The network of 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 agent is injected into the coronary arteries through thin plastic tubes. The distribution of the contrast agent can then be assessed on the X-ray image. This allows the doctor not only to identify the fine branches of the coronary arteries but also to detect narrowings and blockages. This is particularly necessary for patients who have suffered a heart attack, provided they were brought to a hospital early on.
The heart is surrounded by fine coronary arteries that supply it with blood © lom123 | AdobeStock
Based on these findings, the doctor ultimately 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 pressure conditions in the beating heart.
The cardiac catheter was first used in humans to visualize the right coronary arteries in 1929 by Werner Forßmann in a self-experiment. Forßmann received one of the three coveted Nobel Prizes in Medicine in 1956 for his “invention of the cardiac catheter.”
The Cardiac Catheter
The cardiac catheter is a minimally invasive procedure for examining the heart. It allows physicians to examine and treat the heart without making a surgical incision.
The catheter is advanced directly into the heart through the blood vessels. Access points are the veins or arteries
- in the groin,
- the crook of the elbow, or
- the wrist.
Depending on the purpose of the examination, there are various access options. Doctors also distinguish between
- a right heart catheter for examining the vessels of the right heart, and
- a left-heart catheterization to examine the vessels of the left heart.
Cardiac catheterization of the left ventricle is performed more frequently than right heart catheterization. A left heart catheter is primarily used to visualize the coronary arteries and to dilate them using balloon dilatation.
Before the cardiac catheter is inserted, a detailed consultation takes place. During this consultation, the doctor explains the procedure and risks of the cardiac catheterization. This is followed by a physical examination and the determination of current blood values.
Before the actual cardiac catheterization, certain hygiene preparations are necessary. If access to the blood vessels is gained through the groin, the area is shaved, disinfected, and prepared for the procedure with a local anesthetic.
First, the doctor inserts the IV catheter, through which the cardiac catheter will be inserted shortly thereafter.
The catheterization itself is painless, so general anesthesia is not necessary. In cases where the patient is very anxious, a sedative may be administered along with the cardiac catheter.
If a procedure on the coronary arteries becomes necessary during the cardiac catheterization, the surgeon can perform it immediately. At the end of the session, the doctor removes the cardiac catheter and the access site. The patient is given a light pressure bandage to prevent post-procedure bleeding until the following day.
Various Treatment Options
If narrowings or deposits are found in the examined vessels, the doctor can remove them during the same procedure. For narrowings,
- a balloon catheter or
- a stent
. Both stent placement and the use of a balloon catheter are painless procedures.
Stents are made of a special metal alloy. They are only a few centimeters long and have a diameter of just two to four millimeters. Some stents can even release medication to actively prevent the stent from narrowing again later.
Stent implantation using a cardiac catheter © Christoph Burgstedt | AdobeStock
Guide wire of the cardiac catheter
The guidewire runs inside the catheter and helps the cardiac catheter find its way. The tip of the cardiac catheter is usually curved and is slowly guided toward the heart via the guidewire. The wire keeps the curved tip of the cardiac catheter straight during this process.
Once the cardiac catheter has reached its target, the doctor withdraws the guidewire and the tip of the cardiac catheter folds back. To navigate the “tangle” of coronary arteries, the doctor must alternately advance and retract the cardiac catheter and the guidewire. By deliberately straightening and bending the cardiac catheter, it can then turn into a branching vessel.
Cardiac catheters have different tips and bends. Therefore, it may be necessary to change the catheter halfway to the target. This allows even the most tortuous target area to be reached. This is where the actual examination is ultimately performed.
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 access was established is first fitted with a sheath. The sheath acts as a flexible guide through which the cardiac catheter can slide into the blood vessel.
At the same time, the puncture site is sealed, and blood flow out of the vessel is stopped.
Catheter ablation is a specialized form of cardiac catheterization that uses electrical current to treat rapid heart rhythm disorders (tachycardias). For some forms of tachycardia, catheter ablation is already the standard of care.
While medications merely suppress the rapid heartbeat, catheter ablation can cure this condition.
Success rates are quite high; for example, for
- atrial flutter,
- AV nodal reentry tachycardias, or
- WPW syndrome
well over 90%.
Catheter Ablation for Arrhythmias
The basis for subsequent catheter ablation is an electrophysiological study of the heart and the conduction of electrical impulses in the heart muscle. With the help of this study, the doctor determines where in the heart the arrhythmia originates.
The arrhythmia can then be treated using catheter ablation. This procedure requires a special cardiac catheter. The standard access point is in the groin. However, the doctor can just as easily insert the cardiac catheter into a vein in the arm or neck.
To reach the left atrium, the doctor also punctures the septum (the wall separating the atria). To perform the puncture, the doctor inserts a long needle into the right atrium and pierces the heart septum at its thinnest point. The cardiac catheter can then be advanced through the opening in the septum.
