Karl-Heinz Deeg

Dopplersonographische Flußmessungen bei Herzerkrankungen

Neben Erkrankungen des Zentralnvervensystems konnen v. a. kardiovaskulare Erkrankungen zu einer Beeinflussung des Flusprofils und der Flusgeschwindigkeiten in den Hirnarterien fuhren. Erkrankungen des zentralen Nervensystems sind dadurch gekennzeichnet, das in den extrakraniellen hirnversorgenden Arterien A. carotis communis und im extrakraniellen Verlauf beider Vertebralarterien ein normales Flusprofil vorliegt. Das pathologische Flusprofil in den intrakraniellen Hirnarterien und Venen kommt durch intrakranielle Einflusse auf die Hirngefase zustande. Demgegenuber fuhren Erkrankungen des Herzens und des Kreislaufsystems sowohl in den intra- als auch extrakraniellen Arterien zu gleichen Veranderungen der Fluskurve und Flusgeschwindigkeiten. Nicht alle Herzfehler haben jedoch eine pathologische Stromungskurve in den Hirnarterien zur Folge.

Ventricular Septal Defect

Ventricular septal defects are the most frequent congenital cardiac malformation. According to their location, four different types of defects are differentiated including subarterial, perimembranous, inlet and muscular defects. Echocardiographic description of the localization and extension of VSDs always requires the application of various planes. Colour Doppler echocardiography is specifically helpful in the visualization of muscular defects. Pulsed wave and continuous wave Doppler provide the possibility to quantify direction, maximal velocity and duration of shunting across the defect. Application of the modified Bernoulli equation allows to calculate the pressure gradient between both ventricles and to determine the systolic right ventricular and pulmonary arterial pressure noninvasively.

Transposition of the Great Arteries

Transposition of the great arteries is a cardiac malformation, which is characterized by ventriculoarterial discordance. It is easily diagnosed by 2D echo in the precordial and subcostal views, confirming origin of the aorta from the morphologic right and of the pulmonary artery from the morphologic left ventricle. In the majority of cases, transposition of the great arteries is associated with concordant connections of the atria and ventricles. Colour Doppler echocardiography in neonates is essential to visualize shunting between both circulations across the atrial septum and the ductus arteriosus. It is also important in the search for ventricular septal defects, obstruction of the left and right ventricular outflow tract as well as possible obstruction of the aortic arch. PW and CW Doppler can be applied to document flow across an associated VSD, to quantify gradients across the outflow tracts and to assess flow across the aortic arch and ductus arteriosus.

Anomalous Pulmonary Venous Connections

Total anomalous pulmonary venous connection (TAPVC) may occur as an isolated lesion or in association with complex congenital heart disease. 2D echocardiography in patients with isolated TAPVC reveals significant enlargement of the right atrium, right ventricle and pulmonary arteries. Colour Doppler is a valuable tool to identify the pulmonary venous confluence and its connection to the right atrium or systemic veins. Possible sites of anomalous pulmonary venous connection, which should be checked by colour Doppler interrogation, include the right atrium, the coronary sinus, the right and left superior vena cava, the azygos vein, the innominate vein, the inferior vena cava, the portal vein system and the hepatic veins. Echocardiographic detection of TAPVC in the context of complex congenital heart disease requires a systematic sequential approach that starts with clarification of venous connections. Frequently these patients also have anomalies of visceral and atrial situs summarized as heterotaxy syndromes. Partial anomalous pulmonary venous connection (PAPVC) can be associated with various cardiovascular malformations or it may occur as an isolated lesion. Anomalous drainage of the right upper pulmonary vein is frequently encountered in patients with sinus venosus ASD, while PAPVC of the right lower pulmonary vein is an integral part of the Scimitar syndrome.

Tetralogy of Fallot

The characteristic features of tetralogy of Fallot including the large perimembranous malalignment VSD, overriding of the aorta and obstruction of the right ventricular outflow tract can be well displayed by 2D echocardiography. Colour Doppler provides important information regarding shunting across the VSD, allows detection of additional muscular VSDs and helps to clarify the sites of obstruction of the right ventricular outflow tract. Colour Doppler is also required for clarification of collateral lung perfusion and laterality of the aortic arch as well as for detection of subclavian artery anomalies. PW and CW Doppler provide the possibility to quantify the gradient across the right ventricular outflow tract. Following surgical repair, PW and CW Doppler are important tools for quantification of systolic right ventricular pressure, residual gradient across the right ventricular outflow tract and pulmonary regurgitation.

