Radio frequency perforation of cardiac tissue: Modelling and experimental results

Abstract

Radio frequency (RF) current delivered through a thin catheter can be used to perforate the pulmonary valve or the atrial septum to treat pulmonary atresia in newborns. To understand better the mechanisms of RF perforation, a numerical model is developed, and experiments are performed in isolated canine cardiac tissue. The model consists of a cylindrical domain with a tissue layer between two blood layers. The finite-difference method is used to compute both the potential and temperature distributions. When the tissue temperature exceeds 100 degrees C in all points that are directly in front of the catheter, these points are considered to be instantly vaporised, and the catheter advances over these points. The computed temperature time course coincides with measured temperature at small voltages (< 16 V). Simulated perforation occurs when the voltage exceeds a threshold of 70-80 V for a catheter diameter of 0.30-0.44 mm, which coincides with experimental observations in the myocardium. A voltage exceeding this perforation threshold tends to decrease tissue damage. Shorter electrodes (0.7 mm as against 2.4 mm) with smaller diameters produce a more rapid perforation. In conclusion, numerical simulations provide insights into aspects of RF perforation, such as electrode size, current, speed of perforation and collateral damage.

Radiofrequency perforation in the treatment of congenital heart disease

“…Recently, Shimko et al [11] developed a numerical model validated in vitro to characterize RF perforation based on the mechanism of cellular vaporization. The model predicted that as the applied voltage to the electrode tip is increased, the tissue temperature in front of the tip rises even faster, and there is a minimum applied voltage below which tissue temperature stabilizes, cannot reach 100°C, and tissue perforation is not possible.…”

“…At 100°C, cellular vaporization occurs (Fig. 1) [11]. While ablation and perforation both utilize RF energy to modify tissue, the desired effect and the mechanism to achieve the effect are quite different.…”

“…Factors other than the temperatures reached by the tissue also govern RF perforation and ablation and include rate of tissue temperature rise [12], electrode geometry, and electroporation and arcing. The rate of temperature increase is critical to the mechanism of perforation [11]. If the temperature rise is slow, the tissue will desiccate over a large region at around 70°C.…”

“…Technical data, such as mode of current delivery (continuous vs. pulsed), applied power (5–50 W), and duration of energy delivery has varied in clinical applications. As such, the related mechanisms and effects of specific parameters, such as electrode geometry and applied power, remain unclear [11]. The focus of the following discussion will be to detail the biophysical basis behind RF perforation and review its application in the management of congenital heart lesions.…”

Transcatheter creation of atrial septal perforation using a radiofrequency transseptal system: Novel approach as an alternative to transseptal needle puncture

“…A radiofrequency wire has recently been introduced to create a therapeutic perforation for atretic pulmonary valves in pediatric patients with complex congenital heart disease [6–9]. Radiofrequency ablation applied in a controlled fashion potentially provides an alternative to mechanical interatrial septal perforation, overcoming occasional difficulties associated with a thick atrial septum or distorted contour.…”