How to diagnose persistent left SVC and Practical Implications
In patients with dilated coronary sinus, we must exclude persistent left
SVC especially in absence of right sided pressure or volume overload. To
confirm the presence of persistent left SVC, we can use contrast
echocardiography or computed tomography (CT) of the chest.
In patients with persistent left SVC, left arm injection of agitated
saline in echocardiography leads to coronary sinus opacification first
followed by opacification of the right atrium.
It also important to do right arm injection because if it showed right
atrial opacification, this confirms the presence of persistent right SVC
as well.
Superior vena cava abnormalities are frequently discovered as incidental
findings on cardiac imaging such as cardiac CT and echocardiography and
are occasionally associated with important clinical sequalae. When
cardiac imaging is performed, radiologist and imaging specialists should
pay attention to check their imaging features and associations , and
should not miss to differentiate the persistent left-sided SVC from
partial anomalous pulmonary venous drainage of the left upper lobe
[7]. On cross-sectional imaging with computed tomography (CT) or
magnetic resonance imaging (MRI), it may be apparently noted as a vessel
coursing vertically in the mediastinum, lateral to the aortic arch
[7]. In the majority of individuals with this anomaly, a right
superior vena cava is present, although this may be smaller than usual,
and the left innominate vein is typically absent or small. Cardiac MRI
is also a very useful tool to depict anomalous venous anatomy [8].
The likelihood of congenital heart disease is seemed to be increased
unless there is right-sided superior vena cava or if the LSVC drains
into the left atrium (LA) [8]. LSVC has sometimes been associated
with an increased risk of arrhythmias, most commonly atrial fibrillation
as this structure contains the vein of Marshall, whose muscular sleeves
are anatomically extended into the coronary sinus (CS) [9].
Subaortic membrane remains an important differential diagnosis in
hypertrophic cardiomyopathy with LVOT obstruction and in cases of aortic
stenosis. Discrete subaortic stenosis caused by subaortic membrane is
often diagnosed by both transthoracic echocardiography (TTE) and
transesophageal echocardiography (TEE) with a strong association with
aortic valve incompetence [10].