Radiofrequency Thermal Ablation Heat Energy Transfer in an Ex-Vivo Model

Little work has been done to consider the temperature changes and energy transfer that occur in the tissue outside the vein with ultrasound-guided vein ablation therapy. In this experiment, a ex-vivo model of the human calf was used to analyze heat transfer and energy degradation in tissue surrounding the vein during endovascular radiofrequency ablation (RFA). A clinical vein ablation protocol was used to determine the tissue temperature distribution in 10 per cent agar gel. Heat energy from the radiofrequency catheter was measured for 140 seconds at fixed points by four thermometer probes placed equidistant radially at 0.0025, 0.005, and 0.01 m away from the RFA catheter. The temperature rose 1.5°C at 0.0025 m, 0.6°C at 0.005 m, and 0.0°C at 0.01 m from the RFA catheter. There was a clinically insignificant heat transfer at the distances evaluated, 1.4 ± 0.2 J/s at 0.0025 m, 0.7 ± 0.3 J/s at 0.0050 m, and 0.3 ± 0.0 J/s at 0.01 m. Heat degradation occurred rapidly: 4.5 ± 0.5 J (at 0.0025 m), 4.0 ± 1.6 J (at 0.0050 m), and 3.9 ± 3.6 J (at 0.01 m). Tumescent anesthesia injected one centimeter around the vein would act as a heat sink to absorb the energy transferred outside the vein to minimize tissue and nerve damage and will help phlebologists strategize options for minimizing damage.

Risk factors for endovenous heat-induced thrombosis after endovenous radiofrequency ablation performed in Thailand

Objective

We aimed to determine the incidence of and associated risk factors for endovenous heat-induced thrombosis (EHIT) after endovenous radiofrequency ablation (RFA).

Methods

We retrospectively reviewed the medical records of 82 patients with 97 great saphenous veins undergoing RFA from 2012 to 2014.

Results

The incidence of EHIT was 10.3%. Class 1, 2, and 3 EHIT was found in 50%, 30%, and 20% of legs, respectively. No class 4 EHIT, deep vein thrombosis, or pulmonary emboli occurred. Univariate analysis revealed that the associated risk factors for EHIT were a vein diameter of >10 mm, operative time of >40 min, and Caprini score of >6. Multivariate analysis revealed that the independent risk factors associated with EHIT were a vein diameter of >10 mm and operative time of >40 min.

Conclusions

A vein diameter of >10 mm and operative time of >40 min might be predictive factors for EHIT following RFA.