SmartTouch Catheter in Ablation of Ventricular Tachycardia
SmartTouch Catheter in Ablation of Ventricular Tachycardia
The pressure exerted by the ablation catheter on the tissue has been shown to play an
 important role on determining the size and the potential efficacy of the ablation lesions. A
 direct information on the force exerted by the catheter tip obtained from the SmartTouch
 technology might improve the assessment of the scar areas during electroanatomical mapping in
 patients with ventricular tachycardia (VT) due to ischemic disease or cardiomyopathy. The
 objectives of the study are to compare the areas of scar (defined as a low-voltage threshold)
 obtained from the conventional voltage map with those obtained after the contact map
 information is available to the operator and to determine if the availability of the contact
 information allows an improvement of the electroanatomic map by correcting the points taken
 in no-contact areas. Twenty to 30 consecutive patients with ventricular arrhythmias due to
 ischemic heart disease or dilated cardiomyopathy undergoing VT ablation will be included in a
 prospective, one-center, non-randomized study. A voltage map of the left ventricle will be
 obtained using the CARTO-3 navigation system and the scar areas as well as the areas of
 potential interest for ablation will be delineated in the standard way and saved as the
 control map. The force information will be recorded by the system but will not be available
 to the operator until the control map is saved. Following this step the contact map will be
 available to the operator to be compared with the control map and further mapping and point
 acquisition will be allowed to correct the areas previously acquired with poor or no contact.
 The final map after corrections have been made will be saved as the corrected map. The
 ablation procedure will then be performed as usual. Both maps will be compared in a deferred
 way to know how are classified the areas without contact when no pressure information is
 available, and how many non-contact points are falsely assumed to be low-voltage or dense
 scar points. These comparisons will give information on how much the standard electroanatomic
 map can be improved when the force information is added.
The usual ablation catheters do not provide direct information on the pressure applied at the
 contact area of the cardiac structures. However, pressure has been shown to play an important
 role on determining the size and the potential efficacy of the ablation lesions. The physical
 contact of the tip of the catheter with the tissue and the force exerted on this tissue are
 indirectly estimated from other parameters such as the signal voltage, the transmitted force
 to the other end of the catheter felt by the operator and, in a lesser extent, the circuit
 impedance.

 A widespread technique for ablation of ventricular tachycardias (VT) in patients with
 cardiomyopathies or ischemic disease consists on the creation of an electroanatomic map to
 delineate scar areas without electric activity and to look for areas of surviving myocardium
 inside, at the borders or between the scars, operating as a slow conduction channel in a
 reentry circuit and playing an essential role in the genesis of VTs. The distinction between
 scar and normal tissue is predominantly based on the voltage of the unipolar or bipolar
 electrograms (EGM) recorded at the tip of the ablation catheter. However, the amplitude of
 the electrogram depends critically on the distance between the electrode and the source of
 the electric field, in this case the myocardial tissue. The lack of contact between the
 catheter and the endocardium will reduce the EGM voltage and may induce to interpret a normal
 EGM point as a low-voltage point, leading to an erroneous delineation of the real scar areas
 and eventually missing electrically active myocardial paths. Thus a good physical contact
 between the catheter and the tissue is a prerequisite to obtain a reliable voltage map and to
 correctly identify scars and areas potentially involved in the VT maintenance. A direct
 information on the force applied at the tip of the catheter may avoid the interpretation of
 areas with no-contact induced low-voltage as scars.

 Hypothesis.

 The hypothesis of the study is that the information on the force exerted by the catheter tip
 obtained from the SmartTouch technology may improve the assessment of the scar areas during
 electroanatomical mapping in patients with VT due to ischemic disease or cardiomyopathy.

 Study objectives and endpoints.

 Two are the main objectives of this study:

 1. To compare the areas of scar (defined as a low-voltage threshold) obtained from the
 conventional voltage map with those obtained after the contact map information is
 available to the operator.

 2. To determine if the availability of the contact information to the operator allows an
 improvement of the electroanatomic map by correcting the points taken in no-contact
 areas.

 Study protocol.

