Ablation Techniques
Radiofrequency ablation (RFA)
Non irrigated RF ablation catheters
Original/first type of RF ablation catheter.
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Uses RF energy to scar the heart.
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In order to achieve an effective lesion, multiple factors much be achieved
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Good power delivery (measured in watts)
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Good contact (indirectly observed with an initial impedance drop or with a special contact catheter - see below)
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Efficient duration (measured in time)
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During ablation, the tissue heats and can become too hot, leaving risk of rupture/perforation or a steam pop.
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As a safety mechanism, all RF catheters are temperature controlled. When the tip of the electrode is detected to exceed a set temperature (e.g., 60 degrees or 45 degrees for irrigated catheters) the power will drop off in order to reduce the temperature, hence limiting effectivie lesion delivery.
Irrigated RF ablation catheters
Where saline is infused into the catheter tip to provide continuous cooling.
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Infusion will be at a low rate when no ablation is performed, and will increase in rate when ablation is on.
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Achieves a deeper lesion than non irrigated catheter.
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Usually has a higher cost compared to a standard non irrigated catheter.
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Has more to set up, as requires irrigation tubing and pump.
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Generally has lower clot risk (unless there are bubbles which are not detected in the tubing).
High power - short duration ablation
Using high power, short duration ablation provides larger lesion width delivery, while achieving less lesion depth.
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This type of ablation is ideally used for thinner surface structures, where there is concern of rupture/perforation (e.g., posterior PVs).
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Lesion stacking however, may result in deeper than expected lesions.
Contact force ablation catheters
Have a contact force sensor at the cathter tip to determine if the catheter is in contact with the tissue, and if so at what force (stable or too high).
Cryoablation (cryo)
Delivers very cold temperatures which causes permanent myocardial damage.
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Ablation is delivered via either a balloon catheter or focal tip catheter (see picture below).
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Balloon catheter is used only for pulmonary vein isolation (PVI). This involves inflating the balloon at the ostium of the PV, causing occlusion of flow, and then delivering cryo when occlusion is achieved. Ice ball forms on the balloon and helps maintaing position of the catheter during the duration of the lesion (~2-4 minutes per application).
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Focal lesions can be "cryomapped" where a less cold temperature can be delivered to view the response to ablation at that particular area (e.g., -40 degrees as opposed to -80 degrees). This is sometimes utilised if close to the AVN and risk of damage is considered high, as damage is believed to be more reversible than RF application.
Pulsed field ablation (PFA)
PFA results in electroporation by increasing membrane permeability.
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Non-thermal technology.
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Creates a field around where the electrodes have contact with the myocaridum (see picture below)
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Initially said to be tissue specific (has no risk damaging surrounding tissues (e.g., oesphagus, phrenic nerve, etc)), however some off label uses have found it can affect other intended cardiac structures, like the coronary arteries.
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Currently only approved for AF ablations.
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Still rapidly growing area in EP.​
