RESUMEN
The atria are anatomically complex three-dimensional (3-D) structures. Impulse propagation is dynamic and complex during both normal conduction and arrhythmia. Atria activation has traditionally been represented on two-dimensional surface maps, which have inherent inaccuracies and are difficult to interpret. Interactive computerized 3-D display facilitates interpretation of complex atrial activation sequence data obtained from form-fitting multipoint electrodes. Accordingly, the purpose of this article is to describe the application of 3-D form-fitting electrode molds to the 3-D mapping and display system developed in this laboratory for the study of complex cardiac arrhythmias. Computer generated 3-D surface models are created from a database of serial cross-sectional anatomical images. Points chosen on endocardial and epicardial surfaces in each cross-sectional image are processed to create polygons defining myocardial wall boundaries. The polygons from adjacent serial images are then combined, to create a 3-D surface model. The discrete anatomical locations of unit electrodes on multipoint electrode templates are then assigned in the proper position on the surface model. Computer analysis of simultaneous activation data from each unit electrode is performed based on parameters set by the user. Activation data from each unit electrode site are displayed on the computer surface model in a color spectrum correlating with a user-defined time scale. Activation sequence maps can be visualized as static isochrone maps, interval maps, or as dynamic maps at variable speeds, from any 3-D perspective. Thus, an interactive computerized 3-D display system is described, which allows anatomically superior analysis and interpretation of complex atrial arrhythmias.
Asunto(s)
Arritmias Cardíacas/fisiopatología , Atrios Cardíacos/fisiopatología , Sistema de Conducción Cardíaco/fisiopatología , Modelos Cardiovasculares , Arritmias Cardíacas/diagnóstico , Función Atrial/fisiología , Gráficos por Computador , Electrodos Implantados , Electrofisiología , Humanos , Procesamiento de Imagen Asistido por Computador , Procesamiento de Señales Asistido por Computador , Programas InformáticosRESUMEN
BACKGROUND: In humans, chronic ventricular tachycardia (VT) is usually associated with myocardial infarcts that involve the interventricular septum. In an effort to more closely mimic the anatomic substrate that gives rise to chronic VT in humans, we developed a canine model of VT in which the anterior septal coronary artery was ligated. The site of earliest activation, the subsequent activation sequence, and the mechanism of VT associated with the resultant ventricular septal infarct was then evaluated to determine if this model accurately reflected the characteristics of human VT. METHODS AND RESULTS: Seventeen dogs underwent occlusion-reperfusion ventricular septal infarcts. Four to 7 days later, electrophysiological studies were performed. VT was initiated by programmed electrical stimulation and terminated by pacing at a cycle length of 50% to 75% of the VT cycle length. Electrophysiological studies were performed using a 256-channel mapping system. A total of 15 VT morphologies were mapped in 9 animals. Fourteen of 15 morphologies had septal subendocardial sites of earliest activation and 1 had a septal midwall site of earliest activation. VT ablation was performed using a nitrous oxide cryoprobe and confirmed the site of earliest activation by subsequently rendering VT noninducible. Electrophysiological studies demonstrated four distinct VT activation sequences: (1) circular reentrant (n = 7), (2) concentric spread (n = 5), (3) figure-of-eight (n = 2), and (4) septal midwall (n = 1). CONCLUSIONS: This canine model of ventricular septal infarction produces VTs with sites of earliest activation and activation sequences similar to those in humans. A reentrant mechanism as the basis of these arrhythmias is supported by the following observations: (1) all VT was initiated and terminated with programmed electrical stimulation; (2) VT activation sequences were consistent with reentry; and (3) precise interruption of the sequence terminated the VT and rendered it noninducible.
