gram types. Type A has a relatively large spike and a .... spike, and a 'far-field' signal from activation of the large .... [4] Cassidy DM, Vassallo JA, Buxton AE et al.
European Heart Journal (2002) 23, 1131–1138 doi:10.1053/euhj.2001.3110, available online at http://www.idealibrary.com on
Ventricular mapping during atrial and ventricular pacing Relationship of multipotential electrograms to ventricular tachycardia reentry circuits after myocardial infarction C. B. Brunckhorst1, W. G. Stevenson1, W. M. Jackman2, K.-H. Kuck3, K. Soejima1, H. Nakagawa2, R. Cappato3 and S. A. Ben-Haim4 1
2
Cardiovascular Division, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, U.S.A.; Cardiology Division, University of Oklahoma Health Sciences Center, Oklahoma City, OK, U.S.A.; 3Cardiology Division, St. Georg Hospital, Hamburg, Germany; 4Technion Institute of Technology, Haifa, Israel
Aims Conduction through separated myocyte bundles causes multipotential electrograms and reentrant ventricular tachycardia. We hypothesized that without initiating tachycardia, the reentry region could be detected by analysing the change in multipotential electrograms during two different activation sequences. Methods and Results During catheter mapping and ablation in 16 patients with ventricular tachycardia late after infarction ventricular electrograms were recorded from 1072 sites during atrial and right ventricular paced ventricular activation. Multipotential electrograms were present during both activation sequences at 285 (27%) sites, during atrial pacing only at 159 (15%) sites and during right ventricular pacing only at 152 (14%) sites. Sites with multipotential electrograms during both activation sequences were more often related to a ventricular tachycardia circuit isthmus (43%) as compared to sites where such
Introduction Sustained monomorphic ventricular tachycardia late after myocardial infarction is usually due to reentry in the border zone of the infarct. The reentry circuit paths and isthmuses are defined by regions of conduction block. Block may be fixed, due to areas of fibrosis, or functional and present only during reentry due to incomplete recovery from depolarization or to collision of wavefronts[1–3]. Most circuits contain a relatively narrow Revision submitted 14 November 2001, and accepted 21 November 2001. Correspondence: William G. Stevenson, MD, Cardiovascular Division, Brigham and Women’s Hospital, 75 Francis St, Boston, MA 02115, U.S.A. 0195-668X/02/$35.00
electrograms were present during one activation sequence (20%). Multipotential electrograms with >2 low amplitude deflections and a >100 ms difference in duration between the two activation sequences were infrequent but highly predictive of the reentry circuit. Conclusion Regions with fixed multipotentials consistent with conduction block might be useful guides for ablation approaches that target large regions of the infarct, but are not sufficiently specific to be the sole guide for focal ablation approaches. (Eur Heart J, 2002; 23: 1131–1138, doi:10.1053/euhj.2001. 3110) 2002 The European Society of Cardiology. Published by Elsevier Science Ltd. All rights reserved. Key Words: Ventricular tachycardia, catheter ablation, myocardial infarction, reentry, sinus rhythm.
isthmus in the infarct. Radiofrequency catheter ablation aims to interrupt the tachycardia at these narrow isthmus sites, which are a critical part of the circuit. Precise identification of these isthmuses may be impossible, however, when ventricular tachycardia is unstable for mapping due to haemodynamic instability during tachycardia, poor reproducibility of initiation, or frequent transformation from one tachycardia to another. Identification of markers for ventricular tachycardia isthmuses that do not require mapping during tachycardia is desirable, but using analysis of sinus rhythm electrograms for this purpose has been discouraging. Abnormal sinus rhythm electrograms are present over broad regions of the infarct that include reentry circuit sites, but also include bystander regions that are not in the circuit[4–6].
