pulsatile pressures, flows, and oxygen concentrations of the circulation. In particular, the model is used to determine the waveform of the (possibly bidirectional) shunt through the ventricular and atrial septal defects. The results of the computer experiments consist of two parts. The first set of experiments is devoted to the comparison of VSD and TGA with a ventricular septal defect. The results are theoretical in the sense that most parameters have been fixed at the same levels. In each case TGA is represented by changing the connection of the chambers and reversing the compliance of the two ventricles. In the second set of experiments we attempt to simulate conditions clinically observed in a variety of cases of TGA. In each case we use clinical observations to infer parameters as the input to the model. We find that the model (with appropriate choice of parameters) generally exhibits blood pressure, blood flows and oxygen concentrations similar to the clinical observations. As a byproduct of these computer experiments we predict the effects of changing the pulmonary conductance. The comparison between TGA and VSD shows that as the defect conductance increases, the systemic oxygen concentrations decrease in VSD and increase in TGA. Even at large defect conductance, the two conditions remain distinct, however, since the mixing of the right and left ventricular blood pools is incomplete. This phenomenon of incomplete mixing sets quantitative limits on the benefits that can be achieved by surgical enlargement of the defect. A result of this study that may be useful in the management of TGA patients with a ventricular septal defect is the finding that there is a value of the pulmonary conductance that maximizes the effective flow and hence the systemic oxygen concentrations. The optimal pulmonary conductance is approximately equal to the systemic conductance when the defect is large.

Surgical considerations of ventricular septal defect associated with complete transposition of the great arteries and pulmonary stenosis, with special reference to the Rastelli operation

Ventricular septal defect (VSD) associated with complete transposition of the great arteries was studied, and each of the typical anatomic varieties was depicted to emphasize the characteristic features of the VSD. Among the 32 specimens, 13 cases were found to have a VSD lying anterosuperior to the origin of the papillary muscle of the conus, indicating that repair of the VSD could be performed without difficulty. Such a defect situated above the crista supraventricularis has proved to be technically most preferable, as shown in the case report. In contrast, the remaining 19 cases appeared to be inappropriate for the technique, as the VSD was overhung by a part of the tricuspid valve. Additional analysis was made of the angiocardiographic appearances of the VSD, demonstrating some characteristic patterns.

The vectorcardiogram in complete transposition of the great vessels. Analysis of fifty cases

The Frank vectorcardiograms of 50 patients with complete transposition of the great vessels were analyzed, and the findings were correlated with the electrocardiogram and hemodynamics. The patients were divided into four groups according to the presence or absence of ventricular septal defect and left ventricular outflow tract obstruction. In group I, consisting of 20 patients with ventricular septal defect, the vector cardiograms showed evidence of combined ventricular hypertrophy in 80% of the cases, the scalar electrocardiogram, in 40%.

In group II, 13 patients with ventricular septal defect and left ventricular outflow tract obstruction, the vectorcardiogram was consistent with either right, combined, or left ventricular hypertrophy.

In groups III and IV, patients with intact ventricular septum with or without left ventricular outflow tract obstruction, the vectorcardiogram was consistent with right ventricular hypertrophy in the majority of cases.

The electrocardiogram in complete transposition of the great vessels

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