Nowadays, catheter ablation has a very important role for the treatment of many arrhythmias. During the ablation procedure, the ablation catheter usually reaches the endocardium, although recently even the epicardial space has been approached to perform ablation.1 During an application, energy is applied to modify the conduction properties of the underlying tissue. The efficacy of these lesions is, among other factors, related to the delivered total energy and the contact force of the catheter tip.2,3 Recently, developments have been made to improve energy delivery to the underlying tissue. This resulted in the introduction of several improved catheter designs that increase energy delivery such as irrigated tip catheters.4 However, the contact force applied during a radiofrequency (RF) application remained unknown; the operators had to make assumptions of the applied force. Recent data demonstrated that this is very inaccurate, and may lead to the development of insufficient contact forces and result in inappropriate lesion formation or dangerous high forces with the risk of perforating the myocardium.5
With the introduction of a new force-sensing catheter, operators are able to measure the direct contact force of the tip of the catheter. Using this catheter, the applied force can be assessed accurately and the operator can determine if there is appropriate tissue contact for proper lesion formation. Some experience with these force-sensing catheters in adults has been published; however, the possibility of using this technique for pediatric patients has remained unknown.5 In this report, we present the first case of a pediatric, congenital heart disease patient in whom a force-sensing catheter was used.
A 7-year-old girl with a severe Ebstein anomaly who did not have previous cardiac surgery was referred to our center with recurring arrhythmias. The patient presented with symptomatic supraventricular arrhythmias resulting in congestive heart failure one month prior to the procedure. The electrocardiogram showed sinus rhythm, signs of right atrial hypertrophy, and a right bundle branch block (Figure 1). Echocardiography showed a severe tricuspid insufficiency and a large ASDII with bidirectional shunt (Figure 1). The patient was on amiodarone and aspirin. Figure 2 shows a chest x-ray of the patient.
An electrophysiology study was performed. The procedure was performed under general anesthesia. When the patient arrived at the EP lab, she was in sinus rhythm. Three venous sheaths were inserted via the right femoral vein and one sheath in the left femoral artery. Three diagnostic catheters were placed in the coronary sinus (CS), right ventricle, and right atrium, respectively. An open irrigation tip RF catheter with contact force sensing (TactiCath, Endosense SA, Geneva, Switzerland) was placed into the right atrium.
The force-sensing TactiCath system consists of an RF ablation catheter, a base station as a signal processing and displaying unit, and a splitter interfacing between the catheter, the base station, and the RF ablation generator available in the EP lab (Figure 3).5 The force-sensing catheter is a 7 French (Fr), steerable 3.5 mm RF ablation catheter with an open irrigation tip that incorporates 6 holes at the distal tip. To ensure accurate measurement, the catheter first needs to be calibrated while floating in the heart chamber of the caval vein. A contact force sensor at the distal tip measures the amplitude and direction of the applied contact force between the catheter tip electrode and the tissue (Figure 4).3 The sensor stiffens the catheter distal part, making it compatible with 8.5 Fr introducers and straight or steerable sheaths. The contact force sensor is a triaxial force sensor located between the second and third electrode, and has a resolution and sensitivity of about 1 g. The contact force is displayed continuously on the screen and the sensor is able to measure the lateral and axial forces separately and recalculate the forces every 100 milliseconds.3
During the EP study, an accessory pathway, atrioventricular nodal reentrant tachycardia, and WPW syndrome were excluded. The TactiCath catheter was calibrated in the inferior caval vein in the absence of any wall contact. Three-dimensional electroanatomical mapping was performed using the EnSite NavX system. After burst pacing from the CS, a typical cavotricuspid isthmus (CTI) dependent atrial flutter could be induced with a cycle length of 270 ms. Furthermore, a focal atrial tachycardia was seen that originated from the CTI, and had a cycle length of 460 ms. After induction of the tachycardia, an electroanatomical activation map was created. The first RF applications were performed on the CTI that resulted in termination of the tachycardia, and a CTI line was made. After the ablation line, the macroreentrant tachycardia could not be induced. During ablation of the CTI, a 1:1 conduction developed; this resulted in an insufficient cardiac output. During attempts of overpacing the tachycardia, the flutter degenerated to a ventricular tachycardia that was hemodynamically instable. Therefore, external cardioversion needed to be applied. Afterwards, the patient was stable again and the AT could be ablated. The origin of this tachycardia was located on the CTI, although it had a more septal location. During this procedure a total of 10 RF applications were applied with a total ablation time of 9 minutes. The average force during the ablations was 9 g, with an average 4227 gs FTI (force time integral). The maximum force during ablation was 37 g. During the procedure, there was no audible steam pop observed. An overview of the contact force report is presented in Figure 5. At the end of the procedure, no arrhythmias could be induced or recorded during a 30-minute waiting period. The patient is free of the ablated arrhythmias to date.
This case report demonstrates the feasibility and benefits of using a contact force sensing catheter in a pediatric patient with a congenital heart defect. The use of this catheter has special advantages regarding procedural safety. High forces might be applied during catheter manipulation when no feedback is available on contact force. Manipulation of the catheter in small pediatric hearts is often challenging, so contact force information can be useful for safe manipulation. Furthermore, contact force during RF applications is very valuable and might lead to more effective lesion formation. With the introduction of this catheter, information will be provided on the torque of the catheter tip to the underlying tissue. This might help to improve safety and efficacy of RF applications.
In this case report the usefulness of a force-sensing catheter has been demonstrated. Despite the very low experience in congenital heart disease patients, it certainly demonstrates the feasibility and advantages of this novel catheter. More extensive research in larger patient populations is necessary to evaluate the true value of this force-sensing catheter. However, these preliminary results are very promising for the future.
- Della Bella P, Brugada J, Zeppenfeld K, et al. Epicardial ablation for ventricular tachycardia: A European multicenter study. Circ Arrhythm Electrophysiol 2011;4:653–659.
- Yokoyama K, Nakagawa H, Shah DC, et al. Novel contact force sensor incorporated in irrigated radiofrequency ablation catheter predicts lesion size and incidence of steam pop and thrombus. Circ Arrhythm Electrophysiol 2008;1:354–362.
- Thiagalingam A, D’Avila A, Foley L, et al. Importance of catheter contact force during irrigated radiofrequency ablation: Evaluation in a porcine ex vivo model using a force-sensing catheter. J Cardiovasc Electrophysiol 2010;21:806–811.
- Nakagawa H, Yamanashi WS, Pitha JV, et al. Comparison of in vivo tissue temperature profile and lesion geometry for radiofrequency ablation with a saline-irrigated electrode versus temperature control in a canine thigh muscle preparation. Circulation 1995;91:2264–2273.
- Kuck KH, Reddy VY, Schmidt B, et al. A novel radiofrequency ablation catheter using contact force sensing: Toccata study. Heart Rhythm 2012;9:18–23.