Additional Radiofrequency Ablation Research Articles

How to manage the patients with unsatisfactory results after ethanol ablation for thyroid nodules: Role of radiofrequency ablation

Although ethanol ablation (EA) is effective in the treatment of cystic thyroid nodules, it is less effective in nodules with solid component. Therefore refractory cases with solid component require another treatment modality such as radiofrequency ablation (RFA), which is effective in both solid and cystic thyroid nodules. We prospectively evaluated the efficacy of additional RFA and factors related to volume reduction in patients showing unsatisfactory results after a single session of EA. Of 94 patients with predominantly cystic thyroid nodules who underwent EA, 20 patients underwent additional RFA because of incompletely resolved clinical problems (symptomatic score reduction <50%) and presence of residual solid component at 1-month follow-up on ultrasonography. Improvement of clinical symptoms and nodule volume reduction were evaluated 6 month later. We evaluated factors related to nodule volume reduction after EA and RFA. RFA after a single session of EA was effective in reducing mean symptom score from 4.8 to 1.1 (p<0.001), mean cosmetic score from 3.5 to 1.4 (p<0.001) and mean nodule volume from 11.3 to 0.9 mL (p<0.001). The only independent factor related to volume reduction after EA was the presence of a solid component (p<0.001), and EA was less effective in nodules when solid component >20% (p=0.001). We identified no factors related to volume reduction after RFA. RFA is effective in treatment of benign predominantly cystic thyroid nodules in patients whose clinical problems were incompletely resolved after EA.

Application of contrast-enhanced ultrasonography after radiofrequency ablation for renal cell carcinoma: is it sufficient for assessment of therapeutic response?

To assess the efficacy of contrast-enhanced ultrasonography (CEUS) with Sonovue in the evaluation of therapeutic response to radiofrequency ablation (RFA) of renal cell carcinoma (RCC). In a recent 3 years, 63 patients (mean age, 60 years; range 26-81 years) with 64 RCCs were treated by RFA. The lesions had a diameter between 1.8 and 9.8 cm (average diameter, 3.1 cm). The indications for RFA treatment included chronic renal insufficiency (n = 10), presence of solitary kidney (n =3), bilateral renal carcinoma (BRCC) (n =2), advanced age (n =12), significant medical comorbidity (n =29) or refusal of conventional therapy (n =7). Tumors were treated by laparoscopy-assisted (n =41), open surgical (n =18) or percutaneous US guidance (n =4). Follow-up CEUS and contrast-enhanced CT were performed 1 month after treatment to assess the necrotic area. Technical success was defined as elimination of areas that enhanced at imaging within the entire tumor. On the 1-month CEUS and CT imaging after RFA, 62 of 64 tumors (96.9%) were successfully ablated with one session, and residual tumors were found in two RCCs. One of the two tumors was subjected to additional RFA treatment. We could not obtain a complete ablation in the other tumor of a patient with solitary kidney. The diagnostic concordance between the CEUS and 1-month follow-up CT was 100%. Sixty-one patients survived in the follow-up phase which ranged from 2 to 34 months. One patient with solitary kidney died of systemic disease progression and one patient was lost to follow-up. Of the 61 tumors without residual on both CT and CEUS after RFA, four had suspicious findings of recurrence on follow-up CEUS, and two of them were confirmed by subsequent CT examination. With CT as the reference imaging procedure in the assessment of renal tumor ablation, the sensitivity, specificity, positive predictive value, and negative predictive value of CEUS for detecting recurrence during follow-up were 100%, 96.6%, 50%, and 100%. Despite its limitation of false-positive value, CEUS is potentially effective in assessing the therapeutic response to RFA of RCC.