Asunto(s)
Circulación Coronaria , Tabiques Cardíacos , Infarto/complicaciones , Taquicardia Ventricular/etiología , Taquicardia Ventricular/fisiopatología , Animales , Criocirugía , Modelos Animales de Enfermedad , Perros , Electrofisiología , Taquicardia Ventricular/cirugíaRESUMEN
Electrophysiologically guided operations for ventricular tachycardia (VT) have been directed exclusively by activation time maps. Even with computer-assisted mapping, extensive editing is required, which prolongs the duration of the operation and which may introduce significant error. In contrast, potential distribution maps can be constructed in less than 3 minutes and can be viewed as a movie of developing and receding potentials. In 4 patients undergoing operation for VT, endocardial mapping was performed using form-fitting electrodes containing 160 points. A computerized mapping system, capable of simultaneously recording 256 channels of data, was used to analyze data and to display potential distribution maps sequentially at 1-millisecond intervals as a color movie. A total of eight morphologies of sustained VT were mapped. The mean VT cycle length was 340 +/- 40 milliseconds (range, 274 to 394 milliseconds). In 3 patients with ischemic heart disease, four VT morphologies originated from the subendocardium. All were successfully ablated with cryoablation alone or in conjunction with aneurysmectomy and endocardial resection. A fourth patient with VT secondary to cardiomyopathy had multiple morphologies and received an implantable cardioverter defibrillator. Potential distribution maps correlated well with the concomitant activation time maps. Thus, potential distribution mapping provides a rapid and accurate means of identifying the site of origin of VT facilitating intraoperative mapping in patients undergoing surgical ablation.
Asunto(s)
Electrocardiografía , Sistema de Conducción Cardíaco/fisiopatología , Cuidados Intraoperatorios , Taquicardia Ventricular/fisiopatología , Taquicardia Ventricular/cirugía , Potenciales de Acción/fisiología , Anciano , Cardiomiopatía Dilatada/fisiopatología , Cardiomiopatía Dilatada/cirugía , Puente Cardiopulmonar , Criocirugía , Electrocardiografía/instrumentación , Electrocardiografía/métodos , Electrodos Implantados , Diseño de Equipo , Aneurisma Cardíaco/fisiopatología , Aneurisma Cardíaco/cirugía , Tabiques Cardíacos/fisiopatología , Ventrículos Cardíacos/fisiopatología , Humanos , Persona de Mediana Edad , Isquemia Miocárdica/fisiopatología , Isquemia Miocárdica/cirugía , Procesamiento de Señales Asistido por Computador , Elastómeros de SiliconaRESUMEN
Electrocardiographically gated magnetic resonance (MR) image acquisition is not optimal for the quantification of in vivo cardiac deformation, because of the cycle-length dependence of cardiac mechanical events. The authors developed a method for acquisition of cardiac MR images gated to the first derivative of left-ventricular-developed pressure and used the method in a canine model. Application of this method may improve myocardial stress-strain analyses.
Asunto(s)
Imagen de Acumulación Sanguínea de Compuerta/métodos , Imagen por Resonancia Magnética/métodos , Contracción Miocárdica/fisiología , Animales , Diástole , Perros , SístoleRESUMEN
This study evaluated potential distribution mapping as a method for localizing the site of origin of ventricular tachycardia (VT). In contrast to conventional activation time maps, potential distribution maps require less editing and thus can be more automated and rapidly processed for interpretation of multiple beats of VT. As a series of potential distribution maps during VT is required for detailed analysis, an on-line computerized system was designed to display potential distribution maps sequentially at 1-ms intervals as a color movie. Potential distribution maps and activation time maps were constructed from 182 epicardial and endocardial unipolar electrodes during 12 episodes of reproducible monomorphic VT in 9 dogs four to six days after experimental myocardial infarction (mean cycle length, 162 +/- 21 ms). At the onset of each depolarization during VT, a potential minimum abruptly developed on the surviving epicardium and another on the surviving endocardium of the left ventricle, both immediately adjacent to the subendocardial infarct. These two minima on the initial potential distribution maps corresponded to the sites of earliest epicardial and endocardial activation breakthrough recorded on the activation time maps. These two minima subsequently expanded or moved into the adjacent area and coincided with the spread of activation fronts on the epicardial and endocardial surfaces. Thus, the rapid display of sequential, computerized potential distribution maps of multiple beats of VT provides a dynamic means of identifying the site of origin of VT, and therefore should facilitate intraoperative mapping.
