The plexus of the coronary arteries originates from two arterial branches. It is so small that it can only be examined using special X-ray techniques and cardiac catheters.
First, an X-ray contrast medium is injected into the heart arteries via thin plastic tubes. The distribution of the contrast medium can then be checked in the X-ray image. This allows the doctor not only to see the fine branches of the coronary arteries, but also to detect constrictions and blockages . This is particularly necessary for patients who have had a heart attack, provided they were taken to hospital at an early stage.
The heart is surrounded by fine coronary arteries that supply it with blood © lom123 | AdobeStock
Based on these findings, the doctor then decides whether
is necessary.
The development of the cardiac catheter
The cardiac catheter was developed in the 1860s by Etienne-Jules Marey and Auguste Chauveau. Initially, the procedure was used to measure the pressure conditions in the beating heart.
The cardiac catheter was first used in humans to visualize the right coronary artery in a self-experiment by Werner Forßmann in 1929. Forßmann received one of the three coveted Nobel Prizes for Medicine in 1956 for his "invention of the cardiac catheter".
The cardiac catheter
The cardiac catheter is a minimally invasive examination of the heart. It allows doctors to examine and treat the heart without a surgical opening.
The catheter is inserted directly into the heart via the blood vessels. Access points are the venous or arterial arteries
- the groin,
- the crook of the elbow or
- of the wrist.
Depending on the purpose of the examination, there are various access options. Doctors also distinguish between
- a right heart catheter to examine the vessels of the right heart, and
- a left heart catheter to examine the vessels of the left heart.
Cardiac catheterization of the left ventricle is performed more frequently than a right heart catheterization. A left heart catheter is mainly used to visualize the coronary arteries and dilate them using balloon dilatation.
Before the cardiac catheter is used, a detailed consultation takes place . The doctor will explain the procedure and risks of the cardiac catheterization. This is followed by a physical examination and determination of the current blood values.
Some hygienic preparations are necessary before the actual cardiac catheterization. If the blood vessels are accessed via the groin, the groin is depilated, disinfected and prepared for the procedure with a local anaesthetic.
The doctor first places the infusion cannula, through which the cardiac catheter is inserted shortly afterwards.
The actual catheter examination is painless, which is why complete anesthesia is not necessary. In cases where the patient is very anxious, a cardiac catheter can be used together with a sedative.
If an intervention on the coronary arteries is required during the cardiac catheterization, the surgeon can perform this immediately. At the end of the session, the doctor removes the cardiac catheter and the access. The patient is given a light pressure bandage until the following day to prevent secondary bleeding.
Various therapeutic instruments
If constrictions or deposits are found in the examined vessels, the doctor can remove them in the same step. In the case of constrictions
- a balloon catheter or
- a vascular support (stent)
is used. The insertion of a stent and the use of a balloon catheter are also painless procedures.
Stents are made of a special metal alloy. They are only a few centimetres long and have a diameter of just two to four millimetres. Some stents can even release medication to actively prevent the stent from narrowing later on.
Implantation of a stent using a cardiac catheter © Christoph Burgstedt | AdobeStock
Guide wire of the cardiac catheter
The guide wire runs inside the catheter and helps the cardiac catheter to find its way. The tip of the cardiac catheter is normally curved and is slowly guided to the heart via the guide wire. The wire keeps the curved tip of the cardiac catheter straight.
Once the cardiac catheter has reached its target, the doctor pulls back the guide wire and the tip of the cardiac catheter folds in. In order to be able to bend in the "tangle" of the coronary vessels, the doctor must alternately pull the cardiac catheter and guide wire back and forth. The targeted straightening and kinking of the cardiac catheter then bends it into a branching vessel.
Cardiac catheters have different tips and bends. It may therefore be necessary to change the cardiac catheter halfway to the target. This allows even the most angled target area to be reached. This is where the actual examination is carried out.
Changing the cardiac catheter
Occasionally, it is necessary to change the cardiac catheter during a cardiac catheterization. To do this, the blood vessel through which the catheter was inserted is first fitted with a sheath . The sheath acts as a flexible guide rail through which the cardiac catheter can slide into the blood vessel.
At the same time, the puncture site is sealed and the blood flow out of the vessel is stopped.
Catheter ablation is a special form of cardiac catheter surgery that can also treat rapid cardiac arrhythmias (tachycardia) using electricity. Catheter ablation is already the standard therapy for some forms of tachycardia.
While medication merely suppresses the palpitations, catheter ablation can cure this condition.
The success rates are quite high and are, for example, for
- atrial flutter,
- AV node reentry tachycardia or
- WPW syndrome
well over 90 %.
Catheter ablation for arrhythmias
The basis for subsequent catheter ablation is an electrophysiological examination of the heart and the conduction in the heart muscle. With the help of this examination, the doctor determines where in the heart the arrhythmia begins.
The cardiac arrhythmia can then be addressed using catheter ablation. This requires a special cardiac catheter. The usual access point is in the groin. However, the doctor can also insert the cardiac catheter into the vein in the arm or neck.
