Elsevier

Heart Rhythm

Volume 11, Issue 11, November 2014, Pages 1919-1924
Heart Rhythm

Pulmonary vein isolation using “contact force” ablation: The effect on dormant conduction and long-term freedom from recurrent atrial fibrillation—A prospective study

https://doi.org/10.1016/j.hrthm.2014.07.033Get rights and content

Background

Atrial fibrillation (AF) recurrence after pulmonary vein isolation (PVI) is associated with PV to left atrium reconduction. Effective lesion creation necessitates adequate contact force between the ablation catheter and myocardium.

Objective

The purpose of this study was to study the utility of contact force–guided ablation on immediate and long-term outcomes.

Methods

Seventy-five patients with highly symptomatic paroxysmal AF underwent wide circumferential PVI using an irrigated-tip radiofrequency catheter. In 25 patients, ablation was guided by real-time contact force measurements (CF group; SmartTouch, Biosense Webster). A control group of 50 patients underwent PVI using a standard nonforce sensing catheter (standard group; ThermoCool, Biosense Webster). After PVI, all patients underwent adenosine testing to unmask dormant conduction. Patients were followed up at 3, 6, and 12 months and by transtelephonic monitoring as well.

Results

Dormant conduction was unmasked and subsequently eliminated in 4 PV pairs (8%; 16% of patients) in the CF group and 35 PV pairs (35%; 52% of patients) in the standard group (P = .0004 per PV pair; P = .0029 per patient). The single-procedure, off–antiarrhythmic drug freedom from recurrent atrial arrhythmias at 1 year was 88% in the CF group vs 66% in the standard group (P = .047). Procedure duration and fluoroscopy time were significantly longer in the CF group (P = .0038 and P = .0001, respectively).

Conclusion

The use of real-time contact force guidance results in a significant reduction in the prevalence of dormant conduction with improved long-term freedom from recurrent arrhythmias. The utility of a contact force–guided approach requires evaluation in a long-term prospective randomized study.

Introduction

Atrial fibrillation (AF) is the most common sustained cardiac arrhythmia encountered in clinical practice and is associated with reductions in quality of life, functional status, cardiac performance, and overall survival.1 Radiofrequency catheter ablation centered on electrical isolation of triggering foci within the pulmonary veins (PVs) through circumferential lesions around PV ostia (pulmonary vein isolation [PVI]) and/or elimination of the arrhythmic substrate has been shown to be a highly effective option for patients with both paroxysmal and persistent AF.2 Unfortunately, despite initial procedural success, up to 20% to 40% of patients will require a second intervention because of arrhythmia recurrence, which most often is due to recovery of conduction between PVs and the left atrium (LA).3, 4, 5, 6, 7, 8

Ablation electrode–tissue contact is an important determinant of lesion size and ultimately of durability. Conventionally, this has been assessed by the operator using a combination of fluoroscopic and electroanatomic imaging of catheter tip motion, tactile feedback, and local electrogram attenuation and impedance reductions during energy delivery. Although widely used, the accuracy of these surrogate measures is poor.9, 10 Contact force sensing is a newly developed technology that allows for real-time estimation of the contact force between the tip of the catheter and the target myocardium, which providing the operator with accurate quantitative assessment of tissue contact.

One such technology is contained in the ThermoCool SmartTouch mapping and ablation catheter (Biosense Webster, Diamond Bar, CA). The force-sensing capability of this catheter is based on the electromagnetic location technology used in the CARTO system (Biosense Webster). Specifically, a precision spring mounted within the tip of the electrode is connected to a transmitter coil, which emits a location reference signal to 3-location sensor coils mounted within the shaft of the catheter. The micromovements of the spring are sampled every 50 ms and calibrated to produce a contact force reading (in grams) based on the known spring characteristics as well as the location information of the sensor. The purpose of this study was to evaluate the effect of a “contact force”–guided approach on the immediate (prevalence of adenosine-induced dormant PV conduction) and long-term outcomes (freedom from recurrence of atrial tachyarrhythmia) compared to standard ablation.

Section snippets

Study population

Seventy-five consecutive patients with highly symptomatic paroxysmal AF refractory to antiarrhythmic drugs referred for catheter ablation at either of the participating centers (Montreal Heart Institute or Florida Hospital Cardiovascular Institute) between August 2011 and October 2012 were prospectively enrolled in this pragmatic parallel cohort study. All patients had structurally normal hearts as assessed by clinical evaluation and cardiac imaging (echocardiography, computed tomography,

Baseline parameters

A total of 75 consecutive patients (58.8 ± 12.0 years; 82% male) were enrolled in the study protocol. Mean AF duration before enrollment was 61.7 ± 66.1 months. Overall, mean LA diameter was 36.9 ± 9.6mm, and left ventricular ejection fraction (LVEF) was 61.1% ± 5.6%. Only 9 patients (12%) had CHADS score >1. Baseline characteristics broken down by study group are given in Table 1. LVEF was significantly higher in the contact force group (P = .012), although no patient had LVEF <50%. There were

Discussion

The study demonstrated the following key findings. In patients with a history of drug-refractory paroxysmal AF undergoing PVI, use of contact force–guided ablation resulted in a significant reduction in the prevalence of dormant conduction unmasked with adenosine provocation and a superior 1-year freedom from recurrent AF/AT/AFL on intense arrhythmia monitoring.

These findings have important clinical implications. Although wide circumferential PVI is an established treatment for patients

Conclusion

Ablation guided by real-time contact force assessment results in a significant reduction in the prevalence of dormant conduction unmasked with adenosine provocation as well as improved long-term freedom from recurrent AF. The utility of this approach needs to be evaluated in a larger-scale, prospective randomized trial.

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