Physics and engineering of transcatheter cardiac tissue ablation

Abstract

Ablation of arrhythmogenic cardiac tissues has emerged as one of the most important advances in cardiac electrophysiology. With the introduction of transcatheter ablation, the treatment of ventricular tachycardia, Wolff-Parkinson-White syndrome and other cardiac arrhythmias has progressed from an expensive and painful surgical therapy accompanied by a long recovery period to the less expensive, less traumatic transcatheter approach. The feasibility of cardiac ablation, along with the increasing number of physicians using the technique, requires understanding of the anatomic and electrophysiologic bases of transcatheter ablation as well as the different technologies, their limitations and complications. This report provides an overview of the physical, scientific and technical aspects of cardiac ablation performed with the methods currently available and a summary of the limitations of each method and expected future technologic developments in this growing field. Emphasis is placed on radiofrequency and direct current energies, the primary methods now used. Methods such as cryoablation and laser, and microwave and chemical ablation are discussed with less detail because the method of delivering energy for these ablative procedures has not been fully developed.

Blood damage, platelet and clotting activation during application of radiofrequency or cryoablation catheters: a comparative in vitro study

“…Durin g c lin ical ap plication of rad iofreque ncy, blood is also e xpose d to the cath e ter an d on ly a portion of th e tip is in contact with tissue . Furth e rm ore , blood can be trappe d be twe e n the e le ctrode an d tissue [ 19] . Coag ulum is form e d un de r th e se conditions aroun d th e tip of th e cath e te r an d th e im pe dan ce incre ase s, as we observe d in our m ode l. More ove r, sinc e we foun d n o sign i® can t diffe re n ce s be twe e n th e two¯ow conditions in our m ode l, th is could n ot be con side re d the m ain variab le in this study.…”

Superiority of Gold versus Platinum Irrigated Tip Catheter Ablation of the Pulmonary Veins and the Cavotricuspid Isthmus: A Randomized Study Comparing Tip Temperatures and Cooling Flow Requirements

“…Power delivery and tip temperature are the main manipulated variables in RF ablation. While, at a given electrode tip size, the amount of power is the determinant for lesion size, 13 excessive tip temperature leads to char and/or coagulum formation and to a rapid increase of impedance that hampers efficient transmission of RF energy 2,14 . Rise of impedance is observed when there is formation of coagulum at the catheter tip or imminent steam popping and requires termination of the RF application.…”

Cryotherapy of cardiac arrhythmia: From basic science to the bedside

“…This heating is a direct function of the current density at the catheter ablation electrode onto the myocardial interface extending a few millimeters into the tissue. 2,3 Resistive heating increases the tissue's kinetic energy by virtue of increasing molecular movement. In contrast, cryotechnologies Q5 remove heat from tissues, lowering molecular movement and stored kinetic energy, which results in tissue cooling and ice formation.…”