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Thursday, November 21, 2019

Minimally Invasive Coronary Artery Bypass Grafting

Minimally Invasive Coronary Artery Bypass Grafting
Minimally Invasive Cardiac Surgery Coronary Artery Bypass Grafting (MICS CABG)
1.     This technique enables revascularization with a similar configuration as that in a sternotomy technique, using left internal thoracic artery (LITA) harvesting and hand-sewn proximal and distal anastomoses under direct visualization.1,2 Complete revascularization is achieved in 95% of cases,1 allowing access to the anterior, lateral, and inferior walls of the heart, with or without the use of pump assistance.

 Step 1. Surgical Anatomy
s  Anatomic considerations are the same as those for a standard median sternotomy, except that the view is now from the apical position through a small left thoracotomy window.

Step 2. Preoperative Considerations
1. Indications
      These follow the current guidelines for coronary revascularization.
2.  Contraindications
·      Hemodynamic instability or acute ischemia
·      Chest wall deformities and significant pleural adhesions
·      Obesity
·      Intolerance to single-lung ventilation
·      Significant ascending aorta calcification, if aortic proximal anastomoses are planned
·  Poor status of the femoral vessels for peripheral cardiopulmonary bypass (CPB) cannulation, whether planned or not
·      Inadequate distal target size and quality. The right coronary artery and proximal posterior interventricular (PIV), posterolateral (PL), and proximal obtuse marginal (OM) targets are not easily accessible.

Step 3. Operative Technique
1.  Anesthesia
·     Paravertebral block is optional but may be preferred, especially for patients who are being planned for immediate extubation postoperatively.
·   Single-lung ventilation is instituted either through a double-lumen endotracheal tube or through a bronchial blocker.
·    Transesophageal echocardiography (TEE) may provide additional guidance if the patient develops instability. It can identify wall motion abnormalities and recovery. In the case of peripheral CPB cannulation, TEE must guide wire and cannula placement.
·  Ensure that the endotracheal tube is still in the correct position after repositioning the patient.

2. Positioning
   The patient is placed in a semi–right lateral decubitus position (Fig. 5.1). The right arm may be tucked at the patient’s side or extended to enable harvest of the right radial artery. The left arm is placed in a sling held above the patient’s head.
   The hips are placed in a nearly supine position to enable access to the groin in case of CPB, as well as to harvest the saphenous vein.
      External defibrillator pads are placed on the right anterior chest and the left back. Internal defibrillators will not fit through the small surgical access.
      The chest may be marked to identify the area of the LITA bed easily.
  Prepare the skin and place the sterile drapes in such a way that the sternum is easily accessible in case sternotomy conversion is needed.

Figure 5.1 (A) Patient positioning in MICS CABG. (B) Sterile draping in MICS CABG.

3. Incision
·      A 5-cm incision is made in the fifth intercostal space (ICS) at the left midclavicular line, usually located just below the nipple in this positioning.
·      The fascia and muscles are transected layer by layer. The left lung should begin deflating at this stage.
·     Palpation as to the location of the cardiac apex is done to check adequacy of the position. The apex should be around 2 cm caudal to the intercostal opening. This decision should be tailored based on the planned procedure; an incision that is placed too caudally will enable a relatively easy distal anastomosis, but will restrict access to the aorta for the proximal anastomoses and a more difficult mobilization of the proximal portion of the LITA. The ICS opening may be revised as needed.
·  A retractor is placed and is spread gently. The pericardial fat is removed and the pericardium is opened. If a multivessel bypass and an aortic anastomosis are planned, the pericardium is opened from the diaphragmatic surface to the pericardial reflection on the aorta. The distal targets are inspected as a last feasibility check when using the MICS CABG approach.
·    The LITA is harvested throughout its full length, from the bifurcation to the level of the subclavian vein. This is facilitated using ThoraTrak (Medtronic, Minneapolis) and Rultract (Rultract, Independence, OH) retractors (Fig. 5.2). Other necessary accessories are headlights, long fine instruments, and long cautery blades. The LITA may be harvested in a skeletonized or nonskeletonized fashion. Adequate hemostasis is ensured at all times.
·    Systemic heparin is given. We target for an activated clotting time (ACT) of 250 to 300 seconds for an off-pump CABG case (OPCAB) and 480 seconds for a CPB case.

4. Cardiopulmonary Bypass
   An option for beating heart CPB-assisted MICS CABG is available to decompress the heart or to maintain hemodynamic stability.
      Peripheral cannulation is through the femoral vessels.

5. Grafting
   We prefer the sequence of placing all the proximal anastomoses first, followed by the distal grafting.
LITA harvest setup. (A, B) Cephalad traction on the retractor to harvest the midproximal LITA. (C) Caudal retraction on the retractor to harvest the distal LITA (patient’s head is toward the right).
LITA harvest setup. (AB) Cephalad traction on the retractor to harvest the midproximal LITA. (C) Caudal retraction on the retractor to harvest the distal LITA (patient’s head is toward the right).

Proximal Anastomoses
·    The aorta is exposed and brought toward the surgical window (Fig. 5.3A and B):
1.    Pull up the pericardium using stitches.
2.    Place a small sponge to the right of the aorta, pushing it toward the left.
3.    Place continuous positive airway pressure (CPAP) on the right lung.
4.    Place an Octopus on top of the pulmonary artery (PA) to retract and depress it.
5.    Place the patient on CPB.
·    For blood pressure (BP) control, aim for a systolic pressure of 80 to 90 mm Hg.
·    Mobilize the aorta-PA junction and place a side-biting clamp (see Fig. 5.3C).
·   A hand-sewn anastomosis of a conduit to the aorta is similar to the sternotomy approach. Challenges include a deep surgical field and often the inability of the assistant to help because of the restricted field.
·    In patients for whom an aortic anastomosis is not feasible, other options include T-grafting to the LITA or the left subclavian artery.
·  Ensure adequate hemostasis because these will be difficult to re-access further on in the procedure.