2002 The European Society of Cardiology. Published by Elsevier Science Ltd. All rights reserved.
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Reentry circuit isthmuses consist of a proximal and a central part and an exit from which the wavefront leaves the abnormal region and rapidly depolarizes the normal myocardium resulting in the formation of the QRS complex. Conduction through the isthmus or at its entrance and/or exit is often slow due to decreased cell to cell coupling[1]. During ventricular tachycardia multiple potentials and ‘isolated potentials’ are often recorded from these regions. The presence of multiple discrete potentials indicates that conduction block is present between some of the myocyte bundles. Such potentials are sometimes detectable at these sites during sinus rhythm, but low amplitude potentials can be obscured by the signal from the surrounding larger mass of myocardium[6,7]. In regions of block, changing the direction of depolarization can produce greater separation between activation of adjacent bundles, altering the separation of multipotential electrograms. The effect of a change in activation on electrograms in regions of human infarction has not been studied. We hypothesized that regions containing isthmuses and conduction block may be detected without mapping during ventricular tachycardia by analysing electrograms recorded during two different ventricular activation sequences, such as atrial pacing and then right ventricular pacing. This hypothesis was prospectively tested with the use of custom designed software implemented on an electroanatomic mapping system to allow electrogram sampling during both activation sequences with precise spatial localization.
Methods Patients Endocardial catheter mapping and radiofrequency catheter ablation were performed in 16 male patients (mean age 677·4 [range 49–77] years). All patients had at least one remote (>2 months) myocardial infarction (four anterior, 14 infero-posterior, two with infarcts in both locations). The mean left ventricular ejection fraction was 247 (range 15–40%). The patients had had d2 documented episodes of sustained monomorphic ventricular tachycardia within the preceding 6 months (mean: 1713 episodes [range 2–46]). Patients with incessant ventricular tachycardia were excluded. On average 3·62·8 different monomorphic ventricular tachycardias (range 1–11) were inducible per patient. All patients had previously failed antiarrhythmic drug therapy; 13 patients had implanted defibrillators.
Hamburg, Germany and written informed consent obtained from all patients. At electrophysiology study multipolar electrode catheters (6F) were inserted through the femoral veins and positioned in the right atrium, at the His bundle region and in the right ventricular apex. Access to the left ventricle was achieved with a retrograde aortic or transseptal approach. Systemic anticoagulation was maintained with intravenous administration of heparin. Mapping and ablation utilized the electroanatomic mapping system CARTO (Biosense, Tirat Hacarmel, Israel; Cordis Webster, Baldwin Park, CA, U.S.A.). A passive magnetic field location sensor incorporated into a 7F deflectable catheter allows the location of the catheter tip to be stored along with the electrograms for construction of three-dimensional electroanatomical maps with a spatial accuracy of 0·8 mm[8]. The quadripolar catheter has a 4 mm ablation tip incorporating a thermistor and spacing of 1, 7 and 4 mm between electrodes, respectively. Bipolar endocardial electrograms were recorded from the distal and proximal electrode pair and filtered at 10–400 Hz in 12 patients and at 30–400 Hz in four patients. Intracardiac electrograms and the surface ECG were also digitized and stored on a separate optical disc. The first step in the procedure included mapping during stable sinus rhythm. At each left ventricular site (6723 sites per patient) electrograms were recorded during atrial pacing followed by right ventricular pacing. Whenever possible the pacing cycle length was the same for each site in an individual patient (400–1200 ms). Pacing from the ablation catheter was then performed for pace-mapping. At selected sites ventricular tachycardia was also induced by right ventricular stimulation and the electrogram recorded and entrainment performed to define the circuit[9]. For each mapping site all data were acquired and stored using custom software before moving the catheter to another site. At likely isthmus locations (see below), radiofrequency energy (20–50 watts aiming for temperature of 55–65 degrees Celsius) was applied during ventricular tachycardia when possible to assess termination.
Electrogram analysis An automated program analysed each bipolar endocardial electrogram amplitude, and the duration and timing of onset and offset. Each electrogram was later manually reviewed and measurements confirmed. The presence of multiple potential electrograms defined as d2 discrete deflections was determined by inspection. Multipotential electrograms were further classified by their morphology into four different subtypes (Fig. 1):
Electrophysiology study and ablation The protocol was approved by the institutional review boards of Brigham and Women’s Hospital, Boston, MA, University of Oklahoma Health Sciences Center, Oklahoma City, OK, U.S.A. and St. Georg Hospital, Eur Heart J, Vol. 23, issue 14, July 2002
Type A: Potentials of unequal amplitude (>1·5difference) with a relatively large sharp potential and a smaller rounded potential Type B: Potentials of unequal amplitude with a large rounded potential and a small sharp potential
Ventricular mapping during AV pacing
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Statistical analysis Type A
All values are expressed as meanstandard deviation. Continuous variables are compared using the two-tail paired and unpaired t-test as appropriate and the chi square test. A probability value of
