Randomized comparison of efficacy of cooled tip catheter ablation of atrial flutter: anatomic versus electrophysiological complete isthmus block.

There is a subset of patients with failed ablation of the cavotricuspid isthmus (CTI) using standard catheters and with 10% of the patients having recurrences. The purpose of this study was to compare the cooled and standard ablation with regard to acute successful electrophysiological achievement of bidirectional isthmus block and the subacute anatomic characteristics of the lesions. This randomized, experimental study compares the effects of ablation on the isthmus using a cooled catheter with those of a standard ablation catheter in 16 pigs. In 12 animals, CTI block was achieved after ablation (8/8 cooled and 4/8 standard). In two animals, it was not possible to achieve complete isthmus block and two had persistent slow conduction (all four using the standard catheter). After 1 week, the animals were slaughtered. The size of the lesion was greater with the irrigated tip catheters. Transmural lesions were found in 14 animals. A complete line of anatomic isthmus block was not documented after thefirst line in six animals, four with the standard and two with the cooled catheter. A conduction block was never present across gaps > or = 5 mm. In conclusion cooled catheters achieved a complete line of electrophysiological and anatomical block in a significantly higher percentage than the standard catheters.

[Evaluation of the anatomopathological characteristics and the safety of radiofrequency lesions at the atrial level with two different systems of irrigated tip catheters on an experimental level]. / Estudio de las características anatomopatológicas y la seguridad de las lesiones producidas en la aurícula con dos diferentes sistemas de catéteres de punta irrigada en un modelo experimental.

INTRODUCTION AND OBJECTIVES: We performed this study to evaluate the security and efficacy in the lesions produced on the atrial wall by different irrigated catheters in an experimental model. We evaluated the anatomopathologic characteristics of the lesions produced by two different systems of irrigated tip catheters, with opened or closed circuit. METHODS: This study was performed in 16 pigs applying 60 sec radiofrequency pulses with three different energy levels (15, 25 y 50 Watts). Two different systems of radiofrequency ablation irrigated catheters were used, opened and closed. We used 4 pigs in which we performed ablation with a standard catheter as a control group. Under fluoroscopic guidance, catheters were placed on the high and low right atrial lateral wall, where lesions were produced. After 7 days, animals were sacrificed for anatomopathological study. RESULTS: A total of 27 lesions were performed with irrigated catheters (11 closed circuit and 16 opened) and 6 with standard catheters in the control group. We did not find significant differences in the lesion characteristics between the two different systems of irrigated tip catheter used, nevertheless lesions performed with the closed system were slightly greater. Th lesions produced with irrigated catheters were always superior in the control group. Transmurality in the free atrial wall is frequent with both systems. We did not see any perforation in the atrial wall. CONCLUSIONS: We did not find significant differences in the size of the lesions produced with the two systems of irrigated catheters used. These data from an experimental model can provide useful information for atrial tachycardia radiofrequency ablation procedures in humans.

[Macroscopic and microscopic study of the right coronary artery after radiofrequency catheter ablation of cavotricuspid isthmus in an experimental model]. / Estudio macro y microscópico de la arteria coronaria derecha tras ablación con catéter y radiofrecuencia del istmo cavotricuspídeo en un modelo experimental.

INTRODUCTION AND OBJECTIVES: The right coronary artery (RCA) is found in the AV groove, just below the ablation target of atrial flutter, the cavotricuspid isthmus (ICT). After radiofrequency (RF) ablation with standard catheters, there have been no reports of complications, but it may not be successful in 10% of the cases. However, the use of irrigated tip catheters, which create deeper lesions, might potentially damage the coronary tree. METHODS: We analyzed the effects of ICT RF ablation on the coronary tree, with macroscopic and microscopic anatomopathological study. Ablation on ICT was performed using an irrigated tip catheter in 16 pigs and was randomly compared with a standard ablation catheter. There were no clinical problems, modifications of ST or new arrhythmias during the ablation. The heart was extracted at 1 week. RESULTS: The macroscopic study demonstrated that the right coronary artery was preserved, along the ICT, surrounded by the epicardial fat. The microscopic study showed an inflammatory reaction in the epicardial fat that reached the adventitia of the coronary artery, but never produced necrosis in 14 cases. The muscular wall of the artery had signs of focal inflammation without endothelium involvement in 2 cases. However, we found a subepicardial vein completely damaged by the radiofrequency. CONCLUSIONS: Although the right coronary artery is located just below the isthmus, no necrosis was observed in any case. However, there was an inflammatory reaction that focally reached the muscular wall. The veins may be damaged in RF ablation, perhaps due to the different blood flow of each vessel.

[Radiofrequency ablation of recurrent monomorphic ventricular tachycardia in a patient with severe systemic scleroderma]. / Ablación con radiofrecuencia de taquicardia ventricular monomorfa recurrente en una paciente con esclerodermia sistémica severa.

