Cardiac bypass

Definition

A cardiac bypass is a diversion of blood around narrowed and no longer continuous sections of the heart (so-called coronary arteries). A bypass can be compared to a diversion in road traffic at a construction site. In a bypass, a blood vessel, usually from the leg, is taken out, bridging the narrowed section of the coronary artery and suturing the ends of the inserted vessel in front of and behind the narrowed section to the heart vessel. In this way, the blood supply to the heart is ensured despite a blocked cardiac artery.

Indications

In the past, a bypass was the only way to ensure proper blood flow to the heart in the event of a narrowing (stenosis) or complete blockage (infarction) of a cardiac artery. Today, there are other ways of doing this, so that today a bypass operation is only carried out when a coronary vessel is so narrowed that no other measures can be taken or when the vessel is completely blocked. Even if there are contraindications to an alternative treatment measure, bypass is still being considered.

In order to decide whether a bypass should be placed or one of the alternative treatment methods should be used, a number of criteria are taken into account. For example, whether there is a narrowing of a major or minor branch of the coronary arteries, or whether there are one or more narrowings. How severe is the narrowing?

Is it a complete occlusion or a slight narrowing? What causes the narrowing? Is it a calcification or is the narrowing caused by a blood clot?

One of the most decisive criteria is the length of the vessel section that is constricted. Thus, a short-stretched narrowing is usually treated with a stent, while longer narrowings usually have to be circumvented with a bypass to ensure blood flow again. Another important criterion for a bypass operation is the health condition of the patient.

In older patients with many secondary diseases, bypass surgery is not recommended because it is very stressful for the body. The urgency of the operation is also taken into account in the decision. Acute circulatory disorders are usually treated with a stent placed in the cardiac catheter laboratory as an emergency.

The most common cause of a narrowing of coronary vessels is the so-called coronary heart disease (CHD). The diagnosis as to whether a bypass operation is necessary and can be performed is made on the basis of the patient’s clinical symptoms and consolidated by means of a contrast medium imaging of the heart arteries. The imaging of the cardiac vessels is achieved by means of a cardiac catheter examination (coronary angiography).

A wire is inserted via the inguinal artery (A. femoralis) or an arm artery (A. radialis) over the vascular system to just before the heart. Once there, a contrast medium is injected into the patient’s coronary vascular system. The contrast medium spreads through the vascular system within milliseconds.

Using an X-ray machine that is pushed over the patient, images are then taken that show the contrast medium. There is a constriction where recesses and dark spots in the course of the vessels can be seen. In the case of complete occlusions, the contrast medium cannot flow through the vessel at all.

Here you can see an interruption of the white contrast medium course. Nowadays, thanks to new treatment methods, such constrictions can be treated immediately with a stent. A bypass operation is therefore not necessary. In the case of complete occlusions, the catheter examination is terminated after the diagnosis has been made and a bypass operation is usually planned.