RF ablation

The treatment of AF entered a new era after the publication of the landmark observations of Haissaguerre et al (19). Both segmental ostial catheter ablation (20) and left atrial encircling ablation of the pulmonary veins (PVs) (21) have been reported to be successful in the treatment of AF Radiofrequency (RF) ablation is a highly effective therapeutic approach in the treatment of typical isthmus- dependent AFL (22). 

RF catheter ablation is complicated by thromboembolism in about 0.6% of patients (23). The risk of stroke from RF ablation may be higher in paroxysmal AF patients with prior TIA (24). As reflected by elevated plasma D-dimer levels, RF ablation has a thrombogenic effect that persists through the first 48 hours after the procedure (25). Activation of the coagulation cascade in RF ablation procedures is not related to the delivery of RF energy, but is related to the placement of intravascular catheters and to the duration of the ablation procedure (26,27). Furthermore, RF lesions themselves have been shown to be thrombogenic (28). The risk of a thromboembolic complication is higher for left-sided ablations... 

Several medical devices and procedures can affect pacemakers, however electrocautery, cardioversion and defibrillation, lithotripsy, diathermy, neurostimulation units, RF ablation, radiation therapy, and MRl, among others. MRl can have effects through multiple mechanisms other than EMI force and torque, current induction, and heating (Al-Ahmad et al. 2010). 

Solomon et al. (2002) used the PAKY robotic system in 16 patients during CT-guided procedures. The accuracy in the phantom calibration test was 0.6° angular and 1.65 mm linear. All 23 procedures (RF ablation, core needle biopsy, nephrostomy, and neobladder access) were performed successfully without complication. However, in four cases, the target was not met adequately, and fine-tuning adj ustment with joystick control was required to ultimately reach the target. In all cases, however, the study showed that the use of the robot reduced radiation exposure for the patient and medical personnel. 

While conduction of heat to the periphery of the treated tumor is good, conduction of heat away from the tumor is undesirable. Thus, the ideal tumor conducts heat and current, but is surrounded by insulating tissues. In practice, this theory has been validated by Livraghi et al. (1999) who described the oven effect in the RF ablation of hepatocellular carcinoma in cirrhotic liver. Cirrhotic tissue insulates the tumor... 

Methods of decreasing heat tolerance of tissues to optimize the results of RF ablation are experimental at present. They include prior cellular injury from chemotherapy or radiation and prior hypoxia caused by vascular occlusion or antiangiogenesis factors (Goldberg et al. 2000b). 

Currently, three RF ablation systems are commercially available for clinical applications in the United States. These are the Radionics 200-W generator with inter-... 

In order to be eligible for RF thermal ablation, patients must meet certain requirements. As RF ablation is a form of local therapy, the disease to be treated must be confined to the liver, without vascular invasion or extrahepatic metastases (Lencioni et al. 2001) (Figs. 8.3,8.4). Other desirable attributes needed for successful treatment include focal, nodular type... 

For RF ablation of HCC, patients must be Child-Pugh class A or B because in cases with end-stage liver cirrhosis (class C), treatment of tumor probably does not increase patient survival. In patients with hepatic metastases, the rationale for RF tumor ablation is based on the demonstration that in certain types of malignancies, surgical removal of hepatic tumor burden improves survival (Selzner et al. 2000 Benevento et al. 2000). 

The optimal approach for performing RF ablation in the liver is a matter of debate. RF ablation can be performed percutaneouslylaparoscopically or at laparotomy. At our institution the percutaneous approach is preferred because it is the least invasive, has minimal morbidity, can be performed on an outpatient basis, can be performed with ultrasound, CT, or MRI and can be repeated as necessary. Advocates of periopera-... 

The use of radioffequency ablation in the treatment of renal carcinoma was first reported by Zlotta et al. (1997, 1999), who described three patients who underwent RF ablation of small RCC prior to nephrectomy. Since then, several reports of RCC treated with percutaneous RF ablation have appeared. In 1999, McGovern et al. reported a case of RCC treated with RF ablation and left in situ to be followed by imaging. 

With particular attention to the von Hippel-Lindau population, Pavlovich et al. (2002) reported results of RF ablation in 24 tumors all less than 3 cm. A total of 22 tumors were in patients with von Hippel-Lindau disease, and two were in patients with hereditary papillary renal carcinoma. In these... 

Comparison of the Gervais et al. (2000) and Pavlovich et al. (2002) series illustrates some of the limitations inherent in comparing the early reports of RF ablation. Different generators and different electrode design may produce different results. The 50-W RITA generator used in the Pavlovich et al. 

The application of RF ablation to the treatment of isolated foci of metastatic RCC was reported in 2001. Zagoria et al. (2001) reported a case in which RF ablation was used to treat two RCC pulmonary metastases. Over 16 months of follow-up, there was no local recurrence or new metastases on CT. Clinical experience and follow-up in this application of RF ablation remains limited and further studies will be needed to determine the ultimate role of RF ablation in the treatment of metastatic RCC. The use of RF ablation is likely to be limited to a small subset of patients with isolated foci of disease since multifocal disease becomes impractical to treat with local therapy. Although rigid limits are difficult to define, in practice, percutaneous application of RF ablation to more than three to five separate tumors is usually not performed as several ablation sessions are often needed depending on the size of the individual tumors. 

RF ablation has been used as an alternative method for treating certain bone tumors such as painful osteolytic metastatic lesions (Callstrom et al. 2000), osteoid osteoma (Rosenthal et al. 1992,1995,2001), and chondroblastoma (Erickson et al. 2001). 

In their series of 12 adult patients with a single painful osteolytic metastasis, Callstrom et al. (2002) showed onascale of 1 to 10,mean worst pain decreased from 8.4 to 3.1 after treatment. Osteoid osteomas are well suited to RF ablation because they are small, benign, and have finite growth. Approximately 90% of patients with osteoid osteoma are permanently cured after a single treatment. In such patients, percutaneous ablation with radiofrequency is essentially equivalent to operative excision (Rosenthal et al. 1998). 

The aim of this chapter therefore is to describe technical details and the major applications. Furthermore, it will give a short summary of the latest litera-ture-with an emphasis on REA and especially RFA of the liver due to the widespread use of this technique and the clinically accepted indication for RF ablation of liver tumors. 

Fig.39. 3a-c. A 55-year-old male patient with a solitary pulmonary metastasis due to colorectal cancer. The patient did not want to undergo open surgery therefore, RF ablation was performed using CT fluoroscopic guidance (b). Control scan (c) 24-h after treatment showed no complication and the lesion completely covered as indicated by the ground-glass opacities surrounding the metastasis... 

After the initial experience in treatment of hepatic tumours, RF ablation (RFA) was approved as a tissue-sparing, minimally invasive tool for successful tumour eradication resulting in satisfactory survival times in tumours of the kidneys and adrenals, of the lungs, bones, and soft tissue - comparable to surgery even considering the different selection criteria. 

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