[Tachycardia-induced tachycardia: definitive treatment with radiofrequency ablation. Presentation of three cases]. / Taquicardia que induce taquicardia: tratamiento definitivo con ablación con radiofrecuencia. Presentación de tres casos.

Tachycardia-induced tachycardia is the phenomenon in which one tachycardia degenerates into another. Few data are available in patients suffering from AV nodal reentrant tachycardia an atrial fibrillation. For related to AV nodal reentrant triggered by tachycardia; there is a possible effective treatment by eliminating the slow nodal pathway, with radiofrequency ablation, as shown by other authors. In this study we present data on three patients with repeated episodes of documented atrial fibrillation and at least one episode of AV nodal reentrant tachycardia or regular palpitations. Radiofrequency ablation of the slow AV nodal pathway was successfully performed in both, and at a follow up of 6, 9 and 10 months, respectively, no new episode of AV nodal reentrant tachycardia or atrial fibrillation was documented.

Endocardial and epicardial ablation guided by nonsurgical transthoracic epicardial mapping to treat recurrent ventricular tachycardia.

INTRODUCTION: An epicardial site of origin of ventricular tachycardia (VT) may explain unsuccessful endocardial radiofrequency (RF) catheter ablation. A new technique to map the epicardial surface of the heart through pericardial puncture was presented recently and opened the possibility of using epicardial mapping to guide endocardial ablation or epicardial catheter ablation. We report the efficacy and safety of these two approaches to treat 10 consecutive patients with VT and Chagas' disease. METHODS AND RESULTS: Epicardial mapping was carried out with a regular steerable catheter introduced into the pericardial space. An epicardial circuit was found in 14 of 18 mapable VTs induced in 10 patients. Epicardial mapping was used to guide endocardial ablation in 4 patients and epicardial ablation in 6. The epicardial earliest activation site occurred 107+/-60 msec earlier than the onset of the QRS complex. At the epicardial site used to guide endocardial ablation, earliest activation occurred 75+/-55 msec before the QRS complex. Epicardial mid-diastolic potentials and/or continuous electrical activity were seen in 7 patients. After 4.8+/-2.9 seconds of epicardial RF applications, VT was rendered noninducible. Hemopericardium requiring drainage occurred in 1 patient; 3 others developed pericardial friction without hemopericardium. Patients remain asymptomatic 5 to 9 months after the procedure. Interruption during endocardial pulses occurred after 20.2+/-14 seconds (P = 0.004), but VT was always reinducible and the patients experienced a poor outcome. CONCLUSION: Epicardial mapping does not enhance the effectiveness of endocardial pulses of RF. Epicardial applications of RF energy can safely and effectively treat patients with VT and Chagas' disease.

Reduction of radiation exposure time during catheter ablation with the use of pulsed fluoroscopy.

UNLABELLED: Prolonged exposure to radiation during radiofrequency catheter ablation implies a potential risk of radiodermatitis, neoplasm and genetic defects to the patient and to the operator-physician. The use of pulsed fluoroscopy is thought to reduce such a risk because the radiation dose decreases for the same period of time. The aim of the present study was to compare the radiation exposure time during pulse and continuous radiofrequency catheter ablation. METHODS: Procedures were divided according to the sort of fluoroscopy utilized and the last four cases of atrioventricular (AV) junction ablation, four of atrial flutter, five of atrial tachycardia, 16 of AV node reentrant tachycardia, 16 of AV tachycardia and 10 of ventricular tachycardia in which pulsed and continuous fluoroscopy were utilized were respectively separated into Group I (pulse fluoroscopy) and Group II (continuous fluoroscopy) with 55 patients in each group. Fluoroscopy was generated by the same device in the two groups. Continuous fluoroscopy used 2 mA and automatic kV adjustment (automatic brightness stabilizer) ranging from 70 to 110 kV. Pulsed fluoroscopy was set at 7 squares/s with 25 mA and automatic kV adjustment. Fluoroscopy time was registered by the fluoroscopy device counter. RESULTS: Procedure duration, success rate and complications did not differ between Groups I and II. Fluoroscopy time, however, was 4.4+/-4 min during pulsed fluoroscopy and 27+/-23 min during continuous fluoroscopy (p=0.001). CONCLUSION: During radiofrequency catheter ablation procedures, the use of pulsed fluoroscopy set at 7 squares/s, decreases the radiation exposure time by 80% as compared to continuous fluoroscopy without changing procedure duration and success rate.

[Type I atrial flutter radiofrequency ablation. Importance of bidirectional block of isthmus between the inferior vena cava and of tricuspid valve ring]. / Ablação com radiofreqüência do Flutter atrial tipo I. Importância do bloqueio bidirecional do istmo entre a veia cava inferior e o anel da valva tricúspide.

PURPOSE: To determine the clinical importance of a bi-directional line of block demonstration in the inferior vena cava-tricuspid annulus isthmus as an end-point for radiofrequency (RF) atrial flutter (FL) ablation. METHODS: Forty consecutive patients (51 +/- 11 years) with type I FL were divided in 2 groups: GI (30 patients) anatomic, non-electrophysiologic isthmus ablation technique (interruption and non-induction FL criteria); and GII (10 patients) anatomic with electrophysiologic evaluation of bi-directional isthmus conduction. The isthmus activation was analyzed before and after anatomic RF ablation with a cateter exploring each side of the line of block, depending on the conduction evaluation (anterograde or retrograde). RESULTS: FL was interrupted and not reinduced in 26/ 30 (86.6%) GI patients and in 10 (100%) GII patients (p = 0.5558). During follow-up FL recurred in 30% of the patients in both groups. In GII, 6 patients with bi-directional block remained assymptomatic, whereas 3 patients with unidirectional block presented recurrence (p = 0.012). CONCLUSION: Electrophysiologic demonstration of bidirectional line of block in the isthmus is related to long-term success and should be the criterion for interruption of type I atrial FL RF ablation.