With the following protocol, we provide an approach to Ventricular Tachycardia (VT) ablation using high density mapping with a multipolar catheter and 3D mapping system enhancing the success of the procedure.
Ventricular tachycardia (VT) in patients with ischemic cardiomyopathy mainly results from endocardial scars after myocardial infarction; those scars represent zones of slow conduction that allow the occurrence and maintenance of reentrant circuits. Catheter ablation enables substrate modification of those low voltage areas and thus can help to alter the scar tissue in such a way that arrhythmias cannot appear anymore. Hospitalizations of concerned patients decrease, quality of life and outcome rise. Consequently, VT ablation represents a growing field in electrophysiology, especially for patients with endocardial scars in ischemic heart disease after myocardial infarction. However, ablation of ventricular tachycardia remains one of the most challenging procedures in the electrophysiology lab. Precise scar definition and localization of abnormal potentials are critical for ablation success. The following manuscript describes the use of a multipolar mapping catheter and 3-dimensional (3D) mapping system to create a high density electro-anatomical map of the left ventricle including a precise scar representation as well as mapping of fractionated and late potentials in order to allow a highly accurate substrate modification.
Coronary artery disease and myocardial infarction remain major causes for morbidity and mortality in the industrialized world1. Myocardial scars after transmural infarction represent low voltage areas and thus zones of slow electrical conduction and facilitate the appearance and maintenance of macro-reentrant circuits. Ventricular tachycardias (VT) are responsible for repeat hospitalizations, painful shocks of implantable cardioverter defibrillators (ICD) and thus lessen quality of life and cause poor outcome2,3. Catheter ablation can reduce the occurrence of VT, especially in ischemic heart disease4, and should be considered in patients with ventricular arrhythmias and underlying structural heart disease in the presence of an ICD (class IIa B recommendation)5. In patients with structural heart disease with ventricular arrhythmias already suffering from ICD shocks, catheter ablation is recommended (class I B recommendation)5. However, catheter ablation is still a high-risk procedure, considering the often-poor state of health of concerned patients with mostly reduced left ventricular ejection fraction and multiple co-morbidities. Furthermore, the precise localization of scars and abnormal potential can be challenging but are critical for ablation success. The use of 3D mapping systems and multipolar catheters allow electro-anatomical high-density mapping and can considerably facilitate the acquisition of electrical information and thus improve the quality and validity of the 3D model and consequently enhance ablation success and patient outcome. So far, there are 3 different 3D mapping systems available, whereof one is commonly used for VT ablation. The following protocol describes an approach to endocardial ischemic VT ablation using a less common 3 D mapping system in the field of VT ablation and a multipolar catheter (see Table of Materials) for high-density electro-anatomical reconstruction.
The following protocol complies with the guidelines of the human research ethics committee of the department for internal medicine/cardiology of the Hietzing Hospital in Vienna.
1. Preliminary Measures
2. Patient Preparation During the Procedure
3. Groin Puncture and Catheter Positioning
4. Electro-anatomical Reconstruction of the Left Ventricle
5. Programmed Ventricular Stimulation (PVS)
6. Catheter Ablation
7. Post Ablation
The protocol describes in detail catheter ablation of monomorphic ventricular tachycardia in a patient with ischemic heart disease after anterior myocardial infarction with occlusion of the proximal left anterior descendant artery. The patient suffered from multiple ICD shock deliveries. Transthoracic echocardiography showed a severely reduced systolic left ventricular function (ejection fraction 30%) with a large apex aneurysm. VT ablation was performed using a 3D mapping system (see Table of Materials) and a multipolar (16 pole) steerable mapping catheter (see Table of Materials, electrode size 1 mm, electrode spacing 3-3-3). Simultaneous acquisition of numerous mapping points allowed a rapid and precise electroanatomical reconstruction of the left ventricle (see Figures 1, 2 and 3). The close electrode spacing of the multipolar catheter made possible the detection of critical signals such as fragmented and late potentials. Additional pacing from the right ventricle clearly separated the late potential from the first ventricular activation and thus identified the mapped area as a zone of slow conduction and therefore of high importance regarding the occurrence and maintenance of ventricular arrhythmias (see Figure 4). Areas that could not be reached with the multipolar catheter where addressed with the ablation catheter (see Table of Materials), which also has a close electrode spacing of 2-2-2.
