Shlomo Ben-Haim

A Novel Method for Nonfluoroscopic Catheter-Based Electroanatomical Mapping of the Heart: In Vitro and In Vivo Accuracy Results

BACKGROUND Cardiac mapping is essential for understanding the mechanisms of arrhythmias and for directing curative procedures. A major limitation of the current methods is the inability to accurately relate local electrograms to their spatial orientation. The objective of this study was to present and test the accuracy of a new method for nonfluoroscopic, catheter-based, endocardial mapping. METHODS AND RESULTS The method is based on using a new locatable catheter connected to an endocardial mapping and navigating system. The system uses magnetic technology to accurately determine the location and orientation of the catheter and simultaneously records the local electrogram from its tip. By sampling a plurality of endocardial sites, the system reconstructs the three-dimensional geometry of the chamber, with the electrophysiological information color-coded and superimposed on the anatomy. The accuracy of the system was tested in both in vitro and in vivo studies and was found to be highly reproducible (SD, 0.16 +/- 0.02 [mean +/- SEM] and 0.74 +/- 0.13 mm) and accurate (mean errors, 0.42 +/- 0.05 and 0.73 +/- 0.03 mm). In further studies, electroanatomical mapping of the cardiac chambers was performed in 34 pigs. Both the geometry and activation sequence were repeatable in all pigs. CONCLUSIONS The new mapping method is highly accurate and reproducible. The ability to combine electrophysiological and spatial information provides a unique tool for both research and clinical electrophysiology. Consequently, the main shortcomings of conventional mapping-namely, prolonged x-ray exposure, low spatial resolution, and the inability to accurately navigate to a predefined site-can all be overcome with this new method.

Catheter Ablation of Paroxysmal Atrial Fibrillation Using a 3D Mapping System

BACKGROUND We treated paroxysmal recurrent atrial fibrillation (AF) with radiofrequency (RF) catheter ablation by creating long linear lesions in the atria. To achieve line continuity, a 3D electroanatomic nonfluoroscopic mapping system was used. METHODS AND RESULTS In 27 patients with recurrent AF, a catheter incorporating a passive magnetic field sensor was navigated in both atria to construct a 3D activation map. RF energy was delivered to create continuous linear lesions: 3 lines (intercaval, isthmic, and anteroseptal) in the right atrium and a long line encircling the pulmonary veins in the left atrium. After RF application, the atria were remapped to validate completeness of the block lines, demonstrated by late activation of the areas circumscribed by the lines. The mean procedure duration was 312+/-103 minutes (range, 187 to 495), with mean fluoroscopy time of 107+/-44 minutes (range, 32 to 185 minutes). No acute complications occurred, but 1 patient experienced early prolonged sinus pauses and received a pacemaker. During the first day, 17 patients (63%) had AF episodes, but at discharge, 25 patients were in sinus rhythm. After a follow-up of 6. 0 to 15.3 months (average, 10.5+/-3.0 months), 16 patients are asymptomatic, 3 have an almost complete disappearance of symptoms, 1 patient is improved, and 7 patients have their AF attacks unchanged. CONCLUSIONS Paroxysmal recurrent drug-refractory AF can be treated by RF catheter ablation. Creation of long continuous linear lesions necessary to compartmentalize the atria is facilitated by a nonfluoroscopic electroanatomic mapping system.

Preliminary Animal and Clinical Experiences Using an Electromechanical Endocardial Mapping Procedure to Distinguish Infarcted From Healthy Myocardium

