A simulation study to compare the phase-shift angle radiofrequency ablation mode with bipolar and unipolar modes in creating linear lesions for atrial fibrillation ablation

Abstract

Purpose In pulmonary veins (PVs) isolation (PVI), radiofrequency (RF) energy is often used to create a linear lesion for blocking the accessory conduction pathways around PVs. By using transient finite element analysis, this study compared the effectiveness of phase-shift mode (PsM) ablation with bipolar mode (BiM) and unipolar mode (UiM) in creating a continuous lesion and lesion depth in a 5-mm thick atrial wall. Materials and methods Computer models were developed to study the temperature distributions and lesion dimensions in atrial walls created through PsM, BiM, and UiM. Four phase-shift angles - 45°, 90°, 135°, and 180° - were considered in PsM ablation (hereafter, PsM-45°, PsM-90°, PsM-135°, and PsM-180°, respectively). Results At 60 s/30 V peak value of RF voltage, UiM and PsM-45° did not create an effective lesion, whereas BiM created a lesion of maximum depth and width approximately 1.01 and 1.62 mm, respectively. PsM-135° and PsM-180° not only created transmural lesions in 5-mm thick atrial walls but also created continuous lesions between electrodes spaced 4 mm apart; similarly, PsM-90° created a continuous lesion with a maximum depth and width of nearly 4.09 and 6.12 mm. Conclusions Compared with UiM and BiM, PsM-90°, PsM-135° and PsM-180° created continuous and larger lesions in a single ablation procedure and at 60 s/30 V peak value of RF voltage. Therefore, the proposed PsM ablation method is suitable for PVI and linear isolation at the left atrial roof for treating atrial fibrillation.

Computer simulation study on the effect of electrode–tissue contact force on thermal lesion size in cardiac radiofrequency ablation

“…The metabolic heat production per volume term is ignored in our study because it is far smaller than that for the other variables [17]. The heat loss caused by blood perfusion was also negligible because there are no large blood vessels in the myocardial tissue, as noted by Yan et al [18]. The power loss produced by blood flow is modeled by means of forced thermal convection coefficients in the electrodes-blood interface and endocardium-blood interface.…”

Theoretical and experimental analysis of amplitude control ablation and bipolar ablation in creating linear lesion and discrete lesions for treating atrial fibrillation

“…Although tissue injury is the result of several complex mechanisms, thermal lesions created in the atrial wall can be reasonably approximated using an isotherm of 50 C in computer models [17,18] and thermal lesion contour in the experiments is assessed by the "white zone" [19].…”

Modeling Analysis of Thermal Lesion Characteristics of Unipolar/Bipolar Ablation Using Circumferential Multipolar Catheter

“…The values of the electrical and thermal conductivities of the myocardium shown in Table 1 were assessed at an ambient temperature of 37 °C. These two parameters are temperature-dependent and follow unique piecewise relations [19,20]. The electrical conductivity increased exponentially at a rate of 1.5% °C −1 below 100 °C and then dropped by four orders of magnitude between 100 °C and 105 .…”

“…The catheter penetrated the myocardium at a depth of 0.1 mm. The thicknesses of blood, myocardium, connective tissue, and muscle were configured to 9 mm, 5 mm [19,20], 2 mm [22], and 18 mm [23], respectively. The thickness of the lung region (Z), length (X), and width (Y) of the entire model were obtained from a convergence test to avoid boundary effects.…”

“…The application of RF power inflicts irreversible lesions on the biological tissue. Previous studies concluded that the temperature field enclosed by the 50 • C isothermal surface after ablation activity reflects the effective lesion volume [19,20].…”