Outcomes of Radiofrequency Ablation for Barrettʼs Esophagus

Purpose: Endoscopic ablation therapy is increasingly used in Barrett's esophagus (BE), including radio frequency ablation (RFA). The study aim was to investigate overall outcomes for our BE patients treated with RFA. Methods: Patients referred for treatment of BE underwent evaluation including endoscopic resection (EMR) and subsequent RFA therapy. We analyzed results for all patients with at least 6 months follow up data. Patients treated with other ablation methods were excluded. Demographics, endoscopic and histologic findings, complications, and outcomes were analyzed. Results: We identified 45 patients (40 men) treated for BE - no dysplasia (3), LGD (14), HGD/Ca (28) with a mean follow up of 19 months (6.6-46 mts). Mean age was 67 years (46-80 yrs), with mean max. BE segment length 5.5 cm (0.6-17 cm). 13 patients underwent prior mucosal resection. Of 127 total RFA treatments, 30 were circumferential and 97 were focal ablations (mean 2.8 RFA/patient). Overall results are summarized in the Table. 29 patients (65%) had complete resolution of intestinal metaplasia (CR-IM), 9% complete resolution of dysplasia (CR-D), 13% complete resolution of high-grade dysplasia/cancer (CR-HGD). Histology grade was unchanged in 6 patients (13%; 3 LGD, 3 HGD) with very long segments (mean 8.1 cm) after a mean 2.2 RFAs. Analysis based on initial dysplasia grade found CR-IM in all 3 patients without dysplasia (100%), 9/14 LGD patients (64%), and 17/28 HGD/Cancer patients (61%). Complications were limited to strictures in 11 patients (24%), although only 2 were severe, requiring 4 dilations each. Biopsies prior to RFAs of 17 irregular z-lines in 13 patients subsequently showed normal histology. One mild stricture was associated with these additional RFA's that resolved without dilation. Conclusion: RFA is an effective treatment for Barrett's metaplasia and dysplasia especially in shorter BE segments where CR-IM was achieved in <3 RFA treatments. Patients with high-grade dysplasia and longer BE segments required more treatments and are at risk for persistent, RFA-refractory disease that may require EMR or alternative ablation therapies. Patients with unchanged dysplasia grade had the longest BE segments suggesting the most difficult disease for RFA, however, they had the shortest follow up and fewest RFAs to date. Endoscopic assessment of irregular Z lines for complete ablation is unreliable and led to 17 additional RFA's that were performed immediately after biopsies that subsequently found no evidence of BE.Table: [1137] Overall RFA outcomes

Linear Ablation of Right Atrial Free Wall Flutter: Demonstration of Bidirectional Conduction Block as an Endpoint Associated With Long‐Term Success

Ablation for atypical atrial flutter (AFL) is often performed during tachycardia, with termination or noninducibility of AFL as the endpoint. Termination alone is, however, an inadequate endpoint for typical AFL ablation, where incomplete isthmus block leads to high recurrence rates. We assessed conduction block across a low lateral right atrial (RA) ablation line (LRA) from free wall scar to the inferior vena cava (IVC) or tricuspid annulus in 11 consecutive patients with atypical RA free wall flutter. LRA block was assessed following termination of AFL, by pacing from the ablation catheter in the low lateral RA posterior to the ablation line and recording the sequence and timing of activation anterior to the line with a duodecapole catheter, and vice versa for bidirectional block. LRA block resulted in a high to low activation pattern on the halo and a mean conduction time of 201 +/- 48 ms to distal halo. LRA conduction block was present in only 2 out of 6 patients after termination of AFL by ablation. Ablation was performed during sinus rhythm (SR) in 9 patients to achieve LRA conduction block. No recurrence of AFL was observed at long-term follow-up (22 +/- 12 months); 3 patients developed AF. Termination of right free wall flutter is often associated with persistent LRA conduction and additional radiofrequency ablation (RFA) in SR is usually required. Low RA pacing may be used to assess LRA conduction block and offers a robust endpoint for atypical RA free wall flutter ablation, which results in a high long-term cure rate.

Radiofrequency Ablation (RFA) of Benign Thyroid Nodules in Patients with Incompletely Resolved Clinical Problems after Ethanol Ablation (EA)

