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].