A case of progressive systemic scleroderma in a 33 year-old woman who was referred to our Arrhythmia Unit due to daily palpitations and dizziness is presented. The 24-hour Holter recording showed monomorphic ventricular tachycardia which lasted several minutes. Hemodynamic study showed dilated right chambers and right ventricular dysfunction, without pulmonary hypertension. Left ventricular angiography and coronary arteries were normal. During programmed electrical stimulation, two different ventricular tachycardia were induced and ablated with radiofrequency on the right ventricle. The patient remains free of recurrence of tachycardia after (10 months of follow up). Patients with progressive systemic scleroderma may present several different cardiac arrhythmias. Involvement of the right ventricle is particularly frequent as is the origin of ventricular tachycardia in this ventricle. Radiofrequency catheter ablation is safe and effective in the management of these patients.

[Anatomopathological and biochemical correlation of lesions produced by standard and irrigated 4 mm radiofrequency catheters]. / Correlación anatomopatológica y bioquímica de las lesiones producidas por la radiofrecuencia con catéteres estándar e irrigados de 4 mm.

INTRODUCTION AND OBJECTIVES: The influence on the size of radiofrequency lesions by cooling of the tip of the electrode remains unclear. Moreover, the possible effects of two different cooling systems, closed and open, have not been well differentiated. We designed this study to compare both systems of irrigated-tip catheters and the lesions produced with standard 4 mm catheters and also to evaluate the pathological and biochemical marker release correlation (cardiac troponin I) in an experimental model. METHODS: The study was performed in 20 pigs. Applying between 1-8 radiofrequency pulses, at a power of 15, 25 or 50 watts, for 15-60 seconds to each animal. After 7 days, the pigs were sacrificed for anatomopathological study. RESULTS: A total of 54 lesions were produced, 25 with standard catheters and 29 with irrigated catheters. The mean volume of the lesions produced with standard catheters was 146 +/- 110 microl and with irrigated-tip catheters 856 +/- 864 microl (p < 0.001). Peak values of cardiac troponin I were also higher for irrigated catheters (18 +/- 15 ng/ml) than for standard (6.5 +/- 3 ng/ml). The correlation between the size of the lesion and the levels of cardiac troponin I were 0.86 and 0.79 with the standard and irrigated-tip catheters, respectively. The incidence of cratering was higher with standard catheters (60%) than with irrigated (27%). CONCLUSIONS: The lesions produced with an irrigated catheter are greater than those observed with standard catheters. The mean peak value of postablation cardiac troponin demonstrate a good correlation with the real size of the necrosis.

Internal low-energy cardioversion: a therapeutic option for restoring sinus rhythm in chronic atrial fibrillation after failure of external cardioversion.

AIMS: Conventional external cardioversion remains the technique of choice for restoration of sinus rhythm in patients with chronic atrial fibrillation (AF). Recent reports have suggested that internal low-energy cardioversion is efficient and safe in terminating AF in patients with failed external cardioversion. METHODS AND RESULTS: In 20 of 118 consecutive patients with spontaneous chronic AF (>7/days), who underwent low-energy cardioversion, one or more attempts at restoring sinus rhythm with external cardioversion had failed. Low-energy internal cardioversion was performed under light sedation. Shocks were delivered (using an external custom defibrillator) between two nonapolar catheters positioned in the right atrium (cathode) and in the coronary sinus (anode). Heart disease was present in 12 and absent in eight patients ('lone' atrial fibrillation). Atrial fibrillation was established for a period ranging from 12 days to 53 months. Low-energy internal cardioversion restored sinus rhythm in 15 of the 20 patients (75%) with a mean energy of 4.5+/-1.2 J, a mean conversion voltage of 355+/-53 V and a mean impedance of 63+/-8 ohms. No complications were observed. With a mean follow-up of 6+/-7 months, 11 patients (73%) were in stable sinus rhythm. CONCLUSIONS: This study provides evidence in support of low-energy internal cardioversion as a valuable therapeutic option in patients in whom conventional external cardioversion failed. This technique is safe and does not require general anaesthesia.

Tolerance to lower body negative pressure exposure: comparison between patients with neurocardiogenic syncope and controls.

