Keywords
Neonatal shock; Aorta; Persistent fifth aortic arch; Ultrasound
Introduction
Neonatal
shock is a life-threatening condition. Timely diagnosis of the cause of
the shock and management of the hemodynamic disturbance can be
life-saving in the emergency department (ED)1,2.We
present a case of a 13-day-old neonate with shock who was diagnosed with
persistent fifth aortic arch (PFAA) type B with critical coarctation in
the ED by cardiac point-of-care ultrasound (POCUS).
Case presentation
A 13-day-old female neonate was referred to the ED with symptoms and
signs of shock, including drowsiness, tachypnea, and cold, wet, and
cyanotic extremities. Physical examination revealed a pulse rate of
161/min, respiratory rate of 51/min, and blood pressure of 82/47 mmHg.
The neonate had a history of assisted reproductive technology. POCUS was
performed immediately. Notably, generalized cardiac enlargement was
observed (Fig. 1A, videos 1 and 2), with a left ventricular ejection
fraction of 24.6% and a right ventricular fractional area change of
29.8%. Severe pulmonary hypertension was revealed, with significant
valve insufficiency. In addition, an atrial septal defect with
bidirectional shunting (Fig. 1B) and patent ductus arteriosus almost
closed were found (Fig. 1C). Furthermore, two aortic arches were
detected in the high-parasternal and suprasternal notch view: the upper
arch was interrupted distal to the origin of the subclavian artery,
while the lower arch was connected to the descending aorta with
coarctation (Fig. 2). The neonate was diagnosed with PFAA type B with
critical coarctation. Computed tomography angiography and
three-dimensional reconstruction confirmed the congenital abnormalities
of the aortic arch (Fig. 3) with the narrowest diameter of the fifth
aortic arch measuring 0.9 mm. After emergency surgical repairs, cardiac
POCUS showed normal aortic flow velocity (Fig. 4). The neonate was
discharged 24 days postoperatively with normal cardiac function.
Discussion
The symptoms and treatment of
neonatal shock vary significantly with the causes of the condition. The
most common etiological factors underlying neonatal shock include
hypovolemia, myocardial dysfunction, vasodilation, and acute mechanical
blockage of blood flow, such as aortic coarctation
(CoA).1,2 However, PFAA is a rare congenital great
artery variant that can cause neonatal shock. It is generated from
failed degeneration of embryonic fifth pharyngeal
arches3 and is frequently associated with CoA or IAA,
which could cause critical hemodynamic disorder 4-6.
Without prompt medical intervention, neonates are likely to succumb to
multiple organ failure and death7. Therefore, early
recognition and appropriate treatment are crucial1.
PFAA can be classified as type A, B, and C 4-6. The
severity of PFAA type B is dependent on the extent of CoA. Critical
coarctation in our case has not only decreased blood flow to the lower
extremities, but also increased the afterload of neonatal immature
myocardium and further led to biventricular dysfunction. However, there
are many other causes, such as various cardiomyopathies, incessant
arrhythmias, and viral myocarditis, that can result in poor myocardial
function and thus have been mistaken as the etiology of neonatal
shock.2,8 Therefore, PFAA with significant hemodynamic
disturbance needs to be identified early because its prognosis depends
heavily on the correct treatment before severe
outcome9.
Routine physical examinations are limited to seeking the causal factors
underlying neonatal shock while POCUS can be deemed as an
adjunct10. POCUS appears to play a more important role
among neonates and children, where other monitoring techniques may not
be available, but POCUS imaging can be technically easier by reducing
the need for radiation and monitoring progress repeatedly in a
cost-effective manner. In addition, neonates’ and children’s lower lung
volumes, fewer chronic diseases and thinner chest walls guarantee better
image quality for interpretation11. Furthermore, the
high-parasternal and suprasternal notch view can serve to rapidly
evaluate large vessel diseases that will cause hemodynamic instability,
such as PFAA, IAA and CoA12. Scanning from the two
views helped us demonstrate the spatial relationship between these two
almost parallel aortic arches, clarify the scheme of vascular branching
and identify the PFAA with CoA. Therefore, integrating the
high-parasternal and suprasternal notch view into routine cardiac POCUS
can significantly benefit vulnerable neonates and children.
Except for POCUS as a typical screening and monitoring tool, computed
tomography angiography and magnetic resonance angiography can be used to
confirm the abnormalities and assist with surgical planning, because
they ”lights up” blood vessels, and three-dimensional reconstruction can
directly display the branching patterns and entire course of the
aorta.13-15 Prompt causal treatment of the obstruction
could achieve good outcomes.
Conclusion
This case highlights the application of POCUS in the swift diagnosis of
congenital anomalies underlying neonatal shock for the first time and
emphasizes the role of the high-parasternal and suprasternal notch view.
Cardiac POCUS used in critical patients can lead to rapid and well-aimed
therapy. For the pediatric population, congenital anomalies are a
concern. When performing cardiac POCUS, great vessels should also be
evaluated in the high-parasternal and suprasternal notch view.
Fig.1 A: Apical 4-chamber view of the enlarged heart. B: Subcostal view
focused interatrial septum showing atrial septal defect, white arrow
indicted right-to-left shunt. C: Parasternal short-axis focus on
pulmonary artery showed patent ductus arteriosus nearly closed.
Fig. 2 A: Cardiac point-of-care ultrasound parasternal long-axis view of
aortic arch in suprasternal fossa depicting persistent fifth aortic arch
type B. The upper arch was the (fourth) aortic arch (white asterisks)
interrupted, the lower arch was persistent fifth aortic (yellow
asterisks) with critical coarctation at the origin of the ductus
arteriosus (white arrow). B: Continuous wave Doppler echocardiography
demonstrated that the peak flow velocity through the narrowest point of
the descending aorta was 3.1m/s and pressure was 37 mmHg.
Fig. 3 Computed tomography angiography and three-dimensional
reconstruction showing the upper (fourth) aortic arch (white asterisks)
interrupted and the lower persistent fifth aortic arch (yellow
asterisks) with critical coarctation at the origin of the ductus
arteriosus (white arrow).
Fig. 4 A: Postoperative cardiac point-of-care ultrasound showed that the
lower persistent fifth aortic arch was broadened, with the narrowest
measuring 6.5mm. Color Doppler echocardiography showed patent arterial
flow. B: Postoperative continuous wave Doppler echocardiography showed
normal descending aorta flow velocity.