Minimally Invasive Coronary Bypass and Endarterectomy

Minimally invasive coronary bypass surgery reroutes blood around blocked heart arteries through a small incision on the left side of the chest, with the heart still beating; it is often called MICS CABG. Using both internal mammary arteries, a surgeon can graft all three coronary territories with no incision on the legs, a technique known as total arterial revascularisation.

Coronary operations make up 10% of the more than 550 minimally invasive procedures performed by Dr. Udgeath Dhir, Principal Director Cardio Thoracic Vascular Surgery, Fortis Memorial Research Institute, Gurgaon, India. This article describes how his team performs bypass through a small incision, how the grafts are joined to a beating heart, and how they deal with two problems stenting cannot solve: coronary arteries filled with calcium, and stents that have become infected. The complete guide to minimally invasive and robotic cardiac surgery sets this work in the context of the whole field.

What coronary artery bypass grafting does

Coronary artery bypass grafting (CABG) treats narrowed or blocked coronary arteries, the vessels that supply the heart muscle, by attaching a length of healthy blood vessel (a graft) that carries blood past the blockage. One end of a vein graft is joined to the aorta (the proximal anastomosis) and the other to the coronary artery beyond the narrowing (the distal anastomosis). An internal mammary artery, which runs down the inside of the chest wall, can instead be left attached at its origin and joined directly to the coronary artery.

The three main coronary territories are supplied by:

• The left anterior descending artery (LAD), which runs down the front of the heart and supplies the largest share of the left ventricle.
• The circumflex artery and its obtuse marginal branches (OM), which supply the side and back of the left ventricle. A ramus intermedius, present in some people, arises between the LAD and circumflex.
• The right coronary artery and its posterior descending artery (PDA), which supply the underside of the heart.

Grafting all diseased territories is the goal, whatever the incision.

Why minimally invasive coronary bypass is done from the left side

Dr. Dhir drew a simple anatomical rule: valve operations are approached from the right side of the chest, coronary operations from the left. The reason is the left internal mammary artery (LIMA). It lies just behind the left chest wall, and its connection to the LAD is the backbone of coronary bypass surgery. The LIMA-to-LAD graft has the best long-term patency (the likelihood that a graft stays open) of any bypass conduit, which is why surgeons try to use it in nearly every patient.

His team reaches the heart through one of two routes:

• A left anterior thoracotomy, an incision between the ribs on the left side of the chest.
• A lower sternotomy, which divides only the lower part of the breastbone.

Both depend on special retractors that hold a small opening apart and on long instruments designed for working at depth. The operating room is laid out around that small window: as Dr. Dhir put it, there is hardly room to insert a finger, yet the stitching can be done because of the instruments.

Beating-heart bypass: how the grafts are joined

The bypass sequence Dr. Dhir showed was done on a beating heart: "We need not arrest the heart." The sequence runs as follows.

The proximal connection to the aorta

When a vein graft is used, the reversed great saphenous vein is harvested first. The great saphenous vein runs along the inside of the leg; it is reversed so that its valves do not obstruct flow. A side-biting clamp isolates a small part of the aorta while blood keeps flowing through the rest of it. The surgeon makes a small nick in the clamped segment, then uses an aortic punch to cut a neat, round opening, and sews the end of the vein graft onto it.

The distal connection to the coronary artery

To sew onto an artery that is moving with every heartbeat, the team uses a tissue stabiliser known as the octopus, which grips the surface of the heart with suction and holds a small segment still while the rest of the heart continues to beat. The surgeon opens the coronary artery with a blade (an arteriotomy) and stitches the end of the graft to it.

In one case Dr. Dhir showed, the finished result was the LIMA running to the LAD and a vein graft supplying the ramus intermedius. In another, all three territories were grafted through the small incision, with two vein grafts joined to the aorta alongside the LIMA-to-LAD.

Total arterial revascularisation: a garland around the heart

The newest coronary technique Dr. Dhir described uses no veins at all. In total arterial revascularisation, both internal mammary arteries, the left and the right, are taken down from the inside of the chest wall and used to graft all three coronary territories, including the LAD, the obtuse marginal branches and the posterior descending artery. He likened the result to a garland around the heart.

