Electrophysiology

Frequently Asked Questions

Treating Arrhythmias with CryoTherapy

What type of arrhythmias can be treated with CryoTherapy?

Clinical trials in the U.S. have demonstrated CryoTherapy to be safe and effective in the treatment of AVNRT arrhythmias.

CryoCath Products and CryoTherapy System

What kinds of catheters are available from CryoCath in the USA?

Currently available are (1) Freezor®, a cryocatheter for the minimally invasive, percutaneous treatment of AVNRT, (2) Freezor® Xtra, a device for the surgical treatment of cardiac arrhythmias in the pericardial space, and (3) Freezor® MAX , an even more powerful catheter which creates larger and deeper lesions in applications where they are needed.

Why is the default CryoAblation temperature preset at -85°C?

Minus 85°C represents the temperature that is measured at the tip tissue interface via the tip embedded thermocouple. The temperatures inside the expansion chamber may be colder than -85°C. The lowest achievable temperature is the boiling point of nitrous oxide at -88.5°C.

Why can't I reuse the catheter or device?

The catheters have a special chip in them that prevents their re-use to protect the patient and ensure proper performance.

Reversibility in CryoMapping mode

Is permanent damage caused by CryoMapping?

In some instances, cell death may be caused to the cells closest to the tip of the cryocatheter. Damage to cells that are farther away from the tip of the catheter is less likely to occur.

Why -30°C up to 60 seconds?

Minus 30°C refers to the tip/tissue interface. Pre-clinical studies have demonstrated a reversible electrical effect at -30°C for up to 60 seconds.

CryoAblation

Why a 4-minute freeze?

A CryoCath study on lesions has indicated that a 4-minute freeze yielded lesions that were comparable in depth to RF lesions. The size of the frozen tissue zone peaks between 2 and 3 minutes.

Are the electrical markers for ablation different between cryo and RF?

Yes, they are. For AVNRT, cryo may not provide fast junctional beats. For accessory pathways, cryo may or may not provide an abrupt termination of the delta wave.

How do I know if I am close to the arrhythmogenic site or ablation target?

Time-to-effect is the best indicator of proximity to the target.

Does an iceball form in the blood?

The term "ice ball" is a misnomer; a better description would be "frozen tissue zone." There is minimal ice formation around the tip of the catheter due to blood flow. Any "frost" on the catheter quickly melts away as soon as the cryo application is terminated. Therefore, it poses no threat to break off and it will not occlude small vessels.

Is it possible to cause damage by trying to remove the catheter from the heart while there is ice adhesion?

Yes, therefore you should not pull the catheter when it has adhered. However, thawing takes place rapidly once the application is stopped (less than 5 seconds).

What cells are affected by post-thaw cell death?

The cells farthest from the catheter tip but still within the freeze zone may succumb to necrosis or apoptosis. Only cells that have been stressed in some way by the freezing process can be destroyed post-thaw. Necrosis and apoptosis are events that complete the CryoAblation process by filling in the periphery of the lesion. They do not cause new cell damage and do not increase the size of lesion.

Does the patient need general anesthesia?

The procedure does not usually require general anesthesia. The decision to use general anesthesia varies according to the site.

How long is the procedure?

Randomized trials in Europe have concluded that the procedure time for CryoTherapy is comparable to the time needed to perform an RF procedure.

Is the procedure painful for the patient?

The CryoTherapy treatment itself is not painful for patients. When applying RF energy, some patients feel pain which has not been reported to date with CryoTherapy.

CryoTherapy vs. Heat-based Technologies

Is it correct to say that RF generates heat and CryoTherapy uses a refrigerant to generate ice or cold energy?

No. Heat-based methods (such as RF) generate heat directly in target tissue; this has a burning or charring effect on the tissue. Cryo does not involve an analogous "injection" of cold energy; rather, it is a process whereby heat is removed from target tissue, creating a frozen tissue zone.

What advantages does CryoTherapy have in comparison with other energy systems in electrophysiology?

Reversibility: site testing by chilling conducting tissue in the target area to create a transient or reversible electrical effect
CryoAdhesion: the catheter tip firmly attaches to the tissue when it freezes
Connective tissue matrix integrity is maintained
Pre-clinical studies have demonstrated minimal endothelial disruption and thrombus
Reduced risk of pulmonary vein stenosis
No burning or charring