A novel means of cardiac catheter guidance for ablation therapy of ventricular tachycardia

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.Includes bibliographical references (pages 118-123).This work presents a system for identifying the site of origin of ventricular tachycardia (VT) and guiding a catheter to that site in order to deliver radio-frequency (RF) ablation therapy. Myocardial infarction (MI), also known as ischemic heart disease, is one of the most common pathophysiologic substrates for the development of ventricular tachycardia (VT). Implantable cardioverter defibrillators (ICDs) have been found to be successful in terminating VT but do not prevent the initiation of the arrhythmia. Alternatively, the radiofrequency (RF) ablation procedure has been recently used as a potentially curative therapy by delivering a high-frequency current at the arrhythmia site in order to disrupt the re-entrant circuit and to prevent the arrhythmia from occurring. However, RF ablation of VT presents a great challenge. The origin of the arrhythmia may be anywhere in the ventricles, and existing techniques used to locate the site require that patients be maintained in VT for 30 to 45 minutes, which leads to blood pressure collapse in 90% of the patients. Recently, we have developed a novel guidance system for the ablative treatment of VT. This system employs an Inverse Solution Guidance Algorithm (ISGA) based upon a single equivalent moving dipole (SEMD) model for the generation of body surface potentials and is able to localize both the arrhythmia site and the ablation catheter in real-time. With the proposed system VT need be induced and maintained for only a few seconds. This system has been shown in our tank experiment and in vivo animal studies to be highly accurate, low cost and reliable. An optimization analysis of the system is also included in this thesis for the purpose of further reducing the cost and surgical risk of the RF ablative therapy.by Wener Lv.Ph. D

Techniques for epicardial mapping and ablation with a miniature robotic walker

Present treatments for ventricular tachycardia have significant drawbacks. To ameliorate these drawbacks, it may be advantageous to employ an epicardial robotic walker that performs mapping and ablation with precise control of needle insertion depth. This paper examines the feasibility of such a system

A Method to Noninvasively Identify Cardiac Bioelectrical Sources

Background We have introduced a method to guide radiofrequency catheter ablation (RCA) procedures that estimates the location of a catheter tip used to pace the ventricles and the target site for ablation using the single equivalent moving dipole (SEMD). Objective To investigate the accuracy of this method in resolving epicardial and endocardial electrical sources. Methods Two electrode arrays, each of nine pacing electrodes at known distances from each other, sutured on the left- and right-ventricular (LV and RV) epicardial surfaces of swine, were used to pace the heart at multiple rates, while body surface potentials from 64 sites were recorded and used to estimate the SEMD location. A similar approach was followed for pacing from catheters in the LV and RV. Results The overall (RV & LV) error in estimating the interelectrode distance of adjacent epicardial electrodes was 0.38 ± 0.45 cm. The overall endocardial (RV & LV) interelectrode distance error, was 0.44 ± 0.26 cm. Heart rate did not significantly affect the error of the estimated SEMD location (P > 0.05). The guiding process error became progressively smaller as the SEMD approached an epicardial target site and close to the target, the overall absolute error was ∼0.28 cm. The estimated epicardial SEMD locations preserved their topology in image space with respect to their corresponding physical location of the epicardial electrodes. Conclusion The proposed algorithm suggests one can efficiently and accurately resolve epicardial electrical sources without the need of an imaging modality. In addition, the error in resolving these sources is sufficient to guide RCA procedures.National Institutes of Health (U.S.) (Grant 1RO1HL103961)National Institutes of Health (U.S.) (Grant R44 HL079726-04

