#opcab

Isn’t it interesting to know that the first ever successful bypass was done as a beating heart operation? This was way back in 1964 by a Russian surgeon, Colosev. But since then the conventional bypass operation has developed as a safe procedure and has stood the test of time.

Interest in OPCAB was rekindled in the late 80s and 90s. Due to the steep learning curve and lack of evidence for better outcome compared to standard operation, many surgeons lost initial enthusiasm and went back to the old time tested methods. The few who persisted – many of them in India- have provided valuable information regarding the safety and efficacy of this demanding surgery.

From the emerging data across the world it is now clear that OPCAB can be as complete a bypass operation as the standard one. It provides better results in terms of early deaths, strokes and kidney failures. The difference becomes far more apparent in high risk patients especially very old and those having diminished kidney or lung functions. One of the most important areas where OPCAB is making its mark is the field of repeat operations. OPCAB reduces the blood loss and recovery time in those situations.

It is clear that OPCAB would be technically more difficult to perform than conventional bypass for the plain fact that the fine surgical work needs to be done while the surface is still moving. There are certain devices which make the process a bit easier for the surgeon. Most important of them is called a tissue stabilizer. This, when applied over the heart stabilizes a small portion of the heart wall and reduces the movement in that region. This makes surgical procedure a lot easier to perform. There are other devices which add to the safety like shunts which prevent blood loss and blowers which help to clear operating field.

Is OPCAB a ‘key hole’ operation?

Generally this form of operation is done through a standard opening in front of the chest that bypass operation is infamous for. The reason why this approach is widely popular is because of its safety and adaptability. In various unexpected difficult situations it gives the surgeon many options to achieve the desired result. So to put it the right perspective, OPCAB is not a ‘key hole’ operation.

Is OPCAB a more expensive option?

There is no difference in the cost between the standard bypass and OPCAB. In many patients, as the ICU and hospital stay become much shorter and usage of costly antibiotics reduces, the total cost may even be less.

How safe is OPCAB?

Bypass operation has become a very safe operation. The success rate for bypass operations in the best centers over the world is 96-99%. Last year the OPCAB success rate at Medical Trust Hospital was a proud 100%.

If OPCAB is not ‘Key Hole’ operation, what is ‘Key hole Bypass operation’?

The ‘key hole bypass operation’ is known as Minimally Invasive Coronary Artery Bypass or MICAS. In this operation the large wound in front of the chest is totally avoided. Through small incisions at the side of the chest main blocks can be treated. The recovery is much faster and patient can be back to work in 4 weeks.

MICAS can also be combined with Stenting in what is called a HYBrid operation to treat complicated disease patterns. The first HYBrid operation in Kerala was done at Medical Trust Hospital last year.

Patient Selection

Expert Beating Heart Surgeon (> 50 beating heart cases)

With experience OPCAB can be performed safely in the vast majority of cases (>90%). However it is not advisable to perform OPCAB if MULTIPLE unfavorable characteristics are present (e.g. cardiomegaly in a patient with LVEF 25% and small targets)

Operative Steps

  Operating Room Setup and Preparation

Preserve normothermia by keeping the operating room warm, avoiding radiant heat loss and monitoring core body temperature. Ensure that the heart-lung machine and perfusionist are available. It is not necessary to prime the heart-lung machine. Review the chest roentgenogram to assess cardiomegaly before committing to OPCAB. Confirm availability of stabilizer instrument set of choice, a CO2 blower and appropriately sized intracoronary shunts. Assure that the anesthesiologist is comfortable with beating heart surgery as collaboration crucial for success.

Anesthesia

Unlike traditional CABG where the anesthesiologist plays a passive role during the performance of bypass grafting, involvement of the anesthesia team is essential for successful OPCAB. A continuous cardiac output swan ganz catheter and continuous mixed venous saturation monitor are helpful. Maintenance of systolic pressure is important for the heart to tolerate hemodynamically unfavorable positioning. Alpha agents and inotropic agents are important to maintain cardiac output during manipulations. If necessary, an intraaortic balloon can be inserted for temporary support.

Procedure

A traditional sternotomy is performed. All conduits are harvested as for traditional CABG. The left internal mammary should be made as long as possible. This will help avoid excessive tension when the heart is elevated after the graft to the LAD is performed. Hemi-skeletonization of LIMA (the "Suma technique") preferable as maximal length achieved in shortest time. Total arterial revascularization is feasible with OPCAB. Use of composite conduits (Y or T graft) with the left and right IMA and the radial artery is preferred.

The heparin dose (1-1.5 mg/Kg) is 1/3 of the standard dose for cardiopulmonary bypass. The target ACT is greater than 300 seconds. The ACT should be checked every 30 minutes with heparin supplemented as needed.

Sequence of anastomoses

The coronary arteries should be grafted in order of increasing cardiac displacement, i.e. anterior wall vessels followed by inferior wall vessels and finally lateral wall vessels. The guiding principle that more cardiac displacement is tolerated with increasingly complete revascularization. The LIMA to LAD graft is usually first, the inferior wall grafts (PDA, RCA) are usually next and the lateral wall grafts (OM) are usually last.