 1. Inclusion criteria.

 Consecutive patients with ventricular arrhythmias due to ischemic heart disease or
 dilated cardiomyopathy undergoing VT ablation will be included in the study.

 Exclusion criteria will be age <18 years, absence of signed informed consent or critical
 clinical status that precludes a detailed mapping procedure.

 2. Study design and duration.

 The study is planned as a prospective, one-center, non-randomized study. As the
 objectives are purely descriptive no formal calculation of the sample size has been
 performed. Considering the inclusion criteria and the frequency of this type of studies
 in our unit a number of 20 to 30 patients is estimated to be included in 12 months. We
 believe that this number of patients is reasonable to estimate the value of the contact
 map to delineate scars from a clinical point of view.

 3. Protocol and procedure.

 Our standard approach to ischemic VT ablation begins with the acquisition of a voltage
 map of the left ventricle during sinus rhythm of fixed pacing from the right ventricular
 apex using the CARTO-3 navigation system and a Navistar irrigated catheter. During the
 acquisition, points with fragmented or delayed potentials are tagged as areas of
 potential interest for ablation. Once the map is completed we adjust the color code of
 the voltage map trying to decide the areas of dense scar and to look for potential
 narrow paths inside or between the areas of scar. After adjusting the map in this way we
 proceed to the ablation, which is performed during induced VT or guided by the
 anatomical and electrical information in case of non-inducible or non-tolerated VTs.
 Pace-mapping is eventually used if a 12-lead ECG of the clinical VT is available.

 For the patients included in the study the voltage map will be acquired in the same way
 using the Thermo-Cool Smart Touch catheter. The force information will be recorded by
 the system but will not be available to the operator during the map acquisition. The
 completed voltage map with the areas defined as dense scar by the operator, the
 isthmuses found inside or between scars and the areas with fragmented or delayed
 potentials will be saved as the control map. Following this step the contact map will be
 available to the operator to be compared with the control map and further mapping and
 point acquisition will be allowed to correct the areas previously acquired with poor or
 no contact. The final map after corrections have been made will be saved as the
 corrected map. The ablation procedure will then be performed as usual.

 4. Map analysis

 The comparison of the maps will be done in a deferred way. First, the control map and
 the contact map will be compared. The area without contact in the pressure map will be
 estimated. Each point inside this area will be classified as dense scar, low-voltage
 point or normal voltage point according to the properties of the point in the control
 map. We will determine in this way how are classified the areas without contact when no
 pressure information is available, and how many non-contact points are falsely assumed
 to be dense scar. The areas of "real" dense scar and "assumed, non-contact" dense scar
 will be estimated as well. This step of the analysis will give information on how many
 low-voltage areas of the standard electroanatomic map may not be reliable due to lack of
 an appropriate contact.

 The control and the corrected map will then be compared. The areas and the number of
 points defined as dense scar by the operator in both maps will be compared and the
 points changing their status as scar, low or normal voltage from the control to the
 corrected map will be annotated as well. Finally, the differences in the potential
 isthmuses depicted in both maps will be analyzed. These comparisons will give
 information on how much the standard electroanatomic map can be improved when the force
 information is added.

 5. Patient consent.

 The study will be presented to the ethics committee of our centre for approval. A
 written, informed consent will be required to be signed by the patient before entering
 the study.

 6. Time schedule

 The recruitment of patients will start as soon as the project is approved by Biosense
 Webster and by the local ethics committee. The inclusion period would be 12 months. Data
 analysis will be performed during the study period, making the final results available
 shortly after the end of the study. An additional 6 month period is expected to report
 and publish the results in international cardiology journals.

 7. Privacy policy

 All the patient's data will remain in the hospital files and will not be transmitted to any
 external subject. A code will be assigned to each patient in order to allow the analysis of
 the data in an anonymous way .
Inclusion Criteria:

 -  Consecutive patients with ventricular arrhythmias due to ischemic heart disease or
 dilated cardiomyopathy undergoing VT ablation

 Exclusion Criteria:

 -  Age <18 years, absence of signed informed consent or critical clinical status that
 precludes a detailed mapping procedure