The Biophysics and Pathophysiology of Lesion Formation During Radiofrequency Catheter Ablation

Cardiac Electrophysiology:
From Cell to Bedside
, 4th Ed.,
Edited by Zipes and Jalife.
  • The Catheter. A catheter is used to place the lead used for ablation into the heart. Usually it’s inserted into a vein in the leg, and then snaked through the vessels into the right atrium. (Ablating tissue in the left atrium is trickier; you may have to create a small hole between the atria by doing a transseptal puncture.) Catheterization is less invasive than open heart surgery, so some patients can avoid even a single night in the hospital after treatment.
  • Radiofrequency Energy. Ablation is performed using electrical energy with a frequency between 0.3 and 1 MHz (in the frequency band of AM radio). These frequencies are too high to cause direct electrical stimulation of muscles or nerves. The mechanism of ablation is Joule heating, like in your toaster, which raises the temperature of the tissue within a few millimeters of the lead tip.
  • Lesion Formation. Cells become irreversibly damaged at temperatures on the order of 50° C. The temperature of the lead tip is kept below 100° C to avoid boiling the plasma and coagulating proteins.
  • Atrial Fibrillation. Atrial fibrillation is the most common arrhythmia treated with ablation. Fibrillation means that the electrical wave fronts propagate in a irregular and chaotic way, so the mechanical contraction is unorganized and ineffective. Unlike ventricular fibrillation, which is lethal in minutes if not defibrillated, a person can live with atrial fibrillation, but the heart won’t pump efficiently causing fatigue, the backup of fluid into the lungs, and an increased risk of stroke.
  • Electrical Mapping. The first part of the clinical procedure is to map the arrhythmia. Multiple electrodes on the catheter record the electrocardiogram throughout the atrium, locating the reentrant pathway or the focus (an isolated spot that initiates a wave front). If the arrhythmia is intermittent, then it may need to be triggered by electrical stimulation in order to map it.
  • Ablation Sites. Once the arrhythmia is mapped, the doctor can determine where to ablate the tissue. Usually many isolated spots will be ablated to create a large lesion, often located around the pulmonary veins where many reentrant pathways occur.
My copy of Cardiac Electrophysiology:
From Cell to Bedside
, alongside IPMB.

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Professor of Physics at Oakland University and coauthor of the textbook Intermediate Physics for Medicine and Biology.

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Brad Roth

Brad Roth

Professor of Physics at Oakland University and coauthor of the textbook Intermediate Physics for Medicine and Biology.

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