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Posts Tagged ‘SINUS VENOSUS ASD’

Embryology

Sinus venosus ASD (also referred to as SVC ASD)  is a defect in the failure of the sinoatrial orifice to lateralize completely to the right side during atrial septation.Left venous valve, as well as the septum secundum, fails to fuse with the roof of the atria creating interatrial communication. During this process, the developing pulmonary vein overshoot to the right side making PAPVD a mandatory add-on defect. (Harley ,Thorax 1958 ) It can be referred to as embryonal venous migration defect at the level of RA. In the same sense, it is not a true defect in IAS but a defect in septation between SVC/PV. It may also be referred to as unroofing of RUPV. The so-called Inter atrial communication actually is the confluence point of RUPV/SVC/RA.(See TEE images below) 

We know, in SVC ASD-commonest associated anomaly is PAPVC . It is not an ideal term to use though, instead, it is encouraged to use the term PAPVD (drainage) . Technically true PAPVC can not be connected to RA cavity as PV can connect either to cardinal or vitelline vein only. This distinction is helpful when we search for additional PAPVCs cranial to SVC. Sometimes we might recognize this error only after closure of SVC ASD. 

Should we close SVC ASD ? How do we close?

Age, natural history, symptoms, the quantum of shunt will answer an occasional troubling query , “should we close it at all? Surgery is the standard approach till now. What makes device closure popular? Two reasons 1.Patient /or parent’s fear of surgery  2.Cardiologist’s urge for innovative Interventional procedures. (The fact that a simple covered stent will do the job is too tempting to make an attempt) However,please note, the procedure is not at all simple as one would Imagine.

Anatomical prerequisite for device closure 

The defect must fulfill some critical anatomical essentials.  

  • It should be an isolated defect.
  • RA should not be grossly enlarged
  • Re-routing of RUPV to LA should be possible 
  • A significant circumference of RUPV should be committed to LA.
  • There should not be downward extension involving septum secundum making it an SVC + OS ASD 

Technical issues

  • Self-expanding vs balloon expanding stent (Anyone may be chosen)
  • Stent flare-up SVC RA junction crucial
  • Must ensure  RUPV doesn’t get compressed with device.

  • Forces that hold the SVC end of the stent is very important. Sometimes It may require a second proximal stent just to prevent migration of the first stent.
  • Live LA pressure and RUPV monitoring may be critical to recognize PV ostial compromise. For this, a transeptal puncture may be required (Ironically creating another mini ASD !)

 

Finally, and most importantly follow-up is mandatory with device closure since the stent is on the venous circuit as RA, SVC thrombosis expected. (Anticoagulation protocol not clearly  defined as of now )

Final message 

Device closure for SVC ASD is a good Innovation. A perfectly delivered covered stent at the RA/SVC junction will do the trick. However, In my  opinion, surgeons do a neat(More complete)  job It is time-tested. Single or double patch or warden procedure may be done.(Ref 2)

Reference 

1.Hinnerk Hansen, Phuoc Duong, Salim .M. Jivanji, A. Qureshi, Eric Rosenthal Transcatheter Correction of Superior Sinus Venosus Atrial Septal Defects as an Alternative to Surgical Treatment J Am Coll Cardiol. 2020 Mar, 75 (11) 1266-1278.

2.Warden HE, Gustafson RA, Tarnay TJ, Neal WA. An alternative method for repair of partial anomalous pulmonary venous connection to the superior vena cava. Ann Thorac Surg 1984;38:601-5. 

 

https://doi.org/10.1016/j.pedneo.2019.06.013

 

https://doi.org/10.1016/j.athoracsur.2020.03.113

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Atrial  septal defects  are one of the commonest forms of congenital heart disease.

  • The commonest being the ositum secundum ASD     ( Which is in fact is a defect in the development of septum primum)
  • The next common is ostium primum defect which is a part of AV canal or atrio ventricular septal defect.

Other forms of ASD include

  • SVC type /Also  called sinus venosus type of ASD .
  • IVC type
  • Coronary sinus defect -Also called partial or complete forms of unroofed coronary sinus

asd svc asd sinus venosus

SVC type ASDs

They are in the strict sense can not be called as ASD. This is because there is no defect in  any of the  embryological  inter atrial septal component.

There is no direct communication between RA and LA, instead   a window  or passage of communication   between pulmonary vein and SVC. Right upper lobe pulmonary vein  is usually the culprit .Some times more than one PV  communicates with SVC.

The exact area of this PV-SVC window occur between anterior surface of right upper lobe PV with postero lateral surface of SVC.

PAPVC partial anomalous pulmonary venous drainage can be considered an integral part of this defect as RUPV is linked with SVC.

Can we have a combination of SVC ASD and OS ASD ?

This is possible .But two embryological errors need to occur. This is often seen as a large OS ASD with deficient or absent superior rim. So whenever superior rim of IAS is deficient a PAPVC and a SVC ASD should be looked for.

Clinical features

  • SVC type ASDs  generally shunt lesser blood than OS ASDs. (Often<2:1) .This is because it is not the LA that is communicating with RA instead only a
  • It is usually a single PV (some times 2) that shunts from left to right.

There is a distinct possibility of missing this lesion in routine echo.Minimal RA,RV enlargement may give us a clue.The classical subcostal or  4 chamber  view in echocardiography may not visualise  these defects.

So, whenever one encounters mild dilatation  of RA and RV and the IAS appears  intact, a meticulous search and a focused echo in the superior aspect of IAS is warranted. Angled  superior views may pick up this defect.A transesophageal echocardiogram (TEE) is often required to  confirm it.

Therapeutic issues

  • Device closure is not possible
  • Surgery involves little more technicality than ASD OS.
  • Small defects can be patch closed.
  • Some times the SVC has to be disconnected from the PV and anastamosed separately on right atrial appendage. SVC resection  will  aid the surgeon in proper patch closure.
  • Post operative follow up is necessary as SVC obstruction or PV obstruction may be a delayed consequence

References

svc asd sinus venosus

http://ats.ctsnetjournals.org/cgi/content/full/59/6/1588?ijkey=4f42649bc5805f3cf7d60f5728ec7f871356277b

http://asianannals.ctsnetjournals.org/cgi/content/full/10/3/231

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