Summary
Background
Radiofrequency ablation (RFA) of outflow tract ventricular ectopic beats (OTVEBs) can be performed using a 4-mm or externally-cooled tip RFA catheter, but no data are available concerning the safety and efficacy of a large-tip (8-mm) catheter.
Aims
To evaluate the feasibility of using an 8-mm tip catheter in patients with OTVEBs.
Methods
In this prospective cohort study, the 8-mm tip catheter was tested in patients who were referred to our centre for RFA of symptomatic OTVEBs.
Results
The mean age of the 16 patients recruited between September 2008 and March 2010 was 53 ± 18 years and 56.3% were male. Mean left ventricular ejection fraction was 62 ± 9%, mean ventricular ectopic beat width was 144 ± 21 ms, and all patients had left bundle branch block. Fourteen patients had inferior axis QRS morphology and two had superior. The main symptoms were palpitations and pre-syncope. RFA parameters were: procedure time 94 ± 35 min; duration of application 11 ± 10 min; impedance 81 ± 12 Ω; temperature 50 ± 5 °C; and power 46 ± 17 W. RFA succeeded in 15 over 16 patients (93.8%); and recurrence was seen in one patient after a mean follow-up time of 11 ± 6 months. No complications were noted.
Conclusions
This preliminary study suggests that an 8-mm tip catheter may represent an alternative for RFA in patients with OTVEBs in whom a 4-mm tip was not successful. Larger randomized studies are therefore warranted.
Résumé
Introduction
L’ablation par radiofréquence des ESV infundibulaires idiopathiques peut être réalisée par des cathéters de radiofréquence 4 mm ou par des cathéters irrigués, mais il n’y a pas, à notre connaissance, d’expérience rapportée dans la littérature avec des cathéters 8-mm.
Objectifs
Évaluer la faisabilité de l’utilisation d’un cathéter 8-mm dans le traitement des ESV infundibulaires idiopathiques.
Méthode
Étude monocentrique sur l’utilisation d’un cathéter 8-mm dans le traitement de patients avec ESV idiopathiques infundibulaires symptomatiques.
Résultats
Seize patients ont été recrutés de septembre 2008 à mars 2010 avec un âge moyen de 53 ± 18 ans et dont 56,3 % étaient des hommes. La fraction d’éjection moyenne était de 62 ± 9 %, la largeur moyenne des ESV était de 144 ± 21 ms, et tous les patients avaient des ESV de type retard gauche. Quatorze patients avaient des QRS avec un axe inférieur, sauf deux qui avaient des QRS avec un axe supérieur. Les principaux symptômes étaient représentés par des palpitations et des lipothymies. Les paramètres de radiofréquence étaient les suivants : temps moyen de procédure 94 ± 35 min ; durée moyenne d’application, 11 ± 10 min ; impédance moyenne 81 ± 12 Ω ; température moyenne 50 ± 5 °C ; et puissance moyenne de 46 ± 17 W. La procédure de radiofréquence a été réalisée avec succès chez 15 patients sur 16 (93,8 %) et une récidive est survenue au cours d’un suivi moyen de 11 ± 6 mois. Aucune complication n’a été constatée.
Conclusions
Cette étude préliminaire suggère que le cathéter de radiofréquence 8-mm tip peut représenter une alternative de traitement des ESV infundibuliares idiopathiques par rapport au cathéter 4-mm tip, cependant, des études randomisées sont requises pour confirmer de tels résultats.
Background
Ventricular ectopic beats (VEBs) are commonly seen in clinical practice. In most cases, they are largely asymptomatic, but may cause upsetting symptoms in some patients . In normal hearts, VEB occurrence is usually of no clinical relevance. However, in some patients, VEBs may cause significant symptoms that need to be addressed by medical treatment or cured using catheter ablation . In such a clinical setting, outflow tract ventricular ectopic beats (OTVEBs) are the most common idiopathic ventricular tachycardias (VTs), accounting for nearly 10% of all patients referred for VT evaluation . In the absence of overt structural heart disease, these rhythm disturbances are classified as “idiopathic” or “normal heart” VTs, mainly arising from the right ventricular outflow tract (RVOT). VEBs originating from the RVOT have a distinctive electrocardiogram (ECG) appearance, with wide QRS complexes mimicking a left bundle branch block (LBBB) with inferior axis morphology .
Several reports have suggested that the long-term prognosis in patients with truly idiopathic OTVEBs is excellent, despite frequent VT episodes, and that radiofrequency ablation (RFA) should only be considered in highly symptomatic patients . RFA results have been shown to be favourable, especially if VEBs arise from the RVOT, but only minimal data exist regarding the influence of the catheter used . Original publications have reported variable results with 4-mm tip catheters, with success rates ranging from 65% to 97% and a recurrence rate of 5% . Using a cooled-tip catheter is only recommended after failed RFA with a 4-mm tip catheter, but series concerning the safety in this indication are lacking .
