Keywords
congenital heart disease - magnetic resonance imaging - pediatric - cardiovascular
surgery
Introduction
Left atrial isomerism is an uncommon condition associated with complex cardiovascular
abnormalities requiring surgical correction and results in significant morbidity and
mortality. Its combination with a compression of the azygos vein between aorta and
vertebral column is even rarer. Because of this, knowledge of this anomaly and its
anatomical variations play an essential role in cardiac surgery. Here, we present
a unique case of interrupted inferior vena cava (IVC) with azygos continuation as
a part of left atrial isomerism combined with posterior nutcracker phenomenon caused
by compression of the azygos vein diagnosed by noncontrast-enhanced cardiac magnetic
resonance imaging (MRI).
Case Description
A 24-year-old woman presented with a severe aortic regurgitation and moderate pulmonary
stenosis for possible aortic and pulmonary valve surgery. She is status post Ross-Konno
procedure for 14 years, performed to correct multilevel left ventricle outflow tract
obstruction (previously two subaortic resections performed 19 and 22 years earlier).
She has left atrial isomerism with infrahepatic interruption of the IVC with azygos
continuation, connecting to the right superior vena cava (SVC), left SVC continuation
to the coronary sinus, common atrium (surgical correction 24 years earlier), abdominal
situs inversus with malrotation and duodenal stenosis (surgical correction for 24
years).
She presented with NYHA (New York Heart Association) clinical stage II–III. Spiroergometry
demonstrated no obstructive or restrictive ventilation disturbances, no dys- or arrhythmias
or signs of myocardial ischemia were detected on further examinations. Cardiac exercise
capacity was moderately reduced due to limited patient compliance.
Echocardiography confirmed left ventricular (LV) dilatation, severe aortic insufficiency,
and moderate pulmonary stenosis with a pressure gradient of 45 mm Hg; LV ejection
fraction was 54%. Long-term electrocardiogram monitoring showed regular rhythm with
increasing rate of ventricular extrasystole, which had also been noticed by the patient.
Noncontrast-enhanced cardiac MRI revealed sufficient LV pump function with LV dilatation
and hypertrophy. Aortic valve (pulmonary autograft) demonstrated severe regurgitation,
and the pulmonary homograft showed moderate stenosis. The hepatic segment of the IVC
was absent, and hepatic veins drained directly into the right atrium. A large azygos
vein crossed the vertebral column from left to right posterior to the thoracic aorta,
where it is compressed between these two anatomical structures and then connects to
the right SVC ([Figs. 1] and [2]). No symptoms related to this nutcracker phenomenon were found in our patient.
Fig. 1 Magnetic resonance imaging of the azygos vein (white arrow) passing between the aorta
and spinal column and confluences with the right superior vena cava (coronal view).
Fig. 2 Magnetic resonance imaging of the azygos vein (white arrow) compressed between the
aorta and spinal column (horizontal view).
Discussion
Left atrial isomerism is a subset of heterotaxy syndrome due to the disorder of left-right
axis determination and may present with a variety of cardiac lesions and thoracoabdominal
organ abnormalities, which determines a high mortality of up to 75% before 5 years
of age.[1]
[2] Left atrial isomerism is often associated with persistent left SVC, interruption
of the hepatic part of the IVC with azygos/hemiazygos continuation, common atrium,
LV outflow tract obstruction, and gastrointestinal abnormalities,[2]
[3]
[4] which were also present in our patient. Interrupted IVC combined with azygos continuation
is a rare condition with an incidence of 0.6 to 2.0% in patients with congenital heart
disease and less than 0.3% among healthy population.[5] Abnormalities of the IVC have an asymptomatic course and are recognized incidentally
during surgical procedures, radiological investigation or postmortem.[6]
Nutcracker phenomenon refers primarily to compression of the left renal vein (LRV)
between aorta and superior mesenteric artery with impaired blood outflow to the IVC
also known as anterior nutcracker in contrast to posterior nutcracker which occurs
due to compression of the LRV between aorta and vertebral body.[7]
To the best of our knowledge, no case of posterior nutcracker phenomenon involving
azygos vein compression in the context of left atrial isomerism has been described
in the literature. Imaging of this condition on MRI presents a nonradiating diagnostic
option in patients.
Although in the present case no significant symptoms of the azygos vein compression
have been observed, this finding has a great clinical importance for planning cardiac
surgery in terms of the application of the extracorporeal circulation and particularly
adequate and safe venous drainage. Furthermore, symptoms may occur in the future,
and follow-up is necessary.