Lower body negative pressure exposure (LBNPE) produces hemodynamic modifications similar to those produced by head-up tilt test (HUT). Patients with vasovagal syncope are more susceptible to HUT than healthy persons. The supine position during LBNPE would facilitate the simultaneous performance of complementary methods. The aim of this study was to compare tolerance to LBNPE between a group of patients with vasovagal syncope and a group of healthy volunteers. Eleven patients with vasovagal syncope and positive HUT and 13 healthy volunteers without prior history of syncope and negative HUT were included. The following protocol was used: -10 mmHg, 1 minute; -20 mmHg, 1 minute; -30 mmHg, 3 minutes, and -40, -50, -60, and -70 mmHg, 5 minutes for each stage. Tolerance was expressed as: maximum tolerated negative pressure (Max NP), maximum tolerated time (Max T), and sigma P x T, where P = pressure and T = time. Syncope or presyncope during the test was considered positive LBNPE. LBNPE was positive at -50 or -60 mmHg in 8 of 11 patients (73%). One healthy volunteer had presyncope after 5 minutes at -70 mmHg. Tolerance, as expressed by any of the three parameters, was significantly higher for the healthy volunteers (Max NP: -59.1 +/- 7.9 vs -70, P < 0.01; Max T: 19.1 +/- 4.2 vs 24.4 +/- 0.3, P < 0.01; sigma P x T: 836.3 +/- 269.5 vs 1214.6 +/- 18, P < 0.01). We conclude that patients with neurocardiogenic syncope have a significantly lower tolerance to LBNPE than subjects with no previous history of syncope.

[Cardioversion of atrial fibrillation with low energy internal electric shock]. / Cardioversion par choc électrique interne à basse énergie de la fibrillation auriculaire.

The efficacy and safety of low internal cardioversion for the reduction of atrial fibrillation was assessed prospectively in 104 consecutive patients. Sixty-two patients had chronic atrial fibrillation (Group I). 16 patients had paroxysmal atrial fibrillation (Group II) and 26 patients had induced atrial fibrillation (Group III). The average duration of the current episode of atrial fibrillation was 9 +/- 19 months in Group I, 4 +/- 2 days in Group II and 18 +/- 7 minutes in Group III. Two intracardiac defibrillation catheters were used, one (the cathode) in the right atrium and the other in the coronary sinus or left branch of the pulmonary artery (anode). These catheters were connected to an external defibrillator delivering biphasic 3/3 ms shocks with a voltage which could be programmed from 10 to 400 volts. The shocks were synchronised on the R wave. Sinus rhythm was restored in 44 of the 62 patients in Group I (70%), 12 of the 16 patients in Group II (75%) and 20 of the 26 patients in Group III (77%). The average voltages and energies restoring sinus rhythm were 300 +/- 68 volts and 3.5 +/- 1.5 joules respectively in Group I, 245 +/- 72 volts and 2.0 +/- 2.9 joules in Group II, and 270 +/- 67 volts and 2.6 +/- 1.2 joules in Group III. These results show that the energy required to restore sinus rhythm is significantly greater in patients with chronic atrial fibrillation than in patients with paroxysmal or induced atrial fibrillation. There were no ventricular proarrhythmic effects in the 686 shocks synchronised on the R wave. This study shows that internal cardioversion of atrial fibrillation is feasible with low energies under simple sedation. These results support the concept of an implantable atrial defibrillator.

Transvenous cardioversion of atrial fibrillation using low-energy shocks.

Recent reports have suggested that transvenous cardioversion of atrial fibrillation is feasible using low-energy shocks and a right atrium coronary sinus electrode configuration. We evaluated in a prospective study the efficacy and safety of low-energy internal cardioversion of atrial fibrillation in 104 consecutive patients. Sixty-two patients presented with chronic atrial fibrillation (group I), 16 had paroxysmal atrial fibrillation (group II), and 26 had an induced atrial fibrillation episode (group III). The mean duration of the presenting episode of atrial fibrillation was 9 +/- 19 months for group I, 4 +/- 2 days for group II, and 18 +/- 7 minutes for group III. Atrial defibrillation was performed using two intracardiac catheters: one was placed in the right atrium (cathode) and the other in the coronary sinus or in the left branch of the pulmonary artery (anode). The catheters were connected to a customized external defibrillator capable of delivering 3/3-ms biphasic waveform shocks with a voltage programmable between 10 and 400 volts. The shocks were synchronized to the R wave. Sinus rhythm was restored in 44 of the 62 patients in group I (70%), in 12 of the 16 patients in group II (75%), and in 20 of 26 patients in group III (77%). The mean voltage and energy required for cardioversion were respectively 300 +/- 68 V and 3.5 +/- 1.5 J, for group I, 245 +/- 72 V and 2.0 +/- 0.9 J for group II, and 270 +/- 67 V and 2.6 +/- 1.2 J for group III. The leading-edge voltage required for sinus rhythm restoration was significantly higher (p < 0.05) in the chronic atrial fibrillation group than in the paroxysmal or induced groups. No proarrhythmic effects occurred for the delivered 686 R-wave synchronized shocks. This study of a large group of patients confirms and extends the results of previous reports. Such findings may have clinical implications for elective cardioversion of atrial fibrillation and the development of an implantable atrial defibrillator.