Corpus: Coronary artery bypass grafting

Coronary artery bypass or coronary artery bypass grafting is a surgical procedure for the treatment of coronary artery disease (CAD) with high-grade coronary stenosis. It is used when other procedures (e.g. balloon dilatation (PTCA), stent implantation, rotablation, etc.) are not indicated or have been unsuccessful.

Coronary bypass surgery involves the direct bridging of coronary stenoses with autologous arterial or venous vessels (grafts).

Arterial grafts have a better long-term open rate than venous grafts. Therefore, complete arterial revascularisation should be aimed for wherever possible. The open rate of arterial grafts after 10 years is > 90 %. The rate for venous grafts is approx. 50-60 %.

During the procedure, a bypass is created on one or more affected coronary vessels in order to improve the reduced cardiac blood flow behind the stenosis caused by constrictions. The internal thoracic artery (also known as the internal mammary artery) or the veins of the lower leg (e.g. the great saphenous vein) are used for this purpose.

Although veins are easier to remove, they are generally less suitable than arteries. The internal thoracic artery is an artery of the elastic type and is a better solution than the radial artery, which is of the muscular type. There is a risk of vasospasm here.

Vein bypass[Bearbeiten]

This form of bypass is also called aortocoronary venous bypass (ACVB). The great saphenous vein is dissected, a suitable piece is removed and used as an interposition for the stenosed area of the coronary artery. In this way, several bypasses can also be created if several branches of the coronary artery are stenosed. Long-term studies have shown that with this form of coronary artery bypass, an average of around 30% of the bypasses have a stenosis after 10 years.

See also: Jumpgraft

Arterial bypass[Bearbeiten]

In most cases, the internal thoracic artery is mobilised and anastomosed with the stenosed area - often with the distal section of the anterior interventricular ramus (LAD). This form of bypass is also known as LIMA bypass - from the English "left internal mammary artery". The long-term results in terms of restenosis of the bypass vessels are better than when a vein is used as the bypass interposer.

Alternatively, other arteries can also be used for the bypass:

• radial artery (as a free interposition graft)
• Sinus gastro-omental artery (for stenoses of the coronary artery dextra)

The standard approach is via a median sternotomy. The complication rate of this open procedure is around 0.4%, with wound infections and wound healing disorders being the most common.

After clamping the ascending aorta and diverting the blood circulation via a heart-lung machine, the heart is perfused with a cardioplegic solution to induce cardiac arrest. The grafts are sutured as an end-to-side anastomosis distal to the stenosis and then also attached end-to-side to the aorta close to the heart using an aortotomy. If the internal thoracic artery is used, its aortic outlet is left in place. The entire operation takes an average of three to four hours.

Alternatively, a coronary artery bypass without a heart-lung machine (OPCAB) can be performed on the beating heart, but this is not a standard procedure. Other, less frequently used procedures are minimally invasive interventions such as MIDCAB or TECAB.

The absolute indications for a coronary artery bypass are high-grade stenosis of the coronary sinus artery and three-vessel disease. An acute indication arises in the event of complications during a PTCA (e.g. vessel rupture or dissection).

A decision in favour of surgery is favoured by

• previous unsuccessful interventional procedures such as PTCA
• poor pumping function of the ventricle
• Multimorbidity of the patient with increased risk of vascular complications (e.g. diabetes mellitus)

The success rates after 10 years depend on the vascular material used:

• Saphenous vein: approx. 50%
• Internal thoracic artery (mammary artery): approx. 90%
• radial artery: approx. 80%