Many patients with ventriculoarterial discordance have survived to adulthood. Those with complete transposition of the great arteries have often had an atrial switch procedure (Mustard or Senning operation) performed, which leaves the morphological right ventricle (RV) supporting the systemic circulation. RV failure and tricuspid regurgitation are common. Some patients may ultimately require cardiac transplantation. Sinus node dysfunction is increasingly common with longer follow-up, and some patients need pacemaker implantation. Atrial arrhythmias are frequent, and atrial flutter may be a marker for sudden death. Patients with an arterial switch procedure are also surviving to adulthood. Long-term problems include coronary stenoses, distortion of the pulmonary arteries, dilatation of the neoaortic root, and aortic regurgitation. Patients with congenitally corrected transposition have both atrioventricular and ventriculoarterial discordance and therefore also have a morphological RV and delicate tricuspid valve in the systemic circulation. Associated defects, such as abnormalities of the tricuspid valve, ventricular septal defect, and pulmonary stenosis, occur in the majority of patients. Heart block occurs with increasing age. Atrial arrhythmias occur frequently, and their occurrence should prompt a search for a hemodynamic problem. Progressive tricuspid regurgitation occurs with age and is associated with deterioration of RV function. Surgical treatment should be considered at the earliest sign of RV dilatation or dysfunction. All patients should be seen periodically in a center where expertise in the clinical evaluation, imaging, and hemodynamic assessment of adult congenital heart disease is available.

Transposition of the Great Arteries

The hemodynamics of heart valve prostheses can be reproducibly investigated in vitro within circulatory mock loops. By measuring the downstream velocity and shear stress fields the shear stresses which are clinically responsible for damage to platelets and red blood cells can be determined.The mechanisms of damage and the effects of shear stresses on blood corpuscles were investigated by Wurzinger et al. (3, 4) at the Aerodynamics Institute of the RWTH Aachen. In the present study, the above data are incorporated into a mathematical correlation, which serves as a basic model for the estimation of blood damage.This mathematical model was applied to in vitro investigations of 25 different aortic valve prostheses. The results were compared to clinical findings. In most cases agreement was good, indicating that this model may be directly applied to the clinical situation. This new method facilitates the estimation of clinically expected blood damage from in vitro measurements. It may be useful for the develop...

Estimation of shear stress-related blood damage in heart valve prostheses--in vitro comparison of 25 aortic valves.

An algorithm for the solution of the incompressible Navier-Stokes equations in three-dimensional generalized curvilinear coordinates is presented. The algorithm can be used to compute both steady-state and time-dependent flow problems. The algorithm is based on the method of artificial compressibility and uses a third-order flux-difference splitting technique for the convective terms and the second-order central difference for the viscous terms. The accuracy is obtained in the numerical solutions by subiterating the equations in pseudotime for each physical time step. The equations are solved with a line-relaxation scheme that allows the use of very large pseudotime steps leading to fast convergence for steady-state problems as well as for the subiterations of time-dependent problems. The steady-state solution of flow through a square duct with a 90-deg bend is computed, and the results are compared with experimental data. Good agreement is observed. Computations of unsteady flow over a circular cylinder are presented and compared to other experimental and computational results. Finally, the flow through an artificial heart configuration with moving boundaries is calculated and presented.

Steady and unsteady solutions of the incompressible Navier-Stokes equations

Applications of laser-induced breakdown spectroscopy for geochemical and environmental analysis: A comprehensive review

BACKGROUND: Respiratory failure after cardiopulmonary bypass (CPB) remains a major complication after cardiac surgery. The authors tested the hypothesis that atelectasis is an important factor responsible for the increase in intrapulmonary shunt after CPB. METHODS: Six pigs received standard CPB (bypass group). Six other pigs had the same surgery but without CPB (sternotomy group). Another six pigs were anesthetized for the same duration but without any surgery (control group). The ventilation-perfusion distribution was measured with the inert gases technique, extravascular lung water was quantified by the double-indicator distribution technique, and atelectasis was analyzed by computed tomography. RESULTS: Intrapulmonary shunt increased markedly after bypass but was unchanged over time in the control group (17.9 +/- 6.2% vs. 3.5 +/- 1.2%; P < 0.0001). Shunt also increased in the sternotomy group (10 +/- 2.6%; P < 0.01 compared with baseline) but was significantly lower than in the bypass group (P < 0.01). Extravascular lung water was not significantly altered in any group. The pigs in the bypass group showed extensive atelectasis (32.3 +/- 28.7%), which was significantly larger than in the two other groups. The pigs in the sternotomy group showed less atelectasis (4.1 +/- 1.9%) but still more (P < 0.05) than the controls (1.1 +/- 1.6%). There was good correlation between shunt and atelectasis when all data were pooled (R2 = 0.67; P < 0.0001). CONCLUSIONS: Atelectasis is produced to a much larger extent after CPB than after anesthesia alone or with sternotomy and it explains most of the marked post-CPB increase in shunt and hypoxemia. Surgery per se contributes to a lesser extent to postoperative atelectasis and gas exchange impairment.

