The cardiovascular diseases

THE MYOCARDIAL INFARCTION - HEART ATTACK

- Definition
- A few explanations
- The Symptoms
- How to make the diagnosis?
- Gravity diagnosis and prognosis
- The Causes
- Evolution and complications
- Medical treatment
- The Coronarography
- Treatment by angioplasty or "Stent"
- The surgical treatment
- Monitoring
- Conclusion

THE SURGICAL TREATMENT: The aorto-coronary bypass surgery

The second possibility to bring blood and oxygen back to the heart muscle is to achieve a derivation of the blood flow, which will thus pass above the clogged artery.

The bypass surgery is achieved under several conditions:

- Either the lesions of the heart arteries are too numerous, and/or inaccessible to a revascularisation by angioplasty;

- Or an obstruction of the origin of the left coronary artery exists (left coronary trunk), then jeopardising a large cardiac territory.

1 - Principles of the bypass surgery

Blood vessels are therefore put in place to bring blood into the sick coronary artery, downstream the clogged area. These vessels must of course show nolesion and be in a very good condition.

2 - The vessels used to make the bypass surgeries

These vessels are not naturally present around the heart and should therefore be transplanted.

a - The veins:

A vein can be used. It will be connected on the one hand to the aorta, and on the other hand to the sick coronary artery, in order to achieve the “bypass” between the aorta and the sick coronary artery. This vein is taken by the surgeon at the leg level in the beginning of the intervention and it is in most cases the internal saphenous vein.

Of course, this vein must be present and in good condition before the operation, which supposes that the patient has not had a surgical intervention of his veins beforehand. To achieve more complicated bypass surgeries, the surgeon can take the veins on the 2 sides.

Description of a venous “bridge” between the aorta and the heart arteries (coronary arteries).

b - The arteries:

The other possibility for the surgeon is to take an artery in the thorax, which is not indispensable for the irrigation in blood of the tissues. The artery generally concerned is the internal mammary artery, which brings blood to the pectoral and mammary muscle.

This artery is sectioned in its distal extremity, and then connected to the sick coronary artery.

In a few much rarer cases, the surgeon can achieve the bypass surgery with the help of a radial artery (artery taken on the anterior side of the arm), or of a gastric artery (artery of the stomach) or epigastric artery.

3 - Description of the surgical intervention

Since some years, the medical imagery progresses and in particular the videoscopy techniques have been permitting achieving aorto-coronary bypass surgeries without having to open the thorax (a nevertheless relatively rare case).

However, these techniques are reserved for very particular cases at the moment, and the surgeon must also achieve an opening of the rib cage, to be in the direct contact with the heart and its arteries.

a - The classic coronary bypass surgery, by opening of the rib cage:

This intervention requires a considerable precision on the surgeon’s part; it lasts around 1 to 2 hours, but depends a lot on the surgical team and on the number of bypass surgeries to be achieved.

First of all, the physician achieves the withdrawal of the vein or veins at the level of the leg, mainly the internal saphenous vein. This vein is taken from the ankle up to underneath the knee, on the internal face.

If he wants to achieve a bypass surgery with one artery, the surgeon dissects the internal mammary artery (very close to the sternum) and sections it in its terminal portion (the one normally bringing blood to the muscle). All the small collateral arteries are plugged with threads so that blood only heads for the heart artery.

Then, he deactivates the heart and thus achieves an extra corporeal circulation: the aorta is disconnected from the heart and connected on to a machine assuring the heart function. This machine also recovers blood from the veins, then the oxygen, before re-injecting it into the aorta.

This technique permits stopping the heart, so that the surgeon can achieve the bypass surgeries in good conditions. He also achieves a protection of the cardiac muscle while injecting cold blood or hot blood (according to the teams, this procedure is called cardioplegia), into the heart veins.

Once the vein has been taken away, and/or the internal mammary artery left bare, the extra corporeal circulation put in place, and once the heart has been stopped, the surgeon can start implementing the bypass surgeries.

Thus, he delicately perforates the sick coronary artery, in order to make a hole, downstream the obstacle, in which the “bridged” vessel is inserted. This step is very delicate because it is the pledge of a quality bypass surgery.

Then, the venous and/or arterial “bridges” are connected up in the holes thus made, and fixed on with threads.

The final intervention stage consists in warming or cooling the heart so that it starts again, then in disconnecting the extra corporeal circulation.

Thereafter, a monitoring is necessary in a surgical cardiologic resuscitation unit, for a few hours.

b - Intervention by videoscopy:

This type of intervention is rather reserved for the achievement of a bypass surgery on a heart artery, with the internal mammary artery. Some teams have attempted the venous bypass surgeries, which proved to be bad quality surgeries.

Its enormous advantages are to avoid the opening of the thorax (thoracotomy), the extra corporeal circulation, and the stop of the heart. Nevertheless, its main disadvantage is not to have a very large vision of the operative field and not to be able to observe a bleeding that would take place outside of the vision field.

Thus, the surgeon achieves an incision on the left side of the thorax, introduces his camera and achieves the dissection of the internal mammary artery. He regularly practices sutures on this artery, so that bleedings are as weak as possible. Then, he cuts the artery in its extremity and the suture temporarily.

The other step consists in achieving a hole in the sick coronary artery, downstream the clogged area, so that the bypass surgery of the mammary artery can be achieved. Finally, the mammary artery is fixed on to the sick coronary artery with the help of suture thread and to the beating heart, which requires a considerable experience.

4 – Long-term results and control of the permeability of the bypass surgeries

Life span of the bypass surgeries:

The venous bypass surgeries have as a rule a life span lower to the one of the arterial bypass surgeries. On average, this life span is located between 7 and 10 years, then the bypass surgery sometimes plugs either completely or in partially. The symptoms of the angina pectoris or those of the infarct can then occur again.

But, when the bypass surgery functions well, the patient is completely relieved and does not feel these symptoms any longer.

The arterial bypass surgeries are known to be better quality surgeries and their life span often exceeds 10 years. Indeed, some arterial bypass surgeries are more than 25 years old.

Control of the bypass surgeries

In case of recidivation of the angina pectoris pains, a control of the permeability of the bypass surgeries is necessary. A new coronarography will then be achieved, coupled with the control of the bypass surgeries.

In case of obstruction of a bypass surgery, the cardiologist cannot achieve an angioplasty, i.e. a dilation of the bypass surgery at the level of the atheroma plaque.

A new intervention can in some (rare) cases be proposed.

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File last modified on july 24, 2006