BACKGROUND A catheter-based left ventricular (LV) endocardial mapping procedure using electromagnetic field energy for positioning of the catheter tip was designed to acquire simultaneous measurements of endocardial voltage potentials and myocardial contractility. We investigated such a mapping system to distinguish between infarcted and normal myocardium in an animal infarction model and in patients with coronary artery disease. METHODS AND RESULTS Measurements of LV endocardial unipolar (UP) and bipolar (BP) voltages and local endocardial shortening were derived from dogs at baseline (n=12), at 24 hours (n=6), and at 3 weeks (n=6) after occlusion of the left anterior descending coronary artery. Also, 12 patients with prior myocardial infarction (MI) and 12 control patients underwent the LV endocardial mapping study for assessment of electromechanical function in infarcted versus healthy myocardial regions. In the canine model, a significant decrease in voltage potentials was noted in the MI zone at 24 hours (UP, 42. 8+/-9.6 to 29.1+/-12.2 mV, P=0.007; BP, 11.6+/-2.3 to 4.9+/-1.2 mV, P<0.0001) and at 3 weeks (UP, 41.0+/-8.9 to 13.9+/-3.9 mV, P<0.0001; BP, 11.2+/-2.8 to 2.4+/-0.4 mV, P<0.0001). No change in voltage was noted in zones remote from MI. In patients with prior MI, the average voltage was 7.2+/-2.7 mV (UP)/1.4+/-0.7 mV (BP) in MI regions, 17.8+/-4.6 mV (UP)/4.5+/-1.1 mV (BP) in healthy zones remote from MI, and 19.7+/-4.4 mV (UP)/5.8+/-1.0 mV (BP) in control patients without prior MI (P<0.001 for MI values versus remote zones or control patients). In the canine model and patients, local endocardial shortening was significantly impaired in MI zones compared with controls. CONCLUSIONS These preliminary data suggest that infarcted myocardium could be accurately diagnosed and distinguished from healthy myocardium by a reduction in both electrical voltage and mechanical activity. Such a diagnostic electromechanical mapping study might be clinically useful for accurate assessment of myocardial function and viability.

Guidance of Radiofrequency Endocardial Ablation With Real-time Three-dimensional Magnetic Navigation System

BACKGROUND Ablation therapy for certain arrhythmias requires the formation of complex lesions based on electrical and anatomic mapping. We tested the accuracy and reproducibility of a nonfluoroscopic mapping and navigation (NFM) system to guide delivery of radiofrequency (RF) energy in the right atrium (RA) of swine. METHODS AND RESULTS The NFM system uses an ultralow magnetic field to measure the real-time three-dimensional (3D) location of the tip of the locatable catheter. While in stable contact with the endocardium, between 30 and 40 consecutive tip locations were sampled and used for the 3D reconstruction of the RA geometry. The location of the catheter tip was presented in real time, superimposed over the RA geometry. We selected a point on the 3D reconstruction and delivered RF energy to that site via the tip of the locatable catheter. The catheter was then completely withdrawn and renavigated twice to the same point, at which RF energy was delivered again. At autopsy, the distance between the centers of the three ablation points (mean+/-SEM) was 2.3+/-0.5 mm (n=27). Similarly, we used the NFM system to guide the generation of linear lesions. The measured length of the linear lesions on the NFM 3D view was close to the actual lesion length measured at autopsy (correlation coefficient, .96; P=.002; n=6). Furthermore, the location, shape, and continuity of the linear lesions corresponded to the autopsy findings. CONCLUSIONS We conclude that the NFM system can guide the application of RF energy without the use of fluoroscopy in a highly accurate and reproducible manner.

Electromechanical Characterization of Chronic Myocardial Infarction in the Canine Coronary Occlusion Model

