Cryoablation

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Cryoablation is a technology that restores normal electrical conduction by freezing tissue or heart pathways that interfere with the normal distribution of the heart’s electrical impulses. Cryoablation is used in two types of intervention for the treatment of arrhythmias: (1) catheter-based procedures and (2) surgical operations.

A catheter is a very thin tube that is inserted in a vein in the patient’s leg and threaded to the heart where it delivers energy to treat the patient’s arrhythmia. In surgical procedures, a flexible probe is used directly on an exposed heart to apply the energy that interrupts the arrhythmia. By cooling the tip of a cryoablation catheter (cardiology) or probe (heart surgery) to sub-zero temperatures, the cells in the heart responsible for conducting the arrhythmia are altered so that they no longer conduct electrical impulses.

1 Catheter-based procedures
2 Site testing
3 Surgical procedures
4 References

[edit] Catheter-based procedures

Different catheter-based ablation techniques may be used and they generally fall into two categories: (1) cold-based procedures where tissue cooling is used to treat the arrhythmia and (2) heat-based procedures where high temperature is used to alter the abnormal conductive tissue in the heart.

Cold temperatures are used in cryoablation to chill or freeze cells that conduct abnormal heart rhythms. The catheter removes heat from the tissue to cool it to temperatures as low as -75°C. The use of freezing neutralizes these malfunctioning cells so that they can no longer interfere with the normal conduction and distribution of the electrical impulse that controls the heart’s rhythm. The patient does not feel the cold as only the active tip reaches this temperature.

[edit] Site testing

Cryotherapy is able to produce a temporary electrical block by cooling down the tissue believed to be conducting the arrhythmia. This allows the physician to make sure this is the right site before permanently disabling it. The ability to test a site in this way is referred to as site testing or cryomapping.

When ablating tissue near the AV node (a special conduction center that carries electrical impulses from the atria to the ventricles), there is a risk of producing heart block - that is, normal conduction from the atria cannot be transmitted to the ventricles. Freezing tissue near the AV node is less likely to provoke irreversible heart block than ablating it with heat.

[edit] Surgical procedures

As in catheter-based procedures, techniques using heating or cooling temperatures may be used to treat arrhythmias during heart surgery. Techniques also exist where incisions are used in the open heart to interrupt abnormal electrical conduction (Maze procedure). Cryosurgery involves the use of freezing techniques for the treatment of arrhythmias during surgery.

A physician may recommend cryosurgery being used during the course of heart surgery as a secondary procedure to treat any arrhythmia that was present or that may appear during the primary openchest procedure. The most common heart operations in which cryosurgery may be used in this way are mitral valve repairs and coronary artery bypass grafting. During the procedure, a flexible cryoprobe is placed on or around the heart and delivers cold energy that disables tissue responsible for conducting the arrhythmia.