Trial Short Case 3 April 2021Answers

Question 1

What are the indications for surgery in this patient?

Answer

The indications for Coronary Artery Bypass Grafting (CABG) are based on 1) improving survival and 2) relieving symptoms.  This patient has presented with unstable angina despite guideline-directed medical therapy in the setting of severe proximal Left Anterior Descending (LAD) stenosis that is not amenable to Percutaneous Coronary Intervention (PCI). Based on the 2011 ACCF/ACA CABG Guidelines this patient has a Class Iia indication for CABG (with a Left Internal Mammary Artery (LIMA) graft)) to improve survival compared to medical therapy and a Class I indication to improve symptoms.  Calculation of a EUROII Score would assist in determining the mortality of CABG and assist decision making.

Question 2

What are the key issues in performing coronary artery bypass grafting on this patient?

Answer

The key issues are surgical access given the position of the heart posteriorly in the left hemithorax, choice of conduit and a background history of malignancy.

This issues with access include:

·        Access to the Aorta and Right Atrium for cardiopulmonary bypass(CPB). This issue could be overcome by cannulating the femoral vessels for CPB or by performing an off-pump CABG.

·        Access to the LAD for grafting.  Access could be achieved by performing a left posterolateral thoracotomy.  Adhesions would be expected in the post-pneumonectomy space but the pericardial space should be free of adhesions.

·        Access to the Aorta for X-clamp and potential top end anastamosis.  The Ascending aorta could be accessed by a second anterior thoracotomy; however, it would be difficult to place a clamp and/or a cardioplegia cannula given the depth of the aorta in the chest.  Possible solutions include performing off pump CABG, beating heart on-pump CABG (via femoral cannulation) and finding an alternative proximal anastamosis site.

The issues with conduit choice include:

·        The LIMA would be the ideal conduit, however would not reach the LAD as an in-situ graft.  As a free graft, the location for a proximal anastamosis is limited. The descending aorta can’t be accessed due to its posterior position behind the heart and length issues would persist in reaching the ascending aorta.

·        The LRA is compromised by the same length issues.

·        The SVG is not limited by length and options for proximal anastamosis include the ascending aorta, if  a side-bitting clamp was able to be applied via an anterior thoracotomy or the LIMA, accessed and mobilised by an anterior thoracotomy.

Past History of Malignancy:

·        This patient had a pneumonectomy for a typical carcinoid tumour which has a good prognosis post resection.  The CT Chest performed is a good screening for recurrence.

Question 3

You decide to offer the patient CABG. What is your operative strategy?

Answer

Operation: Off-pump Coronary Artery Bypass Grafting via combined left posterolateral thoracotomy and anterior thoracotomy with LIMA-SVG-LAD graft.

Informed consent – discuss benefits and risks of surgery with patient as well as surgical plan.

GA with single lumen tube.  Epidural local anaesthesia catheter.

Positioning of patient in a modified right lateral decubitus position with the shoulders at 60 degrees from the horizontal and the hips at 30 degrees from the horizontal to allow access to the left formal artery and vein and to the saphenous vein for harvest. 

Cardiopulmonary bypass machine prepped and in the room.

Expose femoral vessels in preparation for possible cardiopulmonary bypass

Access via left posterolateral thoracotomy and dissection to and identification of the LAD is performed.

Anterior thoracotomy with dissection and mobilisation of portion of LIMA for proximal anastamosis.

Dissection of path for graft from LIMA, through pericardium to LAD.

Harvest of saphenous vein graft and marking to ensure graft doesn’t twist during course.

Administer half dose of heparin.

Perform proximal anastamosis of SVG to LIMA using bulldogs to occlude blood flow through LIMA.  Pass SVG through pericardium to LAD ensuring no twisting or kinking of graft. De-air graft.

Perform SVG-LAD anastamosis using coronary shunt and CO2 blower.

Give protamine

Close pericardium

Drains in pericardial and pleural space and close thoracotomy

Close groin incision.