Although ethanol ablation (EA) is effective, refractory cases have been reported in 5-25% of patients, with a marked decline in efficacy on subsequent reattempt. The aim of this study was to evaluate the role of radiofrequency ablation (RFA) after EA of benign thyroid nodules in patients with incompletely resolved initial clinical problems. Among 137 patients with 137 benign thyroid nodules who underwent EA, 27 patients (M:F = 5:22; mean age = 38 years, range = 21-60 years) underwent additional RFA if all of the following criteria were fulfilled: (1) complaint of incompletely resolved clinical problems, (2) demonstration of remaining solid component with internal vascularity on 1-month follow-up power Doppler US, and (3) patient desire for additional treatment. After RFA, there was improvement of clinical symptoms and characteristics and volume reduction of the treated nodules as seen on US; complications were evaluated at each follow-up. The mean follow-up duration was 21.2 months (range = 6-38 months) after RFA. The mean symptom grading score of 10-cm visual analog scale, the mean cosmetic grading score on a 4-point scale, and the mean volume reduction of thyroid nodules were all significantly decreased from those seen before RFA (2.4-1.1, 3.7-1.5, and 4.2-1.1, respectively) (P < 0.05). There were no major complications. RFA is an effective and safe method for treating benign thyroid nodules in patients with incompletely resolved clinical problems following EA.

The difference in autonomic denervation and its effect on atrial fibrillation recurrence between the standard segmental and circumferential pulmonary vein isolation techniques

This study examined the difference in autonomic modification (AM) and its effect on paroxysmal atrial fibrillation (PAF) recurrence between segmental pulmonary vein isolation (S-PVI) and circumferential PVI (C-PVI). Successful S-PVI or C-PVI with a basket catheter was achieved in 120 consecutive PAF patients. Serial 24 Holter-recordings were obtained before, immediately, and 1, 3, 6, 12 months after the PVI to analyse the heart rate variability (HRV). Nineteen patients were excluded from analysis because of additional ablation for recurrent PAF after successful PVI. Among the residual 101 patients, 33 had PAF recurrences (S-PVI = 44.0%, C-PVI = 21.6%) at 1 year of follow-up. The root mean square of successive differences and high-frequency power reflecting parasympathetic nervous activity were significantly lower in patients with and without PAF recurrences after C-PVI and patients without PAF recurrences after S-PVI than patients with PAF recurrences after S-PVI (P < 0.005-0.0001). However, there were no significant differences in any HRV parameters in the immediate aftermath of PVI among the patients without PAF recurrences after S-PVI and those with and without PAF recurrences after C-PVI. Although additional radiofrequency ablation for AM may be recommended after S-PVI to reduce PAF recurrences, it should be carefully determined after C-PVI.

Radiofrequency ablation for renal tumors: Our experience

To report our results of percutaneous radiofrequency ablation (RFA) for renal tumors and to assess predictors of therapeutic efficacy. Forty patients (median age 73 years) with renal tumors were treated with RFA under local or epidural anesthesia. All of them had high surgical risk or refused radical surgery. Tumors were punctured percutaneously using the Radionics Cool-tip RF System under computed tomography or ultrasonographic guidance. Median tumor diameter was 24 mm. After RFA, contrast-enhanced computed tomography or magnetic resonance imaging was performed within 1 month. Complete response (CR) was defined as no enhancement inside the tumor. Factors related to the outcome and to renal function were assessed. Median follow up was 16 months. CR was observed in 34 cases (85.0%). A significant difference in CR rate was observed between tumors < or =30 mm and those >30 mm. Outcomes tended to be better for tumors in the mid to lower kidney, and those away from the renal hilum. Recurrence was observed in one case (2.9%), but a CR was obtained again by additional RFA. Out of a total of 77 RFA procedures, complications occurred in only three cases (3.9%), and conservative treatment was possible in all cases. Serum creatinine levels 3 months after RFA did not differ from those before RFA. Percutaneous RFA is a safe and effective treatment for small renal tumors in patients with high surgical risk or who refuse radical surgery.

A unique iatrogenic organized left atrial tachycardia with a gap conduction in previously ablated lesions

This case concerns a 57-year-old woman with an organized left atrial tachycardia (AT) after pulmonary vein (PV) isolation. The left inferior PV (LIPV) exhibited a figure of eight tachycardia around the LIPV ostium with one loop at the anterior aspect and another at the posterior aspect, which corresponded to regular surface P waves. Although a gap ablation of fractionated electrograms changed the LIPV sequence, the atrial potentials were organized with a shortened cycle length accompanied by the same surface P-wave morphology. The elimination of the anterior loop and modification of the posterior loop after the gap ablation might have yielded that specific sequence change of the AT.

