Catheter Ablation Without Fulguration: Design and Performance of a New System

A new system is described for catheter ablation which comprises a short time capacitive power source and a specially designed catheter. The aim of the new system is to deliver high voltages with minimal or no arcing and thus avoid the risks associated with barotrauma. The performance of the new system was compared in a saline tank with that of the conventional system. The new system allowed significant increases in delivered voltage, current and energy without arcing. This new system should allow safer catheter ablation.     

Advances in Catheter Ablation use of Unipolar Electrograms

Ventricular tachycardia in man can be eliminated by relatively small lesions in the reentrant circuit. This report includes a review of available energy sources, and methods for localizing arrhythmias. Methods to assure contact and prevent perforation using low frequency electrograms are presented including the new finding of reverse ST deflection with contact. Experience with laser energy in dogs showed discrete homogenous lesions. When compared with DC shock the animals showed far less arrhythmia and the lack of far field effect greatly reduced echo abnomalities in the post shock period. Studies with radiofrequency show ability to produce localized lesions similar to the laser but with a more flexible catheter. Localization requires a correlation of techniques including pacemapping, activation maps and pacing during tachycardia. Early activation (< −60 ms) at times 180–320 ms, with comparable pace to QRS during tachycardia with no change in morphology best localized the slow zone of the reentrant circuit. The low frequency unipolar electrogram from the tip and immediately proximal electrode revealed contact with ST deviation. The distal deviation was always greater than the proximal RV free wall and posterior basal produced depression rather than elevation of the electrogram. While the mechanism of ST reversal with contact is not understood and may relate to the type of indifferent reference used (Wilson central terminal), the ST depression reveals the same information about contact that elevation does in most other areas of the heart studied in our patients.     

Radiofrequency catheter ablation of accessory pathways. Outcome and use of antiarrhythmic drugs during follow-up.

AIMS: The purpose of this study was to assess the acute and long-term success of accessory pathway ablation in a single large-volume centre, concentrating on long-term recurrences and the clinical use of antiarrhythmic drugs. METHODS AND RESULTS: A total of 519 consecutive patients (mean age 40+/-14 years) underwent radiofrequency ablation of manifest or concealed accessory pathways. The patients were seen in the hospital or by the referring physician at 6 and 12 months. Long-term follow-up information was obtained by questionnaire. Pathway conduction was abolished in 476 cases (91.7%). 'Redo' procedures, due to recurrence, were performed in 38 patients (7.3%) and were successful in 30 (78.9%). Follow-up data were obtained from 454 patients (87.5%) with a follow-up duration of 22. 6+/-12.4 months. Among the 398 patients with successful ablations who responded to the questionnaire, 340 (85.4%) were asymptomatic with only 10.6% taking antiarrhythmic drugs. An additional 20 patients (5.0%) had symptoms suspicious of recurrence. In total, 66 out of 398 successfully treated patients (16.6%) were taking antiarrhythmic drugs. Twenty-three out of 56 (41.1%) patients with failed ablations were asymptomatic, 12 of whom (21.4% of patients with failed ablations) had not been administered antiarrhythmic drugs. In the total group of 454 patients with ablation attempts and available follow-up data, 99 (21.8%) were still taking antiarrhythmic drugs during follow-up. CONCLUSIONS: Patients with successful ablation of accessory pathways show excellent long-term results. However, 17% of successfully treated patients were still taking antiarrhythmic drugs during the period of long-term follow-up. On the other hand, 21% of patients with failed ablations were symptom-free without antiarrhythmic drugs. On an intention-to-treat basis, 22% of the patients with ablation attempts were still taking antiarrhythmic drugs during follow-up.     

