Clinical summary

A female baby, one of twins, was born prematurely by spontaneous delivery at 33 weeks of gestation. The baby weighed 1.7 kilograms and required no resuscitation at birth. She had only mild tachypnoea with no cyanosis and no oxygen requirement. Her blood pressure was 83/52 mmHg with no difference between extremities, respiratory rate 50–60 per minute, and heart rate 145–170 beats per minute. A grade 2–3/6 systolic murmur heard over the upper left sternal border raised the suspicion of cardiac disease. Transthoracic echocardiography showed mild dilation of the left heart cavities with preserved systolic function, mild mitral insufficiency, a secundum atrial septal defect of 5 mm, and no ventricular septal defect. An aortopulmonary window forming a large aortic sac was seen from the high parasternal long-axis view. The aortic arch also appeared interrupted, with two vessels seen before the interruption. A large ductus of the size of the pulmonary artery with bidirectional flow connected the pulmonary artery to the distal aorta from which the left subclavian artery arose. Another vessel also arose from the distal aorta, but its course could not be delineated. She was commenced on diuretics and captopril, and feeds were fortified in an attempt to increase her weight, before reparative surgery. However, tachypnoea and poor weight gain persisted, and hence it was considered that early surgery could not be avoided.

Further delineation of the anatomy was considered necessary before surgical repair. Owing to the neonate's low weight, an attempt with a non-invasive examination, such as cardiac magnetic resonance imaging, was considered more appropriate before embarking on cardiac catheterisation. Our patient was intubated and prepared for magnetic resonance imaging in the neonatal unit and was transferred to the magnetic resonance imaging department for a targeted examination. In our institution, we use a 1 Tesla open-magnet magnetic resonance imaging system (Panorama, Philips, The Netherlands). The patient underwent first-pass three-dimensional magnetic resonance angiography, as well as imaging with T1-weighted black-blood sequences in order to delineate the vascular relationships to the trachea and the oesophagus. For the magnetic resonance imaging angiography, 0.4 ml of Omniscan was used and the sequence was planned with field of view (FOV) = 160 mm, repetition time (TR) = 3.8 ms, echo time (TE) = 1.5 ms, and slice thickness = 3.0/−0.5 mm. The black-blood sequence was planned with TR = 400 ms, TE = 40 ms, slice thickness = 2.5/−0.5 mm, and number of signal averages (NSA) = 4. An aortopulmonary window was clearly demonstrated both on the three-dimensional angiogram (Fig 1) and on the black-blood sequences of the total type.Reference Jacobs, Quintessenza, Gaynor, Burke and Mavroudis ¹ The right subclavian artery appeared to originate from a common vascular trunk arising from the posterior aspect of the ductal arch and travelling aberrantly to the right (Fig 2). Its course did not appear to cause any compression to the oesophagus or the trachea. The neonate was scheduled for surgery and was operated successfully 10 days after the magnetic resonance imaging examination. Cardiac catheterisation was not required before surgery.

Figure 1 Anterior view of the ascending aorta with the origin of the two carotids before the interruption and the aortopulmonary window connecting the main pulmonary artery with the ascending aorta. LCCA = left comman carotid artery; MPA = main pulmonary artery; RCCA = right common carotid artery.

Figure 2 Posterior view of the ductal arch and the common arterial trunk that gives rise to the left subclavian artery (LSCA) and the aberrant right subclavian artery (RSCA).