Here, the catheter can deliver high-frequency current for a short time. With the help of the high-frequency current, the affected area in the heart is “ablated,” thereby stopping the rapid heartbeat. In the case of so-called circular tachycardias, the circuit must be interrupted by one or more applications of current.
In all cases, the ablated tissue gradually scars over and ceases to function in terms of electrical conduction. After catheter ablation, the physician attempts to trigger the tachycardia again as a test. To do this, the physician uses direct stimulation via
- the cardiac catheter or
- certain medications administered intravenously.
The ablation is complete as soon as the arrhythmia can no longer be triggered.
After catheter ablation, the cardiac catheters are removed. The doctor closes the access sites in the groin or the crook of the arm with a pressure bandage.
Strict bed rest for 6 to 24 hours is necessary to prevent the access site from reopening and to avoid post-procedure bleeding.
Image of coronary arteries during an angiography © Pitchy | AdobeStock
For some time now, in addition to catheter ablation using radiofrequency energy, a second method has been available: cryoablation.
In cryoablation, liquid gas is delivered through a metal electrode to the tip of the cardiac catheter. This causes the metal electrode to freeze firmly to the muscle tissue, preventing the cardiac catheter from slipping during the procedure. Temperatures of -80°C also cause cryoablation of an area just a few millimeters in diameter.
Cryoablation is also painless. Furthermore, this method has a major advantage over conventional catheter ablation: there is virtually no tissue shrinkage. Such shrinkage could also lead to narrowing of the blood vessels.
Catheter Ablation: Postoperative Care
Following the cardiac catheterization procedure, a pressure bandage is applied. Heart function is continuously monitored via
Patients are typically discharged from the hospital after about 24 hours.
However, there are some risks associated with cardiac catheterization. The risk of complications is highest in patients with severe heart disease.
Inserting the cardiac catheters can lead to minor vascular injuries, which could be quite dangerous in the area around the heart. In rare cases, blood clots—which can cause a heart attack—and infections may occur.
Catheter Ablation: Success Rate
Today, both atrial arrhythmias and ventricular tachycardias are treated with catheter ablation.
Success rates are strongly dependent on the patient’s overall health. In cases of vascular narrowing, catheter ablation is 90% successful in most people. In patients with pre-existing heart conditions, however, the success rate drops to less than 50%.
Patients with ventricular tachycardia are also often fitted with a defibrillator (similar to a pacemaker).
Research and Cardiac Catheters
The use of catheter ablation for atrial fibrillation is currently a rapidly growing field in cardiac research. For this form of tachycardia, ablation using radiofrequency energy is not yet considered a recognized standard of care.
So far, catheter ablation is used only when all other treatment options have been exhausted or the patient is suffering severely. Since no clear source of the atrial fibrillation can be identified, treatment using a cardiac catheter is all the more difficult. In most cases, ablation must be performed at many different sites to stop atrial fibrillation.
Research on Cardiac Catheters: Pulmonary Veins
Thanks to studies, doctors now know that atrial fibrillation is very often caused by abnormalities in the four pulmonary veins. Small strands of heart muscle connect the heart muscle tissue of the left atrium to the veins at these sites.
Ablating these myocardial tongues is one of the treatment strategies for atrial fibrillation. Cardiologists also refer to this type of cardiac catheterization procedure as “pulmonary vein isolation.”
Pulmonary vein isolation is only an option for patients who suffer from paroxysmal atrial fibrillation. The success rate for this cardiac catheterization procedure currently ranges between 50% and 70%. Sometimes a second treatment is necessary; in other cases, atrial fibrillation cannot be completely stopped. In these cases, patients respond better to antiarrhythmic medications after catheter ablation.
AV node ablation is also a commonly performed ablation procedure. The existing atrial fibrillation is conducted irregularly by the AV node, leading to significant arrhythmias in the ventricles.
If the AV node is ablated, the irregular conduction of signals from the atria ceases. The disadvantage, however, is that the missing AV node—which acts as the heart’s natural pacemaker—must be replaced by a pacemaker. A pacemaker is always necessary following AV node ablation to maintain heart function.
The patient will be 100 percent dependent on the pacemaker going forward. Without its assistance, no electrical impulses would be transmitted from the atria to the ventricles. Should the pacemaker fail, the patient would not die immediately, however, because another natural pacemaker node within the ventricular muscle would then take over. This node generates a replacement rhythm of about 20 to 40 beats per minute and allows the ventricles to continue “beating.”
In the majority of cases, ablation of the AV node and implantation of a pacemaker lead to a significant improvement in quality of life.
The main disadvantage of AV node ablation is that the pacemaker must be replaced several times over the course of a patient’s life. Its batteries wear out over time and must be replaced accordingly. This necessitates several follow-up procedures.