BACKGROUND Defining the presence, extent, and nature of the dysfunctional myocardial tissue remains a cornerstone in diagnostic cardiology. A nonfluoroscopic, catheter-based mapping technique that can spatially associate endocardial mechanical and electrical data was used to quantify electromechanical changes in the canine chronic infarction model. METHODS AND RESULTS We mapped the left ventricular (LV) electromechanical regional properties in 11 dogs with chronic infarction (4 weeks after LAD ligation) and 6 controls. By sampling the location of a special catheter throughout the cardiac cycle at multiple endocardial sites and simultaneously recording local electrograms from the catheter tip, the dynamic 3-dimensional electromechanical map of the LV was reconstructed. Average endocardial local shortening (LS, measured at end systole and normalized to end diastole) and intracardiac bipolar electrogram amplitude were quantified at 13 LV regions. Endocardial LS was significantly lower at the infarcted area (1.2+/-0.9% [mean+/-SEM], P<0.01) compared with the noninfarcted regions (7.2+/-1.1% to 13. 5+/-1.5%) and with the same area in controls (15.5+/-1.2%, P<0.01). Average bipolar amplitude was also significantly lower at the infarcted zone (2.3+/-0.2 mV, P<0.01) compared with the same region in controls (10.3+/-1.3 mV) and with the noninfarcted regions (4. 0+/-0.7 to 10.2+/-1.5 mV, P<0.01) in the infarcted group. In addition, the electrical maps could accurately delineate both the location and extent of the infarct, as demonstrated by the high correlation with pathology (Pearsons correlation coefficient=0.90) and by the precise identification of the infarct border. CONCLUSIONS Chronic myocardial infarcted tissue can be characterized and quantified by abnormal regional mechanical and electrical functions. The unique ability to assess the regional ventricular electromechanical properties in various myocardial disease states may become a powerful tool in both clinical and research cardiology.

New Method for Nonfluoroscopic Endocardial Mapping in Humans Accuracy Assessment and First Clinical Results

BACKGROUND Accurate mapping of the site of origin and activation sequence of a cardiac arrhythmia is essential for a successful catheter ablation procedure. To achieve this, precise and reproducible catheter manipulation is mandatory. The aim of this study was (1) to assess the accuracy of a new nonfluoroscopic mapping system in humans and (2) to report the first result of endocardial activation mapping with this system during sinus rhythm and several types of supraventricular and ventricular tachycardias. METHODS AND RESULTS Fifteen patients were studied. Accuracy measurements were performed in 5 of them (patients 5, 6, 7, 8, and 14). The distances between two subsequent catheter positions in the inferior caval vein as determined by the nonfluoroscopic mapping system were compared with measurements made with calipers by four independent investigators using identification marks on the catheter shaft. The difference between these two methods was 0.95+/-0.8 mm. In 15 patients, activation of the right atrium and/or the right or left ventricle was recorded during sinus rhythm. Three-dimensional activation maps were constructed in patients with atrial and ventricular tachycardias and Wolff-Parkinson-White syndrome. CONCLUSIONS With this new nonfluoroscopic mapping technique, accurate positioning of the catheter tip is possible. A three-dimensional activation map can be reconstructed during sinus rhythm and during supraventricular and ventricular tachycardias of different compartments of the heart.

Altered heart rate variability in panic disorder patients

Resting electrocardiographic recordings were obtained from 10 patients with panic disorder (PD) and 14 normal controls. Signal analysis of the beat-to-beat heart rate variability was performed by means of power spectrum analysis. The analysis revealed that patients with PD had marked reduction in the high-frequency peaks of the power spectrum densities. An Energy Ratio Index (ERI), which accurately differentiated between patients and controls, was calculated. In PD patients, a significant correlation was demonstrated between the clinical ratings and the energy ratios. Our findings suggest that decreased heart rate variability may be a characteristic of PD. The importance of this finding as a diagnostic marker and the underlying pathophysiological mechanisms need to be further explored.

Hemodynamic Evaluation of the Heart With a Nonfluoroscopic Electromechanical Mapping Technique

BACKGROUND Clinical cardiac volumetric measurement techniques are essential for assessing cardiac performance but produce significant inaccuracies in extrapolation of the volume of a three-dimensional (3D) object from two-dimensional images and lack the ability to associate cardiac electrical and mechanical activities. In this study, we tested the accuracy of cardiac volumetric measurements using a new catheter-based system. METHODS AND RESULTS The system uses magnetic technology to accurately locate a special catheter at a frequency of 125 Hz and is currently used in the field of electrophysiology, in which activation maps are superimposed on the 3D geometry of the cardiac chamber. The mapping procedure is based on sequentially acquiring the location of the tip and local electrogram while in contact with the endocardium. The 3D geometry of the chamber is reconstructed in real time, and its volume could be calculated at every time step (8 ms). The volumetric measurements of the system were found to be highly accurate for simple phantoms (mean+/-SEM deviation, 2.3+/-1.1%), left ventricular casts (9.6+/-1.3%), and a dynamic test jig. In addition, left ventricular volumes of 12 swine were measured. Intraobserver and interobserver variabilities were found to be minimal (ejection fraction, 6.5+/-1.9% and 7.1+/-2.0%; stroke volume, 4.5+/-1.0% and 11.3+/-2.4%). Comparison with the thermodilution method for measuring stroke volume showed an average deviation of 8.1+/-2.2%. Typical pressure-volume loops were also obtained. CONCLUSIONS The new mapping image provides, for the first time, simultaneous information regarding cardiac mechanics, hemodynamics, and electrical properties. Furthermore, all this information is achieved without the use of fluoroscopy, contrast medium, or complicated image processing.