In order to reach the left atrium, the doctor also punctures the septum (cardiac septum). For the puncture, the doctor pushes a long needle into the right atrium and pierces the septum at the thinnest point. The cardiac catheter can then be advanced through the opening in the septum.
This can emit high-frequency current for a short time. The high-frequency current is used to "obliterate" the diseased area in the heart and thus stop the palpitations. In the case of so-called circling tachycardia, the circuit must be interrupted by one or more current emissions.
In all cases, the obliterated tissue gradually scars and becomes non-functional in terms of conduction. After the catheter ablation, the doctor attempts to trigger the tachycardia again for control purposes. In doing so, he uses direct stimulation through
- the cardiac catheter or
- certain drugs that are administered intravenously.
The ablation is completed as soon as the arrhythmia can no longer be triggered.
After catheter ablation, the cardiac catheters are removed. The doctor closes the access points in the groin or crook of the arm with a pressure bandage.
Strict bed rest of 6 to 24 hours is necessary to ensure that the access is not reopened and to prevent secondary bleeding.
Depiction of coronary arteries during angiography © Pitchy | AdobeStock
In addition to catheter ablation with high-frequency current, a second form, cryo-ablation, has been available for some time.
In cryo-ablation, liquid gas is fed through a metal electrode to the tip of the cardiac catheter. This causes the metal electrode to freeze to the muscle tissue. This prevents the cardiac catheter from slipping during ablation. The temperatures of - 80° C also lead to cold obliteration of a few millimeters in diameter.
The application of cryo-ablation is also painless. Furthermore, this method has a major advantage over conventional catheter ablation: there is practically no tissue shrinkage. This could also lead to blood vessel constriction.
Catheter ablation: aftercare
A pressure bandage is applied following the cardiac catheterization procedure. Cardiac activity is continuously monitored by
Patients normally leave the clinic again after around 24 hours.
Nevertheless, there are some risks associated with a cardiac catheterization procedure. The risk of complications is highest in the case of severe heart disease.
The insertion of the cardiac catheter can lead to minor vascular injuries, which could be quite dangerous in the area of the heart. Blood clots, which can cause a heart attack, and infections rarely occur.
Catheter ablation: success rate
Today, both atrial arrhythmias and ventricular tachycardias are treated with catheter ablation.
The success rates are very much dependent on the general condition of the patient. For vasoconstriction, catheter ablation is 90% successful in most people. In the case of pre-existing heart conditions, however, the chances of success drop to less than 50%.
Patients with ventricular tachycardia often also receive a defibrillator (similar to a pacemaker).
Research and cardiac catheterization
The use of catheter ablation for atrial fibrillation is currently a booming branch of cardiac research. In this form of tachycardia, ablation using radiofrequency current is not yet a recognized standard form of therapy.
So far, catheter ablation has only been used when all other treatment options have been exhausted or the patient is suffering very severely. Since it is not possible to find a clear site of origin in atrial fibrillation, treatment using cardiac catheterization is all the more difficult. In most cases, many different locations have to be sclerosed in order to stop the atrial fibrillation.
Research on cardiac catheterization: Pulmonary vein
Thanks to studies, doctors now know that atrial fibrillation is very often caused by disorders in the four pulmonary veins. Small myocardial tongues connect the myocardial tissue of the left atrium with the veins.
Sclerosing these myocardial tongues is one of the treatment strategies for atrial fibrillation. Cardiologists also refer to this type of cardiac catheterization as "pulmonary vein isolation".
Pulmonary vein isolation is only possible for patients suffering from paroxysmal atrial fibrillation. The chances of success for this cardiac catheter operation are currently between 50 % and 70 %. Sometimes a second treatment is necessary, in others the atrial fibrillation cannot be stopped completely. In these cases, patients respond better to antiarrhythmic medication after catheter ablation.
AV node ablation is also a frequently performed ablation method. The existing atrial fibrillation is only transmitted irregularly by the AV node and leads to significant arrhythmias in the ventricles.
If the AV node is obliterated, the irregular transmission of the signals from the atrium stops. The disadvantage, however, is that the missing AV node must be replaced by a pacemaker. This pacemaker is always necessary for AV node ablation in order to maintain heart function.
In future, the affected patient will be completely dependent on the pacemaker . Without its help, impulses would no longer be transmitted from the atria to the ventricles. However, if the pacemaker fails, the patient does not have to die immediately, as another natural pacemaker node within the ventricular muscles will kick in. This generates a replacement rhythm of around 20 to 40 beats per minute and keeps the ventricles "beating".
In the majority of cases, ablation of the AV node and implantation of the pacemaker lead to a significant improvement in quality of life.
The biggest disadvantage of AV node ablation is that the pacemaker has to be replaced several times in a lifetime. Its batteries wear out over time and have to be replaced accordingly. This means that several follow-up operations are necessary.
