Temperature analysis of 3D-printed biomaterials during unipolar and bipolar radiofrequency ablation procedure

Abstract

Background: Due to their mechanical properties, the MED625FLX and TPU95A could be appropriate candidates for cardiac 3D surgical guide use during radiofrequency ablation (RFA) treatment.

Methods: RFA aims to destroy the heart tissue, which cause arrhythmias, by applying a radiofrequency (RF) energy at critical temperature above +50.0°C, where the thermal damage is considered not reversible. This study aims to analyze the biomaterials thermal properties with different thicknesses, by testing the response to bipolar and unipolar RFA on porcine muscle samples (PMS), expressed in temperature. For the materials evaluation, the tissue temperature during RFA applications was recorded, firstly without (control) and after with the biomaterials in position. The biomaterials were considered suitable for the RFA treatment if: (1) the PMS temperatures with the samples were not statistically different compared with the control; (2) the temperatures never reached the threshold; (3) no geometrical changes after RFA were observed.

Results: Based on these criteria, none of the tested biomaterials resulted appropriate for unipolar RFA and the TPU95A failed almost all thermal tests also with the bipolar RFA. The 1.0 mm MED625FLX was modified by bipolar RFA in shape, losing its function. Instead, the 2.5 mm MED625FLX was considered suitable for bipolar RFA catheter use only.

Conclusions: The 2.5 mm MED625FLX could be used, in the design of surgical guides for RFA bipolar catheter only, because of mechanical, geometrical, and thermal properties. None of biomaterials tested are appropriate for unipolar ablation catheter because of temperature concerns. Further investigations for clinical use are eagerly awaited.

Keywords: 3D surgical guide; arrhythmias treatment; biomaterial tests; radiofrequency ablation; thermal test.

Figure 1

3D models of biomaterial samples. 3D models of different thickness of semicircular-shaped samples on which the experimental tests were performed. (A) 1.0 mm of thickness; (B) 2.5 mm of thickness.

Figure 2

Ex vivo experimental setting. Ex vivo simulation of radiofrequency ablation (RFA). (A) The J type thermocouples positioned inside the sample D₁ and D₂ holes; (B) Example of unipolar RFA on TPU95A of 2.5 mm.

Figure 3

Temperature behavior of control and biomaterial samples performed by bipolar catheter in D₁. The temperature behavior of the control, the MED625FLX and the TPU95A of 1.0 mm and 2.5 mm at D₁ due to RFA performed by bipolar catheter; the dashed line indicates the threshold set at +43.0°C.

Figure 4

Temperature behavior of control and biomaterial samples performed by bipolar catheter in D₂. The temperature behavior of the control, the MED625FLX and the TPU95A of 1.0 mm and 2.5 mm at D₂ due to RFA performed by bipolar catheter; the dashed line indicates the threshold set at +43.0°C.

Figure 5

Temperature behavior of control and biomaterial samples performed by unipolar catheter in D_1. The temperature behavior of the control, the MED625FLX and the TPU95A of 1.0 mm and 2.5 mm at D₁ due to RFA performed by unipolar catheter; the dashed line indicates the threshold set at +43.0°C.

Figure 6

Temperature behavior of control and biomaterial samples performed by unipolar catheter in D₂. The temperature behavior of the control, the MED625FLX and the TPU95A of 1.0 mm and 2.5 mm at D₂ due to RFA performed by unipolar catheter; the dashed line indicates the threshold set at +43.0°C.

Figure 7

The macroscopically biomaterials changes in geometry after the bi- and uni-polar RFA catheter. The panel on the left shows the biomaterial samples after the bipolar RF ablation, while the panel on the right the biomaterial samples after the unipolar RFA catheter; (A) TPU95A of 2.5 mm; (B) TPU95A of 1.0 mm; (C) MED625FLX of 2.5 mm; (D) MED625FLX of 1.0 mm; (E) TPU95A of 2.5 mm; (F) TPU95A of 1.0 mm; (G) MED625FLX of 2.5 mm; (H) MED625FLX of 1.0 mm. The yellow arrows indicate the material deflection, the red arrow indicates burn trace.