Biophysics Of RF Ablation

Question 1

Catheter Radiofrequency Ablation

Answer 1

A minimally invasive procedure in which doctors insert a therapeutic catheter into the heart through a blood vessel. A small lesion is created to block faulty electrical impulses that can cause heart arrhythmias.

Question 2

RF Energy

Answer 2

An alternating electrical current in the 500 kHz range.

Question 3

Electrode Catheter

Answer 3

A tube with electrical sensors on it, threaded into a patient’s heart through a blood vessel in order to detect electrical activity in the heart.

Question 4

Lesion

Answer 4

A tiny scar in the heart tissue that disrupts the path of abnormal electrical activity.

Question 5

Proximal Electrodes

Answer 5

Electrodes towards the back of the catheter that detect eletrical signals in the heart. Biosense Webster bipolar therapeutic catheters have a set of two.

Question 6

Distal Electrodes

Answer 6

Electrodes towards the front of the catheter. They are key in verifying that a lesion has properly formed.

Question 7

Catheter Tip Electrode

Answer 7

Delivers RF energy into the heart tissue. This electrode is where most therapeutic catheters differ.

Question 8

Small Electrode Catheter

Answer 8

The catheter tip electrode is 4 mm long.

Question 9

Large Electrode Catheter

Answer 9

The catheter tip electrode is 8 mm long.

Question 10

Irrigated Catheter

Answer 10

A saline solution is pumped through holes in the tip to help with cooling. The catheter tip electrode is 3.5 mm long.

Question 11

RF Generator

Answer 11

Generates RF energy and monitors the catheter tip’s temperature.

Question 12

Grounding Pad

Answer 12

Also called the indifferent electrode. Typically placed on the patient’s flank, it completes the circuit for RF ablation by collecting the energy and delivering it back to the generator.

Question 13

Impedance

Answer 13

Resistance to electrical flow between the catheter tip and the grounding pad, i.e., the amount that the patient’s tissue resists the electrical current.

Question 14

Resistive Heating

Answer 14

Generated when current meets resistance as it travels through the myocardial tissue. It spreads from the electrode tip to a depth of 1 – 3 mm.1 This is where tissue is hottest.

Question 15

Conductive Heating

Answer 15

Occurs beyond the area of resistive heating. It occurs as heat spreads further into tissue by conduction, usually 3-7 mm into the tissue.

Question 16

Myocardial Cell Death

Answer 16

Irreversible myocardial tissue damage that occurs when tissue temperature reaches 50° C.

Question 17

Char and Coagulum

Answer 17

At 75-80˚C, blood proteins can start sticking to the catheter and burning (char), and a clot can form around it (coagulum). Causes a sudden, sharp rise in impedance.

Question 18

Steam Pop

Answer 18

At 100° C, the water in the cells can boil and turn to steam, which can cause an explosion within the tissue. This can create a crater or a transmural rupture and cause bleeding around the heart.

Question 19

Transmural rupture

Answer 19

A hole in the heart typically caused by a steam pop.

Question 20

Temperature Control Mode

Answer 20

Also called Standard Mode, it is one of the two modes of controlling the amount of power delivered to a catheter. The generator will deliver whatever power is necessary to maintain the desired temperature and will turn off automatically.

Question 21

Power Control Mode

Answer 21

Also called Manual Mode, it is one of the two modes of controlling the amount of power delivered to a catheter. The physician controls the amount of power manually, turning it on and off as needed.

Question 22

Irrigation Pump

Answer 22

A tool that simplifies irrigation with full pump operation from the generator or remote control.

Question 23

Remote control Generator

Answer 23

A tool that provides full system operation, letting you view and control the procedures from the lab or the observation room.