Andersons pediatric cardiology 1062

in the heart shown at left, whereas the heart at right shows a mouse with pulmonary dominance and interruption of the aortic arch Diagnostic Features Antenatal Diagnosis It might be expected that common arterial trunk would be detected during the mid-trimester scan for fetal anomalies, which is routine in many countries In practice, population-based studies demonstrate that the diagnosis may often be missed,19,20 presumably because the four-chamber view of the heart may appear to be normal on superficial examination Nonetheless, more detailed examination of the fetal heart should reveal a ventricular septal defect An arterial trunk that overrides the defect is the only outlet that arises from the ventricular mass.21 It should be possible to document the degree of regurgitation or stenosis of the truncal valve, and the course and integrity of the aortic arch (Table 40.1).22 One particular challenge in the antenatal examination of fetuses in whom only a single arterial trunk arises from the heart has been in distinguishing those with common arterial trunk from those with tetralogy of Fallot with pulmonary atresia, although using current technologies, including four-dimensional spatiotemporal image correlation echocardiography, this distinction can be achieved in most cases.23 Table 40.1 Key Diagnostic Features in Common Arterial Trunk Diagnostic Method Fetal echocardiogram Four-chamber view Great vessels Aortic arch Clinical examination Inspection Palpation Auscultation Electrocardiogram Features Ventricular septal defect with truncal override (may appear normal) Single arterial trunk Truncal regurgitation Interruption (?) Mild cyanosis Failure to thrive Tachypnea Bounding pulses Liver enlargement Normal first heart sound May have a single second sound (although not always) Ejection click Ejection systolic murmur (?) Diastolic murmur of truncal regurgitation Nonspecific usually combined ventricular hypertrophy Chest radiograph Echocardiogram Parasternal long axis Parasternal short axis Apical four chamber High parasternal Cardiac catheterization Hemodynamics Oximetry Pulmonary vasodilator Angiocardiography Cardiomegaly Increased pulmonary vascular markings Narrow arterial pedicle Truncal origin Ventricular size and mural thickness Ventricular septal defect Velocity of interventricular shunting Truncal regurgitation Morphology of truncal valve Mechanism of truncal regurgitation Origin of pulmonary arteries Stenosis of pulmonary arteries Origin of coronary arteries Ventricular origin of trunk Truncal regurgitation Truncal stenosis Function of atrioventricular valves Aortic arch Arterial duct Interruption of aortic arch Pressure measurement in right and left pulmonary arteries Pressure drop across truncal valve Pulmonary-to-systemic blood flow ratio To assess pulmonary vascular responsiveness Truncal injection to examine the degree of regurgitation Selective pulmonary angiogram Left ventriculogram to evaluate the size and location of septal defects A significant proportion of fetuses will have associated noncardiac anomalies,24 with or without a deletion in chromosome 22.25 Neonatal Presentation The typical patient will present during the neonatal period, or in early infancy, with mild central cyanosis, a hyperactive precordium, and signs of increasing congestive cardiac failure There will be difficulties in feeding, failure to thrive, tachypnea, and hepatic enlargement Although a minor degree of hypoxemia is common, obvious cyanosis is a feature of either raised pulmonary vascular resistance or pulmonary stenosis Once cardiac failure is established, the chest may bulge in consequence of the cardiomegaly At auscultation, the first heart sound is usually normal, whereas the second sound is accentuated Although it might be anticipated that the second sound would always be single in the presence of a common arterial valve, there is splitting of the second sound in approximately one-half of infants, documented by phonocardiography and by auscultation.26 Possible explanations for this are