Pulmonary Atresia and Ventricular Septal Defect

The cardiac anatomy in patients with pulmonary atresia and VSD can be well displayed in the precordial views by 2D echocardiography revealing a biventricular heart, a large perimembranous malalignment VSD and variable dextroposition of the aorta. Colour Doppler echocardiography in the parasternal short axis confirms absence of patency of the right ventricular outflow tract and is an essential tool in the search for central pulmonary arteries. Furthermore colour Doppler is required for clarification of collateral pulmonary blood flow, which may be provided by a patent ductus arteriosus or by MAPCAs. PW and CW Doppler interrogation of flow in the ductus arteriosus and in MAPCAs reveals sites of obstruction and allows noninvasive estimation of gradients in these vessels.

Aortic Stenosis, Regurgitation and Anomalies of the Left Ventricular Outflow Tract

The anatomy of the left ventricular outflow tract and the morphology of the aortic valve can be well displayed by 2D echocardiography allowing the differentiation of subvalvular, valvular and supravalvular stenosis. Colour Doppler displays the jet across the stenotic valve or outflow tract and is essential in the assessment of aortic regurgitation. Pulsed wave and continuous wave Doppler provide the possibility to determine the peak instantaneous and the mean gradient of aortic stenosis. Information of the severity of aortic regurgitation is provided by CW Doppler interrogation of the regurgitant jet with determination of the end-diastolic gradient. Semiquantitative assessment of the severity of aortic regurgitation by determination of diastolic run-off from the aorta is provided by PW and CW Doppler interrogation of flow in the descending aorta and in the systemic arteries.

The Normal Examination

Precordial, suprasternal and subcostal windows offer a multitude of views for the echocardiographic examination of the heart and great vessels in infancy and childhood. While two-dimensional echocardiography provides very good options for detailed morphologic cardiovascular assessment especially in neonates and infants, colour Doppler echocardiography is essential in the evaluation of cardiac valves, flow in the great arteries and veins and search for intracardiac and extracardiac shunts. Pulsed wave and continuous wave Doppler examination provide valuable information regarding blood flow velocities. Based on measurements of blood flow velocities, application of the modified Bernoulli delivers detailed haemodynamic informations regarding pressure gradients and ventricular and pulmonary artery pressures.

Patent Ductus Arteriosus

Patent ductus arteriosus may occur as an isolated lesion or in association with congenital cardiac malformations. Echocardiography in conjunction with colour Doppler displays the morphology of the ductus and its anatomic variations. Analysis of ductal flow by pulsed wave Doppler provides valuable haemodynamic information in neonates allowing to distinguish right to left, bidirectional and left to right shunting. In older children, continuous wave Doppler provides the possibility for noninvasive determination of systolic pulmonary artery pressure by calculation of the pressure gradient across the duct. In patients with complex congenital heart disease, who are dependent on patency of the ductus in the neonatal period, Doppler echocardiography is essential to monitor treatment with prostaglandin E1. Following interventional or surgical closure, colour Doppler is the method of choice to verify the result and to confirm complete closure of the ductus.

Anomalies of Left Ventricular Inflow and Mitral Valve

Obstruction of left ventricular inflow includes pulmonary vein stenosis, cor triatriatum and supravalvular and valvular mitral stenosis. Morphologic diagnosis of these anomalies is greatly enhanced by colour Doppler examination. PW and CW Doppler in pulmonary vein stenosis and in cor triatriatum reveal a continuous systolic-diastolic flow profile. Documentation of flow velocities in patients with significant supravalvular mitral ring stenosis and mitral valvular stenosis requires application of CW Doppler. Description of severity of mitral valve stenosis to a large extent relies on determination of the mean gradient. PW and CW Doppler evaluations of possible pulmonary and tricuspid regurgitation are important tools in the detection of secondary pulmonary hypertension. Congenital mitral regurgitation is encountered in patients with mitral valve prolapse, mitral valve cleft or dysplastic mitral valve. Functional mitral regurgitation is found in children with dilated cardiomyopathy, myocarditis or ischaemic alterations of the papillary muscles and in patients with severe aortic stenosis or anomalous origin of coronary arteries from the pulmonary artery. Colour Doppler helps to visualize the origin and size of the regurgitant jet. However assessment of the severity of mitral regurgitation requires the inclusion of clinical data, 2D echo and PW and CW Doppler.