Chapter 14: Aneurysm of Ductus Arteriosus, Cardiomyopathies, and Aortopulmonary Collaterals^*

SECTION 1: ANEURYSM OF DUCTUS ARTERIOSUS

Introduction

Current echocardiographic imaging demonstrates aneurysmal dilation of the ductus arteriosus in more than 8% of full-term newborns.^1,2 An aneurysm of the ductus arteriosus (ADA) manifests as a saccular dilation originating from the ductus arteriosus's descending aortic origin. An ADA may occur from an in utero process, result from a postnatal complication after a surgical or transcatheter closure of a patent ductus arteriosus, or occur secondarily from ductal endarteritis.^3,4 Proposed in utero mechanisms for an ADA include narrowing or tortuosity of the fetal ductus arteriosus with poststenotic dilatation,⁵ increased fetal ductal flow, or abnormal intimal cushion formation secondary to abnormal elastin expression.⁶

Echocardiography

Either a prenatal or postnatal echocardiogram can demonstrate an ADA. In our experience, a prenatal echocardiogram more often proves a fetal ADA in the mid to late 3rd trimester rather than earlier in gestation. A fetal ADA is usually associated with increased ductal tortuosity, ductal narrowing (Figure 14-1), a variable degree of ventricular asymmetry with right ventricular dominance, and an increased ductal flow velocity. In most cases, the neonatal ADA is an incidental finding noted during an echocardiogram performed for unrelated reasons. In some cases, a neonatal ADA is suspected because a chest radiograph demonstrates a left upper mediastinal mass. On rare occasion an ADA is discovered during evaluations for perinatal distress, pulmonary hypertension, dyspnea, stridor, hoarseness, severe perinatal hypoxia, or neonatal thromboembolic events.

In the neonate, the high-parasternal short-axis echocardiographic view visualizes the ADA just to the left of the main and left pulmonary arteries (Figure and Video 14-2). The ADA may be patent in the early neonatal evaluations with a narrowed pulmonary artery end and a wide-open aortic end. If the ductus is patent, color Doppler usually demonstrates a characteristic horizontal jet, as opposed to the almost vertical jet in the usual patent ductus arteriosus (Figure and Video 14-2). The horizontal ductal jet prevents accurate flow velocity measurement that is needed for estimating the pressure gradient between the aorta and the pulmonary artery.⁵ With color Doppler, a low Nyquist frequency allows visualization of the low blood-flow velocities inside the ADA. Echocardiographic imaging may demonstrate thrombus formation inside the ADA (Figure and Video 14-3). Echocardiography can also rule out potential thrombus migration that can propagate into the descending aorta or the pulmonary arteries.