bifoliate aortic valve, but this is nonspecific If a murmur is present, it is often pan- or midsystolic and of low intensity, indicating the nonrestrictive nature of the ventricular septal defect Measurements of the blood pressure in all four limbs reveal a gradient between the upper and lower limbs irrespective of the method used to measure it, although Doppler appears preferable.37 It should be remembered that differences in pressure of up to 20 mm Hg may be revealed by Doppler interrogation in the normal neonate, presumably owing to the isthmal narrowing that is normal at this stage.38 It is sometimes necessary to measure blood pressures serially if the diagnosis remains unclear Paradoxically, the diagnosis of coarctation can be made more difficult by the administration of prostaglandin Although greatly improving the physical condition, this maneuver leads to significant diminution of the pressure difference between the arms and legs, making the clinical diagnostic process less clear In this situation, there may be appreciable delay in femoral pulses compared with the radial pulses, which is known as as brachiofemoral delay The combination of weak or absent femoral pulses together with a gradient in pressure between the limbs is virtually pathognomonic of aortic coarctation Older Children and Adults It is not uncommon for patients with coarctation to go beyond infancy without detection, either because initially the coarctation was not severe enough to become critical following closure of the arterial duct or because of a significant early collateral circulation The diagnosis usually follows a routine medical examination, where systemic hypertension is found, the murmur is discovered, or femoral pulses are found to be weak The difference in pressure between the upper and lower limbs is frequently greater than 20 mm Hg Headaches, nosebleeds, cold feet, or calf pain on exercise are often experienced.39 Rarely, patients present with end-stage systemic hypertensive disease, such as subarachnoid hemorrhage or hypertensive retinopathy Detection during investigations for coronary arterial disease later in life has been reported With respect to interrupted aortic arch, there are currently over 40 reported cases of interrupted aortic arch presenting in adults.40 Presentation is predominantly due to hypertension and rarely due to congestive heart failure These patients invariably have large, well-developed collateral systems with a closed ductus Interestingly, type A, representing almost 80%, is far more common than type B interruption in this population.41 Physical Findings The physical findings in older patients usually rest on the appreciation of diminished or delayed femoral pulses compared with the pulse in either arm More reliable is measurement of the blood pressures in all limbs.42 Indirect signs of left ventricular hypertrophy, such as a displaced apical beat and heave, are often found on palpation of the precordium On auscultation, the first and second heart sounds are usually normal but may be accompanied by an apical fourth heart sound if the left ventricle is becoming noncompliant The murmur of coarctation is best heard in the left infraclavicular fossa and radiates to the back over the left scapula It is continuous, peaks late in systole, and continues into early diastole, corresponding with the diastolic tail seen on Doppler echocardiography Additional continuous murmurs may be generated by larger collateral arteries, which can restore an adequate flow of blood to the lower body, resulting in palpable femoral pulses, albeit usually reduced and delayed If surgery is considered, this feature will be crucial, as it determines whether or not partial cardiopulmonary bypass is required to maintain adequate perfusion of the lower body and spinal cord while the coarcted segment is excluded with clamps for the repair A unique corkscrew appearance of the retinal arteries has been described on funduscopic exam that differs from the usual hypertensive change.43 Investigations Chest Radiography In infants, cardiomegaly and increased pulmonary vascular markings can be seen on the radiograph In older children with coarctation of the aorta, the heart size is often normal, but if cardiomegaly is present, it is usually caused by left ventricular enlargement secondary to hypertension The two characteristic signs of coarctation in older children are the “figure 3” sign, which appears on the left border of the mediastinum and is caused by prestenotic and poststenotic dilation of the aorta (Fig 45.13), and rib notching, which is usually not seen until 4 to 5 years of age, although its appearance in the first year has been described.44 FIG 45.13 Chest radiographs showing evidence of coarctation, with (A) rib notching (arrows) and (B) the “figure 3” sign By adulthood, around 75% of untreated patients have rib notching It is best seen posteriorly in the medial third of the lower borders of the fourth to eighth ribs (see Fig 45.13) The notching in coarctation is secondary to dilation of the collateralized intercostal arteries branching from the internal mammary Rib notching is classically bilateral, to be differentiated from the unilateral notching seen after a classical Blalock-Taussig shunt, although unilateral notching can also occur with coarctation when a subclavian artery arises aberrantly distal to the site of obstruction In patients with interruption, the heart is usually left-sided with a normal abdominal and bronchial arrangement Cardiomegaly, particularly enlargement of the left atrium, is present in 90% of neonates.45 Increased pulmonary vascular markings with pulmonary edema are also the norm In the rare patients who survive infancy untreated, more specific signs can be seen,46 including absence of the aortic knob, a midline trachea, absence of an aortic impression on the barium swallow, and termination of the proximal descending aorta at the level of the pulmonary trunk Rib notching can also be seen on the side of the subclavian arteries arising from the ascending aorta in the presence of a restrictive or closed arterial duct A narrow mediastinum may suggest absence of the thymus gland, a feature of DiGeorge syndrome Electrocardiography