Trial Short Case 3 April 2022

Answers

Question 1

Potential causes of pulmonary HTN include:

-Lung disease.

-This patient has only mod COPD given the PFT results.

-Heart failure.

-There is only mild LV dysfunction with mild MR, and physical exam does not reveal signs of gross fluid overload, so left ventricular failure and pulmonary congestion as a cause of pulmonary HTN in this patient is less likely.

-Intra-cardiac shunt.

-In this case, the disproportionate dilatation of the atrial chambers in the absence of mitral/tricuspid valve disease raises the suspicion of a volume-overload intracardiac shunt such as an ASD. This is supported by the fixed split second heart sound; a sign of delayed PV closure due to large flow across the PV

-The RV dilatation and dysfunction is again disproportional to the severity of the pulmonary HTN, further pointing to a volume-overloaded right heart with increased pulmonary blood flow as a cause.

This patient requires further structural and functional investigations.  A TOE can better assess the atrium and clearly delineate any inter-atrial communication. The location and size of the ASD can be identified and the flow can be assessed and quantified. Other pertinent anomalies such as pulmonary venous drainage, left sided SVC and mitral and tricuspid morphology can also be accurately assessed.

Cardiac CT can identify anatomic anomalies however this may only be necessary if TOE unable to identify ASD location and remaining cardiac morphology. Cardiac MRI can characterize both the cardiac anatomy and the shunt flows, again unnecessary if TOE accurate.

Right heart catheterization can accurately assess right heart pressures and pulmonary angiography can identify anomalous pulmonary venous drainage.

Pass: candidate identifies lung and cardiac disease as potential causes of pulmonary hypertension, and can recognize that the physical exam and echo findings do not represent a likely explanation for either of these. Further investigation is required.

  - Note: candidate may suggest TOE at time of operation as   investigation. This may be acceptable as long as

  i) Candidate has discussed with patient TOE as investigation   prior to surgical start and may alter surgical plan.

  ii) SVASD and anomalous PV drainage accurately identified and   rectified as part of operation.

Strong pass: candidate recognizes physical exam and echo findings may suggest intra-cardiac shunt and want to investigate accordingly. Identifies specific imaging modalities requested and why.

Question 2

Sinus venosus septal defect occurs due to failure of the development of the sinus venosus component of the inter atrial septum. This component of the interatrial septum arises from the right horn of the sinus venosus as it enlarges and becomes part of the right atrial wall. The right anterior cardinal vein becomes the SVC and right vitelline vein becomes terminal IVC. Both these drain into right horn of sinus venosus hence anatomic location of these defects.

SVASD commonly associated with anomalous pulmonary venous drainage. Most commonly, as in this case, RULPV drains to SVC. RMLPV can also drain to SVC.

An inferior SVASD may have anomalous drainage of the RLLPV to the IVC or RA. A single common drainage vein (“scimitar vein”) may drain the entire right lung to IVA/RA and may be associated right lung hypoplasia. Aortopulmonary collaterals are also common   

All ASDs are associated with increased incidence of persistent left SVC and this should be excluded prior to operation and/or operative strategies to deal with this should be considered prior to commencement of surgery.

Pass: Candidate can describe sinus venosus as part of RA wall (sinus venarum) and identifies superior and inferior types of SVASD.  Must identify anomalous PV’s as common lesion with SVASD.

Strong pass: Clearly describes caval and right atrial embryologic connection via right sinus horn and identifies superior and inferior SVASD with associated pulmonary venous anomalies. Considers left SVC either here or as part of operative approach

Question 3

•OT:

•Incision: sternotomy

•Cannulation: Bicaval-must ensure SVC cannula above the anomalous RULPV. In this case the RULPV drains close to SVC/RA junction so no additional cannulation strategy required.

•CABG x NO (CONDUITS – TARGETS).

•LIMA to LAD plus good quality venous conduit to remaining targets. The benefit of extra arterial conduits are likely to be minimal in this patient, particularly given small lateral wall target

•ASD

•Pericardial patch to close the ASD and baffle the anomalous RULPV to the LA.

•May mention Warden procedure if high RULPV insertion to SVC but not required in this case

•Any AF treatment?

•Given the long-standing nature of the AF and the large left atrium, this AF is likely to be permanent and any ablative surgery is unlikely to restore sinus rhythm. The left atrial appendage may be occluded/oversewn/clipped during the surgery.

Pass: ASD should be closed given RV size and dysfunction. Bicaval cannulation, appropriate targets for CABG and closure of ASD with baffle of RULPV into LA.

Strong pass: Mentions caval cannulation above anomalous RULPV and has considered left SVC. Caution taken with SA node during RA incision/exposure of ASD. Left atrial appendage occlusion may be questioned/considered.