RFA success rates appear to be lower in daily practice than in clinical trials, while serious complications, mainly due to cardiac perforation, have been reported in 1% of patients . For this reason, this prospective cohort study aimed to evaluate the feasibility, safety and efficacy of an 8-mm tip catheter for OTVEB RFA.
Methods
Study population
We evaluated consecutive patients with presumed OTVEBs who were referred to our laboratory for electrophysiological evaluation. Reasons for referral included arrhythmias noted on resting ECG, telemetry monitoring, or exercise stress testing, as well as symptomatic ventricular arrhythmias refractory to medical therapy. Written informed consent was obtained from each participating patient.
Clinical classification
Patients were classified according to the index clinical arrhythmia on presentation: non-sustained ventricular tachycardia (NSVT) (lasting ≥ 3 beats and ≤ 30 s) or repetitive ventricular ectopies.
Non-invasive evaluation
Patients underwent evaluation of cardiac structure, function and ectopy burden, mostly by cardiac magnetic resonance imaging (MRI), 24-hour Holter monitoring, or inpatient telemetry. If necessary, the presence of coronary artery disease was assessed by stress testing or cardiac catheterization (≥ 70% stenosis of any major epicardial vessel). Left ventricular systolic function was quantified using echocardiography, radionuclide ventriculography, or ventricular cine-angiography. Structural heart disease was defined as the presence of coronary artery disease (as defined above), left ventricular ejection fraction (LVEF) less or equal to 50%, or moderate to severe valvular disease. Patients with structural heart disease or coronary artery disease were excluded from participating in the study.
Electrophysiological testing
Patients underwent electrophysiological testing after an overnight fast. Patients were locally anaesthetized with 0.25% bupivacaine and minimally sedated with intravenous midazolam or fentanyl if necessary. Quadripolar 6-F catheters were advanced to the high right atrium, His bundle position, and right ventricular apex, or outflow tract. Bipolar intracardiac electrograms were filtered at 30–500 Hz. If further mapping in the left ventricle was required, a retrograde aortic approach could be used. The stimulation protocol included burst atrial and ventricular pacing, as well as introduction of single atrial extrastimuli and up to triple ventricular extrastimuli from one or two right ventricular sites. Stimuli were delivered as rectangular pulses of 2 ms duration at four-fold diastolic threshold. To facilitate induction of sustained tachycardia, programmed stimulation was repeated if necessary during isoproterenol infusion at a rate that decreased sinus cycle length by approximately 20–30%. The ventricular stimulation protocol was performed in order to eliminate outflow tract sustained VTs. Three-dimensional mapping was not performed.
Mapping and RFA
After all antiarrhythmic drugs had been withdrawn; electrophysiological evaluation and catheter RFA were performed . If clinical VEBs did not occur spontaneously, intravenous isoproterenol administration was infused. During a clinical arrhythmia episode, activation mapping was performed. Initial mapping sites were determined by detailed analysis of the QRS morphology during VEBs. Mapping of VEBs with an inferior axis was started in the RVOT region or directed by premature ventricular complex (PVC) morphology. If suitable ablation sites were not found in the RVOT, pulmonary artery, or right ventricle, left ventricular outflow tract (LVOT) endocardium could be mapped. For mapping and RFA, an 8-F quadripolar bidirectional deflectable catheter with an 8-mm tip electrode (BLAZER II large curve XP 4500 TK2 Boston EP-technologies, San Jose, USA) was used, with a maximum power output of 60 W and maximum target temperature of 60 °C. The site of RFA was identified using:
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bipolar pace mapping. Pace mapping was performed at the cycle length of the targeted VEBs or at the coupling interval of the targeted ventricular ectopic beats. The morphology of the pace map was compared with the spontaneous VEBs or VT. The score for the pace map was considered ‘good’ if 11 or 12 of 12 leads during pacing were identical to the targeted VEBs or NSVTs;
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local bipolar ventricular electrogram, usually 10–60 ms earlier than the onset of the surface QRS ( Fig. 1 );
Figure 1
Endocardial recording during left bundle branch block-like ventricular tachycardia. Note the 8-mm RF bipolar ablation catheter recording at the site of the earliest activation time.
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local unipolar ventricular electrogram, usually 10–60 ms earlier than the onset of the surface QRS with a sharp QS deflection ( Fig. 2 );
Figure 2
Endocardial recording during left bundle branch block-like ventricular tachycardia. Note the 8-mm RF unipolar ablation catheter recording at the site of the earliest activation time.
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the presence of pre-systolic potentials ( Fig. 3 ).
Figure 3
Endocardial recording during left bundle branch block-like ventricular tachycardia. Note the 8-mm RF bipolar ablation catheter recording at the site of ablation (Presystolic recording).
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