(A, B) Proximal anastomosis setup (patient’s head is toward the bottom). (C) Aortotomy as seen through the small thoracotomy.
Figure 5.3 (A, B) Proximal anastomosis setup (patient’s head is toward the bottom). (C) Aortotomy as seen through the small thoracotomy.

Distal Anastomoses
·    The sequence of the distal anastomosis will depend on the surgeon’s judgment. We generally prefer doing the posterior vessels first, followed by the lateral and then the anterior wall vessels. It is important to individualize this based on the patient’s anatomy and clinical status.
·  A Starfish nonsternotomy heart positioner (Medtronic) is prepared. We prefer to use it in a flexible way (armless) whereby we place a tape and suspend the suction tip by clipping it to the outside structures, instead of using the rod. We suspend the heart toward the left shoulder when accessing the posterior vessels and toward the right hip when accessing the lateral vessels (Fig. 5.4). See Video 5.1.
·  An Octopus nonsternotomy tissue stabilizer is placed through a small incision on the left anterior axillary line of the sixth or seventh ICS. Care is taken to push this into the cavity safely using a Seldinger technique, with a red rubber catheter to avoid penetrating injuries to the heart. The Octopus is placed parallel to the target vessel, just as with routine CABG cases, and the rod is anchored solidly to the operating room (OR) table.
·    It is important that the systolic BP be raised to 140 mm Hg prior to manipulating the heart. Once the heart is positioned, its status is observed for a few seconds to ensure that the hemodynamics are stable.
·  To provide bleeding control, we prefer to place a Silastic proximal to the planned anastomosis site prior to opening the vessel. In case of ischemia, a coronary shunt is placed, and the Silastic is removed.
·    Distal anastomoses are performed similar to what is done in routine sternotomy cases (Fig. 5.5). Exposure is facilitated by using a blow mister device and occasionally by the coronary shunt.
·    Immediate graft patency is routinely checked using a transit time flow probe.
Distal anastomosis setup (with video). (A) Exposure of anterior wall vessels. (B) Left anterior descending (LAD) artery arteriotomy, with proximal Silastic control (patient’s head is toward the right). 

Exposure of lateral wall vessels. Exposure of posterior wall vessels
(C) Exposure of lateral wall vessels. (D) Exposure of posterior wall vessels.

6. Closure
    Heparin reversal is carried out with protamine.
  A thoracic drain is placed in the small incision where the Octopus was passed. This is hooked to low suction.
   There is the option of placing intercostal bupivacaine and muscle blockade prior to closing the intercostal space (ICS).
    The thoracotomy is closed using one heavy suture, with routine closure of the fascia and skin.

Step 4. Postoperative Considerations
      Perioperative mortality is low, at 1.3%.1
 Other advantages include decreased need for blood transfusion, lower surgical site infection rates, and earlier return to full physical function.1,3,4
  Postoperative pain can be an issue initially after the procedure but it is transient and control-lable. It rapidly abates by the third postoperative day and is associated with an overall improved postoperative pain picture, with improved pulmonary function.5,6
   The anastomotic patency results have been validated to be very good up to short and intermediate-term follow-up.7,8
      The rate of sternotomy conversion is 3%.
   A left-sided pleural effusion can be an issue, and we maintain the thoracic drain for 3 days.

Step 5. Pearls
      Communication between the surgeon and anesthesiologist is key.
      The surgeon and team should first be facile with sternotomy OPCAB before proceeding to doing MICS CABG.
      CPB assistance helps mitigate the learning curve.
LITA-LAD and saphenous vein–diagonal artery grafts (patient’s head is toward the right).
Figure 5.5 LITA-LAD and saphenous vein–diagonal artery grafts (patient’s head is toward the right).

Keywords : coronary artery, bypass grafting, minimally invasive, MICS CABG, Operations for Coronary Artery Disease

1.  McGinn J, Usman S, Lapierre H, et al. Minimally invasive coronary artery bypass grafting. Circulation. 2009;120(suppl 1):S78–S84.
2.  Chan V, Lapierre H, Sohmer B, et al. Handsewn proximal anastomoses onto the ascending aorta through a small left thoracotomy during minimally invasive multivessel coronary artery bypass grafting: a stepwise approach to safety and reproducibility. Semin Thorac Cardiovasc Surg. 2012;24:79–83.
3.  Lapierre H, Chan V, Sohmer B, et al. Minimally invasive coronary artery bypass grafting via a small thoracotomy versus off-pump: a case-matched study. Eur J Cardiothorac Surg. 2011;40:804–810.
4.  Une D, Lapierre H, Sohmer B, et al. Can minimally invasive coronary artery bypass grafting be initiated and practiced safely? A learning curve analysis. Innovations (Phila). 2013;8(6):403–409.
5.  Lichtenberg A, Hagl C, Harringer W, et al. Effects of minimally invasive coronary artery bypass on pulmonary function and postoperative pain. Ann Thorac Surg. 2000;70(2):461–465.
6.  Walther T, Falk V, Metz S, et al. Pain and quality of life after minimally invasive versus conventional cardiac surgery. Ann Thorac Surg. 1999;67(6):1643–1647.
7.  Ruel M, Shariff M, Lapierre H, et al. Results of the minimally invasive coronary artery bypass grafting angiographic patency study. J Thorac Cardiovasc Surg. 2014;147:203–209.
8.  Hoff S, Ball S, Leacche M, et al. Results of completion arteriography after minimally invasive off-pump coronary artery bypass. Ann Thorac Surg. 2011;91:31–37.

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