Major complications of ultrasound-guided percutaneous radiofrequency ablations for liver malignancies: Single center experience

Background and Aim:  Despite radiofrequency ablation (RFA) for malignant liver nodular lesions having promising therapeutic effects, the trade-off between the risks and benefits must be acceptable. This study analyzed the major complications of ultrasound (US)-guided percutaneous RFA procedures encountered at a single center, by a single physician.
Methods:  A total of 104 patients (total 183 tumors) underwent 172 US-guided percutaneous RFA sessions between May 2003 and March 2006. The definition of major complications was according to the standardized Society of Interventional Radiology grading system (classification C-E).
Results:  Eighty-six patients had hepatocellular carcinoma (HCC) and 18 patients had hepatic metastatic tumors. Nine major complications occurred from 172 RFA sessions (9/172, incidence of 5.2% per session); namely, two cases of transient liver function impairment, two cases of infection (liver abscess and septicemia), two cases of tumor seeding along the ablated track, one case of colon perforation, one case of acalculous cholecystitis and, lastly, a case of hemocholecyst. We further analyzed the possible risk factors precipitating these complications, and found that only tumor size (Pearson's correlation coefficient, 0.324; P  < 0.05) and baseline liver function reserve (compensated 0%, 0/148 vs decompensated 8.3%, 2/24; P  = 0.019) were significant factors for the complication of transient liver function impairment.
Conclusion:  Radiofrequency ablation for liver malignancy is a safe procedure with acceptable incidence of complications. Decompensated baseline liver function reserve and large tumor size are precipitating factors for transient liver function impairment after RFA and warrant a close follow up.     

Bundle Branch Reentrant Tachycardia Treated by Transvenous Catheter Ablation of the Right Bundle Branch

Recurrent episodes of ventricuiar tachycardia not responding to medical treatment occurred in a 56-year-old man. Electrophysiological investigation showed ventricular tachycardia due to bundle branch reentry. Using a method similar to catheter ablation of the atrioventricular junction, ablation of the right bundle branch was performed by an electrical shock of 250 joules. While before the ablation ventricular tachycardia occurred several times a day and its induction by programmed ventricular stimulation was facilitated by the administration of antiarrhythmic drugs, no initiation of ventricular tachycardia was possible after ablation of the right bundle branch. Over a follow-up of 30 months the patient has not suffered from tachycardia and the right bundle branch block persists.     

Assessment of Effects of a Radiofrequency Energy Field and Thermistor Location in an Electrode Catheter on the Accuracy of Temperature Measurement

Accurate measurement of temperature at the interface of the delivery electrode and the tissue during transcatheter delivery of radiofrequency energy (RFE) for ablation would provide better control of lesion production. Electromagnetic energy fields can affect the accuracy of temperature measurement with thermistors. An electrode probe was fabricated with a thermistor and an optical sensor in the center of the delivery electrode. Simultaneous temperature measurements during RFE delivery to cardiac tissue in the 37°C bath showed good agreement between the sensors, indicating that the RFE field did not cause errors in thermistor temperature measurements with the electrode probe used. A second electrode probe was designed to determine optimal thermistor location. It was constructed using two thermistors with identical temperature-resistance curves. One thermistor protruded through a hole in the side of the delivery electrode and was thermally isolated from it. The other thermistor was bonded to the inner surface of the electrode with heat conductive epoxy. The electrode was placed in contact with cardiac tissue in a 37°C bath of flowing saline with the protruding thermistor centered in the area to be heated. Temperatures measured at steady state during RFE delivery with the protruding thermistor were consistently higher than those of the inner wall thermistor, ranging from 1.8°C difference at 46°C to 8.3°C difference at 75°C interface temperature. The thermistor must be in contact with the tissue and thermally isolated from the delivery electrode for accurate determination of electrode/tissue interface temperature.     

Quality assurance and radiofrequency heating

This paper proposes an inexpensive means of assessing radiofrequency (RF) power deposition in a magnet. This is particularly important at 3T where sequences approach Food and Drug Administration approved RF limits. It will also be of interest to operators at 1.5 T as part of their ongoing quality assurance programs. At 3T, we found that the RF power deposited in the magnet was less than that read by the MR power monitor.