Robotic Coronary Artery Bypass: Mammary Harvest to TECAB

Robotic coronary artery bypass surgery uses a surgical robot to harvest one or both internal mammary arteries through small ports in the left chest, after which the bypass grafts are sewn through a short incision between the ribs or, in totally endoscopic surgery, through the ports alone. The breastbone is never divided, and in Dr. Yugal Kishore Mishra's practice up to three vessels are bypassed this way.

This article sets out how Dr. Yugal Kishore Mishra, Chairman, Manipal Institute of Cardiac Sciences | Chief of Cardiovascular Surgery | Chief of Clinical Services, Manipal Hospital, Dwarka, New Delhi, India, performs robotic coronary artery bypass (sometimes called robotic CABG), as he showed it step by step in a session that included doctors in the Jivo Doctor Network across Africa. The wider picture of his robotic programme, including cost, recovery and training, is in the complete guide to robotic-assisted cardiac surgery.

Why bypass surgery moved away from the sternotomy

Coronary artery bypass grafting (CABG) creates new routes for blood around blocked coronary arteries, using arteries or veins taken from elsewhere in the body. For decades the standard route was a full median sternotomy: the breastbone is split from top to bottom and spread apart.

Dr. Mishra described the cost of that route for particular patients. A young patient with diabetes and poorly controlled blood sugar, in whom both internal mammary arteries are used as grafts, sometimes develops wound problems after a sternotomy, and some of these need major reconstructive procedures. Executives want a fast, independent return to normal life and cannot sit out three months. Manual workers cannot accept an unstable or divided sternum. For these patients an alternative route was needed, and that, in his account, is how his unit started doing minimally invasive bypass surgery.

The internal mammary arteries (also called internal thoracic arteries) run down the inside of the front chest wall on either side of the breastbone. The left internal mammary artery (LIMA) grafted to the left anterior descending artery (LAD), the main artery supplying the front of the heart, is the most durable graft in coronary surgery. Using the right internal mammary artery (RIMA) as well gives the surgeon a second arterial graft.

Bypass through the ribs: the left thoracotomy behind robotic bypass

The left thoracotomy is the small-incision route on which Dr. Mishra's robotic bypass programme is built. Minimally invasive coronary artery bypass surgery (MICS CABG) performs the same operation through a small incision in the fourth intercostal space on the left side, going between the ribs instead of through bone.

Dr. Mishra listed the benefits of the approach:

• Complete revascularisation: every significantly blocked territory is bypassed, not just the front of the heart.
• The same principles as conventional off-pump surgery: off-pump bypass is performed on the beating heart without the heart-lung machine.
• Small incisions, quicker recovery and a shorter hospital stay.

Through this small left thoracotomy his team performs triple vessel bypass. The sequence he demonstrated runs as follows:

1. The surgeon sits in a set position and places the retractors.
2. A fourth intercostal space incision is made on the left side, between the ribs.
3. A dedicated mammary harvesting retractor is set in place.
4. The mammary artery is dissected free, slowly and in skeletonised form, meaning the artery alone is taken without the surrounding veins and tissue.
5. The pericardium, the sac around the heart, is opened and the target vessels are identified.
6. The bypasses are performed, and the upper (proximal) ends of any saphenous vein grafts can also be joined to the aorta through the same small cut.

For the proximal connections to the aorta, he uses atraumatic clamps, placed on the aorta through the small incision while the graft is sewn on.

How robotic coronary artery bypass works: closed-chest mammary harvest

In robotic coronary artery bypass, as Dr. Mishra practises it, the robot's specific job is to take down the two mammary arteries; the bypass is then completed. He showed this from the surgeon's console: the surgeon sits at the robotic system, away from the patient, and dissects the internal mammary artery with the chest closed, using robotic instruments introduced through ports.

The left mammary artery is dissected in skeletonised form along its length, and the right mammary artery can be dissected the same way. Once the dissection is complete, heparin is given to prevent clotting, the artery is divided, and the bypass is performed.

In one case he showed, a young patient, both mammary arteries were harvested (a LIMA and RIMA, or bilateral mammary, strategy) and used to bypass three territories through the thoracotomy: first the LAD on the front of the heart, then the lateral wall and finally the inferior wall. He chose both mammary arteries because the patient was young; arterial grafts are generally preferred in younger patients for their long-term durability. His summary of the technique was that, with or without the robot, a surgeon can harvest two mammary arteries, or two mammaries and a radial artery, and perform triple vessel bypass without a sternotomy.