By means of all the above-mentioned mapping strategies, a very precise map could be generated, showing a scar area at the left ventricular apex and adjacent areas (see Figures 1, 2 and 3, scar area 54 cm2). However, mapping time could be limited to 27 min.
During programmed ventricular stimulation and ablation, a total of 4 VTs could be induced. One of them (see Supplementary Figure 3) could be entrained and successfully ablated at the lateral border zone of the scar. Additionally, substrate modification was performed by encircling the scar, ablating all late abnormal potentials and ablating sites of pace maps matching the induced VTs.
At the end of the procedure, no VT could be induced with the stimulation sequences that enhanced the VTs at the beginning of the procedure. Only a VT with presumably epicardial origin could be induced with very aggressive stimulation. We decided to stop the procedure at that point.
The described method helps to improve ablation success and patient outcome.
Supplementary Figure 1: ECG electrode position. The position of the surface ECG electrodes on the front chest (taken and adapted from the user handbook of the 3D mapping system8). Please click here to view a larger version of this figure.
Supplementary Figure 2: 3D mapping system patch position. The position of the EnSite Precision™ patches on the body (taken and modified from the user handbook of the 3D mapping system8). Please click here to view a larger version of this figure.
Supplementary Figure 3: Clinical tachycardia. One of four induced ventricular tachycardias during the procedure, written with 50 mm/s, cycle length 440 ms. Please click here to view a larger version of this figure.
Figure 1: Voltage map range 0.5 to 1.5 mV. RAO (left side) and LAO (right side) projections of a voltage map of the endocardial left ventricle. Small yellow dots represent electro-anatomical mapping points. The voltage of ventricular signals is defined as scar below 0.5 mV (grey), the low voltage between 0.5 and 1.5 mV (from red to blue) and the normal voltage above 1.5 mV (purple, see the scale on the left side of the figure). Large green dots represent late potentials. Please click here to view a larger version of this figure.
Figure 2: Voltage map range 0.2 to 1.5 mV. RAO (left side) and LAO (right side) projections of the same voltage map, this time with a low voltage range between 0.2 and 1.5 mV. Note the now patchy still viable and thus conducting tissue inside the scar. Late potentials (green dots) are located those areas that presumably represent zones of slow conduction. Please click here to view a larger version of this figure.
Figure 3: Voltage map with ablation lesions. RAO (left side) and LAO (right side) projections of the voltage map of the endocardial left ventricle (low voltage range between 0.2 and 1.5 mV) including ablation lesions (large red dots). Please click here to view a larger version of this figure.
Figure 4: Intracardiac electrogram with late potentials. Intracardiac electrogram at a site where late potentials could be recorded. 12-lead ECG on top of the screen; RVAd: catheter in the right ventricular apex; Grid: multipolar catheter (16 poles); CS: 8-pole catheter in the coronary sinus. (A) in sinus rhythm. The late potential visible on the multipolar catheter (marked with the red arrow) is located directly after the first ventricular activation. (B) during RVA-stimulation at the same site. The late potential visible on the multipolar catheter (red arrow) is now clearly separated from the first ventricular activation. Please click here to view a larger version of this figure.
The use of 3D mapping systems in complex electrophysiological procedures is a well-established method to acquire detailed and precise anatomical information and reduce radiation time and enables the creation of substrate and activation maps9. However, data acquisition can be challenging due to difficult catheter movement, especially in the left ventricle. Furthermore, point by point map acquisition takes a lot of time and thus prolongates the electrophysiological procedure. Wide electrode spacing at the tip of the mapping catheter reduces resolution and quality of the created map, critical signals may be overlooked. The use of a multipolar catheter for mapping of the ventricle solves the above-mentioned issues: several mapping points can be taken simultaneously; procedure time decreases. The narrow-spaced electrodes guarantee a very high resolution of the map, important signals are not so easily missed anymore.
Currently, there are 3 different 3D mapping systems available, all of them allowing the use of multipolar mapping catheters.
