Effect of Electrode Orientation on Lesion Sizes Produced by Irrigated Radiofrequency Ablation Catheters

Abstract

Effect of Electrode Orientation on Lesion Sizes. Background: Irrigated radiofrequency (RF)ablation catheters may produce different lesion sizes dependent upon the electrode orientation to the tissue. This study examined the effect of irrigated electrode orientation on the lesion size and explores a potential mechanism for this effect.Methods and Results: Lesions were created in isolated porcine myocardium using an open irrigation, closed irrigation, and nonirrigated RF catheter (all 3.5-4 mm tips). Lesions were created with the electrodes with all permutations of electrode orientation (vertical or horizontal), contact pressure (6 or 20 g), and saline superfusate flow (0.2 or 0.4 m/sec) over tissue interface. The effect of electrode irrigation without RF delivery on tissue temperature was assessed with intramyocardial temperature probes and infrared thermal imaging. For both irrigated catheters, the horizontal orientation produced 25-30% smaller lesion volumes than the vertical orientation despite equal or greater power deliveries. The horizontal orientation produced larger lesion volumes for the nonirrigated catheter. Higher superfusate flow rates were associated with decreased lesion volumes for the irrigated catheters but greater lesion volumes for the nonirrigated catheter. Catheter irrigation alone without RF delivery reduced intramyocardial temperatures up to 4.9 • C and the horizontal orientation produced a 2-fold greater area of tissue cooling than the vertical orientation.Conclusion: Horizontal electrode orientations reduce lesion volumes for irrigated RF catheters. This effect may be in part due to greater areas of active tissue cooling in the horizontal orientation

Comparative Analysis of Different Methods of Modeling the Thermal Effect of Circulating Blood Flow During RF Cardiac Ablation

“…Since Method 4 provides the most realistic modeling approach, this was considered as the reference method, and the results from the other three methods were compared to it. We considered that the differences in lesion depth and width were insignificant for values lower than 1 mm, since this value is approximately that of the deviation (±0.5 mm) observed in experimental RFCA studies with a non-irrigated electrode [22,36]. Likewise, the differences in T max_tissue or T max_blood were considered to be insignificant for values lower than 4ºC, since this value is approximately that of the observed deviation (±2ºC) [22].…”

Endocardial Versus Epicardial Ventricular Radiofrequency Ablation

“…Lesions characteristics, if RF had been applied at different sites, may have been different because of differing loads on the catheter dependent on the angle at which the catheter tip makes contact with the tissue. 8 Other variables such as electrode surface area in contact with the tissue and local blood flow known to effect lesion formation could not be controlled. Prevalence of ventricular arrhythmias during RF application is much higher in animal model compared with patients.…”

“…The electrode orientation has previously been shown to influence lesion characteristics in a bench model. 8 In atrium, optimal CF has been evaluated around 20 g. 6,[9][10][11] Concerning safety, minimal forces to perforate ventricles mechanically (without RF delivery) are higher than for atria ; however, the force required to perforate when RF is delivered can be as low as 77 g in the atrium. 13 Whereas it has been shown that CF was correlated with lesion volume, 6 it seems that a parameter coupling instantaneous total force and application duration (FTI) 4 was more accurate to predict lesion size.…”

Use of a Novel Endoscopic Catheter for Direct Visualization and Ablation in an Ovine Model of Chronic Myocardial Infarction

“…This is in contrast to contact irrigated catheter ablation, in which energy delivery may vary significantly depending on catheter orientation as a result of the variable electrode/myocardial interface and loss of energy to the surrounding blood pool. 22 Finally, the flat 6-mm distal hood surface is also less likely to lead to cardiac perforation; we have never seen a perforation despite aggressive catheter manipulation in this animal model.…”