Richard Derksen

LocaLisa New Technique for Real-Time 3-Dimensional Localization of Regular Intracardiac Electrodes

BACKGROUND Estimation of the 3-dimensional (3D) position of ablation electrodes from fluoroscopic images is inadequate if a systematic lesion pattern is required in the treatment of complex arrhythmogenic substrates. METHODS AND RESULTS We developed a new technique for online 3D localization of intracardiac electrodes. Regular catheter electrodes are used as sensors for a high-frequency transthoracic electrical field, which is applied via standard skin electrodes. We investigated localization accuracy within the right atrium, right ventricle, and left ventricle by comparing measured and true interelectrode distances of a decapolar catheter. Long-term stability was analyzed by localization of the most proximal His bundle before and after slow pathway ablation. Electrogram recordings were unaffected by the applied electrical field. Localization data from 3 catheter positions, widely distributed within the right atrium, right ventricle, or left ventricle, were analyzed in 10 patients per group. The relationship between measured and true electrode positions was highly linear, with an average correlation coefficient of 0.996, 0.997, and 0.999 for the right atrium, right ventricle, and left ventricle, respectively. Localization accuracy was better than 2 mm, with an additional scaling error of 8% to 14%. After 2 hours, localization of the proximal His bundle was reproducible within 1.4+/-1.1 mm. CONCLUSIONS This new technique enables accurate and reproducible real-time localization of electrode positions in cardiac mapping and ablation procedures. Its application does not distort the quality of electrograms and can be applied to any electrode catheter.

Pulmonary Vein Ostium Geometry Analysis by Magnetic Resonance Angiography

Background—During a catheter ablation procedure for selective electrical isolation of pulmonary vein (PV) ostia, the size of these ostia is usually estimated using fluoroscopic angiography. This measurement may be misleading, however, because only the projected supero/inferior ostium diameters can be measured. In this study, we analyzed 3-dimensional magnetic resonance angiographic (MRA) images to measure the minimal and maximal cross-sectional diameter of PV ostia in relation to the diameter that would have been projected on fluoroscopic angiograms during a catheter ablation procedure. Methods and Results—In 42 patients with idiopathic atrial fibrillation who were scheduled for selective electrical isolation of PV ostia, the minimal and maximal diameters of these ostia were measured from 3-dimensional MRA images. Thereafter, these images were oriented in a 45° right or left anterior oblique direction and the projected diameter of the PV ostia were measured again. The average ratio between maximal and minimal diameter was 1.5±0.4 for the left and 1.2±0.1 for the right pulmonary vein ostia. Because of the orientation and oval shape of especially the left pulmonary vein ostia, their minimal diameters were significantly smaller than the projected diameters. Conclusion—Pulmonary vein ostia, especially those at the left, are oval with the short axis oriented approximately in the antero/posterior direction. Consequently, PV ostia may sometimes be very narrow despite a rather normal appearance on angiographic images obtained during a catheter ablation procedure.

Sudden Death in Noncoronary Heart Disease Is Associated With Delayed Paced Ventricular Activation

Background—Slowed or delayed myocardial activation and dispersed refractoriness predispose to reentrant excitation that may lead to ventricular fibrillation (VF). Increased ventricular electrogram duration (&Dgr;ED) in response to extrastimuli and increased S1S2 coupling intervals at which electrogram duration starts to increase (S1S2delay) are seen both in hypertrophic cardiomyopathy (HCM) in those at risk of VF and in patients with idiopathic VF (IVF). Methods and Results—&Dgr;ED and S1S2delay have been measured using paced electrogram fractionation analysis in 266 patients with noncoronary heart disease. Of these, one group of 61 patients had a history of VF and included 21 HCM, 17 IVF, 13 long-QT syndrome (LQTS), 5 dilated cardiomyopathy (DCM), and 5 others. These were compared with 205 patients with similar diseases with no VF history (non-VF group) and a control group (n=12) without heart disease. Results from HCM VF patients (&Dgr;ED, 19±3.3 ms; S1S2delay, 350±9.7 ms) differed sharply from observations in HCM non-VF patients (&Dgr;ED, 7.3±1.35 ms; S1S2delay, 312±6.7 ms;P <0.001). DCM VF patients had longer delays (&Dgr;ED, 14.3±5.9; S1S2delay, 344±11.2) than DCM non-VF patients (&Dgr;ED, 5.8±1.87 ms; S1S2delay, 311±5.7 ms;P <0.001), with major differences also seen comparing LQTS VF (&Dgr;ED, 12.4±5.3 ms; S1S2delay, 343±13.8 ms) and LQTS non-VF patients (&Dgr;ED, 11.0±2.7 ms; S1S2delay, 320±5.4 ms;P <0.001). IVF patients had both severely abnormal and normal areas of myocardium. Conclusions—Slowed or delayed myocardial activation is a common feature in patients with noncoronary heart disease with a history of VF, and its assessment may allow the prospective prediction of VF risk in these patients.