So far, one of them using a magnetic field is widely used, especially in VT ablation, due to its user-friendly handling and highly accurate electroanatomical reconstruction. A suitable mapping catheter, a 20-pole steerable catheter with narrow electrode spacing, can access even difficult anatomies due to its special configuration (star shape) and provides precise high density maps10.
A relatively new 3D mapping system also allows a very quick and precise acquisition of multiple mapping points by means of a 64-electrode mapping catheter with a basket shape11,12.
The 3D mapping system used in the protocol (see Table of Materials) combines impedance and magnetic field technology and thus allows precise navigation and accurate tracking of mapping and ablation catheters, either conventional or sensor enabled. The created electro-anatomical maps are highly accurate and don´t need further post-processing compared with former versions of the mapping system. A huge advantage for accurate mapping is the morphology matching feature, which allows continuous comparison of QRS morphologies during map acquisition. The suitable 16-pole mapping catheter (see Table of Materials) allows the acquisition of multiple points simultaneously and makes possible high resolution and the detection of even small critical signals due to its narrow electrode spacing (3-3-3).
To further improve the quality of the map and identify critical potentials, we changed the low voltage range from 0.5-1.5 mV to 0.2-1.5 mV (to identify viable and conducting tissue inside the scar). Interestingly, most late potentials were detected in viable zones within the scar (see Figure 1 and Figure 2).
By pacing from the catheter in the right ventricle, late potentials could clearly be separated from the first ventricular activation (see Figure 4B).
Despite the steerability of the 16-pole mapping catheter, we could not access all regions of the left ventricle. Those sites had to be addressed with the ablation catheter, which also has close electrode spacing (2-2-2), as well as a pressor sensor to guarantee adequate wall contact.
Despite all the above-mentioned advantages, the more sophisticated a method gets, the more prone it is to disturbances. Catheter noise can occur and make the interpretation of signals very difficult. Artifacts can simulate electrically interesting potentials and misguide the investigator. Multipolar catheters require more cables that can be damaged, the connection can be disturbed, troubleshooting costs time.
Despite those disadvantages, multipolar catheters, if used correctly and by experienced investigators, are very useful for complex electrophysiological procedures and have a large potential in the future. Reduction of procedure time helps to prevent adverse events in these often very ill patients. The additional electrical information provided has to be interpreted carefully and along with other parameters available
The authors have nothing to disclose.
None.
NaVX EnSite Precision 3 D mapping system | Saint Jude Medical | ||
EnSite Precision Surface Electrode Kit | St. Jude Medical | EN0020-P | |
Ampere RF Ablation generator | St. Jude Medical | H700494 | |
EP-4, Cardiac Stimulator | St. Jude Medical | EP-4I-4-110 | |
LabSystem PRO EP recording system, v2.4a | Boston Scientific | ||
octapolar diagnostic catheter, EP-XT | Bard | 200797 | electrode spacing 2-10-2 |
supreme quadripolar diagnostic catheter | St. Jude Medical | 401441 | electrode spacing 5-5-5 |
Agilis NxT 8.5F, 71/91 cm steerable sheath, large curl | St. Jude Medical | G408324 | |
BRK transseptal needle, 98 cm | St. Jude Medical | 407206 | |
Advisor HD Grid mapping catheter, sensor enabled | St. Jude Medical | D-AVHD-DF16 | electrode spacing 3-3-3 |
quadripolar irrigated tip ablation catheter, TactiCath SE | St. Jude Medical | A-TCSE-F | electrode spacing 2-2-2 with pressure sensor |
Cool Point pump for irrigated ablation | St. Jude Medical | IBI-89003 | |
Cool Point tubing set | St. Jude Medical | 85785 | |
GEM PCL Plus Instrumentation laboratory | IL Werfen India Pvt. Ltd. | activated clotting time measurement device | |
X-ray equipment | Philips | ||
Heartstart XL defibrillator and associated patches | Philips | ||
12 F Fast-Cath sheath | St. Jude Medical | 406128 | |
6 F sheath | Johnson-Johnson | ||
5 F sheath | Johnson-Johnson | ||
BD Floswitch™ | Becton Dickinson | ||
Isozid®-H gefärbt | Novartis |