Atelectasis is a major cause of hypoxemia and shunt after cardiopulmonary bypass: an experimental study

In this study we have employed a single channel, pulsed ultrasonic Doppler velocimeter to measure instantaneous velocity distributions within the pumping chamber of a ventricular assist device. Instantaneous velocities have been decomposed into periodic mean and turbulent fluctuating components from which estimates of Reynolds stresses within the chamber and mean shear stresses along the wall of the chamber have been obtained. A review of the complete data set indicates a maximum value of the mean wall shear stress of 25 dynes/cm2 and a maximum Reynolds stress of 212 dynes/cm2 . These values are lower than those measured distal to aortic valve prostheses in vitro and are well below levels known to damage blood components. Core flow patterns, wall washing patterns and flow stagnation points are also revealed.

Pulsed ultrasonic Doppler velocity measurements inside a left ventricular assist device.

An automatic control system has been developed to balance and control the output of an artificial heart. The system consisted of 2 linked negative feedback loops. The left ventricle was controlled by a Servo-Stroke Optimizer, which insured complete filling and full stroke operation of the left pump with each beat and changed the beat rate in accord with changes in aortic pressure. The right ventricle was controlled by a Servo-Variable Systolic Duration unit, which changed the stroke of the right ventricle to maintain the left atrial pressure within a preset band. In the initial animal studies, control pressures (aortic and left atrial pressure) were obtained from implanted transducers. More recently, a method has been devised whereby the control pressures were obtained from specific points on the left air line pressure wave, obviating the need for implanted transducers. The control system has been evaluated in a mock circulatory loop and in 9 calves with implanted artificial hearts. The system has provided balance of the 2 implanted ventricles and changes in flow rate in response to changes in peripheral resistance. The need for an operator to make manual adjustment to the power units has been considerably reduced. Further studies are indicated to evaluate the function of the control system in animals performing moderate-to-maximal exercise. Furthermore, the ultimate benefits of full stroke operation vs fill limited mode operation remain to be delineated.

Automatic control of the artificial heart.

Surgical intervention in infants with coarctation of the aorta.

Retrospective analysis of 14 patients undergoing circulatory support for postcardiotomy cardiogenic shock during the past 3 yrs has demonstrated the ability of the profoundly depressed myocardium to recover. Four patients were totally weaned from circulatory support and 2 are long-term survivors. Our results suggest that improved survival is dependent on the absence of certain peri-operative complications. To improve future clinical results we suggest that prompt application of assist pumping is necessary to eliminate prolonged cardiopulmonary bypass times and subsequent massive bleeding; those circulatory support systems requiring systemic anticoagulation are of no value in the treatment of postcardiotomy cardiogenic shock; the use of atrial cannulation may be advantageous in certain patients to eliminate critical inflow obstruction, further prolongation of cardiopulmonary bypass, and additional myocardial damage; and that the high incidence of right ventricular failure that is refractory to medical therapy makes the ability to support both ventricles mandatory.

Mechanical circulatory assistance for postoperative cardiogenic shock: a three year experience.

Pulmonary vascular obstructive disease developed postoperatively in an infant with aortopulmonary transposition and intact ventricular septum who underwent a Mustard operation in 3 months of age. Preoperative catheterization had shown normal pulmonary artery pressures. Four months after surgery, catheterization showed pulmonary artery systolic pressure above the systemic level and a tortuous, attenuated pulmonary vascular tree visualized angiographically. Early corrective surgery may not preclude the development of pulmonary vascular obstructive disease in patients with aortopulmonary transposition.

Pierce Ws

Papers

Pulsed ultrasonic Doppler velocity measurements inside a left ventricular assist device.

Automatic control of the artificial heart.

Surgical intervention in infants with coarctation of the aorta.

Mechanical circulatory assistance for postoperative cardiogenic shock: a three year experience.

The development of pulmonary vascular obstructive disease after successful Mustard operation in early infancy.