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examples of ductal aneurysms, especially those occurring postoperatively In the case of the clinically silent and nonhypertensive duct, little evidence exists that its presence is an endarteritis risk, relative to its anticipated high incidence (0.5% to 1%),46,70,86 despite several case reports documenting its occurrence.87–91 Pulmonary Hypertension and the Persistent Duct Although the pulmonary arterial pressure is usually normal or only slightly elevated in patients with persistently patent ducts, occasionally it is raised sufficiently to modify the physical findings The implications of pulmonary hypertension secondary to an increased flow, as opposed to that caused by increased resistance, are markedly different, and the two situations should be clearly differentiated When the duct is widely patent and pulmonary vascular resistance is low, systolic pulmonary arterial pressure equals systemic systolic pressure and blood flow to the lungs is several times greater than that in the systemic circuit The pulmonary arterial diastolic pressure may equal or be slightly lower than that in the aorta These patients usually experience severe congestive heart failure, with failure to thrive and recurrent respiratory infections Their electrocardiogram shows combined ventricular hypertrophy, and the chest radiograph reveals cardiomegaly with marked pulmonary plethora The echocardiogram will reveal enlargement of the left heart chambers Such patients respond poorly to medical therapy, and the correct management is to eliminate the shunt Successful ligation or catheter occlusion usually restores pulmonary arterial pressure to normal There appears to be little risk of subsequent pulmonary vascular changes in this group of patients Some individuals respond to pulmonary venous distension, and to the left atrial enlargement secondary to high pulmonary blood flow because of reflex pulmonary vasoconstriction partially protecting themselves against the full effects of unrestricted ductal flow If studied hemodynamically, these patients will be found to have a moderate left-to-right shunt, with pressure in the pulmonary circulation at systemic levels, with or without a high pulmonary capillary wedge pressure Pulmonary arterial pressure usually falls with administration of oxygen or in response to pulmonary vasodilators Successful elimination of the shunt usually restores pulmonary arterial pressure to normal Fixed and high pulmonary vascular resistance may result from progressive structural changes in patients who originally have large left-to-right shunts and normal pulmonary vessels Alternatively, it may exist from birth.92,93 Civen and Edwards94 suggested that patients in this category represent a form of persistence of the fetal pulmonary circulation As yet, there is poor understanding of the factors, which initiate and maintain the progressive pulmonary vascular damage It is instructive to follow the clinical changes that accompany the rise in pulmonary vascular resistance Initially, the pulmonary diastolic pressure approaches systemic levels, decreasing diastolic flow across the duct As flow diminishes, the diastolic component of the continuous murmur becomes attenuated and eventually disappears At this stage the patient has a pansystolic murmur With a further increase in resistance, systolic pressures begin to equalize, systolic flow diminishes, the systolic murmur shortens, and eventually it also disappears Concurrent with these changes, the second sound becomes closely split or even single and there is accentuation of the pulmonary component The clinical findings become those of severe pulmonary hypertension, with marked right ventricular hypertrophy and a loud, often palpable second pulmonary sound; a pulmonary ejection click is almost always audible The second sound is loud and difficult to split A high-pitched early diastolic murmur, the Graham Steel murmur of pulmonary regurgitation, may be added to these sounds, as may a pansystolic murmur of tricuspid regurgitation when right heart failure supervenes Equalization of pressures with balanced resistances also brings reversal of the direction of flow through the duct; the magnitude of the flow increases concomitant with the rise in pulmonary vascular resistance In some patients, it is possible to recognize differential cyanosis, the blue discoloration being confined to the lower body, and with clubbing of the toes but not the fingers Unless there is differential cyanosis, it is not possible to recognize a duct clinically in patients with severe pulmonary hypertension and high pulmonary vascular resistance The diagnosis will depend on cardiac catheterization and angiography, or cross-sectional echocardiography and color flow Doppler studies Until heart failure develops, the chest radiograph shows, at most, mild cardiomegaly, with marked prominence of the pulmonary arterial segment (see Fig 41.11, left) Right axis deviation, right atrial hypertrophy, and right ventricular enlargement are usually evident in the electrocardiogram However, in some cases a picture of combined, or even left, ventricular hypertrophy may still be seen It is impossible to calculate accurately the risk of progressive pulmonary vascular disease in patients with a large persistent duct Surgical treatment has been available almost as long as clinical recognition The information in terms of natural history necessary to answer the question is not available, nor would such a study now be feasible Campbell75 did not address this problem in his calculations, although there are several reports in the literature concerning this complication.95–97 However, these are based on selected groups of patients and overemphasize the frequency of the problem Nor do they all distinguish adequately between pulmonary hypertension with high flow and true pulmonary vascular disease The presence of pulmonary hypertension secondary to structural changes within the pulmonary vasculature increases the risk of closure, especially once there is right-to-left shunting, with a reported mortality in more than half of a small group of such patients.95 The complication should be largely avoided by early recognition and treatment of the hypertensive duct In patients with pulmonary vascular resistance greater than 8 Woods units per meter square, lung biopsy has been recommended to determine candidacy for closure, but unfortunately it may not be fully predictive of outcome.98 Such patients may be hemodynamically worse after closure, with the development of suprasystemic pulmonary arterial pressure, low cardiac output, and right ventricular failure.99,100 Patients have been described with severe histologic changes consistent with irreversible pulmonary vascular disease, which resolves completely after closure of the duct.101 In the occasional patient who escapes early detection, cardiac catheterization with a vasodilator challenge or temporary balloon occlusion of the duct100,102 may be useful in determining the extent of pulmonary vascular changes and their potential for reversal Aneurysm of the Duct True aneurysm of the duct is rare It manifests in two distinct forms, the first presents at or shortly after birth,103,104 the so-called spontaneous aneurysm of infancy (Fig 41.15).105 The second form presents in childhood or later life.106,107 Recent studies suggest that the incidence may be as high as 8%.108 The true incidence remains unknown because the definition is not precise and many aneurysms detected by fetal or neonatal echocardiography resolve spontaneously, without clinically apparent sequels.109 Approximately 25% of patients will have an underlying disorder, such as trisomy 21 or 13, SmithLemli-Opitz syndrome, type IV Ehlers-Danlos syndrome, or Marfan