No leg incision: endoscopic vein and radial artery harvest

In Dr. Mishra's unit the saphenous vein and the radial artery are both removed through an endoscope, so the patient has no long leg or forearm scar. Many patients who have had conventional bypass surgery carry a long scar on the thigh or leg where the saphenous vein was removed. Dr. Mishra's unit does not make that incision. Instead, the saphenous vein is removed endoscopically: a small cut is made, an endoscope (a thin camera) is passed along the vein under the skin, and the vein is dissected and removed through it. In his unit a physician assistant performs this harvest. In the example he showed, one large saphenous vein was suitable for three bypasses.

The radial artery, in the forearm, is harvested the same way. A small nick is made, the endoscope is introduced and the artery is dissected out under endoscopic vision. Using the radial artery together with the mammary arteries allows total arterial revascularisation, in which every graft is an artery and no vein is used.

Redo bypass surgery without reopening the chest

A patient who has already had bypass surgery can, in selected cases, receive a new graft without a repeat sternotomy. One case he described as very interesting was a patient with a previous bypass operation. Years earlier he had received a LIMA graft to the LAD, which was still open, and a saphenous vein graft to the right side of the heart, which had failed. His right coronary artery (RCA) was 100% blocked, and he could not be treated by percutaneous transluminal coronary angioplasty (PTCA), the balloon and stent procedure, because the target was poor.

A repeat sternotomy carried a specific danger: reopening the front of the chest could damage the working LIMA graft. Dr. Mishra's team therefore performed what he called a posterior MIDCAB (minimally invasive direct coronary artery bypass), leaving the LIMA untouched:

• A radial artery was used as the new graft.
• The descending aorta, the part of the aorta running down the back of the chest, was partially clamped, and the proximal end of the radial artery was joined to it.
• The other end of the radial artery was grafted to the posterior descending artery (PDA), a fairly good-sized branch of the right coronary system.

He described this as a modified approach to the problem: it delivered a new graft to the blocked territory without touching the previous one.

Totally endoscopic coronary artery bypass (TECAB): how the approach evolved

Totally endoscopic coronary artery bypass is the latest of four stages Dr. Mishra traced in his unit's coronary surgery:

1. Midline sternotomy, the conventional full opening.
2. Lower partial sternotomy, through which both mammary arteries were dissected.
3. Left thoracotomy, now the standard minimally invasive route, with neatly healed incisions.
4. Totally endoscopic coronary artery bypass (TECAB), in which robotic arms carry out the bypass without an incision beyond the ports.

As the team gained experience, he said, incisions that were large in the early days were steadily cut down.

Can a myocardial bridge be treated robotically?

A myocardial bridge is a segment of coronary artery that dips into the heart muscle instead of running on its surface, so that the overlying muscle compresses the artery with each heartbeat. Asked whether this can be managed with minimally invasive surgery, Dr. Mishra said yes: with the robot, the bridge can be unroofed without opening the chest, by removing the bridging heart muscle from over the artery, provided the exact site of the bridge is located first. Most bridges cause no symptoms and need no treatment, and symptomatic bridges are treated first with beta blockers or non-dihydropyridine calcium channel blockers; when surgery is needed for symptoms that persist despite medicines, the robotic route has the advantage that the chest is not opened.

Who is suitable for robotic coronary bypass, and what it costs

Selection for robotic and minimally invasive bypass rests on imaging and lung function. Dr. Mishra's patients being considered for coronary bypass undergo CT aortography, a detailed evaluation of the peripheral vessels, evaluation of the LIMA, and pulmonary function tests, because the operation requires single-lung ventilation. For bypass surgery, the left lung is deflated. The broader contraindications and the role of CT and Doppler studies are covered in port-access heart valve surgery: technique and selection.

For patients and referring doctors, the trade-off is time against cost. Dr. Mishra put the cost of minimally invasive surgery at roughly one and a half times that of regular surgery, with robotic surgery costlier still, against a return to work in about three weeks instead of three months. Indicative costs for conventional bypass are on the CABG cost page.

How this compares with other approaches

Minimally invasive bypass without the robot, including coronary endarterectomy for heavily calcified arteries, is covered from a different surgeon's perspective in Dr. Udgeath Dhir's minimally invasive coronary bypass and endarterectomy. The questions doctors asked Dr. Mishra, including on myocardial bridges and anaesthesia, are on the Live Discussion page. More on the specialty is on the cardiac surgery hub.