Accuracy of the LocaLisa system in catheter ablation procedures.

Estimation of the 3-dimensional (3D) position of ablation electrodes from fluoroscopic images is inadequate in the ablation of complex arrhythmogenic substrates. We developed a new technique for real-time 3D localization of intracardiac electrodes. Regular catheter electrodes are used as sensors for a high-frequency transthoracic electrical field, which is applied via standard skin electrodes. We investigated localization accuracy by comparing measured and true interelectrode distances between the tip and the 10th electrode of a decapolar catheter, and the tip and the 4th electrode of a quadripolar catheter during catheter ablation procedures. Long-term stability was analyzed by localization of the proximal His bundle before and after slow pathway ablation. Accuracy achieved with the 54-mm distance between the two outer electrodes of the decapolar catheters was 101% +/- 15%, 95% +/- 10%, and 97% +/- 8% in the right atrium, right ventricle, and left ventricle, respectively. During catheter ablation procedures, the measured distance between the tip and 4th electrode of the mapping catheter was 100% +/- 15% in atrial flutter, 100% +/- 12% in slow pathway ablation, and 100% +/- 14% in ablations for left ventricular tachycardia. After 2 hours, localization of the proximal His bundle was reproducible within 1.4 +/- 1.1 mm. The LocaLisa technique allows for reproducible, real-time nonfluoroscopic 3D visualization of standard mapping and ablation catheters and is sufficiently accurate for the creation of linear radiofrequency lesions. The freedom of catheter choice makes the LocaLisa system an invaluable tool in catheter mapping and ablation procedures.

Tissue discontinuities affect conduction velocity restitution - A mechanism by which structural barriers may promote wave break

Background—The mechanism by which structural barriers promote wave break and fibrillation is unclear. Conduction velocity (CV) restitution is an important determinant of wave break. Abnormal CV restitution is associated with ventricular fibrillation in patients with heart disease and arises preferentially in fibrotic myocardium. We hypothesize that tissue discontinuities imposed by structural barriers cause abnormal CV restitution. Methods and Results—Tissue discontinuities were simulated in cultures of neonatal rat heart cells grown in 8-armed star patterns. Premature stimulation was applied at the extremity of 1 arm (n=12) while extracellular electrograms were recorded at 24 sites throughout the star. Action potentials were recorded at the following 3 sites: in the stimulated arm and at the discontinuity both proximal to and distal from the star center. Extracellular recordings revealed progressive increases in activation delay (indicative for abnormal CV restitution) only at the discontinuity from arms proximal to the star center. The mean increase in delay was 0.81±0.41 ms/10 ms for recording sites proximal to and 3.13±0.58 ms/10 ms for sites distal from this discontinuity. Depolarizing currents were determined in single cells during premature stimulation and for voltage configurations similar to those arising at the discontinuity. Both voltage-clamp measurements and computer simulations showed that delay at the discontinuity was associated with biphasic, prolonged activation and delayed inactivation of depolarizing current. Conclusions—Tissue discontinuities cause abnormal CV restitution. Rapid increase in activation after an initial slow activation and delayed inactivation at the discontinuity lengthen the duration of depolarizing current and cause the abnormal restitution.