Asunto(s)
Sistema de Conducción Cardíaco/fisiopatología , Procesamiento de Imagen Asistido por Computador , Cuidados Intraoperatorios , Infarto del Miocardio/fisiopatología , Sistemas en Línea , Taquicardia/fisiopatología , Potenciales de Acción , Conversión Analogo-Digital , Animales , Perros , Electrocardiografía , Electrodos Implantados , Electrofisiología , Femenino , Masculino , Contracción MiocárdicaRESUMEN
To delineate the propagation of electrical activation in the atrial septum, atrial epicardial and atrial septal maps were recorded intraoperatively using a 156-channel computerized mapping system in 12 patients during sinus rhythm (n = 10), supraventricular tachycardia associated with septal pathways in Wolff-Parkinson-White syndrome (n = 3), atrioventricular (AV) node reentrant tachycardia (n = 4), and atrial flutter (n = 5). The epicardial and septal data were recorded simultaneously from 156 atrial electrodes, digitized, analyzed, and displayed as isochronous maps on a two-dimensional diagram of the atria. During sinus rhythm, the activation wave fronts propagated most rapidly along the large muscle bundles of the atrial septum. During supraventricular tachycardia associated with Wolff-Parkinson-White syndrome, the earliest site of retrograde atrial activation usually corresponded to the position of atrial insertion of the septal pathways. However, the earliest site of activation during orthodromic supraventricular tachycardia was different from that during ventricular pacing in 1 patient with a posterior septal accessory pathway localized by the epicardial mapping study. The data document the rationale for dividing the ventricular end of the accessory pathways (ie, the endocardial technique) rather than the atrial end (ie, the epicardial technique) in patients with Wolff-Parkinson-White syndrome. During AV node reentrant tachycardia, atrial activation data suggested that atrial tissue lying outside the confines of the anatomical AV node is a necessary link in this common arrhythmia. Thus, these atrial septal maps explain why surgical dissection, or properly positioned small cryolesions placed in the region of the AV node, can ablate AV node reentrant tachycardia without altering normal AV node function. The maps recorded during atrial flutter suggest the importance of the atrial septum as one limb of a macroreentrant circuit responsible for the arrhythmia, and imply that atrial flutter is amenable to control by surgical techniques. These studies demonstrate the details of normal atrial septal activation, the importance of the atrial septum in a variety of different atrial arrhythmias, and the basis of and potential for surgical ablation of the most common types of supraventricular arrhythmias.
Asunto(s)
Arritmias Cardíacas/fisiopatología , Sistema de Conducción Cardíaco/fisiología , Tabiques Cardíacos/fisiología , Procesamiento de Imagen Asistido por Computador , Adolescente , Adulto , Aleteo Atrial/fisiopatología , Estimulación Cardíaca Artificial , Niño , Electrocardiografía/instrumentación , Electrodos , Diseño de Equipo , Femenino , Atrios Cardíacos , Humanos , Masculino , Persona de Mediana Edad , Taquicardia por Reentrada en el Nodo Atrioventricular/fisiopatologíaRESUMEN
A recently developed computer program is capable of rapidly (less than 5 minutes) constructing a series of potential-distribution maps (PDMs) for every msec of a 4-second window of ventricular tachycardia (VT). This study was performed to assess the ability of a series of PDMs to localize the site of earliest activation of VT originating in the interventricular septum. In 12 dogs, 13 morphologies of VT were initiated with programmed electrical stimulation 3-6 days after anterior septal coronary artery infarction. VT was mapped with endocardial and epicardial unipolar electrodes with a multipoint, computer-assisted mapping system. PDMs were compared with activation-time maps, and the former correctly identified the site of earliest activation of all 13 VT morphologies. When PDMs were viewed in sequence on a computer monitor, the site of earliest activation was signaled by abrupt development of a negative potential of less than -3.0 mV. The initial negative point subsequently expanded, and the spread of this negative-potential field correlated with activation sequence. PDMs provide an accurate, unambiguous, rapid means of analyzing large numbers of electrograms acquired with multipoint, computer-assisted mapping systems.