Arrhythmogenic Potential of Pulmonary Venous Tissue: Triggers for Atrial Fibrillation Identified within the Remnant of a Vein

Pulmonary veins (PVs) have frequently been identified as triggers for atrial fibrillation (AF), and higher arrhythmogenic potential of superior PVs has been attributed to their larger size, which can more rigorously support abnormalities of impulse formation and/or conduction. Contrary to this belief, we report our observations in a 63-year-old patient with history of lung cancer, S/P left upper lobectomy, undergoing ablation for paroxysmal AF. Circular mapping (Lasso) and ablation (ABL; 8-mm) catheters were deployed in left atrium (LA). Intracardiac ultrasound revealed separate right superior (RS) and inferior (RI) PVs and a single left PV. Segmented LA anatomy from the CT angiogram images corroborated this, although on the latter there appeared to be a "stump" at superior aspect of the left PV. This stump likely was the remnant of the left superior (LS) PV. Thus, the patent left vein was likely the dilated left inferior (LI) PV. With the Lasso and ABL deployed at the LIPV ostium and LSPV remnant, respectively, AF was reproducibly seen to initiate with earliest activity in the latter. Single radio-frequency ablation (RFA) lesion within the LSPV remnant abolished AF triggers. Additional RFA was done to isolate LI, RS, and RI PVs. Over a follow-up period of 24 months, this patient has remained free from AF off any drugs. Our observations suggest that even very proximal remnants of PVs can serve as triggers for AF. Recognition of this phenomenon was facilitated by the use of advanced imaging technique and the deployment of multiple catheters.

Combined Resection And Radiofrequency Ablation For Bilobar Liver Metastases

Introduction: Surgical resection remains the only potential curative treatment for colorectal cancer liver metastases (CRCLM). Bilobar disease was traditionally considered unresectable. Novel techniques such as radiofrequency-ablation (RFA) have been employed as an adjunct to traditional hepatic resection, however few have reported outcomes using this approach. The present study's aim is to report our experience of hepatic resection combined with intra-operative RFA in patients with initially unresectable bilobar CRCLM compared with patients who underwent simple resection of unilobar metastases. Patients: 95 patients underwent resection for CRCLM between 2000-2007. Of these 16 patients had additional RFA for bilobar disease at the time of resection. The majority of the total population were > 75 years (83%), male (57%), had metachronous disease (64%) and a single liver metastasis (57%). Those who had additional RFA had a median number of liver metastases of 3 (2-7). Results: Median follow-up of the survivors was 26.7 months (24.4 months for RFA plus resection and 31.4 months for resection alone); during which 48 died, 44 from recurrent cancer. Median hospital stay was 11 days for both groups. 30-day morbidity rate was 25% for each group. There was no peri-operative mortality. Acturial 3-year survival rates were 50% for liver resection alone and 54% for RFA plus resection. One patient who underwent RFA plus resection is alive at 57 months. Conclusions: In our experience those who undergo RFA plus resection for bilobar liver metastases can achieve perioperative and survival outcomes comparable to patients who have resection alone for unilobar metastases.

Radiofrequency Ablation for an Autonomously Functioning Thyroid Nodule

Radiofrequency Ablation for an Autonomously Functioning Thyroid Nodule

Therapeutic response assessment of percutaneous radiofrequency ablation for hepatocellular carcinoma: Utility of contrast-enhanced agent detection imaging

Purpose: To assess the utility of contrast-enhanced agent detection imaging (ADI) in the assessment of the therapeutic response to percutaneous radiofrequency (RF) ablation in patients with hepatocellular carcinoma (HCC). Materials and methods: Ninety patients with a total of 97 nodular HCCs (mean, 2.1 ± 1.3 cm; range, 1.0–5.0 cm) treated with percutaneous RF ablation under the ultrasound guidance were evaluated with contrast-enhanced ADI after receiving an intravenous bolus injection of a microbubble contrast agent (SH U 508A). We obtained serial contrast-enhanced ADI images during the time period from 15 to 90 s after the initiation of the bolus contrast injection. All of the patients underwent a follow-up four-phase helical CT at 1 month after RF ablation, which was then repeated at 2–4 month intervals during a period of at least 12 months. The results of the contrast-enhanced ADI were compared with those of the follow-up CT in terms of the presence or absence of residual unablated tumor and local tumor progression in the treated lesions. Results: On contrast-enhanced ADI, technical success was obtained in 94 (97%) of the 97 HCCs, while residual unablated tumors were found in three HCCs (3%). Two of the three tumors that were suspicious (was not proven) for incomplete ablation were subjected to additional RF ablation. The remaining one enhancing lesion that was suspicious of a residual tumor on contrast-enhanced ADI was revealed to be reactive hyperemia at the 1-month follow-up CT. Therefore; the diagnostic concordance between the contrast-enhanced ADI and 1-month follow-up CT was 99%. Of the 94 ablated HCCs without residual tumors on both the contrast-enhanced ADI and 1-month follow-up CT after the initial RF ablation, five (5%) had CT findings of local tumor progression at a subsequent follow-up CT. Conclusion: Despite its limitations in predicting local tumor progression in the treated tumors, contrast-enhanced ADI is potentially useful for evaluating the early therapeutic effect of percutaneous RF ablation for HCCs.