Because no vein is needed, there is no incision on the legs. The only wound is the chest incision. The appeal of using arteries rather than veins is durability: arterial grafts are less prone to the progressive narrowing that affects vein grafts over the years after surgery.

Coronary endarterectomy: when an artery is too calcified to stent

Coronary endarterectomy removes the calcified core of a diseased coronary artery so that the vessel can be grafted. Some coronary arteries are so heavily calcified along their whole length that a stent cannot be placed, and a bypass graft has nowhere healthy to land. Dr. Dhir described these as patients who are often told that surgery is not possible either.

His answer is coronary endarterectomy. In the case he showed, he opened a heavily calcified LAD and, on a beating heart and with special instruments, removed the calcium as a single continuous cast running all the way to the apex of the heart. He then grafted the LIMA to the cleared LAD. The removed segment, displayed intact, showed the extent of the disease: calcium along the whole course of the artery.

Endarterectomy is a demanding technique and is not needed in most bypass operations. Its value is in patients who would otherwise be told there is no option.

Infected coronary stents and mycotic aneurysms

An infected coronary stent has to come out, because antibiotics alone rarely clear an infection that lives on a metal implant. A second group of patients come to surgery because of a complication of earlier stenting. Dr. Dhir described patients whose coronary stents had become infected, forming an abscess around the stent. This is an endovascular infection akin to infective endocarditis (infection of the heart's inner lining or its valves), but arising in the coronary arteries rather than at the heart valves, the usual site. The infection can produce mycotic aneurysms, infected bulges in the wall of the coronary artery.

Dr. Dhir's team removes the infected stent, performs an endarterectomy to clear the diseased vessel, and restores blood flow with a graft. His unit has also operated on many patients with infective endocarditis of the heart valves.

The same principle applied in a case outside the coronary arteries. A young female patient had previously had a stent placed for coarctation of the aorta, a congenital narrowing of the main artery. The stent became infected and formed an abscess, and she developed an abscess in the spleen as well. After a turbulent course, the source of the infection was traced to the stent. Dr. Dhir's team removed the infected segment of the aorta and repaired it.

Who is suitable for minimally invasive coronary bypass

Not every patient referred for minimally invasive bypass receives it. At Dr. Dhir's unit, a high-resolution CT scan of the chest is protocol before any minimally invasive coronary operation.

One referral showed why. A man came specifically for a minimally invasive bypass. His CT showed the pleura, the lining of the lung, completely calcified, with the left lung small and encased and the right lung over-inflated to compensate. The cause was tuberculosis earlier in life. The minimally invasive route was ruled out. He received total arterial bypass grafting, but through a conventional open sternotomy.

That decision reflects Dr. Dhir's broader view. About 60% of his operations remain conventional, and a sternotomy, whether planned or as a conversion during a minimally invasive case, is never a failure. The article on minimally invasive valve surgery shows how the same customised approach applies to the aortic, mitral and tricuspid valves.

Recovery and cost of minimally invasive coronary bypass

The benefits of a small incision for coronary patients are those Dr. Dhir described across his practice: limited blood loss, less pain and faster recovery. Most patients are extubated in theatre, and a thoracic epidural provides continuous pain relief for the first 24 hours.

Dr. Dhir put the cost of minimally invasive valve and coronary operations at $6,500 to $18,000, depending on the complexity of the case and the consumables used. Indicative package ranges for bypass surgery are on the CABG treatment-cost page.

When a stent is not an option: guidance for referring doctors

For referring doctors, the coronary cases in this masterclass carry a practical lesson. A patient told that their arteries are too calcified for a stent, or whose stent has become infected, is not necessarily beyond help: endarterectomy and stent removal with grafting remain options at an experienced surgical centre. Signs that should prompt a cardiac referral in the first place, such as exertional chest pain and breathlessness, are covered in the complete guide, and attendees' questions are answered on the Live Discussion page.

For a different surgeon's account of bypass surgery performed with robotic assistance, see Dr. Yugal Kishore Mishra's guide to robotic cardiac surgery. Related content is collected on the cardiac surgery specialty page.