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

Figures & data

Figure 1. Four kinds of phase shift ablation modes (PsM-45°, PsM-90°, PsM-135°and PsM-180°) with a phase shift angle range of 45–180° in 45° step sizes.

Figure 2. The geometry of the computational model (not to scale). The thickness of the atrial wall is 5 mm. Electrode diameter D = 2.31 mm (7 Fr), electrode length L = 4 mm, insertion depth 0.5 mm and electrode spacing 4 mm.

Table 1. Thermal and electrical characteristics of the elements of the numerical models.

Element/material	σ (s/m)	λ (W/m·T)	ρ (kg/m3)	c (J/kg·T)
Electrode	4.6 × 10^−6	71	21500	132
Atrial tissue	0.54	0.53	1060	3111
Plastic probe	10^−5	0.026	70	1045
Connective tissue	0.09	0.4	1000	3200

Measurement temperature at 37 °C.

Figure 3. Electrical and thermal boundary conditions of the models: (A) phase shift mode, (B) bipolar mode and (C) unipolar mode.

Figure 4. Temperature distribution in the tissue after 60 s of RF ablation across 5 mm wall thickness and 4 mm catheter spacing, considering three modes of ablation: (A) unipolar mode, (B) bipolar mode, and (C∼F) phase shift angle ablation PsM-45°, PsM-90°, PsM-135°, PsM-180°. The solid black line is the thermal damage border.

Table 2. Lesion dimensions for three modes of RF ablation: PsM mode, BiM mode and UiM mode.

Ablation mode	Max depth (mm)	Transmural depth > 5	Max width (mm)	Gap length (mm)	Max tissue temp (°C)
PsM-45°	–	No	–	Discontinuity	46.06
PsM-90°	4.09	No	6.12	Continuity	64.86
PsM-135°	6.29	Yes	9.96	Continuity	83.63
PsM-180°	6.89	Yes	10.8	Continuity	91.18
UiM	–	No	–	Discontinuity	39.55
BiM	1.01	No	1.62	2.38	50.66

Max depth, the maximum lesion depth contour; Max width, the maximum ablation width contour; Gap length, the length of incomplete isolation in the surface of tissue (between electrode spacing); –, does not generate effective thermal injury.

Figure 5. Current density distribution in the tissue considering three modes of ablation UiM, BiM and PsM.