Persistent left superior vena cava

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Definition

Persistent left superior vena cava (LSVC) results from failure of obliteration of the left common cardinal vein, and it typically drains the left jugular and subclavian veins into the right atrium via the coronary sinus.[1] It is the most common variant of thoracic venous drainage, and it is present in 0.5% of the general population. Its incidence increases to 3-10% in patients with congenital heart disease.[2]

In 80-90% of the cases a co-existent right superior vena cava is also present, although it can be smaller than usual.[1]

Besides coronary sinus, other drainage sites are also possible. In less than 10 percent the persistent LSVC drains directly into the left atrium or in a pulmonary vein. This type of drainage is almost always associated with other congenital anomalities. It results in right to left shunt and has been associated with cyanosis, paradoxical embolism or brain abscess.[3]

Echocardiographic diagnosis

LSVC is often an incidental finding during transthoracic echocardiography. It is diagnosed indirectly through recognition of a dilated coronary sinus in parasternal long axis view.

Coronary sinus is a circular structure in the atrioventricular groove, located anterior to the pericardium. A dilated coronary sinus must be differentiated from descending aorta, pericardial effusion or pulmonary vein.[4]From four-chamber view with posterior angulation coronary sinus can be viewed in the long axis passing behind the left atrium towards the right one.

Differential diagnosis of coronary sinus dilatation[5] include:

  • Persistence of left superior vena cava
  • Any cause of elevated right atrial pressure
  • Partial anomalous pulmonary venous drainage
  • Coronary arterio-venous fistula
  • Unroofed coronary sinus with shunt flow between left atrium and coronary sinus

In case of a dilated coronary sinus contrast injection in the antecubital veins can help establish the diagnosis of a persistent LSVC. Contrast echocardiography from the left antecubital vein will classically show early coronary sinus opacification, before the right atrium and right ventricle. Imaging is usually done from the parasternal long axis view. In the rare cases of left atrial drainage contrast injection in the left arm will determine opacification of the left atrium.[4]Right antecubital vein contrast injection is followed by a normal sequence of opacification starting from the right atrium and followed by the right ventricle, with no contrast in the coronary sinus.

Therefore, echocardiographic criteria for LSVC diagnosis[5] are:

  • Dilated coronary sinus in the absence of elevated right side filling pressure
  • Coronary sinus opacification before the right atrium when contrast (“bubble study”) is injected in the left antecubital vein
  • Normal sequence of opacification after right arm antecubital vein injection.

Figure 1. Transthoracic echocardiography, parasternal long axis view. A dilated coronary sinus is noticed (asterix). Descending thoracic aorta can also be seen (arrow).

Figure 2. Contrast injection in the left antecubital vein is followed by opacification of the coronary sinus.

Figure 3. At a later moment, after coronary sinus opacification, the contrast also appears in the right ventricle.

Figure 4. Parasternal long axis, M-mode showing initial opacification of the coronary sinus (arrow) followed after approximately three cardiac cycles by contrast appearance in the right ventricle. From Popescu BA, et al. Rev Rom Cardiol. 2010;25:31-32, with permission.

While most often the study is performed during transthoracic echocardiography, it can also be done during transesophageal echocardiography.

It has been suggested that coronary sinus shape in parasternal long axis view might help differentiate between the two most frequent causes of coronary sinus dilatation: elevated right heart pressure and LSVC. While in the first situation there is a symmetric distention of the vessel, in LSVC persistence the dilated coronary sinus maintains its oval shape, with an eccentricity index <0.8.[6]

Clinical relevance

Isolated persistence of left superior vena cava with drainage to the coronary sinus has no hemodynamic significance as venous return is essentially normal. However, it may pose challenges during invasive procedures which require upper limb venous access like transvenous pacing or during cardiopulmonary bypass with retrograde cardioplegia. Its diagnosis should however prompt further search for associated anomalies like aortic coarctation, atrial and ventricular septal defect, cor triatriatum, etc.[1]

Other imaging modalities for persistent LSVC are cardiovascular magnetic resonance, contrast-enhanced computed tomography or conventional contrast venography.[7]

Other aspects

Persistence of left superior vena cava can be diagnosed during fetal echography by coronary sinus enlargement or abnormal three-vessel view. As LSVC persistence detected in the prenatal period is associated with an increased risk of congenital heart disease, its incidental finding should prompt referral for detailed fetal echocardiographic examination.[8]

References

  1. 1.0 1.1 1.2 Irwin RB, Greaves M, Schmitt M. Left superior vena cava: revisited. Eur Heart J Cardiovasc Imaging. 2012;13:284-291.
  2. Zeller TM, Hagler DJ, Julsrud PR. Accuracy of two-dimensional echocardiography in diagnosing left superior vena cava. J Am Soc Echocardiogr. 1989;2:132-138.
  3. 3. Butera G, Salvia J, Carminati M. When side matters: contrast echocardiography with injection from the left antecubital vein to detect a persistent left superior vena cava draining to the left atrium in a patient with cerebral stroke. Circulation. 2012;125:e1.
  4. 4.0 4.1 Feigenbaun H, Armstrong WF, Ryan T. Abnormal systemic venous connections. In: Feigenbaun H, Armstrong WF, Ryan T. Feigenbaum’s Echocardiography. 6th ed. Lippincott Williams&Wilkins. 2005;608-610.
  5. 5.0 5.1 Goyal SK, Punnam SR, Verma G, Ruberg FL. Persistent left superior vena cava: a case report and review of the literature. Cardiovascular Ultrasound. 2008;6:50.
  6. Kolski BC, Khadivi B, Anawati M, et al. The dilated coronary sinus: utility of coronary sinus cross-sectional area and eccentricity index in differentiating right atrial pressure overload from persistent left superior vena cava. Echocardiography. 2011;28:829-832.
  7. Povoski SP, Khabiri H. Persistent left superior vena cava: review of the literature, clinical implicantions, and relevance of alterations in thoracic central venous anatomy as pertaining to the general principles of central venous access device placement and venography in cancer patients. World Journal of Surgical Oncology. 2011;9:173.
  8. Pasquini L, Fichera A, Tan T, et al. Left superior caval vein: a powerful indicator of fetal coarctation. Heart. 2005;91:539-540.
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