Catheter Ablation of Incisional Atrial Tachycardia Using a Novel Mapping System: LocaLisa

MOLENSCHOT, M., et al.: Catheter Ablation of Incisional Atrial Tachycardia Using a Novel Mapping System: LocaLisa. Incisional atrial tachycardia occurs due to reentry around surgical scars. Pharmacological therapy is often ineffective. This study assessed the efficacy of a novel mapping system (LocaLisa) in facilitating catheter ablation of incisional atrial tachycardia circuits. Eight consecutive patients (four men, four women) with incisional atrial tachycardia (median age 23.5 years, range 9–44) following previous repair of congenital heart defects underwent transcatheter mapping and ablation of the arrhythmogenic substrate using a mapping system (LocaLisa) that allows localization of endocardial electrodes in a three‐dimensional space. Critical isthmuses for the tachycardia circuits were identified by demonstrating concealed entrainment using standard pacing and mapping techniques. Scars and natural anatomic barriers were marked on the LocaLisa image. Lines of block were created by radiofrequency current application between scars and natural anatomic barriers, or between two scars, to close isthmuses demonstrated to be critical for the reentrant circuit. All lines of block were verified in both directions. All reentrant circuits around incisions were successfully ablated. Seven additional tachycardia mechanisms were identified in four patients (common atrial flutter [n = 4], atrioventricular nodal [AVN] reentry [n = 2], ectopic atrial tachycardia [n = 1]) and were also ablated in a single session. The mean fluoroscopy time was 28.4 ± 13.8 minutes. All patients are arrhythmia‐free at a median follow‐up of 20 (6–22) months. The LocaLisa mapping system is effective for identification of scars and ablation targets, for confirming lines of block, and facilitating ablation of complex reentrant circuits.

Radiofrequency catheter ablation of junctional ectopic tachycardia with preservation of atrioventricular conduction

Junctional ectopic tachycardia is a relatively rare disorder, frequently refractory to drug therapy, and with a poor prognosis in childhood. This report describes a successful radiofrequency catheter ablation of the focus of this arrhythmia in a 9‐year‐old girl with preservation of normal atrioventricular conduction, using precise catheter navigation with the LocaLisa system and carefully titrated RF delivery. (PACE 2003; 26:1284–1288)

Can Implantable Cardioverter-Defibrillator Therapy Reduce Healthcare Costs?*

This article presents a comparison of the costs and the cost effectiveness of defibrillator implantation in a hypothetical scenario for the years 1996-2000, with recently reported actual data from the Dutch prospective study over the years 1989-1993. Recently, technological advances in pulse generator and leads have revolutionized implantable cardioverter-defibrillator (ICD) therapy. Major advances include (1) transvenous single lead positioning and (2) tremendously reduced size, combined with prolonged longevity of the pulse generator. Both have simplified implantation technique and provided for superior effectiveness and lower costs. This suggests that a more favorable cost-effectiveness is to be expected. The study group reported here consisted of patients successfully resuscitated after cardiac arrest due to malignant ventricular tachyarrhythmias in the chronic stage of myocardial infarction. During a mean follow-up of 27 months, starting on the day of therapeutic decision making, total costs and the cost-effectiveness ratio were estimated. Actual data from the prospective study in 1989-1993 are compared with a hypothetical scenario for 1996-2000. Mortality and costs for hospitalization per day, per procedure, and per device are taken from the prospective study and equalized for both scenarios. Transthoracic lead positioning and abdominal implantation of a Ventak P (CPI) defibrillator with +/- 3 years longevity were characteristic of the recently completed prospective study. The hypothetical future scenario uses the Ventak Mini-2 with assumed 5 years longevity, implanted pectorally and connected to a single transvenous lead. Implantation will be carried out in the catheterization laboratory and as first-choice treatment. Due to prolonged longevity of the device and shorter hospitalization, a cost reduction of US

Ventricular Tachycardia as a Complication of Atrial Flutter Ablation

11,530 per patient is expected. Total costs per patient in the 1989-1993 prospective study in the (1) conventional arm (drugs first choice), (2) early ICD arm (ICD first choice), and (3) early ICD arm in the 1996-2000 study (ICD first choice) are

Activation Delay After Premature Stimulation in Chronically Diseased Human Myocardium Relates to the Architecture of Interstitial Fibrosis

63,032,