Transvenous Catheter Cryoablation for Treatment of Atrial Fibrillation:

Pulmonary vein (PV) isolation using radiofrequency (RF) ablation can induce PV stenosis. Cryoablation may offer a safer alternative energy source for PV isolation. PV isolation with cryoablation was attempted in 31 patients with paroxysmal atrial fibrillation (AF). Event monitors were used to measure the AF episode burden. Serial spiral CT scans were obtained to monitor PV stenosis pre- and postcryoablation. Cryoablation was immediately successful for PV isolation in 29 of 31 patients (94%), with 5.9 +/- 1.2 months of follow-up. Additional RF ablation was performed for AF recurrences in seven patients. The remaining 22 patients with a single cryoablation procedure demonstrated a time-dependent, long-term reduction in the frequency of AF episodes. At 6 months of follow-up, 18 of 22 of cryo-treated only patients (82%) were free of symptomatic AF episodes, and antiarrhythmic drugs were discontinued in 12 of 22 patients. Serial spiral CT scans demonstrated no change in the cryo-treated PV ostial diameter. PV cryoablation was effective to control paroxysmal AF in most patients. Early recurrences of AF postcryoablation were common, though tended to resolve within 6 months postablation, consistent with a process of reverse atrial remodeling. Cryoablation of the PVs did not cause PV stenosis or other serious adverse events.

Prevalence and characteristics of idiopathic outflow tract tachycardia with QRS alteration following catheter ablation requiring additional radiofrequency ablation at a different point in the outflow tract.

Subtle variations in QRS morphology occurs during idiopathic outflow tract ventricular tachycardia (OTVT), but no studies have clarified the prevalence and characteristics of the OTVT with altered QRS morphology following radiofrequency catheter ablation (RFA), which then require an additional RF application at a different portion of the outflow tract to abolish OTVT. Of 202 patients with a monomorphic VT or premature ventricular contraction (PVC) originating from the outflow tract, 6 (3%) showed changes in QRS morphology in the OTVT following RFA, requiring an additional RF application to the outflow tract at a different portion. In all six patients, RFA was applied for the first or second OTVT to a right or left ventricular endocardial site, with the other site being the left sinus of Valsalva. In each patient, OTVT before or after the changes in QRS morphology had characteristic ECG findings originating from a particular portion of the outflow tract. Changes in QRS morphology consistently included an increase or decrease in R wave amplitude in all inferior leads. Detailed continuous observation of QRS morphology in OTVT, especially R wave amplitude in inferior leads, is important for identifying changes of QRS morphology during catheter ablation. Mapping and ablation at a different portion of the outflow tract is then needed for cure.

