Andersons pediatric cardiology 1083

These auscultatory findings are only for an uncomplicated persistent duct in a child It should be remembered that these features may differ in infancy or be altered by the development of complications Investigations Electrocardiogram Patients with an isolated persistent arterial duct usually have some electrocardiographic evidence of left atrial and ventricular hypertrophy, reflecting volume overload of the left heart Occasionally, the electrocardiogram may show combined ventricular hypertrophy or, if the duct is small, be entirely normal The electrical axis is usually normal, and deviation to the right, with right atrial and/or right ventricular hypertrophy, suggests the presence of additional defects or pulmonary hypertension The electrocardiographic changes are less predictable in infants and clinically less helpful.56 Prolongation of the PR interval, which disappears or decreases after closure, has been observed in about 20% of cases.57 Atrial fibrillation may develop in adult life.58,59 When the shunt is large enough to equalize the systemic and pulmonary arterial pressures, biventricular hypertrophy is likely to develop With the onset of pulmonary vascular disease, the predominant findings will be those of right ventricular hypertrophy Chest Radiography The chest film may be normal in patients with a small shunt Cardiomegaly is present in those where flow to the lungs is close to twice systemic flow or greater Increased pulmonary vascular markings are seen, with an obvious bulge of the pulmonary trunk at the left border of the cardiac silhouette The aorta is also prominent Both it and the pulmonary trunk tend to enlarge with age Enlargement of the left atrium is usually present and reflects increased pulmonary venous return due to the left-to-right shunt Increased pulmonary vascularity may be more marked on the right, as is often seen with other left-toright shunts (Fig 41.11) The duct may calcify, although this complication is more common when the vessel is closed rather than patent The aortic end of the duct, the ductal ampulla, may be seen on the chest radiograph and can be demonstrated angiographically during the first week of life These findings may be modified, especially if pulmonary vascular disease develops FIG 41.11 Chest radiographs from patients with small ducts Left, Note the minimally increased pulmonary vascularity Right, Child with a larger ductal communication There is increased pulmonary vascularity and cardiomegaly Echocardiography Persistent patency beyond the neonatal period is readily diagnosed from the characteristic clinical features Cross-sectional echocardiography will help to rule out other structural cardiac malformations The duct can be imaged throughout its length using a high left parasternal view,60,61 allowing evaluation of ductal size and the presence of tissue within the lumen, indicating imminent closure In preterm infants, imaging may be difficult due to emphysematous lungs from high ventilatory pressures A subxiphoid view can be used Characteristic diastolic flow in the pulmonary trunk identified by Doppler interrogation increases the confidence of diagnosing ductal shunting Flow through the duct can be quantified by analysis of Doppler tracings of diastolic flow in either the left pulmonary artery or the descending aorta Colorflow Doppler techniques have been more useful in revealing ductal patency This is currently the most sensitive method for detecting and semiquantifying ductal flow (Fig 41.12).62 Qualitatively, the presence of bidirectional, or pure right-toleft, shunting is specific for elevated pulmonary arterial pressures.63,64 In children with high pulmonary vascular resistance, with a low-velocity Doppler signal or right-to-left flow, the duct may be very difficult to demonstrate by color flow imaging, even if it is large Associated findings such as septal flattening, unexplained right ventricular hypertrophy, or high-velocity pulmonary regurgitation should prompt an investigation for a patent duct Contrast echocardiography may also be helpful in this setting, identifying microbubbles in the descending aorta in consequence of ductal right-to-left shunting but not in the ascending aorta In addition, using color flow mapping, Doppler measurements of velocity can be used to estimate pulmonary arterial pressure.65,66 M-mode studies provide an assessment of left atrial and ventricular size, which gives some idea of the magnitude of the shunt In children with a small duct, the chambers are usually of normal size, although mild left atrial and/or left ventricular enlargement may be seen In children with a moderate or large duct, the left atrium and ventricle are enlarged Echocardiography is probably most valuable in the diagnosis of ductal patency in the premature infant It will be discussed further in that section FIG 41.12 Left, Echocardiogram (high left parasternal view) showing a large duct in a newborn Note the proximity to the left pulmonary artery Middle, Color flow Doppler mapping, with mild turbulence confirming the presence of flow (orange) entering the pulmonary trunk (orange pattern) Right, Spectral Doppler trace showing the direction, timing, and velocity of flow in the duct LPA, Left pulmonary artery; MPA, main pulmonary artery Recent echocardiographic studies using color flow Doppler have further identified the presence of small ductal communications in the absence of any typical murmur of patency, this degree of shunting giving uncharacteristic soft vibratory systolic murmur or no murmur at all.46,67–69 These findings have a significant impact on estimates of the incidence of ductal patency and the risk of endocarditis