The proximal anastomoses can be performed before or after the distal anastomoses. The advantage of completing the proximal anastomosis first is immediate perfusion through the graft after the completion of the distal anastomosis. The author's preference is to perform the proximal anastomoses first.

Positioning the heart with mechanical stabilization for target vessel presentation

Proper positioning and stabilization are critical for the success of OPCAB! The use of a dedicated instrument for target vessel stabilization strongly encouraged, especially for the beginner beating heart surgeon (see preference cards)

For Anterior LV wall (Figure 1) presentation (Anterior Descending, Diagonal, Ramus), a deep pericardial retraction suture, (DPRS, #1 Silk or Ethibond) is placed 1-2 centimeters above the left superior pulmonary vein ( Figure 2), pulled taut and secured to the drape on the left side of the patient. If necessary, especially for the Ramus, an additional deep pericardial retraction suture (second in figure 2) is placed anterior to the phrenic nerve and caudal to the first deep pericardial retraction suture. Additional deep pericardial retraction sutures are positioned until the target vessel is midline in the sternal incision. Placement of these deep pericardial retraction sutures must be done deliberately and quickly. The retraction required to expose the posterior pericardium causes severe hemodynamic compromise. The blood pressure will recover faster if the patient is head down with preparatory volume loading.

For Lateral LV wall presentation (Obtuse Marginals, Posterolateral branches of right coronary artery) the OR table is placed in steep Trendelenburg position (Figure 3) and the table is raised and rotated toward the right (Figure 4). This will allow gravity to displace heart to the right and apex anteriorly. Suspensory sutures on the right side of the pericardium are removed. The right pleural space is opened and the right pericardial incision is extended towards the inferior vena cava. These maneuvers allow the heart to move toward the right pleural space. Additional deep pericardial retraction sutures are placed on the posterior pericardial surface on a line drawn from the left inferior pulmonary vein to the inferior vena cava, halfway between the cava and pulmonary vein (third in Figure 2).

For Inferior LV Wall presentation (distal Right Coronary Artery and Posterior Descending Artery), with the table in steep trendelenberg position, the tension applied to the deep pericardial retraction sutures is modulated to expose the target vessel in the center of the operative field (Figure 5, 6). The posterior descending artery is the preferred site for grafting the right coronary distribution. The necessary temporary occlusion of the artery, if proximal to the bifurcation, can cause ischemia of the AV node with resultant bradycardia. For grafting the right coronary artery the table made flat and retraction sutures are relaxed with the heart failing to the left side.

Stabilization of target site is accomplished using one of the many excellent stabilizers available on the market. These devices work by compression with or attachment (suction or direct) to the stabilizing arm (Figures 7,8). It is important that these devices be used as stabilizers, not retractors. The techniques described above are used to expose the vessel, the stabilizers create an immobile field. If used as retractors the heart will slip and compression will cause hemodynamic compromise.

Anastomosis

Proximal occlusion of target vessel is accomplished with an encircling suture or silastic tape passed widely around the vessel proximal to the site chosen for anastomosis. No distal occlusion is necessary (Figure 9). The use of intracoronary shunts is recommended whenever possible, especially for LAD and RCA. These are very useful when hemodynamically significant ischemia develops (Figure 10). The anastomosis is performed in a routine manner according to the surgeon's preference.

Preference Card

Genzyme OPCAB retractor system. This system uses silastic tapes to surround the vessel, attaching it to a template that immobilizes the vessel.

Guidant (formerly CardioThoracic Systems) Ultima II retractor and stabilizer. This system uses compression to immobilize the vessel.

Guidant Flocoil intracoronary shunt (sizes from 1.5 mm to 2.5 mm in 0.25 mm increments).

Medtronic Octopus 2 Stabilizer. This system attaches to the existing reusable retractor. Suction is used to secure the heart to the retractor and immobilize the vessel.

Tips & Pitfalls

Meticulous attention to detail is critical to success, as safety margin with OPCAB is reduced compared to traditional CABG.

Intracoronary shunts are extremely useful in minimizing the amount of ischemia and improving the safety of the operation. In cases of a training institution use of shunts allows residents to be safely trained in OPCAB.

Allow extra time to obtain the best presentation and stabilization for obtuse marginal vessels. Do not compromise your exposure. If adequate exposure cannot be obtained the anastomosis should not be compromised and the traditional approach should be used.

A CO2 blower is crucial for beating heart surgery but has to be used VERY sparingly at a flow rate not > 5 L /min, to prevent damage to the coronary endothelium. Avoid directing the gas jet directly into the vessel lumen to prevent gas embolization.

Heparin reversal is not mandatory. The author's preference is to administer one-half the calculated protamine dose.

Anastomosis of the obtuse marginal vessels is easier from the left side of the table.