Percutaneous Radiofrequency Ablation of Inoperable Primary Lung Cancer

Purpose: To present the initial experience of percutaneous radiofrequency ablation (RFA) of inoperable primary lung cancer, and to assess the technical feasibility and potential complications. Materials and Methods: Twenty patients with inoperable lung cancer underwent percutaneous RFA. Nineteen of 20 patients had stage III or IV non-small cell lung cancer, and the remaining one had stage I lung cancer with pulmonary dysfunction. The mean tumor size was 4.60.4 cm (range, 1.8-8.4 cm). RFA was performed with a single (n=18) or cluster (n=2) cool-tip RF electrode and a generator under CT guidance using local anesthesia and conscious sedation. Twenty tumors were treated in 28 sessions. Patients were assessed by contrastenhanced CT in all cases at 1 week, 1 month, and 3 months. Eleven patients received chemotherapy (n=10) or radiotherapy (n=1) after RFA. Results: RFA was technically successful and well tolerated in all patients. Complete necrosis was attained in 7 lesions (35%), near complete (90-99%) necrosis in 10 lesions (50%), and partial (50-89%) necrosis in 3 lesions (15%). During the mean follow up of 202 days (21 to 481 days), tumor size was decreased in 13 patients, unchanged in 3, and increased in 4. In the latter four, additional RFA was performed. One patient underwent surgery three months after RFA and the histopathologic findings showed a large cavity with thin fibrotic wall suggestive of complete necrosis. During or after the procedure, pneumothorax (n=10), moderate pain (n=4), blood tinged sputum (n=2), and pneumonia (n=2) were developed. Chest tube drainage was required in only 1 patient due to severe pneumothorax. Other patients were managed conservatively. Seven patients died at 61 to 398 days (mean, 230 days) after RFA. The remaining 13 patients were alive 21 to 481 days (mean, 187 days) after RFA. Conclusion: RFA appears to be a technically feasible and relatively safe procedure for the cytoreductive treatment of inoperable, non-small cell lung cancer and warrants further investigation as a complementary treatment to chemotherapy or radiation therapy.

Recurrent hepatocellular carcinoma: percutaneous radiofrequency ablation after hepatectomy.

To evaluate the therapeutic efficacy and safety of percutaneous radiofrequency (RF) ablation for recurrent hepatocellular carcinoma (HCC) in the liver after hepatectomy. Forty-five patients with 53 recurrent HCC tumors in the liver underwent percutaneous RF ablation with ultrasonographic guidance. All patients had a history of hepatic resection for HCC. The mean diameter of recurrent tumors was 2.1 cm (range, 0.8-4.0 cm). All patients were followed up for at least 10 months after ablation (range, 10-40 months; mean, 23 months). Therapeutic efficacy and complications were evaluated with multiphase helical computed tomography (CT) at regular follow-up visits. Overall and disease-free survival rates were calculated. At follow-up CT after initial RF ablation, 11 (21%) of 53 ablated HCC tumor sites showed residual tumor or local tumor progression. After additional RF ablation, complete ablation of 46 (87%) of 53 tumors was attained. Also at initial follow-up CT, before either additional RF ablation or other treatment was performed, 21 (47%) of 45 patients were found to have 41 new HCC tumors at other liver sites. Of these, nine tumors in eight patients were treatable with a second application of RF ablation. Overall survival rates at 1, 2, and 3 years were 82%, 72%, and 54%, respectively. No deaths or complications requiring further treatment occurred as a result of RF ablation. Percutaneous RF ablation is an effective and safe method for treating recurrent HCC in the liver after hepatectomy, with a good overall patient survival rate.

Alternation of QRS Morphology and Effect of Radiofrequency Ablation in Idiopathic Ventricular Tachycardia

We performed electrophysiological studies in 13 patients with idiopathic VT and attempted radiofrequency (RF) catheter ablation in 4 of them. VT was induced by programmed stimulation in all patients and the mean cycle length was 363 +/- 58 msec. In 8 of 13 patients (62%), alternation of either the cycle length and/or morphology of VT was observed. Transient entrainment was achieved in all patients by rapid pacing from the right ventricular outflow tract so reentry was considered the underlying mechanism of VT. The site of earliest activation (EAS) during VT was located at the apicoposterior portion of the left ventricular septum and used as the target site for RF catheter ablation. Spikelike presystolic activity was detected 20-40 msec prior to the large deflection of the local electrogram in four patients. VT was terminated by a few seconds of RF current in all four patients, but subsequently new VTs with a slightly different morphology were induced in three of them and re-mapping showed a shift of the EAS. After additional RF ablation at the new EAS, VT was no longer induced. No complication was noted and VT did not recur during a follow-up period for a mean of 9.3 +/- 5.2 months. RF catheter ablation seems useful and safe for idiopathic VT. The alternation of QRS morphology and the findings at the time of catheter ablation suggest that an alternative pathway or multiple exists may be present in some patients with idiopathic VT, because the change in VT morphology was associated with a shift of the EAS.