Cardiac Contractility Modulation by Electric Currents Applied During the Refractory Period in Patients With Heart Failure Secondary to Ischemic or Idiopathic Dilated Cardiomyopathy

We assessed the feasibility of cardiac contractility modulation (CCM) by electric currents applied during the refractory period in patients with heart failure (HF). Extracellular electric currents modulating action potential and calcium transients have been shown to potentiate myocardial contractility in vitro and in animal models of chronic HF. CCM signals were biphasic square-wave pulses with adjustable amplitude, duration, and time delay from sensing of local electric activity. Signals were applied to the left ventricle through an epicardial vein (in 12 patients) or to the right ventricular (RV) aspect of the septum endocardially (in 6 patients). Simultaneous left ventricular (LV) and aortic pressure measurements were performed using a Millar catheter (Millar Instruments, Houston, Texas). Hemodynamics during RV temporary dual-chamber pacing was regarded as the control condition. Both LV and RV CCM stimulation increased dP/dt(max) to a similar degree (9.1 +/- 4.5% and 7.1 +/- 0.8%, respectively; p <0.01 vs controls), with associated aortic pulse pressure changes of 10.3 +/- 7.2% and 10.8 +/- 1.1% (p <0.01 vs controls). Regional systolic wall motion assessed quantitatively by color kinesis echocardiography was markedly enhanced near the CCM electrode, and the area of increased contractility involved 4.6 +/- 1.2 segments per patient. In 6 patients with HF with left bundle branch block, CCM signals delivered during biventricular pacing (BVP) produced an additional 16.1 +/- 3.7% increase in dP/dt(max) and a 17.0 +/- 7.5% increase in pulse pressure compared with BVP alone (p <0.01). CCM stimulation in patients with HF enhanced regional and global measures of LV systolic function, regardless of the varied delivery chamber or whether modulation was performed during RV pacing or BVP.

Novel magnetic technology for intraoperative intracranial frameless navigation: in vivo and in vitro results.

OBJECTIVE To characterize the accuracy of the Magellan electromagnetic navigation system (Biosense Webster, Tirat HaCarmel, Israel) and to demonstrate the feasibility of its use in image-guided neurosurgical applications. DESCRIPTION OF INSTRUMENTATION The Magellan system was developed to provide real-time tracking of the distal tips of flexible catheters, steerable endoscopes, and other surgical instruments, using ultra-low electromagnetic fields and a novel miniature position sensor for image-correlated intraoperative navigation and mapping applications. METHODS An image registration procedure was performed, and static and qualitative accuracies were assessed in a series of phantom, animal, and human neurosurgical studies. EXPERIENCE AND RESULTS During the human study phase, an accuracy error of up to 5 mm was deemed acceptable. Results demonstrated that this degree of accuracy was maintained throughout all procedures. All anatomic landmarks were reached with precision and were accurately viewed on the display screen. Navigation that relied on the system was also successful. No interference with operating room equipment was noted. The accuracy of the system was maintained during regular surgical procedures, using standard surgical tools. CONCLUSION The system provides precise lesion localization without limiting the line of vision, the mobility of the surgeon, or the flexibility of instruments. Electromagnetic navigation promises new advances in neuronavigation and frameless stereotactic surgery.