Cryoablation

With Cryoablation is a technology that uses a cold stimulus to change certain myocardial cells so that they can no longer generate or transmit an electrical stimulus. The technique represents an alternative to heat-based radiofrequency ablation and, like it, represents a minimally invasive method for ablating heart muscle cells in the right or left atrium in order to treat recurrent atrial fibrillation.

What is cryoablation?

Cryoablation is a cooling technique used to treat cardiac arrhythmia, especially recurrent atrial fibrillation. It represents an alternative to high-frequency ablation, in which certain cell areas in the right or left atrium are obliterated with heat using a cardiac catheter.

It is also a minimally invasive procedure based on a cardiac catheter that is advanced into the right atrium via suitable veins - usually starting from the groin. The left atrium is reached by puncturing the atrial septum. The cell areas that are responsible for generating the arrhythmia are pre-cooled by the tip of the cryoablation catheter and then permanently electrically inactivated at temperatures down to below minus 75 degrees Celsius. You can then neither generate nor transmit electrical impulses.

The cells are only changed in their electrophysical properties, so they do not die completely. The cryoablation is largely painless. Ablation by means of a cryoballoon catheter can be viewed as a variant of ablation by means of a cryoablation catheter. The technique is used to electrically isolate the pulmonary veins in the left atrium, which play an essential role in recurrent atrial fibrillation by transmitting uncoordinated electrical impulses.

Function, effect & goals

In addition to the precise obliteration of benign and malignant tumors, the main area of ​​application of cryoablation is in the therapy of recurrent atrial fibrillation. The method can be carried out as an alternative to radio frequency or radio frequency ablation.

Scientific studies have shown that atrial fibrillation is mainly caused by muscle cells in the pulmonary veins that open into the left atrium. One of the main goals of cryoablation is therefore to electrically isolate the pulmonary veins from the left atrium so that the uncoordinated electrical signals from the atria can no longer be passed on. The cryoablation catheter is advanced through a suitable vein into the right atrium and after puncturing the atrial septum it can be placed in the left atrium near the junctions of the pulmonary veins.

First of all, the tissue to be ablated is pre-cooled and the physician performing the procedure can electrophysiologically check whether the subsequent planned ablation would be effective and whether there are no unintended side effects or complications. Conversely, this means that the cryoablation can be terminated after the electrical check and the pre-cooled cells recover and remain functional. The cryoablation thus offers additional security because the effect can be checked before the actual irreversible ablation. This is especially important when tissue near the AV node in the right atrium needs to be ablated.

The ablation itself consists of an extraordinary cold stimulus that is transmitted from the catheter tip to the surrounding heart muscle cells. The cells treated in this way irreversibly lose their ability to generate or transmit electrical impulses themselves. The cryoablation catheter can be used in the left as well as in the right atrium. As an alternative to the cryoablation catheter, the cryoballoon catheter was developed, which is used exclusively for the treatment of electrical pulmonary vein isolation. At the front end of the cryoballoon catheter, a tiny balloon can be filled with gaseous coolant.

The actual cold stimulus to obliterate the adjacent tissue is created by the evaporation of the coolant. The catheter is placed in such a way that the tiny balloon successively closes the entrances to the four pulmonary veins in the left atrium as completely as possible in order to achieve electrical insulation of the veins by inactivating the surrounding heart muscle cells. During the treatment it can be checked whether the isolation of the pulmonary veins was successful.

The cryoballoon procedure is somewhat easier and safer to use than ablation with the cryoablation catheter, so that the technique can also be used by clinics that do not have a differentiated heart center. The active principle of cryoablation has been used in open heart surgery for decades. Only the minimally invasive methods are relatively new.

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Risks, side effects & dangers

One of the main problems after cryoablation for the treatment of atrial fibrillation is the recurrence of cardiac arrhythmia, which can usually be resolved with one or two re-ablations. But even then, the success rate is only 70 to 80 percent. A period of two years in which no more recurrent atrial fibrillation has occurred is assumed to be a success.

After a cryoballoon treatment, it is possible that only one or two of the four pulmonary veins are electrically connected again, which can be taken into account for any re-ablation that may become necessary. The risk of myocardial cells becoming inoperable during the ablation of myocardial cells near the AV node is significantly lower with cryoablation than with high-frequency ablation, because the possibility of functional testing after the tissue area has been precooled largely eliminates this risk.

A rare complication can be the formation of a blood clot (thrombus) on the catheter, which can loosen and in extreme cases cause a stroke. To minimize this problem, the patient should be put under coagulation inhibition prior to the procedure. In the electrical insulation of the pulmonary veins, infections can occur in very rare cases. If puncture of the atrial septum is required, bleeding at the puncture site has been reported in very rare cases.