A Method to Noninvasively Identify Cardiac Bioelectrical Sources

Background We have introduced a method to guide radiofrequency catheter ablation (RCA) procedures that estimates the location of a catheter tip used to pace the ventricles and the target site for ablation using the single equivalent moving dipole (SEMD). Objective To investigate the accuracy of this method in resolving epicardial and endocardial electrical sources. Methods Two electrode arrays, each of nine pacing electrodes at known distances from each other, sutured on the left- and right-ventricular (LV and RV) epicardial surfaces of swine, were used to pace the heart at multiple rates, while body surface potentials from 64 sites were recorded and used to estimate the SEMD location. A similar approach was followed for pacing from catheters in the LV and RV. Results The overall (RV & LV) error in estimating the interelectrode distance of adjacent epicardial electrodes was 0.38 ± 0.45 cm. The overall endocardial (RV & LV) interelectrode distance error, was 0.44 ± 0.26 cm. Heart rate did not significantly affect the error of the estimated SEMD location (P > 0.05). The guiding process error became progressively smaller as the SEMD approached an epicardial target site and close to the target, the overall absolute error was ∼0.28 cm. The estimated epicardial SEMD locations preserved their topology in image space with respect to their corresponding physical location of the epicardial electrodes. Conclusion The proposed algorithm suggests one can efficiently and accurately resolve epicardial electrical sources without the need of an imaging modality. In addition, the error in resolving these sources is sufficient to guide RCA procedures.National Institutes of Health (U.S.) (Grant 1RO1HL103961)National Institutes of Health (U.S.) (Grant R44 HL079726-04

Accuracy of cardiac ablation catheter guidance by means of a single equivalent moving dipole inverse algorithm to identify sites of origin of cardiac electrical activation

We have developed a system that could potentially be used to identify the site of origin of ventricular tachycardia (VT) and to guide a catheter to that site to deliver radio-frequency ablation therapy. This system employs the Inverse Solution Guidance Algorithm based upon Single Equivalent Moving Dipole (SEMD) localization method. The system was evaluated in in vivo swine experiments. Arrays consisting of 9 or 16 bipolar epicardial electrodes and an additional mid-myocardial pacing lead were sutured to each ventricle. Focal tachycardia was simulated by applying pacing pulses to each epicardial electrode at multiple pacing rates during breath hold at the end-expiration phase. Surface potentials were recorded from 64 surface electrodes and then analyzed using the SEMD method to localize the position of the pacing electrodes. We found a close correlation between the locations of the pacing electrodes as measured in computational and real spaces. The reproducibility error of the SEMD estimation of electrode location was 0.21 ± 0.07 cm. The vectors between every pair of bipolar electrodes were computed in computational and real spaces. At 120 bpm, the lengths of the vectors in the computational and real space had a 95% correlation. Computational space vectors were used in catheter guidance simulations which showed that this method could reduce the distance between the real space locations of the emulated catheter tip and the emulated arrhythmia origin site by approximately 72% with each movement. We have demonstrated the feasibility of using our system to guide a catheter to the site of the emulated VT origin.NIH (grant R44 HL079726-04

Cardiac Ablation Catheter Guidance by Means of a Single Equivalent Moving Dipole Inverse Algorithm

Background We developed and evaluated a novel system for guiding radiofrequency catheter ablation therapy of ventricular tachycardia. This guidance system employs an inverse solution guidance algorithm (ISGA) using a single equivalent moving dipole (SEMD) localization method. The method and system were evaluated in both a saline tank phantom model and in vivo animal (swine) experiments. Methods A catheter with two platinum electrodes spaced 3 mm apart was used as the dipole source in the phantom study. A 40-Hz sinusoidal signal was applied to the electrode pair. In the animal study, four to eight electrodes were sutured onto the right ventricle. These electrodes were connected to a stimulus generator delivering 1-ms duration pacing pulses. Signals were recorded from 64 electrodes, located either on the inner surface of the saline tank or on the body surface of the pig, and then processed by the ISGA to localize the physical or bioelectrical SEMD. Results In the phantom studies, the guidance algorithm was used to advance a catheter tip to the location of the source dipole. The distance from the final position of the catheter tip to the position of the target dipole was 2.22 ± 0.78 mm in real space and 1.38 ± 0.78 mm in image space (computational space). The ISGA successfully tracked the locations of electrodes sutured on the ventricular myocardium and the movement of an endocardial catheter placed in the animal's right ventricle. Conclusion In conclusion, we successfully demonstrated the feasibility of using an SEMD inverse algorithm to guide a cardiac ablation catheter.National Institutes of Health (U.S.) (Grant 4 R44H L079726-02)National Institute on Aging (Grant 1R21AG035128)National Institutes of Health (U.S.) (Grant 1RO1HL103961)Center for Integration of Medicine and Innovative Technolog